Patent ID: 6984755

Claim:
A process for the preparation of an carboxylic anhydride by reaction of an ethylenically unsaturated compound with carbon monoxide and an carboxylic acid in the presence of a catalyst comprising: a) a source of a group VIII metal; b) a bidentate diphosphine of formula I, wherein R 1 represents a bivalent radical that together with the phosphorus atom to which it is attached is an optionally substituted 2-phospha-tricyclo[3.3.1.1{3,7}]-decyl group or a derivative thereof in which one or more of the carbon atoms are replaced by heteroatoms (“2-PA” group); wherein R 2 and R 3 independently represent univalent radicals of up to 20 atoms or jointly form a bivalent radical of up to 20 atoms; and wherein R represents a bivalent organic bridging group; and, c) a complexing anion; wherein the complexing anion is the anion of the carboxylic acid, and wherein any additional stronger acid than the carboxylic acid is present in a molar ratio to the group VIII metal of less than 0.5:1.