Alkynyl-Dicobalt Hexacarbonyl Complexes of Menthyl Cations: Isolobal Substitution of [Co(CO)3]+ by Fe(CO)3 as a Structural Model

The addition of phenylethynyl- or trimethylsilylethynyl-lithium to (−)-menthone yields primarily the alkynyl-menthols in which the alkynyl substituent occupies an equatorial site. The stereochemistry of both the axial and equatorial isomers was established unequivocally by an X-ray crystallographic study of their dicobalt hexacarbonyl derivatives. Treatment of these alkynol-Co2(CO)6 complexes with iron pentacarbonyl yields neutral iron−cobalt …