The present invention provides a process for the preparation of a complex of formula (A) or (B): wherein, M is a platinum group metal atom; each X is an anionic monodentate ligand; is a bidentate phosphine ligand; and R1 and R2 are independently selected from the group consisting of straight-chain C1-10 alkyl, branched-chain C3-10 alkyl, C3-10 cycloalkyl and optionally substituted aryl; comprising the steps of: (a) preparing  by reacting the lithium salt of R1R2PH with a dihaloalkane in a solvent comprising an alkyl ether and, optionally, an alkane, provided the alkyl ether is not diethyl ether; (b) reacting  with a platinum group metal precursor compound to form the complex of formula (A) or formula (B).