Synthesis, Structures, and Properties of Group 9− and Group 10−Group 6 Heterodinuclear Nitrosyl Complexes

The reaction of the group 9 bis(hydrosulfido) complexes [Cp*M(SH)2(PMe3)] (M = Rh, Ir; Cp* = η5-C5Me5) with the group 6 nitrosyl complexes [Cp*M′Cl2(NO)] (M′ = Mo, W) in the presence of NEt3 affords a series of bis(sulfido)-bridged early−late heterobimetallic (ELHB) complexes [Cp*M(PMe3)(μ-S)2M′(NO)Cp*] (2a, M = Rh, M′ = Mo; 2b, M = Rh, M′ = W; 3a, M = Ir, M′ = Mo; 3b, M = Ir, M′ = W). Similar reactions of the group 10 bis(hydrosulfido) complexes [M(SH)2(dppe)] (M = Pd, Pt; dppe = Ph2P(CH2)2PPh2), [Pt(SH)2(dppp)] (dppp = Ph2P(CH2)3PPh2), and [M(SH)2(dpmb)] (dpmb = o-C6H4(CH2PPh2)2) give the group 10−group 6 ELHB complexes [(dppe)M(μ-S)2M′(NO)Cp*] (M = Pd, Pt; M′ = Mo, W), [(dppp)Pt(μ-S)2M′(NO)Cp*] (6a, M′ = Mo; 6b, M′ = W), and [(dpmb)M(μ-S)2M′(NO)Cp*] (M = Pd, Pt; M′ = Mo, W), respectively. Cyclic voltammetric measurements reveal that these ELHB complexes undergo reversible one-electron oxidation at the group 6 metal center, which is consistent with isolation of the single-electron oxidation products [Cp*M(PMe3)(μ-S)2M′(NO)Cp*][PF6] (M = Rh, Ir; M′ = Mo, W). Upon treatment of 2b and 3b with ROTf (R = Me, Et; OTf = OSO2CF3), the O atom of the terminal nitrosyl ligand is readily alkylated to form the alkoxyimido complexes such as [Cp*Rh(PMe3)(μ-S)2W(NOMe)Cp*][OTf]. In contrast, methylation of the Rh−, Ir−, and Pt−Mo complexes 2a, 3a, and 6a results in S-methylation, giving the methanethiolato complexes [Cp*M(PMe3)(μ-SMe)(μ-S)Mo(NO)Cp*][BPh4] (M = Rh, Ir) and [(dppp)Pt(μ-SMe)(μ-S)Mo(NO)Cp*][OTf], respectively. The Pt−W complex 6b undergoes either S- or O-methylation to form a mixture of [(dppp)Pt(μ-SMe)(μ-S)W(NO)Cp*][OTf] and [(dppp)Pt(μ-S)2W(NOMe)Cp*][OTf]. These observations indicate that O-alkylation and one-electron oxidation of the dinuclear nitrosyl complexes are facilitated by a common effect, i.e., donation of electrons from the group 9 or 10 metal center, where the group 9 metals behave as the more effective electron donor.