Use of stannylenes and germylenes as polymerization catalysts for heterocycles

1. In the process of polymerizing heterocyclic compounds, the improvement comprising using a polymerization catalyst of the formula

wherein

M is tin or germanium;

L 1 and L 2 are individually selected from the group consisting of -E 14 (R 14 )R′ 14 )(R″ 14 )(R′ 15 ) and -E 16 (R 16 ), or together form -L′ 1 -A-L′ 2 ;

A is a saturated or unsaturated chain comprising one, two or three elements of group 14 of the Periodic Table, substituted by one member selected from the group consisting of alkyl, cycloalkyl and aryl, each unsubstituted or substituted with a member selected from the group consisting of halogen, alkyl, aryl, nitro and cyano;

L′ 1 and L′ 2 are individually selected from the group consisting of -E 14 (R 14 )(R′ 14 )-, E 15 (R 15 )- and -E 16 -;

E 14 is an element of group 14 of the Periodic Table;

E 15 is an element of group 15 of the Periodic Table;

E 16 is an element of group 16 of the Periodic Table;

R 14 , R′ 14 , R″ 14 , R 15 , R′ 15 and R 16 are individually selected from the group consisting of hydrogen, alkyl, cycloalkyl and aryl, unsubstituted or substituted with a member selected from the group consisting of halogen, aryl, cycloalkyl, aryl, nitro and cyano or -E′ 14 RR′R″-,

E′ 14 is an element of group 14 of the Periodic Table;

R, R′ and R″ are individually selected from the group consisting of hydrogen, alkyl, cycloalkyl, and aryl, unsubstituted or substituted by a member selected from the group consisting of halogen, alkyl, aryl, nitro and cyano.

2. The process of claim 1 wherein M is tin.

3. The process of claim 1 wherein L 1 and L 2 are individually selected from the group consisting of -E 14 (R 14 (R′ 14 )(R″ 14 ), -E 15 (R 15 )(R′ 15 ) and -E, 16 (R 16 ).

4. The process of claim 1 wherein

E 14 is carbon or silicon;

E 15 is nitrogen or phosphorus;

E 16 is oxygen or sulfur;

R 14 , R′ 14 , R″ 14 , R 15 and R 16 are individually selected from the group consisting of hydrogen, alkyl and E′ 14 RR′R″;

E 14 is carbon or silicon;

R, R′ and R″ are individually selected from the group consisting of hydrogen or ackyl.

5. The process of claim 1 wherein

L 1 and L 2 are individually -E 15 (R 15 )R′ 15 or -E 16 (R 16 );

E 15 is nitrogen;

E 16 is oxygen;

R 15 and R′ 15 are individually alkyl or -E′ 14 RR′R

R 16 is alkyl;

E′ 14 is silicon;

R, R′ and R″ are individually hydrogen or alkyl.

6. The process of claim 1 wherein the compound of formula 1 is

-[(Me 3 Si 2 )N] 2 Sn or

-{[Me 3 Si) 2 n]Sn(Ot)Bu)} 2 .

7. The process of claim 1 wherein the heterocycle is a cyclic ether.

8. The process of claim 7 wherein the cyclic ether is propylene oxide.

9. The process of claim 1 wherein the heterocycle is a cyclic ester.

10. The process of claim 1 wherein the heterocycle compound is a cyclic ester polyner of lactic acid and/or glycolic acid for obtaining a polymer of lactic acid and/or glycolic acid as the heterocyclic.

11. In a process for the preparation of block or random copolymers or polymers comprising introducing one or more heterocyclic monomers, a polymerization catalyst and optionally a polymerization solvent an copolymerizing said monomers, at a temperature between ambient temperature and 250° C., for a duration of a few minutes up to 300 hours, the improvement comprising using as the chain initiator and the polymerization catalyst having the formula

of claim 1 .

12. The process of claim 11 wherein the one or more heterocyclic monomers are selected from the group consisting of epoxides and cyclic esters of lactic and/or glycolic acid.