| abstract |
Bidentate ligand of formula II: R1R2M1-R-M2R3R4, wherein M1 and M2 are independently P, As or Sb; R1, R2, R3 and R4 independently represent tertiary alkyl groups, or R1 and R2 together and/or R3 and R4 together represent an optionally substituted bivalent cycloaliphatic group whereby the two free valencies are linked to M1 or M2, and R represents a bivalent aliphatic bridging group containing from 2 to 6 atoms in the bridge, which is substituted with two or more substituents. A catalyst system comprising (a) a source of group VIII metal cations, (b) a source of such a bidentate ligand, and (c) a source of anions. Use of such a catalyst system in a process for the carbonylation of optionally substituted ethylenically or acetylenically unsaturated compounds by reaction with carbon monoxide and a coreactant. |