Alkyl, alkynyl, and olefin complexes of bis(π-cyclopentadienyl)-molybdenum or -tungsten : a reversible metal-to-ring transfer of an ethyl group

Abstract

The compounds [(π-C₅H₅)₂M(CH₂ CHR)H]⁺PF₆ ^– where M = Mo, W, R = H; M = W, R = Me, (π-C₅H₅)₂M(C₂H₄), (π-C₅H₅)₂MoEtCl, (π-C₅H₅)₂MMe₂, (π-C₅H₅)₂M(CCPh)₂ have been prepared and studied. The reversible reaction [(π-C₅H₅)₂M(CH₂ CHR)H]⁺→ H⁺+(π-C₅H₅)₂MCH₂ CHR has been demonstrated. With tertiary phosphines the ethyl complex gives the endo-ethyl derivatives (π-C₅H₅)(1 -endo-EtC₅H₅)MoPR₃Cl. The complex (π-C₅H₅)(1 -endo-EtC₅H₅)MoPClMe₂Ph reacts with thallium tetrafluoroborate to give the ethyl cation [(π-C₅H₅)₂MoPR₃Et]⁺BF₄ ^–. This and related cations may also be prepared from the hydridoethylene cations and tertiary phosphine. Mechanisms for these reactions are discussed.