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

Exchange of the aqua ligands in [(H 2 O) 9 Mo 3 S 4 ][pts] 4 ·9H 2 O for Cp‘ ligands (Cp‘ = methylcyclopentadienyl; pts = p -toluenesulfonate) yielded the novel cluster salt [(η 5 -Cp‘) 3 Mo 3 S 4 ][pts] ([ 1 ][pts]). Reactions of [ 1 ][pts] in the presence of triphenylphosphane with [Ni(cod) 2 ] (cod = 1,5-cyclooctadiene) or [Pd 2 (dba) 3 ] (dba = dibenzylidenacetone) afforded the heterobimetallic cubane-like cluster compounds [(η 5 -Cp‘) 3 Mo 3 S 4 M‘(PPh 3 )][pts] ([ 2 ][pts]: M‘ = Ni; [ 3 ][pts]: M‘ = Pd). By reaction of [ 1 ][pts] with [Pt(nor) 3 ] (nor = 2-norbornene) at ambient temperature [(η 5 -Cp‘) 3 Mo 3 S 4 Pt(nor)][pts] ([ 4 ][pts]) was isolated and further converted to [(η 5 -Cp‘) 3 Mo 3 S 4 Pt(PPh 3 )][pts] ([ 5 ][pts]) at 60 °C. A 31 P{ 1 H} NMR spectroscopic characterization of [ 5 ][pts] revealed a coupling constant 1 J (PtP) of 6656 Hz, whose size supports the view that the platinum atom is Pt 0 - rather than Pt II -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.