Synthesis and Reactivity of Thiolate‐Bridged NiIIMI Heterodinuclear Complexes (M = Rh, Ir) with an S‐Bidentate NiP2S2 Metalloligand

Abstract

The mononuclear complex [Ni(meppp)] {H2meppp = meso‐1,3‐bis[(2‐mercaptoethyl)(phenyl)phosphino]propane} was used as an S‐bidentate NiP2S2 metalloligand to prepare a series of NiIIMI complexes with various neutral ligands, namely, [Ni(µ‐meppp)ML2]PF6 [M = Rh, L = 1/2cod (1a; cod = 1,5‐cycloocatadiene), CO (1b), XylNC (1c; Xyl = 2,6‐dimethylphenyl), P(OPh)3 (1d); M = Ir, L = 1/2cod (2a), CO (2b), XylNC (2c)]. The reactivities of 1 and 2 toward methyl iodide and tertiary hydrosilanes were examined. Complexes 1c, 2a, and 2b reacted with MeI to afford the oxidative addition products [Ni(µ‐meppp)M(L)2(Me)(I)]PF6 [M = Rh, L = XylNC (3c); M = Ir, L = 1/2cod (4a)] and [Ni(µ‐meppp)Ir(CO)(Me)(I)2] (5). In the reactions with hydrosilanes, only 2c exhibited an interesting reactivity to afford the NiII(µ‐H)IrIII silyl complexes [Ni(µ‐meppp)(µ‐H)Ir(XylNC)2(Si)]PF6 [Si = SiEt3 (6a), SiMe2Ph (6b), SiMePh2 (6c), SiPh3 (6d)]. The reaction proceeded via the intermediate isomers [Ni(meppp)(µ‐H)Ir(XylNC)2(Si)]PF6 (7); intermediate 7d (Si = SiPh3) was characterized and has an NiII(µ‐H)IrIII silyl structure with the hydrido ligand nesting in the reverse side of the Ni(µ‐S)2Ir pocket to that of 6d. These results demonstrated that the reactivities of the bis(thiolate)‐bridged NiIIMI heterodinuclear complexes can be tuned by changing the metal ions and ancillary ligands. In addition, the S‐bidentate NiP2S2 metalloligand [Ni(meppp)] plays an important role in the stabilization of the bridging hydrido ligand in both pockets of the NiII(µ‐H)IrIII core owing to the flexibility of the hinged Ni(µ‐SR)2Ir structure.