Synthesis, structures and properties of bis(carbodiimido) complexes of Ni(ii), Pd(ii) and Pt(ii)

Abstract

Bis(azido)–Group 10 metal complexes (M(N₃)₂L₂) reacted with two equivalents of isocyanides (CNR) to give the corresponding bis(carbodiimido) complexes, M(NCN–R)₂L₂ {[Pd(NCN–2,6-Me₂C₆H₃)₂L₂]: L = PMe₃ (1), PEt₃ (2), PMe₂Ph (3); [Pd(NCN–2,6-Et₂C₆H₃)₂L₂]: L = PMe₃ (4); [Ni(NCN–2,6-Me₂C₆H₃)₂L₂]: L = PMe₃ (5), PEt₃ (6); [Pt(NCN–2,6-Me₂C₆H₃)₂L₂]: L = PMe₃ (7), PEt₃ (8)} in relatively high yields. Reaction schemes have been proposed on the basis of isolated intermediates such as Ni[CN₄(R)](NCN–R)(PMe₃)₂ (R = 2,6-Me₂C₆H₃) (9), trans-Pt[CN₄(R)]₂(PMe₃)₂ (10), and Pt[CN₄(R)](NCN–R)L₂ (L = PMe₃ (11) or PEt₃, (12)). Molecular structures of 1, 2, 4, 6, 8, and 11 have been determined by X-ray diffraction, demonstrating that the nitrogen of the carbodiimido (NCN) group is directly bonded to the metal center. The chelating phosphine analogues M(N₃)₂(L–L) {M = Pd or Ni; L–L = depe (1,2-bis(diethylphosphino)ethane), dppp (1,3-bis(diphenylphosphino)propane), or dppe (1,2-bis(diphenylphosphino)ethane)} reacted with isocyanides to also give the corresponding bis(carbodiimido) complexes, M(NCN–R)₂(L–L) {M = Pd: L–L = depe (13), dppp (14); M = Ni, L–L = dppe (15)} in high yields. Treating Pd(NCN–2,6-Me₂C₆H₃)₂(PMe₃)₂ (1) with two equivalents of benzoyl chloride (PhCOCl), phenyl chloroformate (PhOCOCl), and 2-thiophenecarbonyl chloride (C₄H₃SCOCl) gave organic cyanamides, PhCON(CN)-2,6-Me₂C₆H₃, PhO(CO)N(CN)-2,6-Me₂C₆H₃, and C₄H₃SCON(CN)-2,6-Me₂C₆H₃, respectively.