Reactivity of the zwitterionic ligand EtNHC(S)Ph2PNPPh2C(S)NEt towards [Ru3(CO)12]. Sulfur transfer and ligand fragmentation leading to the methideylamide [-N(Et)-CH(R)-] μ3-bridging moiety

Abstract

The reaction of EtNHC(S)Ph₂PNP⁺Ph₂C(S)N⁻Et (HEtSNS) with [Ru₃(CO)₁₂] has been carried out under two different experimental conditions: in the first case [Ru₃(CO)₁₂], previously turned into the labile intermediate [Ru₃(CO)₁₀(CH₃CN)₂], afforded, at room temperature in dichloromethane, the trinuclear clusters [Ru₃(CO)₁₁(CNEt)] (1), {Ru₃(CO)₉(μ-H)[(μ-S:κ-P)Ph₂PNPPh₂C(S)NEt]} (2), {Ru₃(CO)₉(μ-H)[(μ-S:κ-P)Ph₂PNP(S)Ph₂]} (3) and {Ru₃(CO)₁₀[(μ-κ²P)Ph₂PNHPPh₂]} (4). Ligand fragmentation occurs via loss of EtNC or EtNCS, without sulfur transfer to the cluster core. In the second case, [Ru₃(CO)₁₂] reacted with HEtSNS in toluene at 70 °C, giving the trinuclear clusters 4, {Ru₃(CO)₇(CNEt)(μ₃-S)[(μ₂-N:η¹-C:κ¹-P)Ph₂PNPPh₂C(H)NEt]} (5), {Ru₃(CO)₈)(μ₃-S)[(μ₂-N:η-C:κ-P)Ph₂PNPPh₂C(H)NEt]} (6) and {Ru₃(CO)₆(μ₃-CO)(μ₃-S)(EtNC)[(μ-κ²P) Ph₂PNHPPh₂]} (7). The last three compounds derive from ligand fragmentation and sulfur transfer to the metal cluster. All compounds were characterized by spectroscopy (NMR, IR) and the molecular structures of 2, 5 and 7 were determined by single-crystal X-ray diffraction. Cluster 2 preserves the original Ru₃ triangular core in which an edge is bridged by a hydride ligand and by the sulfur atom of the Ph₂PNPPh₂C(S)NEt ligand. Cluster 5 shows an open triangle of Ru atoms capped by a μ₃-sulfide and by the unprecedented methideylamide –N(Et)CH(R)–μ₃-bridging moiety of the Ph₂PNPPh₂C(H)NEt ligand. It formally derives from cluster 6 by substitution of ethyl isonitrile with one CO molecule. Finally, cluster 7 displays a Ru₃(μ₃-S)(μ₃-CO) trigonal bipyramidal core.