Hydrometalation of PCBut and Activation of the P-C Bond by a Tetrairidium Carbonyl Cluster:? Solution Characterization of [Ir4Pt(dppe)(CO)n{µ-PC(H)But}(µ-PPh2)] (n = 10 and 9) and Crystal and Molecular Structures of the Phosphinidine Complex [HIr4Pt(dppe)(µ-CO)(CO)7(µ-PCH2But)(µ-PPh2)] and of the Partially Encapsulated Phosphide Compound [Ir4Pt(dppe)(µ-CO)(CO)8(µ5-P)(µ-PPh2)]

Reaction of [HIr4(CO)10(µ-PPh2)], 1, with [Pt(dppe)(?2-PCBut)] yields four Ir4Pt clusters [Ir4Pt(dppe)(CO)n{µ-PC(H)But}(µ-PPh2)] (n = 10, 2, and 9, 3), [HIr4Pt(dppe)(µ-CO)(CO)7(µ-PCH2But)(µ-PPh2)], 4, and [Ir4Pt(dppe)(µ-CO)(CO)8(µ5-P)(µ-PPh2)], 5. These compounds contain fragments arising from hydrometalation and cleavage of the P-C triple bond of the phosphaalkyne. The structures of compounds 2 and 3, isolated as a mixture, were proposed on the basis of multinuclear NMR and mass spectrometry. To our knowledge these are the first examples of clusters containing a phosphido fragment {µ-PC(H)But} originating from hydrometalation of the phosphaalkyne. Compounds 4 and 5 were characterized in solution by multinuclear NMR spectroscopy, and their solid-state structures were determined by X-ray analyses. A remarkably low 1JP-Pt coupling constant in the Pt(dppe) fragment of the former square-based pyramidal compound is discussed.