US Patent 7169729 Use of zinc derivatives as cyclic ester polymerization catalysts

The invention concerns the use of zinc derivatives of general formula (I) wherein: L1 represents a group of formula: —E14(R14)(R′14)(R″14), —E15(R15) (R′15) or —E16(R16); E is an atom of group 15; L2 and L3 independently represent a group of formula: —E14(R14)(R′14)(R″14), —E15(R15)(R′15) or —E16(R16), or together form a chain of formula —L′2—A—L′3—; A represents a saturated or unsaturated chain comprising one, two or three elements of group 14; L′2 and L′3 independently represent a group of formula —E14(R14)(R′14) —E15(R15) or —E16—; E14 is an element of group 14; E15 is an element of group 15; E16 is an element of group 16; R14, R′14, R″14, R15, R′15 and R16 represent various groups, as (co) polymerisation catalysts of cyclic esters