Rhodium and iridium complexes with thiolate and tertiary phosphineligands. The synthesis and structures of trans-[Ir(SC6H3Cl2-2,6)(CO)(PPh3)2], [Rh2(μ-SC6H3Pri3-2,4,6)2(CO)2(PPh3)2], [Rh2H2(μ-SC6H4PPh2-2)2(CO)2(PPh3)2][BF4]2, and [Rh2I6(MeSC6H4PPh2-2)2]

Abstract

Reaction of [MF(CO)(PPh₃)₂] (M = Rh or Ir) with bulky aromatic thiols ArSH gave the binuclear complexes [M₂(μ-SAr)₂(CO)₂(PPh₃)₂] (M = Rh, SAr = SC₆H₂Prⁱ₃-2,4,6 or SC₆H₃Me₂-2,6) and mononuclear complexes [M(SAr)(CO)(PPh₃)₂] (M = Rh or Ir, SAr = SC₆H₃Cl₂-2,6 or SC₆H₄SiPh₃-2; M = Ir, SAr = SC₆H₂Prⁱ₃-2,4,6 or SC₆H₃Me₂-2,6. The crystal structure of [Rh₂(μ-SC₆H₃Prⁱ₃-2,4,6)₂(CO)₂(PPh₃)₂] showed a binuclear thiolate bridged core while that of [Ir(SC₆H₃Cl₂-2,6)(CO)(PPh₃)₂] revealed a conventional square planar geometry with trans PPh₃ ligands. Three rhodium complexes were shown to be efficient catalysts for the hydroformylation of hept-1-ene under mild conditions with good selectivity for linear aldehyde for SAr = SC₆H₄SiPh₃-2. Reaction of [MF(CO)(PPh₃)₂] with phosphinothiolate proligands PSH gave the monomeric complexes [M(PS)(CO)(PPh₃)₂] (M = Rh or Ir; PS = SC₆H₄PPh₂-2 or S(CH₂)₃PPh₂; M = Rh, PS = SCH₂CH₂PPh₂ or SCH(CH₃)CH₂PPh₂). The complex [Rh(SC₆H₄PPh₂-2)(CO)(PPh₃)] reacted reversibly with protons (HBF₄) to give the dimeric dication [Rh₂(μ-SC₆H₄PPh₂-2)₂(CO)₂(PPh₃)₂]²⁺, shown by a crystal structure be a thiolate bridged dimer with an Rh–Rh bond and pseudo-octahedral geometry about each Rh^III. Electrophilic attack by [Me₃O][BF₄] on [Rh(SC₆H₄PPh₂-2)(CO)(PPh₃)] occurred at sulfur to give [Rh(MeSC₆H₄PPh₂-2)(CO)(PPh₃)]⁺ and excess of MeI gave [Rh₂I₆(MeSC₆H₄PPh₂-2)₂], with octahedral Rh^III linked by a double iodide bridge. Attack at sulfur also occurred in [Rh(SC₆H₄PPh₂-2)(CO)(PPh₃)] with I(CH₂)₃I and ICH₂CO₂H to give [Rh(2-Ph₂PC₆H₄SCH₂CH₂CH₂)(CO)(PPh₃)] and [RhI₂(2-Ph₂PC₆H₄SCH₂CO₂)(PPh₃)] respectively. The complex [RhI₃(CO)(PPh₃)₂] was a by-product and shown by a crystal structure to have a pseudo-octahedral structure with trans-PPh₃ ligands.