Tris(diphenylthiophosphinoyl) methanide as tripod ligand in rhodium(III), iridium(III) and ruthenium(II) complexes

Article abstract of DOI:10.1016/S0022-328X(97)00381-1

Reaction of the complex [{(η⁵-C₅Me₅)RhCl₂}₂], in CH₂Cl₂ solution, with AgBF₄ (1:2 molar ratio) and (SPPh₂)₃CH leads to the cationic compound [(η⁵-C₅Me₅)RhCl{η²-(SPPh₂)₂CH(SPPh₂)-S,S′}]BF₄ (1) which is deprotonated by thallium(I) pyrazolate affording [(η⁵-C₅Me₅)Rh{η³-(SPPh₂)₃C-S,S′,S″}]BF₄ (2a). The iridium dimer [{(η⁵-C₅Me₅)IrCl₂}₂] reacts with silver salts and (SPPh₂)₃CH, in CH₂Cl₂ or Me₂CO, under analogous conditions, affording mixtures of [(η⁵-C₅Me₅)IrCl{η²-(SPPh₂)₂CH(SPPh₂)-S,S′}]⁺ and [(η⁵-C₅Me₅)Ir{η³-(SPPh₂)₃C-S,S′,S″}]A [A = BF^-₄ (3a), PF^-₆ (3b)]. Addition of Et₃N to the mixture gives pure complexes 3. The ruthenium complexes [{(η⁶-arene)RuCl₂}₂] (arene = C₆Me₆, p-MeC₆H₄Prⁱ) react with (SPPh₂)₃CH, in the presence of AgA (A = PF^-₆ or BF^-₄) or Na BPh₄, in CH₂Cl₂ or Me₂CO, yielding only the deprotonated complexes [(η⁶-arene)Ru{η³-(SPPh₂)₃C-S,S'′,S″}]A [arene = C₆Me₆, A = BF₄; arene = p-MeC₆H₄Prⁱ, A = BPh₄ (4a), PF₆ (4b)]. The crystal structures of 3a and 4a were established by X-ray crystallography. Compound 3a crystallizes in the orthorhombic space group Pna2₁, with lattice parameters a = 41.477(6), b = 10.6778(11), c = 20.162(3) A and Z = 8. Complex 4a crystallizes in a monoclinic lattice, space group P2₁/n, with a = 20.810(4), b = 12.555(3), c = 23.008(4) A, β = 95.82(2)° and Z = 4. Both cationic complexes exhibit analogous pseudo-octahedral molecular structures with the anionic (SPPh₂)₃C^- ligand bonded via the three sulphur atoms in a tripodal, tridentate fashion. Each metal centre completes its coordination environment with a η⁵-C₅Me₅ (3a) or a η⁶-MeC₆H₄Prⁱ group (4a). A quite interesting result concerns the non-planarity of the methanide carbon which display P-C-P angles in the range 112.6-114.4(5)° in 3a and 111.9-113.6(4)° in 4a. The redox chemistry of the complexes was investigated by cyclic voltammetry. The Rh(III) complexes are quasi-reversibly reduced to Rh(I) and the Ir(III) complex is irreversibly reduced to Ir(I) in acetonitrile solutions. The Ru(II) complex undergoes a quasi-reversible reduction to Ru(I) and a reversible oxidation to Ru(III).