Patent ID: 7834215

Claim:
A ligand system having the structure of general formula (I) wherein * represents stereocenter; R 3 and R 4 are each independently selected from the group consisting of (C 1 -C 8 )-alkyl, (C 1 -C 8 )-alkoxy, 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; R 7 and R 8 are each independently H, R 3 , or R 3 and R 7 and/or R 7 and R 8 and/or R 8 and R 4 are joined to one another via a (C 3 -C 5 )-alkylene bridge; R 1 and R 2 are each independently (C 1 -C 8 )-alkyl, (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, (C 3 -C 8 )-cycloalkyl-(C 1 -C 8 )-alkyl, (C 1 -C 8 )-alkyl-O, (C 6 -C 18 )-aryl-O, (C 7 -C 19 )-aralkyl-O, (C 3 -C 8 )-cycloalkyl-O, (C 1 -C 8 )-alkyl-NH, (C 6 -C 18 )-aryl-NH, (C 7 -C 19 )-aralkyl-NH, (C 3 -C 8 )-cycloalkyl-NH, ((C 1 -C 8 )-alkyl) 2 N, ((C 6 -C 18 )-aryl) 2 N, ((C 7 -C 19 )-aralkyl) 2 N, or ((C 3 -C 8 )-cycloalkyl) 2 N; and A is a ring system having the following structure: wherein Q is O, NH, NH—NH, NR—NR, NOR, NR, S, CH 2 or C═C(R) 2 ; R is H, (C 1 -C 8 )-alkyl, (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; R′ is R or R′″; and R′″ is one or more electron-withdrawing groups selected from the group consisting of flourine, chlorine, CF 3 CO, CF 3 SO 2 , CF 3 , and CnF 2n+1 .