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.