The reactions of the anions [Cp2(CO)4Mo2(μ-PRR′)]− (R, R′ = H, Ph) towards chloroarsines and chlorophosphines; synthesis of complexes containing both bridging phosphido and arsenido groups

Abstract

Deprotonation of the complexes [Cp₂(CO)₄Mo₂(μ-PR¹R²)(μ-H)] (R¹ and R² = H or Ph; Cp = cyclopentadienyl) in THF yields the related anions [Cp₂(CO)₄Mo₂(μ-PR¹R²)]⁻. The reactivity of these anions towards Ph₂PCl, (EtO)₂PCl, Ph₂AsCl and Me₂AsCl has been investigated. The outcome of the reactions with chlorophosphines depends on the nature of the substituents on the bridging phosphido ligand. Thus reaction of [Cp₂(CO)₄Mo₂(μ-PH₂)]⁻ with Ph₂PCl yields [Cp₂(CO)₄Mo₂{μ-P(H)PPh₂}(μ-H)], whereas the analogous reaction with [Cp₂(CO)₄Mo₂(μ-PPhR)]⁻ yields [Cp₂(CO)_xMo₂(μ-PPh₂)(μ-PPhR)] (R = H, x = 4; R = Ph, x = 2). Thermolysis of [Cp₂(CO)₄Mo₂(μ-PPhH)(μ-PPh₂)] in toluene yields [Cp₂(CO)₂Mo₂(μ-PPhH)(μ-PPh₂)] and [Cp₂(CO)(O)Mo₂(μ-PPhH)(μ-PPh₂)]. In contrast, the reaction of [Cp₂(CO)₄Mo₂(μ-PR¹R²)]⁻ with chloroarsines is not dependent on the nature of the R groups either on the phosphorus or arsenic atoms, yielding [Cp₂(CO)₄Mo₂(μ-PR¹R²)(μ-AsR³₂)] in all cases. These complexes are the first example of transition metal compounds containing both a bridging phosphido and a bridging arsenido group. The crystal structures of [Cp₂(CO)₄Mo₂{μ-P(H)PPh₂}(μ-H)], [Cp₂(CO)₄Mo₂(μ-PPhH){μ-P(OEt)₂}], and [Cp₂(CO)₄)Mo₂(μ-PH₂)(μ-AsMe₂)] are reported.