A supported catalyst system is based on a transition metal carbene including the moiety M1=CR*).sub.2, wherein M.sup.1 is the transition metal and R* is hydrogen or a C.sub.1-C.sub.8 hydrocarbyl. The catalyst system can be supported on a metal oxide support such as silica or the catalyst can be self-supporting. Methods of making the catalyst system can involve precursors based on and/or reacted with aluminum alkyls, halides, and/or alkoxides. Methods of polymerizing cyclic olefins with the catalyst system can obtain polyalkenamers, cyclic olefin polymers, cyclic olefin copolymers, and other metathesis reaction products. The supported catalyst and/or monomer can be recovered and recycled to the polymerization reactor.

The present disclosure relates to a method for regenerating a waste organic zinc catalyst by performing surface modification using a dicarboxylic acid and a zinc compound. When using the method for regenerating an organic zinc catalyst according to the present disclosure, the organic zinc catalyst can be regenerated using a convenient method which modifies the dicarboxylic acid and the zinc compound in an alternately repeated manner.

The present invention provides unimolecular metal complexes having increased activity in the copolymerization of carbon dioxide and epoxides. Also provided are methods of using such metal complexes in the synthesis of polymers. According to one aspect, the present invention provides metal complexes comprising an activating species with catalytic activity tethered to a ligand that is coordinated to the active metal center of the complex.

Described herein are methods of producing prebiotic compositions that are made up of oligosaccharide compositions, as well as methods of using such prebiotic compositions in nutritional compositions and methods of producing such oligosaccharide and nutritional compositions.

The present invention relates to a composition comprising at least one tertiary amino compound (A), and at least one copper(II)-compound (B), a process for the manufacture of said composition, the use of said composition as a catalyst, in particular, as catalyst for the reaction of at least one isocyanate compound with at least one isocyanate-reactive compound, in particular for the manufacture of polyisocyanate polyaddition products, such as polyurethanes, in particular, polyurethane foams.

This invention relates generally to olefin metathesis catalysts, to the preparation of such compounds, compositions comprising such compounds, methods of using such compounds, and the use of such compounds in the metathesis of olefins and in the synthesis of related olefin metathesis catalysts. The invention has utility in the fields of catalysis, organic synthesis, polymer chemistry, and in industrial applications such as oil and gas, fine chemicals and pharmaceuticals.

In one aspect, phosphine compounds comprising three adamantyl moieties (PAd.sub.3) and associated synthetic routes are described herein. Each adamantyl moiety may be the same or different. For example, each adamantyl moiety (Ad) attached to the phosphorus atom can be independently selected from the group consisting of adamantane, diamantane, triamantane and derivatives thereof. Transition metal complexes comprising PAd.sub.3 ligands are also provided for catalytic synthesis including catalytic cross-coupling reactions.

A tetraanionic OCO pincer ligand metal-oxo-alkylidene complex is prepared from a trianionic pincer ligand supported metal-alkylidyne. The metal can be tungsten or other group 5-7 transition metal. The tetraanionic pincer ligand metal-oxo-alkylidene complex, a trianionic OCO pincer ligand metal complex, or a trianionic ONO pincer ligand metal complex can be used to polymerize cycloalkenes. The poly(cycloalkene)s are predominantly cis-alkene macrocyclics.

The present disclosure provides a stannous salt complex catalyst and a method for producing L-lactide by using the same. The catalyst is obtained by reacting stannous salt and phosphite in a solvent, which can effectively inhibit the oxidation of divalent stannous ions to tetravalent tin ions, effectively reduce the conversion rate of meso-lactide, increase the yield of L-lactide, and obtain nearly white L-lactide. In the crude lactide produced after the depolymerization reaction, the content of L-lactide is more than or equal to 95 %; the content of meso-lactide is less than or equal to 3.8 %, while ensuring that the color of the residual liquid is close to milky white.

A tetraanionic OCO pincer ligand metal-oxo-alkylidene complex is prepared from a trianionic pincer ligand supported metal-alkylidyne. The metal can be tungsten or other group 5-7 transition metal. The tetraanionic pincer ligand metal-oxo-alkylidene complex, a trianionic OCO pincer ligand metal complex, or a trianionic ONO pincer ligand metal complex can be used to polymerize cycloalkenes. The poly(cycloalkene)s are predominantly cis-alkene macrocyclics.