Conversion of alk-1-ynes into alkyne, alkynyl, alkylidyne and alkylidene complexes of molybdenum and tungsten

Abstract

A variety of alkyne, alkynyl, alkylidyne and alkylidene complexes has been obtained from the alkynes RCCH (R = Ph, CO₂Me or CO₂Et). The reactions of these alkynes with trans-[M(N₂)₂(dppe)₂](M = Mo or W, dppe = Ph₂PCH₂CH₂PPh₂) and trans-[Mo(N₂)₂(depe)₂](depe = Et₂PCH₂CH₂PEt₂) give the alkyne complex [Mo(HCCPh)₂(dppe)₂]A, the alkynyl complexes [MH₂(CCR)₂(L–L)₂]B(M = Mo or W; R = Ph, CO₂Me or CO₂Et; L–L = dppe; M = Mo, R = Ph, L–L = depe) and trans-[M(CCR)₂(dppe)₂]C(M = Mo or W; R = Ph, CO₂Me or CO₂Et) depending on the conditions. The redox properties and interconversion of B and C are described and the X-ray crystal structures of B(M = W, R = CO₂Me, L–L = dppe) and C(M = Mo, R = Ph) are presented. The complexes [WH₂(CCR)₂(dppe)₂]B(R = CO₂Me or Ph) react with HBF₄ to give [WF(CCH₂CO₂Me)(dppe)₂]D and [WF(CHCH₂Ph)(dppe)₂]BF₄E respectively. The polymerisation of RCCH (R = H or Ph) at these metal centres is also discussed.