Alkyne addition and coupling reactions of [W2(η-C5H4R)2X4](X = Cl or Br)

Abstract

The WW triply bonded dimers [W₂(η-C₅H₄Prⁱ)₂X₄](X = Cl or Br) react with alkynes C₂R₂ to afford the dimetallatetrahedrane complexes [W₂(η-C₅H₄Prⁱ)₂X₄(µ-C₂R₂)](X = Cl, R = Et or SiMe₃; X = Br, R = Me, Et or Ph†) or poorly defined polynuclear complexes [{W(η-C₅H₄Prⁱ)Br₂(CR)}_3x](R = Me or Et) depending upon the reaction conditions. Treatment of [W₂(η-C₅H₄R)₂X₄](X = Cl, R = Prⁱ or Me; X = Br, R = Prⁱ) with an excess of but-2-yne affords the corresponding flyover bridge complexes [W₂(η-C₅H₄R)₂X₄(µ-C₄Me₄)]; treatment of [W₂(η-C₅H₄Prⁱ)₂Cl₄] with pent-2-yne gives a mixture of the isomers [W₂(η-C₅H₄Prⁱ)₂Cl₄{µ-(2,3)-C₄Et₂Me₂}] and [W₂(η-C₅H₄Prⁱ)₂Cl₄{µ-(1,4)-C₄Et₂Me₂}]. The planar bridging C₄Me₄ moiety in the crystallographically characterised trans-[W₂(η-C₅H₄Me)₂Cl₄(µ-C₄Me₄)] is found to be perpendicular to the W–W bond and bound to each metal atom in a tetrahapto fashion. Treatment of [W₂(η-C₅H₄Prⁱ)₂Cl₄(µ-C₂Et₂)] or [{W(η-C₅H₄Prⁱ)Br₂(CEt)}_3x] with an excess of but-2-yne affords the mixed-alkyne flyover bridge complexes [W₂(η-C₅H₄Prⁱ)₂X₄{µ-(1,2)-C₄Et₂Me₂}](X = Cl or Br). The complexes [W₂(η-C₅H₄R)₂Cl₄(µ-C₄Me₄)](R = Me or Prⁱ) are readily hydrolysed in wet acetone to form the corresponding monooxo complexes [W₂(η-C₅H₄R)₂Cl₂O(µ-C₄Me₄)]†. Complexes labelled † have been crystallographically characterised.