Core Conversion Reactions of the Cubane-Type Metal-Sulfido Clusters: Shape Shift, Contraction, and Expansion of the MM′Re₂S₄ Cubanes (M = Ir, Rh, Ru; M′ = Pt, Pd)

Treatment of incomplete cubane-type clusters [(Cp*M){Re(L)}2(μ3-S)(μ2-S)3] (M = Ir (1a), Rh (1b); Cp* = η5-C5Me5; L = S2C2(SiMe3)2) and [{(Pmb)Ru}{Re(L)}2(μ3-S)(μ2-S)3] (Pmb = η6-C6Me5H) with 1 equiv of [Pt(PPh3)3] gave tetranuclear tetra(sulfido) clusters having raft-type cores, [(Cp*M){Pt(PPh3)2}{Re(L)}2(μ3-S)4] (M = Ir (3a), Rh) and [{(Pmb)Ru}{Pt(PPh3)2}{Re(L)}2(μ3-S)4], which presents a sharp contrast to the reactions with [Pd(PPh3)4] reported previously, affording the cubane-type clusters [(Cp*M){Pd(PPh3)}{Re(L)}2(μ3-S)4] (M = Ir (2a), Rh) and [{(Pmb)Ru}{Pd(PPh3)}{Re(L)}2(μ3-S)4]. The reactions of 2a with diphosphines P2 resulted in the conversion of its cubane-type core into the analogous raft-type frameworks, forming [(Cp*Ir){Pd(P2)}{Re(L)}2(μ3-S)4] (P2 = cis-Ph2PCHCHPPh2 (6), Ph2PCH2CH2PPh2, Ph2PCH2CH2CH2PPh2). On the other hand, when 2 was allowed to react with Ph2PCH2PPh2 (dppm) as P2, the trinuclear tri(sulfido) cluster [(Cp*Ir){Re(L)}2(μ3-S)2(μ2-S)(μ2-dppm)] (9a) was obtained. Alternatively, this cluster 9a and its Rh analogue 9b were derived from the incomplete cubane-type clusters 1a and 1b by treatment with dppm. It has also been found that further treatment of the cubane-type cluster 2a with excess [Pd(PPh3)4] affords the heptanuclear tetra(sulfido) cluster [(Cp*Ir){Pd(PPh3)}4Re2(μ3-L)2(μ3-S)4] (10). The detailed structures have been determined by the X-ray analyses for 3a, 6, 9a, and 10.