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′ = Bu^t, 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.