Catalytic systems for immortal ring-opening polymerisation of cyclic esters and cyclic carbonates

1. A complex of a divalent metal of formula [LO]-M-X, wherein M is selected from Group 2 or 12 of the Periodic Table; wherein X is hydrocarbyl, or alkoxide group OR″ wherein R″ is hydrocarbyl, aryl, silyl, or amino group NR* 2 wherein R* is SiMe 3 , iso-propyl, methyl or ethyl, and wherein [LO] is represented by formula

wherein

R 1 is

 wherein m is 1, 2 or 3 and n≧1

R 2 is hydrocarbyl group having 1 to 10 carbon atoms;

R 3 is the same as R 1 or is hydrocarbyl group having 1 to 20 carbon atoms.

2. The complex of claim 1 wherein the metal M is selected from Zn, Mg, Ca, Sr or Ba.

3. The complex of claim 1 wherein X is selected from methyl, ethyl, n-butyl, phenyl, or an amido group, or an alkoxide group.

4. The complex of claim 3 wherein X is selected from ethyl, n-butyl or N(SiMe 3 ) 2 .

5. The complex of claim 1 , wherein R 2 is selected from methyl, ethyl, iso-propyl, tert-butyl or neo-pentyl.

6. The complex of claim 1 , wherein R 3 is alkyl selected from methyl, ethyl, iso-propyl, tert-butyl, neo-pentyl, cumyl, trityl.

7. A method for preparing the complex of claim 1 by reacting precursor MX 2 with pro-ligand of formula

wherein M, X, R 1 , R 2 and R 3 are as defined in the preceding claims.

8. The complex of claim 1 , wherein R 3 is an aryl selected from phenyl, 2,4,6-trimethylphenyl, and 2,6-diisopropylphenyl.

9. The complex of claim 1 , wherein the metal M is selected from Zn, Mg and Ca.

10. The complex of claim 3 , wherein X is an amido group selected from N(SiMe 3 ) 2 , NMe 2 , NEt 2 , and NiPr 2 , or an alkoxide group selected from OEt, OiPr, OtBu, OCH 2 Ph, and OSiPh 3 .

11. The complex of claim 1 , wherein R 3 is the same as R 1 .

12. The complex of claim 1 , wherein R 3 is a hydrocarbyl group having 1 to 20 carbon atoms.

13. The complex of claim 1 , wherein [LO] is 2-R 1 , 4-R 2 , 6-R 3 —C 6 H 2 O.