A molybdenum-centred (6 + 2)π addition of alkynes to cyclo-octatetraene and cycloheptatriene; structural evidence for an arrested 1,3-hydorgen shift
Abstract
Depending on the choice of the alkyne, reaction of [Mo(NCMe)(η2-RC2R′)2(η-C5H5 or η5-C9H7)][BF4] with cyclo-octatetraene or cycloheptatriene in MeCN affords either bicycolo[4.2.2]decatetraenes and bicyclo[4.2.1]nonatrienes or neutral complexes containing both η3-allyl and η4-1,3-diene ligands; X-ray crystallographic studies show that protonation of one of these neutral complexes affords a cation which models the initial stage of a 1,3-hydrogen shift process.