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.