LACTIDE POLYMERISATION
20170022320 ยท 2017-01-26
Inventors
Cpc classification
C08L83/00
CHEMISTRY; METALLURGY
B29C65/48
PERFORMING OPERATIONS; TRANSPORTING
C07F7/2208
CHEMISTRY; METALLURGY
C08G77/70
CHEMISTRY; METALLURGY
C08L83/00
CHEMISTRY; METALLURGY
C07F7/00
CHEMISTRY; METALLURGY
C08G63/823
CHEMISTRY; METALLURGY
B01J31/00
PERFORMING OPERATIONS; TRANSPORTING
International classification
Abstract
The present invention relates to a compound having the formula L.sub.aM(OR.sup.1).sub.bR.sup.2.sub.cX.sub.d wherein M is a metal selected from Ti, Zr and Hf; L is a ligand selected from permethylpentalene, (hydro)permethyl-pentalene, (hydro)pentalene, cyclopentadiene, indene and ethylene- or silane-bridged indene, preferably (bis)indene; R.sup.1 is a 1-6C alkyl, substituted or unsubstituted phenyl, or a substituted or unsubstituted phenylalkylene group; R.sup.2 is Me or Et; X is halogen; a=1 to 3, b=1 to 3, c=0 or 1 and d=0, 1, 2 or 3; and dimers thereof, the use of the compound as an initiator in the polymerisation of lactide monomer and a process for producing a polylactide performed by contacting a lactide monomer with the compound.
Claims
1. A compound having the formula
L.sub.aM(OR.sup.1).sub.bR.sup.2.sub.cX.sub.d wherein M is a metal selected from Ti, Zr and Hf; L is a ligand selected from permethylpentalene, (hydro)permethyl-pentalene, (hydro)pentalene, cyclopentadiene, indene and ethylene- or silane-bridged indene; R.sup.1 is a 1-6C alkyl, substituted or unsubstituted phenyl, or a substituted or unsubstituted phenylalkylene group; R.sup.2 is Me or Et; X is halogen; a=1 to 3, b=1 to 3, c=0 or 1 and d=0, 1, 2 or 3; or a dimer thereof.
2. The compound according to claim 1, wherein L is permethylpentalene and X is Cl.
3. The compound according to claim 1, wherein R.sup.1 is a group selected from -.sup.tBu, C.sub.6H.sub.3(R.sub.3).sub.2, where R.sup.3 is 1-4C alkyl, and CH(R.sup.4)Ph, where R.sup.4 is H or 1-4C alkyl.
4. The compound according to claim 3, wherein R.sup.1 is selected from 2,6-dimethylphenyl, 2,6-diisopropylphenyl and 2,6-di.sup.tbutylphenyl.
5. The compound according to claim 3, wherein R.sup.4 is Me.
6. The compound according to claim 1, wherein M is Ti.
7. The compound according to claim 1, wherein M is Zr.
8. The compound according to claim 1, wherein M is Hf.
9. The compound according to claim 1, wherein M is Zr, L is indene or ethylene bridged indene or silane bridged indene.
10. The compound according to claim 9, wherein R.sup.1 is a group selected from .sup.tBu and C.sub.6H.sub.3(R.sup.3).sub.2, where R.sup.3 is a 1-4C alkyl group.
11. The compound according to claim 10, wherein R.sup.3 is Me and c=1.
12. A method for polymerizing a lactide monomer, wherein an initiator in the polymerisation of a lactide monomer is a compound having the formula
L.sub.aM(OR.sup.1).sub.bR.sup.2.sub.cX.sub.d wherein M is a metal selected from Ti, Zr and Hf; L is a ligand selected from permethylpentalene, (hydro)permethyl-pentalene, (hydro)pentalene, cyclopentadiene, indene and ethylene- or silane-bridged indene; R.sup.1 is a 1-6C alkyl, substituted or unsubstituted phenyl, or a substituted or unsubstituted phenylalkylene group; R.sup.2 is Me or Et; X is halogen; a=1 to 3, b=1 to 3, c=0 or 1 and d=0, 1, 2 or 3; or a dimer thereof.
13. The method according to claim 12, wherein the lactide monomer is L-lactide.
14. The method according to claim 12, wherein the lactide monomer is rac-lactide.
15. A process for producing a polylactide which comprises contacting a lactide monomer with a compound having the formula
L.sub.aM(OR.sup.1).sub.bR.sup.2.sub.cX.sub.d wherein M is a metal selected from Ti, Zr and Hf; L is a ligand selected from permethylpentalene, (hydro)permethyl-pentalene, (hydro)pentalene, cyclopentadiene, indene and ethylene- or silane-bridged indene; R.sup.1 is a 1-6C alkyl, substituted or unsubstituted phenyl, or a substituted or unsubstituted phenylalkylene group; R.sup.2 is Me or Et; X is halogen; a=1 to 3, b=1 to 3, c=0 or 1 and d=0, 1, 2 or 3; or a dimer thereof.
16. The process according to claim 15, wherein the lactide monomer is L-lactide and the polylactide is isotactic polylactide.
17. The process according to claim 15, wherein the lactide monomer is rac-lactide and the polylactide is atactic polylactide.
18. The compound according to claim 1, wherein L is (bis)indene.
Description
[0058] Further advantages and features of the subject-matter of the present invention can be taken from the following detailed description taking in conjunction with the drawing, in which:
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EXAMPLE 1
Synthesis of [(Pn*)Ti(O-2,6-Me-C.SUB.6.Me.SUB.2.)Cl]
[0072] [.sup.8-(Pn*)TiCl(-Cl)].sub.2 (150 mg, 0.26 mmol) and [K(O-2,6-MeC.sub.6H.sub.3)] (78 mg, 0.50 mmol) were combined in toluene (30 mL) and left to stir for 25 h at room temperature. The resultant solution was filtered before being concentrated in vacuo. X-ray quality single crystals were obtained on storing the toluene concentrated solution at 35 C. for 24 h. Yield=52%. .sup.1H NMR (benzene-d.sub.6, 25 C., 300 MHz): 7.04 (d, 2H, .sup.3J.sub.HH=7.3 Hz, ArH), 6.82 (t, 1H, .sup.3J.sub.HH=7.4 Hz, ArH), 2.11, 2.06, 1.68 (s, 6H each, Pn-CH.sub.3), 1.61 (s, 6H, ArCH.sub.3). .sup.13C{.sup.1H} NMR (toluene-d.sub.8, 25 C., 75.1 MHz): 130.69, 126.16, 14.36, 123.41, 120.41 (Quaternary Carbons), 180.9 (ArCH.sub.3) 13.20, 12.47, 11.11 (Pn-CH.sub.3). The quaternary bridgehead carbon atoms were not observable and certain quaternary carbon signals were obscured by solvent resonances. Analysis calculated for C.sub.22H.sub.27ClTiO (%): C, 67.62; H, 6.98. found: C, 67.70; H, 7.03.
EXAMPLE 2
Synthesis of [.SUP.8.-(Pn*)Ti(O-2,4-.SUP.t.Bu-C.SUB.6.H.SUB.3.)Cl]
[0073] [.sup.8-(Pn*)TiCl(-Cl)].sub.2 (150 mg, 0.25 mmol) and [K(O-2,4-.sup.tBu-C.sub.6H.sub.3)] (120 mg, 0.50 mmol) were stirred in toluene (30 mL) at room temperature for 48 h. The resultant solution was filtered and the solvent removed in vacuo. Subsequent dissolution in minimal hot benzene and storing at room temperature for 24 h led to the formation of X-ray quality single crystals. Yield=55%. .sup.1H NMR (benzene-d.sub.6, 25 C., 300 MHz): 7.54 (d, 1H, .sup.4J.sub.HH=2.4 Hz, meta-ArH), 7.18 (dd, 1H, .sup.3J.sub.HH=8.1 Hz, .sup.4J.sub.HH=2.4 Hz, meta-ArH), 6.41 (d, 1H, .sup.3J.sub.HH=8.3 Hz, ortho-ArH), 2.07, 1.80, 1.64 (s, 6H each, Pn-CH.sub.3), 1.59 (s, 9H, C(CH.sub.3)), 1.35 (s, 9H, C(CH.sub.3)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 25 C., 75.1 MHz): 161.21 (ipso-Ar), 142.66, 140.76, 139.1, 0 135.5, 7 130.28, 124.62 (quaternary carbons), 123.82, 123.77 (meta-Ar) 122.82 (quaternary carbon) 121.22 (ortho-Ar), 35.55, 34.55 (Ar-CM.sub.3), 31.95, 30.88 (ArCH.sub.3), 13.04, 12.48, 10.84 (Pn-CH.sub.3). Analysis calculated for C.sub.28H.sub.39TiClO (%): C, 70.8; H, 8.29. found: C, 70.65; H, 8.23.
EXAMPLE 3
Synthesis of [.SUP.8.-(Pn*)Ti(O-2,6-Me-C.SUB.6.H.SUB.3.).SUB.2.]
[0074] [.sup.8-Pn*TiCl(-Cl)].sub.2 (150 mg, 0.25 mmol) and [K(O-2,6-Me-C.sub.6H.sub.3)] (160 mg, 0.50 mmol) were stirred in toluene (30 mL) for 24 h at 25 C. The resultant solution was filtered and subsequently concentrated in vacuo. X-ray quality single crystals were obtained on storing the toluene concentrated solution at 35 C. for 24 h. Yield=62%. .sup.1H NMR (benzene-d.sub.6, 25 C., 300 MHz): 6.96 (d, 4H, .sup.3J.sub.HH=7.5 Hz, meta-ArH), 6.69 (t, 2H, .sup.3J.sub.HH=7.3 Hz, para-ArH), 2.13 (s, 12H, Pn-CH.sub.3), 1.81 (s, 12H, ArCH.sub.3), 1.77 (s, 6H, Pn-CH.sub.3). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 25 C., 75.1 MHz): 162.52 (ipso-Ar), 139.73 130.97 125.22 120.47 118.89 (quaternary carbons), 17.73 (ArCH.sub.3), 11.90 10.89 (Pn-CH.sub.3). The quaternary bridgehead carbon atoms were not observable. Analysis calculated for C.sub.30H.sub.36TiO.sub.2(%): C, 75.62; H, 7.63. Found: C, 75.48; H, 7.77.
EXAMPLE 4
Synthesis of [.SUP.8.-(Pn*)Ti(O.SUP.t.Bu)Cl]
[0075] [.sup.8-(Pn*)TiCl(-Cl)].sub.2 (150 mg, 0.25 mmol) and [K(O.sup.tBu)] (53 mg, 0.50 mmol) were combined in toluene (30 mL) and left to stir for 2 h at room temperature. The resultant solution was filtered and the solvent was removed under reduced pressure. Minimal hot hexane was added and X-ray quality single crystals were obtained on cooling to room temperature and storing at 35 C. for 24 h. Yield=54%. .sup.1H NMR (benzene-d.sub.6, 25 C., 300 MHz): 2.09, 1.90, 1.62 (s, 6H each, Pn-CH.sub.3), 1.31 (s, 9H, C(CH.sub.3)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 25 C., 75.1 MHz): 138.41, 136.38 (Pn-bridgehead), 128.86, 122.16, 121.91 (Pn), 81.16 (C(CH.sub.3)), 32.48 (C(CH.sub.3)), 13.09, 12.85, 10.86 (Pn-CH3).
EXAMPLE 5
Synthesis of [.SUP.8.-(Pn*)Ti(O.SUP.t.Bu).SUB.2.]
[0076] [.sup.8-(Pn*)TiCl(-Cl)].sub.2 (20 mg, 0.035 mmol) and [K(O.sup.tBu)] (16 mg, 0.14 mmol) were combined in benzene-d.sub.6 (1 mL). The resulting dark red solution was filtered and allowed to undergo a slow evaporation, which led to the formation of X-ray quality single crystals. .sup.1H NMR (benzene-d.sub.6, 25 C., 300 MHz): 2.08 (s, 12H, Pn-CH.sub.3), 1.76 (s, 6H, Pn-CH3), 1.31 (s, 18H, C(CH.sub.3)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 25 C., 75.1 MHz): 134.38, 128.71, 116.58 (Pn) 76.44 (C(CH.sub.3)) 33.60 (C(CH.sub.3)) 13.07, 10.81 (Pn-CH.sub.3). The quaternary bridgehead carbon atoms were not observable.
EXAMPLE 6
Synthesis of [.SUP.5.-(Pn*H)Ti(O-2,6-Me-C.SUB.6.H.SUB.3.)C).SUB.2.]
[0077] [.sup.5-Pn*TiCl(-Cl)].sub.2 (350 mg, 0.57 mmol) and [H(O-2,6-Me-C.sub.6H.sub.3)] (139 mg, 1.14 mmol) were stirred in toluene (50 mL) at 85 C. for 24 h, before being filtered and concentrated under vacuum. X-ray quality single crystals were formed on storing the concentrated solution at 35 C. for 24 h. Yield=68%. .sup.1H NMR (benzene-d.sub.6, 25 C., 300 MHz): 6.82-6.72 (m, 3H, ArH), 3.19 (q, 1H, .sup.3J.sub.HH=7.3 Hz, Pn-H), 2.24 (s, 6H, ArCH.sub.3), 2.23, 2.12, 2.08, 1.79, 1.44 (s, 3H each, Pn-CH.sub.3), 0.84 (d, 3H, .sup.3J.sub.HH=7.5 Hz, Pn-CH.sub.3). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 25 C., 75.1 MHz) 162.73 (ipso-Ar), 150.62, 147.79, 141.18, 136.86, 129.80, 129.07 (Quaternary Carbons), 128.13 (meta-Ar) 123.70 (Quaternary Carbons) 123.06 (para-Ar), 44.19 (sp.sup.3 Pn), 17.22 (ArCH.sub.3), 15.53, 14.08, 13.53, 13.23, 11.75, 11.59 (Pn-CH3). The quaternary bridgehead carbon atoms were not observable. Analysis calculated for C.sub.22H.sub.28Cl.sub.2TiO (%): C, 61.84; H, 6.62. Found: C, 61.71; H, 6.70.
EXAMPLE 7
Synthesis of [.SUP.5.-(Pn*H)Ti(O-2,6-Me-C.SUB.6.H.SUB.3.).SUB.3.]
[0078] A solution of [.sup.5-(Pn*H)Ti(OC.sub.6H.sub.3Me.sub.2-2,6)Cl.sub.2] (50 mg, 0.12 mmol) and [K(O-2,6-Me.sub.2C.sub.6H.sub.3)](37.5 mg, 0.24 mmol) in toluene (10 mL) was stirred for 30 minutes at 100 C. The resultant bright orange solution was filtered and the solvent removed under reduced pressure. Subsequent dissolution in minimal hot hexane followed by storage at 35 C. for 24 h led to the formation of X-ray quality single crystals. Yield=65%. .sup.1H NMR (benzene-d.sub.6, 25 C., 300 MHz): 6.90 (d, 6H, .sup.3J.sub.HH=7.2 Hz, meta-ArH), 6.73 (t, 3H, .sup.3J.sub.HH=7.3 Hz, para-ArH) 3.59 (q, 1H, .sup.3J.sub.HH=7.7 Hz, Pn-H) 2.28 (s, 18H, ArCH.sub.3) 2.21, 2.14, 1.96, 1.58, 1.53 (s, 3H each, Pn-CH.sub.3) 1.08 (d, 3H, .sup.3J.sub.HH=7.32 Hz, Pn-CH.sub.3). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 25 C., 75.1 MHz) 164.05 (ipso-Ar), 147.30, 144.11, 138.88, 130.71 (Pn), 129.06 (Ar), 128.93 (Pn), 127.41 (Ar), 122.49 (Pn), 120.79 (Ar), 116.96 (Pn), 44.46 (sp.sup.3 Pn), 18.15 (sp.sup.3 Pn-CH.sub.3), 15.33, 13.37, 12.49, 11.99, 11.75, 11.58 (Pn-CH.sub.3).
Crystallographic Details
.SUP.8.-(Pn*)Ti(O-2,6-Me-C.SUB.6.H.SUB.3.)Cl
[0079] Single crystals were grown from a toluene solution at 35 C., C.sub.22H.sub.27ClOTi, M.sub.r=390.81, triclinic, P-1, a=11.2997(2) , b=11.6154(2) , c=15.7437(3) , =77.0104(7), =89.3195(7), =85.2957(8), V=2006.66(6).sup.3, Z=4, T=150 K, prism, red brown, 9129 independent reflections, R(int)=0.038, R.sub.1=0.046 wR.sub.2=0.133 [I>2(I)].
.SUP.8.-(Pn*)Ti(O-2,4-.SUP.t.Bu-C.SUB.6.H.SUB.3.)Cl
[0080] Single crystals were grown from a benzene solution at 35 C., C.sub.28H.sub.39ClOTi, M.sub.r=474.97, monoclinic, P.sub.21/n, a=11.7910(1) , b=9.5199(1) , c=23.5743(3) , =102.4652(5), =90 =90, V=2583.82(5) .sup.3, Z=4, T=150 K, block, purple, 5884 independent reflections, R(int)=0.029, R.sub.1=0.038 wR.sub.2=0.091 [I>2(I)].
.SUP.8.-(Pn*)Ti(O-2,6-Me-C.SUB.6.H.SUB.3.).SUB.2
[0081] Single crystals were grown from a toluene solution at 35 C., C.sub.30H.sub.36O.sub.2Ti, M.sub.r=476.51, Orthorhombic, Pbca, a=9.2631(1) , b=15.4563(1) , c=35.7542(3) , =90, =90 =90, V=5.119.32(8).sup.3, Z=8, T=150 K, block, dark red, 5807 independent reflections, R(int)=0.036, R.sub.1=0.047 wR.sub.2=0.092 [I>2(I)].
.SUP.8.-(Pn*)Ti(O.SUP.t.Bu)Cl
[0082] Single crystals were grown from a hexane solution at 35 C., C.sub.18H.sub.27ClOTi, M.sub.r=342.76, triclinic, P-1, a=8.8527(1), b=10.1475(2), c=10.7183(2), =79.8812(7), =78.4070(7), =73.9368(7), V=898.98(3).sup.3, Z=2, T-150 K, block, dark red, 4073 independent reflections, R(int)=0.016, R.sub.1=0.034 wR.sub.2=0.085 [I>2(I)].
.SUP.8.-(Pn*)Ti(O.SUP.t.Bu).SUB.2
[0083] Single crystals were grown from a benzene solution at 35 C., C.sub.22H.sub.36O.sub.2Ti, M.sub.r=380.43, monoclinic, P2.sub.1/n, a=12.7185(2), b=10.9762(1), c=15.9690(2), =90, =93.2853(6), =90, V=2225.62(5).sup.3, Z=4, T=150 K, prism, red brown, 5062 independent reflections, R(int)=0.022, R, =0.075 wR.sub.2=0.188 [I>2(I)].
.SUP.5.-(Pn*H)Ti(O-2,6-Me-C.SUB.6.H.SUB.3.)Cl.SUB.2
[0084] Single crystals were grown from hexane solution at 35 C., C.sub.22H.sub.28Cl.sub.2TiO, M=427.27, monoclinic, P21/c, a=8.5552(2), b=17.7148(5), c=14.6706(4), ==90.000, =106.6445(11), V=2130.22(10).sup.3, T=150(2) K, Z=4, 4844 independent reflections, R(int)=0.019 R.sub.1=0.054 wR.sub.2=0.119 [I>2(I)].
.SUP.5.-(Pn*H)Ti(O-2,6-Me-C.SUB.6.H.SUB.3.).SUB.3
[0085] Single crystals were grown from hexane solution at 35 C., C.sub.38H.sub.4TiO.sub.3, M=598.68, monoclinic, P21/n, a=8.9702(2), b=24.3863(6), c=14.6936(4), ==90.000, =91.352(2), V=3213(14).sup.3, T=150(2) K, Z=4, 6634 independent reflections, R(int)=0.060 R.sub.1=0.056 wR.sub.2=0.141 [I>2(I)].
Experimental Detail II
Relating to (Hydro)Permethylentalenes
General Procedure
[0086] All organometallic syntheses were performed under an inert atmosphere of nitrogen gas, utilizing standard Schlenk techniques on a dual vacuum-inlet gas manifold or Braun glove box. Where necessary, solvents were dried by reflux over the appropriate drying agent: NaK (Et.sub.2O), sodium (THF) and SPS drying system (hexane, pentane, soluene). Solvents were distilled from the desiccant under a flowing stream of nitrogen and transferred using a siphoning technique via steel cannulae and stored in flame-dried glass ampoules under an atmosphere of nitrogen. Deuterated NMR solvents were dried over NaK (benzene-d.sub.6, toluene-d.sub.8) or CaH.sub.2 (pyridine-d.sub.5), vacuum transferred and freeze-pump-thaw-degassed three times prior to use. Elemental analyses were conducted by Mr Stephen Boyer at the elemental analysis service at London Metropolitan University. NMR spectra were recorded using Young's tap NMR tubes on a Varian Mercury VX-Works 300 MHz spectrometer. .sup.1H and .sup.13C{.sup.1H} NMR spectra were referenced to the residual protio-solvent peak.
X-Ray Crystallography
[0087] Crystals were mounted on glass fibres using perfluoropolyether oil, transferred to a goniometer head on the diffractometer and cooled rapidly to 150 K in a stream of cold nitrogen using an Oxford Cryosystems CRYOSTREAM unit. Data collections were performed using an Enraf-Nonius FR590 KappaCCD diffractometer, utilising graphite-monochromated Mo K.sub. X-ray radiation (=0.71073 ). Intensity data were processed using the DENZO-SMN package. Structures were solved using the direct-methods program SIR92, and refined using full-matrix least squares refinement on all F2 data using the CRYSTALS program suite.
Polymerisation Procedure
[0088] The lactide monomer (40 mg) and the complex were introduced in an NMR tube following the desired monomer:initiator ratio. Then 0.57 mL of chloroform-d.sub.1 was added to the compounds, leading to an initial monomer concentration of [LA].sub.0=0.5 M. The solution was monitored by .sup.1H NMR spectroscopy. The conversion was determined by integration of the methane area of the polymer versus the monomer.
EXAMPLE 8
Synthesis of Pn*(H)SnMe.SUB.3
[0089] To a slurry of Pn*(H)Li (20.9 g, 10.7 mmol) in pentane (20 mL) at 78 C. was added a solution of SnMe.sub.3Cl (2.14 g, 10.7 mmol) in pentane (10 mL). The reaction mixture was warmed to room temperature and stirred for 3 h to afford an orange solution and colourless precipitate of LiCl. This was filtered and the volatiles were removed in vacuo to afford Pn*(H)SnMe.sub.3 (50:50 mixture of diastereomers judged by .sup.1H NMR spectroscopy) as an orange oil. Yield: 3.56 g (97%). .sup.1H NMR (benzene-d.sub.6, 23 C.): 2.98 (q, 1H, .sup.3J.sub.HH=7.2 Hz, Pn*(H)), 20.9 2.05 2.00 (s, 3H each, CH.sub.3-Pn*(H)), 1.95 (overlapping s, 3H each, CH.sub.3-Pn*(H)) 1.93 1.83 (s, 3H each, CH.sub.3-Pn*(H)), 1.70 (overlapping s, 3H each, CH.sub.3-Pn*(H)), 1.59 (s, 3H, CH.sub.3-Pn*(H)), 1.18 (d, 3H .sup.3J.sub.HH=7.2 Hz, 1-CH.sub.3-Pn*(H)), 0.94 (d, 3H, .sup.3J.sub.HH=6.9 HZ, 1-CH.sub.3-Pn*(H)), 0.01 (s, 9H, .sup.2J.sub.1H-119Sn=25.2 Hz, .sup.2J.sub.1H-117Sn=24.2 Hz, 5-SnMe.sub.3-Pn*(H))0.03 (s, 9H, .sup.2J.sub.1H-119Sn=25.3 Hz, .sup.2J.sub.1H-117Sn=24.3 Hz, 5-SnMe.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 150.2 147.2 144.6 144.4 129.8 129.4 121.3 119.6 (6overlapping resonances, (q-Pn*(H)), 44.3 41.8 (1-Pn*(H)), 13.5 13.4 12.8 12.4 121.3 12.2 12.1 12.0 (2overlapping resonances CH.sub.3-Pn*(H)), 18.2 17.6 (1-CH.sub.3-Pn*(H)), 8.8 (5-SnMe.sub.3-Pn*(H), .sup.2J.sub.1H-119Sn=153 Hz, .sup.2J.sub.1H-117Sn=148 Hz), 9.2 (5-SnMe.sub.3-Pn*(H), .sup.2J.sub.1H-119Sn=157 Hz, .sup.2J.sub.1H-117Sn=150 Hz).
EXAMPLE 9
Synthesis of Pn*(H)TiCl.SUB.3
[0090] To a slurry of TiCl.sub.4(thf).sub.2 (0.408 g, 1.44 mmol) in benzene (2 mL) was added a solution of Pn*(H)SnMe.sub.3 (0.505 g, 1.44 mmol) in benzene (2 mL) to afford a dark-purple solution. The reaction mixture was heated to 80 C. for 4 hr. The volatiles were removed in vacuo to afford Pn*(H)TiCl.sub.3, as a purple powder. Yield: 0.363 g (74%). Single crystals suitable for an X-ray diffraction study were grown from saturated Et.sub.2O solution at 35 C. .sup.1H NMR (benzene-d.sub.6, 23 C.): 0.85 (d, 3H, .sup.3J.sub.HH=7.5 Hz, 1-CH.sub.3-Pn*(H)), 1.57 1.89 2.02 2.03 2.14 (s, 3H each, CH.sub.3-Pn*(H)), 3.80 (q, 1H, .sup.3J.sub.HH=8.5 Hz, Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 153.6 152.7 147.4 140.6 133.3 131.3 127.4 (q-Pn*(H)), 46.8 (1-Pn*(H)), 15.4 (1-CH.sub.3-Pn*(H)), 14.5, 14.4, 14.2, 12.2, 11.6 (CH.sub.3-Pn*(H)).
EXAMPLE 10
Synthesis of [Pn*(H)ZrCl.SUB.3.]2
[0091] To a slurry of ZrCl.sub.4 (0.995 g, 4.27 mmol) in benzene (5 mL) was added a solution of Pn*(H)SnMe.sub.3 (1.50 g, 4.27 mmol) in benzene (5 mL). The reaction mixture was heated to 80 C. for 72 h to afford a dark-green solution. The volatiles were removed in vacuo to yield a green solid. To this was added pentane (15 mL) and the reaction mixture was sonicated for 15 minutes to afford a fine, olive-green powder and a pale-yellow solution. The reaction mixture was filtered and the filtrate was dried under reduced pressure to afford [Pn*(H)ZrCl.sub.3].sub.2, as an olive-green powder. Yield: 1.42 g (87%). Single crystals were grown from a saturated benzene solution at 23 C. .sup.1H NMR (benzene-d.sub.6, 23 C.): 0.92 (d, 3H, .sup.3J.sub.HH=7.5 Hz, 1-CH.sub.3-Pn*(H)), 1.81 2.01 2.06 2.17 2.19 (s, 3H each, CH.sub.3-Pn*(H)), 3.50 (q, .sup.3J.sub.HH=7.5 Hz, Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 151.0 147.0 142.1 133.5 129.5 127.4 120.7 (q-Pn*(H), 46.0 (1-Pn*(H)), 15.6 (1-CH.sub.3-Pn*(H)), 14.2 13.6 13.5 12.3 12.2 (CH.sub.3-Pn*(H)).
EXAMPLE 11
Synthesis of [Pn*(H)HfCl.SUB.3.].SUB.2
[0092] To a slurry of HfCL.sub.4 (0.164 g, 0.467 mmol) in benzene (2 mL) was added a solution of Pn*(H)SnMe.sub.3 (0.149 g, 0.467 mmol) in benzene (2 mL). The reaction mixture was heated to 80 C. for 2 h to afford an orange solution. The volatiles were removed in vacuo to yield [Pn*(H)HfCL.sub.3].sub.2, as a pale-yellow solid. Single crystals were grown from a saturated benzene solution at room temperature. .sup.1H NMR (benzene-d.sub.6, 23 C.): 0.93 (d, 3H, .sup.3J.sub.HH=7.4 Hz, 1-CH.sub.3-Pn*(H)), 1.62 1.84 2.01 2.01 2.10 (s, 3H each, CH.sub.3-Pn*(H)), 3.42 (q, .sup.3J.sub.HH=7.4 Hz, Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 150.0, 142.3, 137.2, 123.9, 117.4 (q-Pn*(H)), 45.5 (1-Pn*(H)), 15.9 (1-CH.sub.3-Pn*(H)) 12.2 12.1 12.0 11.9 11.6 (CH.sub.3-Pn*(H)).
EXAMPLE 12
Synthesis of .SUP.5.-Pn*(H)Ti(O.SUP.t.Bu).SUB.3
[0093] Pn*(H)TiCl.sub.3 (0.020 g, 0.059 mmol) and KO.sup.tBu (0.020 g, 0.18 mmol) were combined in benzene-d.sub.6 (0.5 mL) and sonicated for 5 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded Pn*(H)Ti(O.sup.tBu).sub.3, 1, as a pale-yellow powder. .sup.1H NMR (benzene-d.sub.6, 23 C.): 3.35 (q, .sup.3J.sub.HH=7.2 Hz, Pn*(H)), 2.27 2.24 2.12 2.08 1.84 (s, 3H each, CH.sub.3. Pn*(H)), 1.30 (s, 27H, OC(CH.sub.3).sub.3), 1.25 (d, 3H .sup.3J.sub.HH=7.3 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 141.5 135.1 132.9 128.6 121.0 115.6 110.5 (q-Pn*(H)), 75.4 (OC(CH.sub.3).sub.3), 43.7 (1-Pn*(H)), 33.4 (OC(CH.sub.3).sub.3), 16.2 (1-CH.sub.3-Pn*(H)), 12.7 12.6 12.1 12.1 11.4 (CH.sub.3-Pn*(H)).
EXAMPLE 13
Synthesis of .SUP.5.-Pn*(H)Zr(O.SUP.t.Bu).SUB.3
[0094] [Pn*(H)ZrCl.sub.3].sub.2(0.028 g, 0.036 mmol) and KO.sup.tBu (0.024 g, 0.22 mmol) were combined in benzene-d.sub.6 (0.5 mL) and sonicated for 5 minutes to afford a clear pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded Pn*(H)Zr(O.sup.tBu).sub.3 as a pale-yellow powder. .sup.1H NMR (benzene-d.sub.6, 23 C.): 3.33 (q, .sup.3J.sub.HH=6.9 Hz, Pn*(H)), 2.25 2.22 20.9 2.05 1.83 (s, 3H each, CH.sub.3-Pn*(H)), 1.35 (s, 27H, OC(CH.sub.3).sub.3), 1.23 (d, 3H, .sup.3J.sub.HH=6.9 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 142.8 137.5 134.4 129.3 123.4 117.8 112.9 (q-Pn*(H)), 80.2 (OC(CH.sub.3).sub.3), 43.8 (1-Pn*(H)), 33.1 (OC(CH.sub.3).sub.3), 15.9 (1-CH.sub.3-Pn*(H)), 13.7, 12.8, 12.7, 12.3 12.2 (CH.sub.3-Pn*(H)).
EXAMPLE 14
Synthesis of .SUP.5.-Pn*(H)Zr(OCH.SUB.2.C.SUB.6.H.SUB.5.).SUB.3
[0095] [Pn*(H)ZrCl.sub.3].sub.2(0.100 g, 0.131 mmol) and KOCH.sub.2C.sub.6H.sub.5 (0.115 g, 0.786 mmol) were combined in C.sub.6H.sub.6 (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded Pn*(H)Zr(OCH.sub.2C.sub.6H.sub.5).sub.3 as a pale-yellow oily solid at room temperature. .sup.1H NMR (benzene-d.sub.6, 23 C.); 7.37-7.03 (overlapping m, 15H, CH.sub.2C.sub.6H.sub.5), 5.10 (s, 6H, CH.sub.2C.sub.6H.sub.5), 3.12 (q, 1H, .sup.3J.sub.HH=7.3 Hz, Pn*(H)), 2.13 20.9 1.99 1.90 1.68 (s, 3H each CH.sub.3-Pn*(H)), 1.13 (d, 3H .sup.3J.sub.HH=7.3 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 143.9 (CH.sub.2-1-C.sub.6H.sub.5), 143.0 135.4 133.2 (q-Pn*(H)), 128.5 (CH.sub.2-2,3,4-C.sub.6H.sub.5), 127.1 (q-Pn*(H)), 126.9 126.4 (CH.sub.2-2,3,4-C.sub.6H.sub.5), 122.0 116.5 111.3 (q-Pn*(H)), 71.7 (CH.sub.2C.sub.6H.sub.5), 43.2 (1-Pn*(H)), 16.2 (1-CH.sub.3-Pn*(H)), 12.3 11.8 11.5 11.0 10.4 (CH.sub.3-Pn*(H)).
EXAMPLE 15
Synthesis of .SUP.5.-Pn*(H)Zr(OSCH{CH.SUB.3.}C.SUB.6.H.SUB.5.).SUB.3
[0096] Pn*(H)ZrCl.sub.3 and SKOCH{CH.sub.3}C.sub.6H.sub.5 were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded .sup.5-Pn*(H)Zr(OSCH{CH.sub.3}C.sub.6H.sub.5).sub.3, as a pale-yellow oily solid at room temperature. .sup.1H NMR (benzene-d.sub.6, 23 C.): Two diastereomers: 7.40 (d, 6H, .sup.3J.sub.HH=7.3 Hz, 2,6-C.sub.6H.sub.5), 7.11 (m, 3H, 4-C.sub.6H.sub.5), 5.30 (q, 3H, .sup.3J.sub.HH=6.1 Hz, CHMe), 3.14 30.9 (q, .sup.3J.sub.HH=6.9 HZ, Pn*(H)), 2.11 2.11 2.08 2.05 1.97 1.97 1.89 1.88 1.70 1.65 (overlapping s, 3H each, CH.sub.3-Pn*(H)), 1.44 (d, 9H, .sup.3J.sub.HH=6.1 Hz, CHMe), 1.12 (d, 3H, .sup.3J.sub.HH=6.9 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): Diastereomer 1: 148.7 142.7 135.5 133.3 (q-Pn*(H)), 128.6 (3,5-C.sub.6H.sub.5), 126.9 (2,6-C.sub.6H.sub.5), 125.7 (q-Pn*(H)), 125.7 (4-C.sub.6H.sub.5), 122.0 116.4 111.4 (q-Pn*(H)), 77.0 (CHMe), 43.4 (1-Pn*(H)), 28.4 (CHMe), 16.1 (1-CH.sub.3-Pn*(H)), 12.2 11.8 11.8 11.2 10.6 (CH.sub.3-Pn*(H)). Diastereomer 2: 148.7 142.7 135.3 133.2 (q-Pn*(H)), 128.5 (3,5-C.sub.6H.sub.5), 126.9 (2,6-C(H.sub.5), 125.9 (4-C.sub.6H.sub.5), 125.5 (q-Pn*(H)), 121.8 116.4 111.1 (q-Pn*(H)), 77.0 (CHMe), 43.3 (1-Pn*(H)), 28.4 (CHMe), 16.1 (1-CH.sub.3-Pn*(H)), 12.2 11.8 11.7 11.2 10.5 (CH.sub.3-Pn*(H)).
EXAMPLE 16
Synthesis of .SUP.5.-Pn*(H)Zr(O-rac-{CH.SUB.3.}C.SUB.6.H.SUB.5.).SUB.3
[0097] Pn*(H)ZrCL.sub.3 and rac-KOCH{CH.sub.3}C.sub.6H.sub.5 were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded .sup.5-Pn*(H)Zr(O-rac-CH{CH.sub.3}C.sub.6H.sub.5).sub.3, as a pale-yellow oily solid at room temperature. .sup.1H NMR (benzene-d.sub.6, 23 C.): Mixture of diastereomers: 7.48-7.10 (overlapping m, 15H, C.sub.6H.sub.5), 5.24 (overlapping q, 3H, CHMe), 3.06 (q, 1H, .sup.3J.sub.HH=7.3 Hz, Pn&(H)), 2.12 2.12 2.08 2.07 1.98 1.98 1.90 1.69 1.67 (overlapping s, 3H each, CH.sub.3-Pn*(H)), 1.50 1.45 1.44 1.41 (overlapping d, 9H .sup.3J.sub.HH=6.4 Hz, CHMe), 1.12 (d, 3H, .sup.3J.sub.HH=7.3 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): Mixture of diastereomers: 148.7 142.7 135.5 133.3 (q-Pn*(H)), 128.4 (3,5-C.sub.6H.sub.5), 127.3 (q-Pn*(H)), 126.9 (2,6-C.sub.6H.sub.5), 125.6 (4-C.sub.6H.sub.5), 122.0 116.4 111.4 (q-Pn*(H)), 77.0 (CHMe), 43.3 (1-Pn*(H)), 28.4 (CHMe), 16.1 (1-CH.sub.3-Pn*(H)), 12.2 11.8 11.7 11.2 10.6 (CH.sub.3-Pn*(H)). Values reported in the .sup.13C{.sup.1H} NMR spectrum are the central values of the multiple overlapping resonances observed.
EXAMPLE 17
Synthesis of .SUP.5.-Pn*(H)Zr(O-2,6-Me-C.SUB.6.H.SUB.3.).SUB.3
[0098] [Pn*(H)ZrCl.sub.3].sub.2 and KO-2,6-Me.sub.2C.sub.6H.sub.3 were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded Pn*(H)Zr(O-2,6-Me-C.sub.6H.sub.3).sub.3, as a pale-yellow powder. .sup.1H NMR (benzene-d.sub.6, 23 C.): 6.93 (d, 6H, .sup.3J.sub.HH=7.4 Hz, 3,5-C.sub.6H.sub.3), 6.75 (t, 3H, .sup.3J.sub.HH=7.3 Hz, 4-C.sub.6H.sub.3, 3.31 (q, .sup.3J.sub.HH=7.4 Hz, Pn*(H)), 2.25 (s, 18H, O-2,6-CH.sub.3C.sub.6H.sub.3), 2.20 2.12 1.96 1.69 1.54 (s, 3H each, CH.sub.3-Pn*(H)), 10.9 (d, 3H, .sup.3J.sub.HH=7.4 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 159.7 (1-C.sub.6H.sub.3), 145.3 139.7 135.6 (q-Pn*(H)), 128.9 (3,5-C.sub.6H.sub.3), 128.0 (q-Pn*(H)), 126.6 (2,6-C.sub.6H.sub.3), 125.7 (q-Pn*(H)), 120.4 (4-C.sub.6H.sub.3), 119.0 113.7 (q-Pn*(H)), 43.9 (q-Pn*(H)), 17.9 (O-2,6-CH.sub.3C.sub.6H.sub.3), 15.7 (1-CH.sub.3-Pn*(H)), 12.5 11.8 11.7 11.0 (CH.sub.3-Pn*(H)).
EXAMPLE 18
Synthesis of .SUP.5.-Pn*(H)Zr(O-2,6-.SUP.i.Pr-C.SUB.6.H.SUB.3.).SUB.3
[0099] [Pn*(H)ZrCl.sub.3].sub.2(0.174 g, 0.225 mmol) and KO-2,6-.sup.iPr.sub.2C.sub.6H.sub.3 (0.2925 g, 1.35 mmol) were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded .sup.5-Pn*(H)Zr(O-2,6.sup.iPrC.sub.6H.sub.3).sub.3, as a yellow-green powder. Anal. Calcd for C.sub.50H.sub.70O.sub.3Zr: C, 74.11; H, 8.71. Found: C, 67.68; H, 8.60. .sup.1H NMR (benzene-d.sub.6, 23 C.): 7.11-7.03 (overlapping d, 6H, 3,5-C.sub.6H.sub.3), 6.96 (app. t, 3H, .sup.3J.sub.HH=6.7 Hz, 4-C.sub.6H.sub.3), 3.52 (overlapping sept., 6H .sup.3J.sub.HH=6.7 Hz, CH(CH.sub.3).sub.2), 3.11 (q, 1H, .sup.3J.sub.HH=7.4 Hz, Pn*(H)), 2.17 2.13 1.93 1.85 1.44 (s, 3H each, CH.sub.3-Pn*(H)), 1.32 (d, 12H, .sup.3J.sub.HH=6.7 Hz, CH(CH.sub.3).sub.2, 1.01 (d, 3H, .sup.3J.sub.HH=7.4 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 155.9 155.8 (1-C.sub.6H.sub.3), 146.8 (q-Pn*(H)), 140.6 (q-Pn*(H)), 137.9 137.7 (2,6-C.sub.6H.sub.3), 136.4 127.4 (q-Pn*(H)), 123.6 123.5 (3,5-C.sub.6H.sub.3), 122.1 122.1 (4-C.sub.6H.sub.3) 120.5 116.2 (q-Pn*(H)), 43.3 (1-Pn*(H)), 27.3 27.2 (CH(CH.sub.3).sub.2), 24.9 24.8 24.0 23.9 (CH(CH.sub.3).sub.2), 15.6 (1-CH.sub.3-Pn*(H)), 12.1 12.0 12.0 11.8 10.9 (CH.sub.3-Pn*(H)). One quaternary resonance accounting for a Pn*(H) carbon was overlapping with the residual protio solvent resonance.
EXAMPLE 19
[0100] Synthesis of .sup.5-Pn*(H)ZrCl.sub.2(O-2,6-.sup.tBu-C.sub.6H.sub.3).
[0101] [Pn*(H)ZrCl3]2 (0.239 g, 0.310 mmol) and KO-2,6-.sup.tBu.sub.2C.sub.6H.sub.3 (0.152 g, 0.62 mmol) were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded .sup.5-Pn*(H)ZrCl.sub.2(O-2,6-.sup.tBu-C.sub.6H.sub.3), as a yellow-green powder. Yield: 0.072 g (42%). .sup.1H NMR (benzene-d.sub.6, 23 C.): 7.13 (d, 2H, .sup.3J.sub.HH=7.7 Hz, 3,5-C.sub.6H.sub.3), 6.78 (t, 1H, .sup.3J.sub.HH=7.7 Hz, 4-C.sub.6H.sub.3), 2.96 (q, 1H, .sup.3J.sub.HH=7.4 Hz, Pn*(H)), 2.20 2.05 1.98 1.69 (s, 3H each, CH.sub.3-Pn*(H)), 1.41 (br. s, 18H, C(CH.sub.3).sub.3), 1.32 (s, 3H, CH.sub.3-Pn*(H)), 0.86 (d, 6H, .sup.3J.sub.HH=7.4 Hz, CH(CH.sub.3).sub.2). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 161.0 (1-C.sub.6H.sub.3), 148.2 145.9 134.4 132.3 (q-Pn*(H)), 125.4 (3,5-C.sub.6H.sub.3), 125.2 (q-Pn*(H)), 121.4 (4-C.sub.6H.sub.3), 119.6 (q-Pn*(H)), 44.7 (1-Pn*(H)), 35.6 (C(CH.sub.3).sub.3), 32.1 (C(CH.sub.3).sub.3), 15.5 (1-CH.sub.3-Pn*(H)), 14.0 12.9 12.4 12.4 116 (CH.sub.3-Pn*(H)). Two quaternary resonances accounting for the 2,6-C.sub.6H.sub.3 and a Pn*(H) carbon were overlapping with the residual protio solvent resonance.
EXAMPLE 20
Synthesis of .SUP.5.-Pn*(H)Hf(O-2,6-Me-C.SUB.6.H.SUB.3.).SUB.3
[0102] [Pn*(H)HfCl.sub.3].sub.2 and KO-2,6-Me.sub.2C.sub.6H.sub.3 were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded Pn*(H)Hf(O-2,6-Me-C.sub.6H.sub.3).sub.3, as a pale-yellow powder. .sup.1H NMR (benzene-d.sub.6, 23 C.): 6.93 (d, 6H, .sup.3J.sub.HH=7.4 Hz, 3,5-C.sub.6H.sub.3), 6.74 (t, 3H, .sup.3J.sub.HH=7.4 Hz, 4-C.sub.6H.sub.3), 3.27 (q, 1H, .sup.3J.sub.HH=7.4 Hz, 4-C.sub.6H.sub.3), 3.27 (q, 1H, .sup.3J.sub.HH=7.4 Hz, Pn*(H)), 2.24 (s, 18H, O-2,6-CH.sub.3C.sub.6H.sub.3), 2.24 2.16 1.99 1.68 1.56 (s, 3H each, CH.sub.3-Pn*(H)), 1.10 (d, 3H, .sup.3J.sub.HH=7.4 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 159.4 (1-C.sub.6H.sub.3), 145.1138.7 134.0 (q-Pn*(H)), 129.0 (3,5-C.sub.6H.sub.3), 127.8 (q-Pn*(H)), 126.9 (2,6-C.sub.6H.sub.3), 124.1 (q-Pn*(H)), 120.4 (4-C.sub.6H.sub.3), 117.6 112.1 (q-Pn*(H)), 43.9 (1-Pn*(H)), 17.8 (O-2,6-CH.sub.3C.sub.6H.sub.3), 15.5 (1-CH.sub.3-Pn*(H)), 12.4 11.8 11.6 11.4 10.9 (CH.sub.3-Pn*(H)).
EXAMPLE 21
[0103] Synthesis of .sup.5-Pn*(H)HfCl(O-2,6-.sup.iPr-C.sub.6H.sub.3).sub.2.
[0104] [Pn*(H)HfCl.sub.3].sub.2 and KO-2,6-.sup.iPr.sub.2C.sub.6H.sub.3 were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. Filtration followed by drying of the filtrate in vacuo afforded .sup.5-Pn*(H)HfCl(O-2,6-.sup.iPr-C.sub.6H.sub.3).sub.2, as a pale-yellow powder. .sup.1H NMR (benzene-d.sub.6, 23 C.): 7.10-6.86 (overlapping m, 6H, 3,4,5-C.sub.6H.sub.3), 3.52 (overlapping sept., 4H, CH(CH.sub.3).sub.2), 3.11 (q, 1H, .sup.3J.sub.HH=7.4 Hz, Pn*(H)), 2.25 2.20 1.92 1.92 1.49 (s, 3H each, CH.sub.3Pn*(H)), 1.30 (d, 12H, .sup.3J.sub.HH=6.5 Hz, CH(CH.sub.3).sub.2), 1.24 1.23 (overlapping d, 6H each, .sup.3J.sub.HH=6.5 Hz, CH(CH.sub.3).sub.2) 1.05 (d, 3H, .sup.3J.sub.HH=7.4 Hz, 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 155.7 155.6 (1-C.sub.6H.sub.3), 146.3 139.1 (q-Pn*(H)), 137.9 137.8 (2,6-C.sub.6H.sub.3), 134.7 127.6 125.6 (q-Pn*(H)), 123.9 123.5 (3,5-C.sub.6H.sub.3), 122.1 122.0 (4-C.sub.6H.sub.3), 118.5 114.5 (q-Pn*(H)), 43.5 (1-Pn*(H)), 27.1 27.0 (CH(CH.sub.3).sub.2), 24.9 24.9 24.1 24.0 (CH(CH.sub.3).sub.2), 15.5 (1-CH.sub.3-Pn*(H)), 11.9 11.8 10.8 (CH.sub.3-Pn*(H)).
EXAMPLE 22
Synthesis of .SUP.5.-Pn*(H)HfCl.SUB.2.(O-2,6-.SUP.t.Bu-C.SUB.6.H.SUB.3.)
[0105] [Pn*(H)HfCl.sub.3].sub.2 and KO-2,6-.sup.tBu-C.sub.6H.sub.3 were combined in benzene (5 mL) and stirred for 10 minutes to afford a clear, pale-yellow solution and colourless precipitate. .sup.5-Pn*(H)HfCl.sub.2(O-2,6-Bu-C.sub.6H.sub.3), was identified as the sole product by NMR spectroscopy. NMR yield: (99.5%). .sup.1H NMR (benzene-d.sub.6, 23 C.): 7.19 (d, 2H, .sup.3J.sub.HH=7.7 Hz, 3,5-C.sub.6H.sub.3), 6.80 (t, 1H, .sup.3J.sub.HH=7.7 Hz, 4-C.sub.6H.sub.3), 2.95 (q, 1H, .sup.3J.sub.HH=7.4 Hz, Pn*(H)), 2.29 2.16 2.06 1.71 (s, 3H each, CH.sub.3-Pn*(H)), 1.42 and 1.44 (br. overlapping s, 18H, C(CH.sub.3).sub.3), 1.36 (s, 3H, CH.sub.3-Pn*(H)), 0.91 (d, 3H, .sup.3J.sub.HH=7.4 Hz 1-CH.sub.3-Pn*(H)). .sup.13C{.sup.1H} NMR (benzene-d.sub.6, 23 C.): 160.7 (1-C.sub.6H.sub.3), 147.5 143.3 133.0 129.6 127.6 (q-Pn*(H) or 2,6-CH.sub.3), 125.4 (3,5-C.sub.6H.sub.3), 123.0 (q-Pn*(H) or 2,6-C.sub.6H.sub.3), 121.2 (4-C.sub.6H.sub.3), 117.7 (q-Pn*(H) or 2,6-C.sub.6H.sub.3), 44.5 (1-Pn*(H)), 35.6 (C(CH.sub.3).sub.3), 32.1 (C(CH.sub.3).sub.3, 15.5 (1-CH.sub.3-Pn*(H)), 13.7, 12.6 12.0 11.4 (CH.sub.3-Pn*(H)). One quaternary resonance accounting for either the 2,6-C.sub.6H.sub.3 or a Pn*(H) carbon was overlapping with the residual solvent resonance.
Experimental Detail III
Relating to Indenyl-Base Catalysts
General Details
[0106] Air and moisture sensitive compounds were manipulated under an inert atmosphere of nitrogen, using standard Schlenk line techniques on a dual manifold vacuum/nitrogen line or a Braun Unilab glove box. Reaction solvents (pentane, hexane, and toluene) were dried using an MBraun SPS-800 solvent purification system. Hexane, toluene, and pentane were stored over pre-activated 3 molecular sieves. Dry solvents were stored in oven-dried ampoules under an atmosphere of nitrogen, sealed with either Rotoflo or Young's taps. Deuterated solvents used in NMR analysis of air-sensitive compounds were dried over the appropriate drying agent, freeze-thaw degassed and vacuum transferred prior to use: chloroform-d.sub.1 (Sigma-Aldrich) was stored over pre-activated 3 molecular sieves. NMR spectra were recorded on a 300 MHz Varian Mercury VX-Works spectrometer. .sup.1H (300.27 MHz) and .sup.13C{.sup.1H} (75.50 MHz) spectra were recorded at 25 C. unless otherwise stated, and referenced internally to the residual protio-solvent peak in the deuterated solvent used. .sup.1H and .sup.13C{.sup.1H} chemical shifts, , are given in parts per million (ppm), are given relative to the residual solvent peaks. Air sensitive samples were prepared under an inert atmosphere in a glove box, using dried solvents in Young's taps NMR tubes. [(Ind).sub.2ZrMe.sub.2], and complex were synthesised according to literature procedures. [(EBI)ZrCl.sub.2] (Strem Chemicals) was hot re-crystallised in toluene.
Polymerisation Procedure
[0107] All polymerisations were carried out in Young's tap NMR tubes containing 40 mg of lactide in a chloroform-d.sub.1 solution of initiator (20 mg initiator in 4 mL chloroform-d.sub.1), ensuring that the lactide:initiator ratio was 50:1. chloroform-d.sub.1 was then added to ensure the initial lactide concentration was [LA].sub.0=0.50 M. Polymerisations involving addition tert-butanol were prepared as usual, and tert-butanol was added to the chloroform-d.sub.1 solution via microsyringe, ensuring the lactide:initiator:tert-butanol ratio was 50:1:1.
X-Ray Crystallography
[0108] Crystals were mounted on MiTeGen MicroMants using perfluoropolyether oil, and cooled rapidly to 150 K in a stream of cold nitrogen using an Oxford Cryosystems CRYOSTREAM unit. Data collections were performed using an Enraf-Nonius FR590 KappaCCD diffractometer, utilising graphite-monochromated Mo K.sub. X-ray radiation (=0.71073 ). Raw frame data were collected at 150(2) K using a Nonius KappaCCD diffractometer, reduced using DENZO-SMN and corrected for absorption using SORTAV. The structure was solved using SuperFlip and refined using full matrix least-squares using CRYSTALS.
Crystallographic Data of [EBI)Zr(O-2,6-Me-C.sub.6H.sub.3)Cl]
[0109] Single crystals were grown from a toluene solution at room temperature, C.sub.2H.sub.25BCIOZr, M.sub.r=504.17, orthorhombic, Pcab, a=15.7733(2) , b=23.7683(3) , c=23.9207(4) , =90, =900, =90, V=8968.0(2) .sup.3, Z=6, T=150 K, block, yellow, 10201 independent reflections, R(int)=0.070, R.sub.1=0.057 wR.sub.2=0.137 [I>2(I)].
EXAMPLE 23
Synthesis of [(EBI)Zr(O-2,6-Me-C.SUB.6.H.SUB.3.)Cl]
[0110] To one equivalent of [EBI)ZrCl.sub.2] (100 mg, 0.24 mmol) in toluene (10 mL), one equivalent of 2,6-dimethylphenol (29 mg, 0.24 mmol) in toluene (10 mL) was added at room temperature. The yellow suspension was left stirring for 18 h, resulting in a clear, yellow solution. Solvent was removed in vacuo to afford [(EBI)Zr(O-2,6-Me-C.sub.6H.sub.3)Cl], as a yellow crystalline solid with a yield of 80% (96 mg, 0.19 mmol). .sup.1H NMR (chloroform-d.sub.1, 25 C., 300 MHz): 7.84 (1H, dd, ArH, .sup.3J.sub.HH=8.7 Hz, .sup.4J.sub.HH=0.9 Hz), 7.61 (1H, dd, ArH, .sup.3J.sub.HH=8.6 Hz, .sup.4J.sub.HH=0.9 Hz), 7.30-7.27 (2H, m, ArH), 7.20-7.10 (2H, m, ArH), 7.03 (1H, t, ArMe.sub.2H, .sup.3J.sub.HH=7.5 Hz), 6.78 (2H, d, ArMe.sub.2H, .sup.3J.sub.HH=7.4 Hz), 6.63-6.55 (2H, m, ArH), 6.54 (1H, d, CpH, .sup.3J.sub.HH=3.2 Hz), 6.41 (1H, d, CpH, .sup.3J.sub.HH=3.2 Hz), 6.15 (1H, d, CpH, .sup.3J.sub.HH=3.2 Hz), 6.02 (1H, d, CpH, .sup.3J.sub.HH=3.2 Hz), 3.88-3.62 (4H, m, bridge), 1.91 (6H, s, ArMe.sub.2). .sup.13C{.sup.1H} NMR (chloroform-d.sub.1, 25 C., 75.5 Mhz): 128.2, 126.6, 125.7 125.6, 125.4, 123.7, 123.6, 122.7 121.7, 120.9, 119.5, 115.7, 113.2, 108.4, 106.1 (all non-quaternary ring carbons) 29.6 (C.sub.2H.sub.4), 28.7 (C.sub.2H.sub.4), 18.0 (2ArMe.sub.2). Quaternary carbons unassigned.
EXAMPLE 24
Synthesis of [Ind.SUB.2.Zr(O-2,6-Me-C.SUB.6.H.SUB.3.)Me]
[0111] To one equivalent of [Ind.sub.2ZrMe.sub.2] (100 mg, 0.28 mmol) in toluene (5 mL), one equivalent of 2,6-dimethylphenol (34 mg, 0.28 mmol) in toluene (5 mL) was added at room temperature. The clear, straw-coloured solution was left stirring for 18 h. Solvent was removed in vacuum to afford [(Ind).sub.2Zr(O-2,6-Me-C.sub.6H.sub.3)Me], as a colourless oil with a yield of 75% (0.21 mmol, 96 mg). .sup.1H NMR (chloroform-d.sub.1, 25 C., 300 Mhz): 7.48-7.43 (2H, m, ArH), 7.34-7.29 (2H, m, ArH), 7.07-7.00 (2H, m, ArH), 6.92-6.85 (2H, m, ArH), 6.82 (2H, d, ArMe.sub.2H, .sup.3J.sub.HH=7.4 Hz), 6.59 (1H, t, ArMe.sub.2H, .sup.3J.sub.HH=7.4 Hz), 6.20 (2H, m, CpH), 5.91 (2H, m, CpH), 5.76 (2H, t, CpH, .sup.3J.sub.HH=3.4 Hz), 1.86 (6H, s, ArMe.sub.2), 0.22 (3H, s, ZrMe). .sup.13C{.sup.1H} NMR (chloroform-d.sub.1, 25 C., 75.5 Mhz): 159.4 (CO, Ar), 128.0 (2CH, Ar), 125.7 (2C quaternary, Ar), 124.6 (2CH, Ar), 124.3 (2CH, Ar), 124.0 (2C quaternary, Ar), 123.9 (2CH, Ar), 123.8 (2C quaternary, Ar), 123.6 (2CH, Ar), 118.9 (CH, Ar), 117.6 (2CH, Cp), 100.6 (2CH, Cp), 99.0 (2CH, Cp), 27.8 (ZrMe), 17.6 (2ArMe.sub.2).
EXAMPLES
Polymerisation of Lactides
(I)
Polymerisation of L- and Rac-Lactide
L- and Rac-Lactide Monomers
[0112] ##STR00003##
[0113] To study the difference between the aryloxide group, pseudo-first order kinetic data of the polymerisation of lactide monomers were carried out with a monomer:initiator: ratio of 50 at 100 C. in chloroform-d.sub.1. The results are shown in Table 1 and illustrated in
TABLE-US-00001 TABLE 1 L-lactide polymerisation: Variation of the aryloxide substituted T k.sub.obs M.sub.n Complex ( C.) (h.sup.1) (g .Math. mol) M.sub.w/M.sub.n 2 100 0.113 0.014 7 100 0.479 0.032 8 100 0.391 0.022 7,547 1.74 9 100 0.043 0.003 10 100 0.364 0.027 9,176 1.45 11 100 0.463 0.029 11,680 1.60 12 100 0.086 0.020 7,669 1.53 Polymerisation conditions: 100 C., [LA].sub.0 = 50, [LA].sub.0 = 0.5M, chloroform-d.sub.1.
[0114]
[0115] As can be seen in
[0116] The polydispersities are relatively high (1.45<M.sub.w/M.sub.n<1.74) certainly due to high temperature of polymerisation. The molecular weights are slightly higher than the theoretical ones (7,547<Mn<11,680 g/mol).
[0117] The effect of variation of the alkoxide group substituent on the polymerisation of L-lactide has been studied at 100 C., with a monomer:initiator: ratio of 50 in chloroform-d.sub.1. When complexes .sup.5-Pn*(H)Ti(O.sup.tBu).sub.3, 1, and .sup.5-Pn*(H)Zr(O.sup.tBu).sub.3 3, were used no conversion was achieved after 1 h. However, changing the tert-butyl group for a benzylic type substituent dramatically increased the rate of the polymerisation with conversion above 90% for .sup.5-Pn*(H)Ti(OCH.sub.2Ph).sub.3, 4, .sup.5-Pn*(H)Zr(OSCH{CH.sub.3}C.sub.6H.sub.5).sub.3, 5, .sup.5-Pn*(H)Zr(O-rac-CH{CH.sub.3}C.sub.6H.sub.5).sub.3, 6, (93, 96 and 97% respectively).
[0118] To study the effect of the chirality on the initiating group, pseudo-first order kinetic data of the polymerisation of lactide monomers were carried out with a monomer:initiator: ratio of 50 at 100 C. in chloroform-d.sub.1. The results are shown in Table 2 and illustrated in
TABLE-US-00002 T k.sub.obs M.sub.n Complex ( C.) LA (h.sup.1) (g/mol) M.sub.w/M.sub.n 5 100 L- 3.319 0.754 4,549 1.37 6 100 L- 3.442 0.000 4,313 1.37 5 100 rac- 1.885 0.268 3,056 1.44 6 100 rac- 2.782 0.168 2,693 1.36 5 80 L- 1.166 0.068 3,993 1.15 6 80 L- 1.954 0.063 4,106 1.18 5 80 rac- 1.342 0.055 3,109 1.18 6 80 rac- 1.667 0.053 3,856 1.24 5 60 L- 0.484 0.037 6 60 L- 0.850 0.063 5 60 rac- 0.491 0.031 6 60 rac- 0.767 0.037 Polymerisation conditions: [LA].sub.0/[M].sub.0 = 50, [LA].sub.0 = 0.5M, chloroform-d.sub.1.
[0119]
[0120]
[0121] Both complexes .sup.5-Pn*(H)Zr(OSCH{CH.sub.3}C.sub.6H.sub.5).sub.3, 5, .sup.5-Pn*(H)Zr(O-rac-CH{CH.sub.3}C.sub.6H.sub.5).sub.3, 6 demonstrated very high rate of polymerisation for L- and rac-lactide (1.885<k.sub.obs<3.442 h.sup.1) at 100 C. Over the three temperatures (60, 80 and 100 C.), the racemic complex polymerised faster both lactide monomers. At 60 C., the observed propagation rates when using rac-.sup.5-Pn*(H)Zr(OCH{CH.sub.3}C.sub.6H.sub.5).sub.3, 6 are around 70% faster (k.sub.obs of 0.850 h.sup.1 for L-lactide and 0.767 h.sup.1 for rac-lactide) than when .sup.5-Pn*(H)Zr(OSCH{CH.sub.3}C.sub.6H.sup.5).sub.3 5 was used (k.sub.obs of 0.484 h.sup.1 for L-lactide and 0.491 h.sup.1 for rac-lactide). L- and rac-lactide appears to be polymerised at similar rates of polymerisation.
[0122] The polydispersities decreased with decreasing temperature (1.27<M.sub.w/M.sub.n<1.44 for 100 C. and 1.15<M.sub.w/M.sub.n<1.24 for 80 C.). The molecular weight experimental are half of the theoretical (2,693<M.sub.n<4,549 g/mol).
[0123] The activation parameters for the ring-opening polymerisation of L- and rac-lactide initiated using .sup.5-Pn*(H)Zr(OSCH{CH.sub.3}C.sub.6H.sub.5).sub.3, 5, .sup.5-Pn*(H)Zr(O-rac-CH{CH.sub.3}CH.sub.5).sub.3, 6 were determined using Eyring plots and found to be 30.4<H.sup.#<46.6 kJ/mol and 411.4<S.sup.#<640 J/(mol K),
[0124]
[0125] Pseudo-first order kinetic data of the polymerisation of L-lactide to study the effect of variation of the concentration of the monomer:initiator ratio at 100 C. in chloroform-d.sub.1 using .sup.5-Pn*(H)Zr(O-2,6.sup.iPrC.sub.6H.sub.3).sub.3, 8. The results are collated in Table 3 and illustrated
TABLE-US-00003 TABLE 3 L-lactide polymerisation: Variation of the concentration [LA].sub.0/ k.sub.obs M.sub.n Complex [Zr].sub.0 (h.sup.1) (g/mol) M.sub.w/M.sub.n 8 25 0.521 0.021 6,920 1.72 8 50 0.391 0.022 7,547 1.74 8 100 0.377 0.015 9,870 1.40 8 200 0.235 0.004 17,042 1.54 Polymerisation conditions: 100 C., [LA].sub.0 = 0.5M, chloroform-d.sub.1.
[0126]
[0127] As expected the rate of the polymerisations of L-lactide at 100 C. in chloroform-d.sub.1 increased with decreasing monomer:initiator ratio (k.sub.obs of 0.235, 0.377, 0.391 and 0.521 h.sup.1 for [LA].sub.0/[Zr].sub.0 of 200, 100, 50 and 25 respectively). Furthermore, the molecular weights, M.sub.n, increased with increasing concentration from 6,920 to 17,042 g/mol for initial monomerinitiator ratio of 25 to 200 respectively. The polydispersities, M.sub.w/M.sub.n, are varying between 1.40<M.sub.w/M.sub.n<1.74.
[0128] The observed rate of the propagation of L-lactide using .sup.5-Pn*(H)Zr(O-2,6-PrC.sub.6H.sub.3).sub.3, 8, demonstrated a pseudo first-order kinetic as a function of the initiator (
[0129]
[0130] Pseudo-first order kinetic data of the polymerisation of L-lactide to study the effect of temperature with monomer:initiator ratio of 50 in chloroform-d.sub.1 using .sup.5-Pn*(H)Zr(O-2,6-PrC.sub.6H.sub.3).sub.3, 8. The results are collated in Table 4 and illustrated
TABLE-US-00004 TABLE 4 L-lactide polymerisation: Variation of the temperature T k.sub.obs M.sub.n Complex ( C.) (h.sup.1) (g/mol) M.sub.w/M.sub.n 8 100 0.391 0.022 6,920 1.72 8 90 0.151 0.008 7,751 1.59 8 80 0.092 0.006 6,348 1.58 Polymerisation conditions: [LA].sub.0/[M].sub.0 = 50, [LA].sub.0 = 0.5M, chloroform-d.sub.1.
[0131]
[0132] As expected the rate of the polymerisations of L-lactide in chloroform-d.sub.1 decreased with decreasing temperature (k.sub.obs of 0.391, 0.151 and 0.092 h.sup.1 for T of 100, 90 and 80 respectively). The molecular weights, M.sub.n, remain constant between 6,348 to 7,751 g/mol which are very close to the theoretical ones. However, the polydispersities, M.sub.w/M.sub.n, decreased with decreasing temperature from 1.72 to 1.58 for 100 to 80 C. respectively.
[0133] The activation parameters for the ring-opening polymerisation of L-initiated using .sup.5-Pn*(H)Zr(O-2,6-PrC.sub.6H.sub.3).sub.3, 8 were determined using Eyring plots and found to be H.sup.#=75.9 kJ/mol and S.sup.#=1847 J/(mol K),
[0134]
[0135] The synthesized polylactides were characterised by .sup.1H, .sup.1H{.sup.1H} and .sup.13C{.sup.1H} NMR spectroscopy. The NMR spectra demonstrated no epimerisation when L-lactide was polymerised and an isotactic biased PLA when rac-lactide was polymerised.
[0136] They have also been characterised by MALDI-TOF and .sup.13C{.sup.1H} NMR spectroscopy to determine the end of chains. It was shown that the lactide monomers inserted in the metal-oxygen bond.
(II)
[0137] Pseudo-first order kinetic data of the polymerisation of L-lactide at 80 C. in beneze-d.sub.6, with an initiator: monomer ratio of 1:50, using selected permethylpentalene complexes are shown in
[0138] The complex that exhibited by far the highest activity towards the ring-opening polymerisation of lactide isomers was [.sup.5-(Pn*)Ti(O-2,6-Me-C.sub.6H.sub.3).sub.2]. It demonstrates a rate of polymerisation similar to published titanium complexes (k.sub.obs=69.910.sup.3 h.sup.1).sup.37 and ten times faster than the complexes [.sup.8-(Pn*)Ti(O-2,6-Me-C.sub.6H.sub.3)Cl] and [.sup.8-(Pn*)Ti(O-2,4-Bu-C.sub.6H.sub.3)Cl] at 80 C. which demonstrated similar rates of propagation, (k.sub.obs=7.210.sup.3 h.sup.1 and 7.010.sup.3 h.sup.1 respectively). These rates of propagation being 3.5 times faster than when [.sup.5-(Pn*)Ti(O-2,6-Me-C.sub.6H.sub.3)Cl.sub.2] was used (k.sub.obs=1.910.sup.3 h.sup.1).
[0139]
[0140] As is shown in
[0141]
[0142] Polymerisations of L-lactide using [.sup.8-(Pn*)Ti(O-2,6-Me-C.sub.6H.sub.3).sub.2] were carried out in the temperature range of 80 to 100 C. and the results were collated to an Eyring plot. From the Eyring plot an estimation of the activation parameters were obtained: H.sup.#=75.15 kJ mol.sup.1, S.sup.#=125.85 J K.sup.1 mol.sup.1, G.sup.# (100 C.)=87.74 kJ mol.sup.1. The modest value of H.sup.# is typical for attack on a carbonyl group coordinated to a metal centre and the negative and relatively high value of S.sup.# implies a high degree of order in the transition state. As such, all parameters are consistent with a coordination insertion mechanism displaying a highly ordered transition state. The polymerisation of L-lactide leads to isotactic PLA and rac-lactide to atactic PLA.
(III)
[0143] Pseudo-first order kinetic data of the polymerisation of L-lactide using [(EBI)Zr(O-2,6-Me-C.sub.6H.sub.3)Cl], [(Ind).sub.2Zr(O.sup.tBu)Me], and [(Ind).sub.2Zr(O-2,6-Me-C.sub.6H.sub.3)Me] are shown in
[0144]
[0145] As [(Ind).sub.2Zr(O.sup.tBu)Me] showed the highest rate of polymerisation, further studies were carried out to investigate its stereoselectivity and estimate its activation. Polymerisations using [(Ind).sub.2Zr(O.sup.tBu)Me] as the initiator were carried out between 60 C. and 100 C., with the same LA:initiator ratios and [LA].sub.0 as used previously. The enthalpy of activation (H.sup.) and the entropy of activation (S.sup.) were calculated from a plot of ln(k.sub.obs/T) vs. (1/T) (
[0146] Furthermore, it was found that polymerisation of L-LA (k.sub.obs=0.24 h.sup.1) was twice as fast as rac-LA (k.sub.obs=0.11 h.sup.1) with [(Ind).sub.2Zr(O.sup.tBu)Me] at 80 C. with similar [LA].sub.0:[2].sub.0 ratio of 50:1 (
[0147] The .sup.1H{.sup.1H} NMR spectrum of the polymerisation of rac-LA using [(Ind).sub.2Zr(O.sup.tBu)Me] as initiator demonstrated a bias towards isotactic PLA, P.sub.i of 72%.
[0148] Polymerisations of L-LA and rac-LA were repeated at 80 C. with the addition of terf-butanol in stoichiometric amounts with [(Ind).sub.2Zr(O.sup.tBu)Me]. The addition of tert-butanol has little effect on k.sub.obs for both L-LA and rac-LA. The rate of polymerisation for L-LA without alcohol is similar to the one with (k.sub.obs of 0.24 h.sup.1 and 0.23 h.sup.1 respectively). Similarly the rates for the polymerisations of rac-LA were (k.sub.obs of 0.11 h.sup.1 and 0.10 h.sup.1 respectively). The molecular weights and polydispersities of the polymerisation of L-LA and rac-LA with and without tert-butanol are collated in Table 5. As an initiator, [(Ind).sub.2Zr(O.sup.tBu)Me]demonstrated highly controlled polymerisation of L-LA and rac-LA at 80 C. with a LA:initiator ratio of 50:1 in chloroform-d.sub.1, as shown by low polydispersities (1.08<M.sub.w/M.sub.n<1.12). The addition of tert-butanol does not affect the polydispersities; however, the experimental molecular weights appear more controlled in the presence of the alcohol, as expected of immortal polymerisation.
TABLE-US-00005 TABLE 5 Polymerisation data for L- and rac-lactide using 2.sup.a M.sub.n, theo/ M.sub.n, exp.sup.b Alcohol M.sub.n, exp (g .Math. mol1) M.sub.w/M.sub.n.sup.b rac-La no 1.96 11171 1.08 rac-LA yes 0.96 5779 1.10 S, S-LA no 2.19 13813 1.12 S, S-LA yes 1.45 9065 1.09 .sup.aPolymerisation conditions; [LA].sub.0/[2].sub.0 = 50, [LA].sub.0 = 0.5M, 80 C. Measured by GPC with polystyrene standards in THF. M.sub.n, theo = [LA].sub.0/[2].sub.0 M.sub.LA conv.