Synthesis of mononuclear complexes of Ru and Os and heterobimetallic M–M′(M = Ru or Os; M′= Rh, Ir, or Au) compounds with pyrazolate or imidazolate type ligands. X-Ray crystal structure of [(Ph3P)2(OC)HRu(µ-bim)Rh(cod)](bim = dianion of 2,2′-bi-imidazole, cod = cyclo-octa-1,5-diene)

Abstract

The synthesis and characterization of several mono- and poly-(di-, tri-, or tetra)-nuclear compounds are reported. The mononuclear compounds are of the type [MH(CO)(HL)(PPh₃)₂][M = Ru or Os; [HL = Hbim (monoanion of 2,2′-bi-imidazole), Hbbzim (monoanion of 2,2′-bibenzi-imidazole)], or [RuH(pz)(CO)(Hpz)(PPh₃)₂][Hpz(pyrazole)]. They react with [{M′(µ-OMe)(diolefin)}₂]{M′= Rh or Ir; diolefin = cyclo-octa-1,5-diene (cod) or tetrafluorobenzobarrelene (tetrafluorobenzo-[5,6]bicyclo[2.2.2]octa-2,5,7-triene)(tfbb)}, giving the heterodinuclear complexes [(Ph₃P)₂(OC)HMLM′(diolefin)]. In some of these compounds the diolefin can easily be displaced by carbon monoxide yielding [(Ph₃P)₂(OC)HRuL₂M′(CO)₂][L₂= bbzim, M′= Rh; L₂=(pz)₂, M′= Rh or Ir]. The structure of [(Ph₃P)₂(OC)HRu(µ-bim)Rh(cod)] was established by X-Ray crystallography: the crystals are monoclinic, space group P2₁/n, a= 16.209 1 (7), b= 14.437 1 (5), c= 18.960(1)Å, β= 93.700(4)°, and Z= 4. The molecule is binuclear with a 2,2′-bi-imidazolate ligand bridging, as a tetradentate bichelating group, two different metallic centres, a square-planar rhodium(I) and a slightly distorted octahedral ruthenium(II). In this molecule, the rhodium co-ordination sphere, the bridging anion, and the carbonyl and hydride ligands are planar. The Ru–N bond distances are markedly asymmetric [2.283(5) and 2.180(5)Å, to N(1) and N(2)] reflecting their different trans groups: a hydride and a carbonyl. The compound [RuH(CO)(Hbim)(PPh₃)₂] reacts with [Au(PPh₃)]BF₄ in different proportions affording heteropolynuclear Ru(µ-H)Au complexes of formula [(Ph₃P)₂(OC)HRu(µ-bim){Au(PPh₃)}₂]BF₄, [(Ph₃P)Au(µ-H)(Ph₃P)₂(OC)Ru(µ-bim){Au(PPh₃)₂][BF₄]₂, and [(Ph₃P)Au(µ-H)(Ph₃P)₂(OC)Ru(µ-Hbim){Au(PPh₃)}][BF₄]₂.