Dipalladium complexes with a bridging arylene or diarylene ligand. Synthesis and CNR′ and CO insertion into the Pd–C bonds
Abstract
The complexes trans-[PdEt2L2] (L = PMe3 or PEt3) reacted with 4,4′-dibromobiphenyl, 4,4′-diiodobiphenyl, 1.4-diiodobenzene, di(4-bromophenyl) ether, di(4-chlorophenyl) sulfone, 9,10-dibromoanthracene and 4,4′-dibromooctafluorobiphenyl to give various bimetallic palladium(II) complexes with a bridging arylene or diarylene ligand, trans,trans-[L2XPdRPdXL2] (L = PMe3 or PEt3; R = C6H4C6H4, C6H4, C6H4OC6H4, C6H4SO2C6H4, C14H8 or C6F4C6F4; X = Br, Cl or I). The structure of trans,trans-[(Et3P)2BrPdC6H4C6H4PdBr(PEt3)2] has been determined by X-ray crystallography. The complex trans,trans-[(Me3P)2BrPdC6H4C6H4PdBr(PMe3)2] reacts with tert-butyl, cyclohexyl and phenyl isocyanides to give the iminoacylpalladium complexes trans,trans-[(Me3P)2BrPdC(NR′)C6H4C6H4C(NR′)PdBr(PMe3)2] (R′ = But, C6H4 or Ph) through insertion of the isocyanide into the two aryl–palladium bonds. Reactions of trans,trans-[L2IPdRPdIL2] (R = C6H4C6H4, L = PEt3; R = C6H4, L = PMe3 or PEt3) with CO (1 atm) proceeded smoothly to give trans,trans-[(Et3P)2IPdCOC6H4C6H4PdI(PEt3)2] and trans,trans-[L2IPdCOC6H4PdIL2] (L = PMe3 or PEt3), respectively, through insertion of CO into one of the aryl–palladium bonds.