Heterobimetallic Cubane-like Cluster Compounds Prepared as the Homologous Series [(η⁵-Cp‘)₃Mo₃S₄M‘(PPh₃)]⁺(M‘ = Ni, Pd, Pt). Crystal Structures Show that Platinum Is Smaller than Palladium

Abstract

Exchange of the aqua ligands in [(H2O)9Mo3S4][pts]4·9H2O for Cp‘ ligands (Cp‘ = methylcyclopentadienyl; pts = p-toluenesulfonate) yielded the novel cluster salt [(η5-Cp‘)3Mo3S4][pts] ([1][pts]). Reactions of [1][pts] in the presence of triphenylphosphane with [Ni(cod)2] (cod = 1,5-cyclooctadiene) or [Pd2(dba)3] (dba = dibenzylidenacetone) afforded the heterobimetallic cubane-like cluster compounds [(η5-Cp‘)3Mo3S4M‘(PPh3)][pts] ([2][pts]: M‘ = Ni; [3][pts]: M‘ = Pd). By reaction of [1][pts] with [Pt(nor)3] (nor = 2-norbornene) at ambient temperature [(η5-Cp‘)3Mo3S4Pt(nor)][pts] ([4][pts]) was isolated and further converted to [(η5-Cp‘)3Mo3S4Pt(PPh3)][pts] ([5][pts]) at 60 °C. A 31P{1H} NMR spectroscopic characterization of [5][pts] revealed a coupling constant 1J(PtP) of 6656 Hz, whose size supports the view that the platinum atom is Pt0- rather than PtII-like. Single-crystal X-ray studies of the complete homologous series [2][pts], [3][pts], and [5][pts] demonstrated that the cluster cations are isostructural with M‘−P bond lengths in the order Ni < Pt < Pd.