Insertion reactions of hydridonitrosyltetrakis(trimethylphosphine) tungsten(0)

Abstract

[W(H)(NO)(PMe₃)₄] (1) was prepared by the reaction of [W(Cl)(NO)(PMe₃)₄] with NaBH₄ in the presence of PMe₃. The insertion of acetophenone, benzophenone and acetone into the W–H bond of 1 afforded the corresponding alkoxide complexes [W(NO)(PMe₃)₄(OCHR¹R²)] (R¹ = R² = Me (2); R¹ = Me, R² = Ph (3); R¹ = R² = Ph (4)), which were however thermally unstable. Insertion of CO₂ into the W–H bond of 1 yields the formato-O complex trans-W(NO)(OCHO)(PMe₃)₄ (5). Reaction of trans-W(NO)(H)(PMe₃)₄ with CO led to the formation of mer-W(CO)(NO)(H)(PMe₃)₃ (6) and not the formyl complex W(NO)(CHO)(PMe₃)₄. Insertion of Fe(CO)₅, Re₂(CO)₁₀ and Mn₂(CO)₁₀ into trans-W(NO)(H)(PMe₃)₄ resulted in the formation of trans-W(NO)(PMe₃)₄(µ-OCH)Fe(CO)₄ (7), trans-W(NO)(PMe₃)₄(µ-OCH)Re₂(CO)₉ (8) and trans-W(NO)(PMe₃)₄(µ-OCH)Mn₂(CO)₉ (9). For Re₂(CO)₁₀, an equilibrium was established and the thermodynamic data of the equilibrium reaction have been determined by a variable-temperature NMR experiments (K_298K = 104 L mol⁻¹, ΔH = −37 kJ mol⁻¹, ΔS = −86 J K⁻¹ mol⁻¹). Both compounds 7 and 8 were separated in analytically pure form. Complex 9 decomposed slowly into some yet unidentified compounds at room temperature. Insertion of imines into the W–H bond of 1 was also additionally studied. For the reactions of the imines PhCHNPh, Ph(Me)CNPh, C₆H₅CHNCH₂C₆H₅, and (C₆H₅)₂CNH with 1 only decomposition products were observed. However, the insertion of C₁₀H₇NCHC₆H₅ into the W–H bond of 1 led to loss of one PMe₃ ligand and at the same time a strong agostic interaction (C17–H⋯W), which was followed by an oxidative addition of the C–H bond to the tungsten center giving the complex [W(NO)(H)(PMe₃)₃(C₁₀H₆NCH₂Ph)] (10). The structures of compounds 1, 4, 7, 8 and 10 were studied by single-crystal X-ray diffraction.