Ylide-functionalised phosphanes for use in metal complexes and homogeneous catalysis

Metal complexes having phosphane ligands of formula (I)

• wherein On is a phosphonium group —P(R3R4R5), in which R3, R4 and R5 are independently selected from the group consisting of C1-6 alkyl groups, C4-10 cycloalkyl groups, C6-10 aryl groups, X is selected from the group consisting of linear, branched-chain or cyclic C1-6 alkyl groups, C6-10 aryl groups, mono- or polyunsaturated linear, branched-chain or cyclic C2-6 alkenyl groups, a trialkylsilyl (—SiR3R4R5), arylsulfonyl group, and R1 and R2 are C6-10 aryl groups or C1-6 alkyl and cycloalkyl groups, with the proviso that ligands where R1 and R2 are phenyl, On is triphenylphosphine (PPh3) and X is phenyl or methyl are excluded.