Reaction of the Cationic Cluster [Os₃(μ-H)(CO)₁₀(μ-η¹:η²-CCCMe₂)]BF₄ with Triphenylphosphine. Formation and Transformations of the σ-Acetylide Cluster [Os₃(μ-H)(CO)₁₀(PPh₃)(σ-C⋮CCMe₂PPh₃)]BF₄ and Two Isomeric Clusters [Os₃(μ-H)(CO)₉(PPh₃)(μ-σ:η²-C⋮CCMe₂PPh₃)]BF₄

Abstract

The complex [Os3(μ-H)(CO)10(μ-η1:η2-CCCMe2)]BF4 (1) reacts with PPh3 at −78 °C to give isomeric phosphonium derivatives of the formula [Os3(μ-H)(CO)10(μ-σ:η2-C⋮CCMe2PPh3)]BF4 (2 and 3); the isomerization 2 → 3 takes place. The second PPh3 molecule attacks 3 at the metal atom, substituting a CO in the Os(CO)4 unit to form the cluster [Os3(μ-H)(CO)9(PPh3)(μ-σ:η2-C⋮CCMe2PPh3)]BF4 (4), which further transforms to the acetylide σ-complex [Os3(μ-H)(CO)10(PPh3)(σ-C⋮CCMe2PPh3)]BF4 (5). The latter decarbonylates in the temperature range 25−55 °C to yield the cluster [Os3(μ-H)(CO)9(PPh3)(μ-σ:η2-C⋮CCMe2PPh3)]BF4 (6), which is isomeric with 4. Complex 5 is considered to be an intermediate in the isomerization of the clusters [Os3(μ-H)(CO)9(PPh3)(μ-σ:η2-C⋮CCMe2PPh3)]BF4 (4, 6). Clusters 2−6 have been characterized by their 1H, 31P, and 13C NMR spectra, and X-ray structural analyses have been performed for complexes 5 and 6.