Tri- and tetra-nuclear cluster compounds of platinum(0), which contain tertiary phosphines and carbon monoxide

Abstract

New trinuclear cluster compounds [Pt₃(CO)₃L₄](L = PPh₃, PPh₂Me, and PPh₂Et) and [Pt₃(CO)₃L₃](L = PPh₂PhCH₂) are obtained by decomposition of the complexes [Pt(CO)₂L₂]; however their preparation is generally more convenient without the isolation of [Pt(CO)₂L₂], from an alkali tetrachloroplatinate, a phosphine, and carbon monoxide. Further rearrangement and absorption of carbon monoxide by the trinuclear cluster compounds give the tetranuclear species [Pt₄(CO)₅L₄] and [Pt₄(CO)₅L₃]. The [Pt₄(CO)₅L₄] species have been obtained in two isomeric forms, in the first the carbonyl groups are both terminal and bridging (L = PPh₂PhCH₂ or AsPh₃), and in the second only bridging (L = PPh₃ or PPhMe₂). Some unusual properties of these cluster compounds, such as lability and associated variability in the co-ordination numbers, are noted.