Platinum(0) complexes of cyclic alkynes and allenes from base-induced dehydrohalogenation of bromocycloalkenes

Article abstract of DOI:10.1021/om00028a079

Treatment of 1-bromocycloheptene or a mixture of 1-, 2-, and 3-bromocycloheptatrienes with t-BuOK in the presence of (Ph₃P)₃Pt has been confirmed to lead to predominant formation of (Ph₃P)₂Pt π-complexes of the corresponding cyclic allenes. In contrast, reaction of these same halides and 1-bromocyclohexene with LDA in THF in the presence of (Ph₃P)₃Pt leads exclusively to (Ph₃P)₂Pt complexes of the corresponding cyclic akynes. These reactions provide the first metal complexes of cycloheptadienynes and a convenient alternate method for the preparation of Pt(O) complexes of cyclohexyne and cycloheptyne. The mechanism of formation of the complex of 1,2-cycloheptadiene is briefly discussed and an X-ray crystal structure of one of the cyclheptadienyne complexes is reported.