Patent ID: 7361786

Claim:
A ligand represented by formula (I), wherein R 3 and R 4 are independently selected from the group consisting of (C 1 -C 8 )-alkyl, (C 2 -C 8 )-alkoxyalkyl, (C 6 -C 18 )-aryl, (C 7 -C 19 )-aralkyl, (C 3 -C 18 )-heteroaryl, (C 4 -C 19 )-heteroaralkyl, (C 1 -C 8 )-alkyl-(C 6 -C 18 )-aryl, (C 1 -C 8 )-alkyl-(C 3 -C 18 )-heteroaryl, (C 3 -C 8 )-cycloalkyl, (C 1 -C 8 )-alkyl-(C 3 -C 8 )-cycloalkyl, and (C 3 -C 8 )-cycloalkyl-(C 1 -C 8 )-alkyl, and R 1 and R 2 represent a (C 3 -C 5 )-alkylene bridge mono or polysubstituted with (C 1 -C 8 )-alkyl, HO—(C 1 -C 8 )-alkyl, (C 1 -C 8 )-alkoxy, (C 2 -C 8 )-alkoxyalkyl, (C 6 -C 18 )-aryl, (C 7 -C 19 )-aralkyl, (C 1 -C 8 )-alkyl-(C 6 -C 18 )-aryl, (C 3 -C 8 )-cycloalkyl, (C 1 -C 8 )-alkyl-(C 3 -C 8 )-cycloalkyl or (C 3 -C 8 )-cycloalkyl-(C 1 -C 8 )-alkyl, optionally linked to a polymer enlargement, or R 1 , R 2 , R 3 and R 4 represent a (C 3 -C 5 )-alkylene bridge mono or polysubstituted with (C 1 -C 8 )-alkyl, HO—(C 1 -C 8 )-alkyl, (C 1 -C 8 )-alkoxy, (C 2 -C 8 )-alkoxyalkyl, (C 6 -C 18 )-aryl, (C 7 -C 19 )-aralkyl, (C 1 -C 8 )-alkyl-(C 6 -C 18 )-aryl, (C 3 -C 8 )-cycloalkyl, (C 1 -C 8 )-alkyl-(C 3 -C 8 )-cycloalkyl or (C 3 -C 8 )-cycloalkyl-(C 1 -C 8 )-alkyl, optionally linked to a polymer enlargement; A is represented by wherein R* is selected from the group consisting of H, (C 1 -C 8 )-alkyl, (C 6 -C 8 )-aryl, (C 7 -C 19 )-aralkyl, (C 1 -C 8 )-alkyl-(C 6 -C 18 )-aryl, (C 3 -C 8 )-cycloalkyl, (C 1 -C 8 )-alkyl-(C 3 -C 8 )-cycloalkyl, (C 3 -C 8 )-cycloalkyl-(C 1 -C 8 )-alkyl, and a link to a polymer enlargement.