A catalyst includes 1 part by mole of a palladium complex and 500 to 10000 parts by mole of an amine compound. The palladium complex has a chemical structure of

##STR00001## in which X is halogen, each of R.sup.1 is independently C.sub.1-8 linear alkyl group or C.sub.3-8 cycloalkyl group, and each of R.sup.2 is independently H or C.sub.1-4 alkyl group. The amine compound has a chemical structure of

##STR00002## in which R.sup.3 is C.sub.1-8 alkylene group, and Z is

##STR00003##

Catalysts and methods for dinitrogen conversion to secondary silyamines or ammonia (N.sub.2RR) are provided. The catalysts are a metalacyclic platform characterized by a pocket with tunable dimensions and conditions. The catalysts show dramatically improved N.sub.2RR activity compared to previously reported early d-block catalysts. The tetraphenolate-supported bimetallic lanthanide or group IV metal complex undergoes multiple two-electron reductions, the last of which leads to the reductive activation of dinitrogen. The inclusion of a weak acid and silyl electrophiles during the reduction enables the catalytic conversion of N.sub.2 to purely secondary amines.

A multidentate phosphite ligand comprising a backbone which comprises a substituted or unsubstituted spirobiindane compound and at least two organophosphite groups chemically bonded to the backbone, wherein the organophosphite groups are alkyl phosphite groups or wherein the organophosphite groups are aryl phosphite groups, wherein the aryl moieties on the aryl phosphite groups are phenyl rings substituted with one or more C.sub.1-C.sub.4 alkyl groups; or which comprises a substituted or unsubstituted spirodifluorene compound and at least two organophosphite groups chemically bonded to the backbone.

The present invention provides a catalyst for synthesizing a cyclic carbonate and a preparation method and use thereof. A diamine compound X, a salicylaldehyde-containing compound and a metal source M are subjected to reaction, and then added with a phenothiazine compound Y for continuous reaction to obtain a phenothiazine metal Schiff base catalyst. The formation of phenothiazine free radicals by phenothiazine compounds with a central metal can protect the central metal in the course of reaction and inhibit inactivation caused by the self-polymerization of the central meta, thus improving the activity and stability of a catalyst. Phenothiazine compounds can be present as a polymerization inhibitor to inhibit the generation of by-products such as polycarbonates and polyethylene glycol and enhance the selectivity of the catalyst during the reaction. The phenothiazine compounds are alkaline and can adsorb and activate carbon dioxide during reaction, which helps to improve the reaction efficiency. The phenothiazine metal Schiff base catalyst prepared in the present invention has high activity, strong stability and good selectivity and thus, can achieve the efficient catalyzed synthesis of cyclic carbonates under mild conditions.

The present invention provides a catalyst for synthesizing a cyclic carbonate and a preparation method and use thereof. A diamine compound X, a salicylaldehyde-containing compound and a metal source M are subjected to reaction, and then added with a phenothiazine compound Y for continuous reaction to obtain a phenothiazine metal Schiff base catalyst. The formation of phenothiazine free radicals by phenothiazine compounds with a central metal can protect the central metal in the course of reaction and inhibit inactivation caused by the self-polymerization of the central meta, thus improving the activity and stability of a catalyst. Phenothiazine compounds can be present as a polymerization inhibitor to inhibit the generation of by-products such as polycarbonates and polyethylene glycol and enhance the selectivity of the catalyst during the reaction. The phenothiazine compounds are alkaline and can adsorb and activate carbon dioxide during reaction, which helps to improve the reaction efficiency. The phenothiazine metal Schiff base catalyst prepared in the present invention has high activity, strong stability and good selectivity and thus, can achieve the efficient catalyzed synthesis of cyclic carbonates under mild conditions.