Patent ID: 8183382

Claim:
A compound of the formula (II) or (III) wherein Z is —S—, —S(O)— and S(O) 2 —, X1 and X2 are the same or different and are each an anionic ligand, Y, R, R′ and R 1 to R 4 are each independently selected from the group of hydrogen, (C 1 -C 8 )-alkyl, (C 1 -C 8 )-alkoxy, (C 6 -C 18 )-aryloxy, HO—(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.