Complexes of the platinum metals. Part 37. Benzotriazole and 5,6-dimethylbenzotriazole derivatives. X-Ray crystal structure of carbonylhydrido[hydrogenbis(benzotriazolato)]bis(triphenylphosphine)osmium(II)

Abstract

The ruthenium and osmium complexes [MH(Cl)(CO)(PPh₃)₃](M = Ru or Os) each react with benzotriazole (Hbta) in cold benzene to form a pair of geometrical isomers [MH(Cl)(Hbta)(CO)(PPh₃)₂](H trans to Hbta or Cl). The dihydrides [MH₂(CO)(PPh₃)₃] react with excess of benzotriazole in boiling benzene (M = Ru) or toluene (M = Os) to afford products of the form [MH(bta ⋯ H–bta)(CO)(PPh₃)₂] containing a hydrogen-bonded benzotriazole–benzotriazolate pair co-ordinated as an NN′ chelate ligand. Similar chelate ligands are found in the products trans-[M(bta ⋯ H–bta)₂(Hbta)(PPh₃)] obtained from [RuH₂(PPh₃)₄] and Hbta in boiling benzene, or from [MCl₂(PPh₃)₃], Hbta, and triethylamine in boiling benzene (M = Ru) or toluene (M = Os). Isomeric forms of the complexes trans-[M(bta ⋯ H–bta)₂(Hbta)(PPh₃)] are thought to involve N²- or N³-co-ordinated Hbta ligands. Treatment of [IrCl(CO)(PPh₃)₂] with Hbta leads to reversible formation of the oxidative-addition product [IrH(Cl)(bta)(CO)(PPh₃)₂] in solution. The same reagents in the presence of NEt₃ afford the known complex [Ir(bta)(CO)(PPh₃)₂]. Benzotriazole also reacts with mer-[IrH₃(PPh₃)₃] to form [IrH₂(bta ⋯ H–bta)(PPh₃)₂] and with [Pt(PPh₃)₄] to generate [Pt(bta)₂(PPh₃)₂]. The nature of the hydrogen-bonded composite (bta ⋯ H–bta) ligand has been confirmed by an X-ray diffraction study on the osmium complex [OsH(bta ⋯ H–bta)(CO)(PPh₃)₂]. The crystals are triclinic, space group P, with a= 10.059(4), b= 11.876(1), c= 20.629(3)Å, α= 74.57(1), β= 83.08(2), γ= 65.96(2)°, and Z= 2. A parallel series of complexes have been obtained using 5,6-dimethylbenzotriazole.