Reactions of transition-metal vapours with cycloheptatriene and cyclo-octatetraene

Abstract

The co-ordination of cycloheptatriene in reactions with transition-metal atoms in the condensed phase at low temperature is accompanied by extensive hydrogen migration. Thus, condensation of C₇H₈ with the vapours of Ti, V, Cr, Fe, and Co affords [Ti(η-C₇H₇)(η⁵-C₇H₉)], V(C₁₄H₁₆), [Cr(η-C₇H₇)(η⁴-C₇H₁₀)], [Fe(η⁵-C₇H₇)(η⁵-C₇H₉)] or FeC₁₄H₁₈, and CoC₁₄H_n(n= 15, 17, or 19) respectively. No organometallic products have been isolated from vapours of Mn, Ni or Pd. Condensation of a PF₃–C₇H₈ mixture with vapours of Cr or Co affords [Cr(C₇H₈)(PF₃)₃] or [Co(C₇H₇)(PF₃)₃] respectively. Condensation of C₈H₈ with vapours of Ti, Fe, and Co gives intractable polymers, but with chromium vapour [Cr₂(C₈H₈)₃] is obtained. The use of metal atoms in the preparation of olefinic metal complexes is compared with conventional reductive methods.