Rhodium and iridium complexes with thiolate and tertiary phosphine ligands. 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 RhIII. 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 RhIII 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.