Chemistry of the tricobalt carbon cluster. Part XI. Bicyclo[2.2.1]-hepta-2,5-diene, cyclohexa-1,3-diene, and cyclopentadienyl derivatives

Abstract

The reactivity of dienes towards methylidynetricobalt enneacarbonyls is discussed; in particular the preparation and physicochemical properties of [YCCo₃(CO)₇(diene)]{diene = bicyclo[2.2.1]hepta-2,5-diene (bhd) and cyclohexa-1,3-diene (chd)} and the η-cyclopentadienyl derivatives [YCCO₃(CO)₄(cp)₂](Y = alkyl, aryl, or F) are described. The ¹H n.m.r. spectra show that the bhd derivatives are non-rigid in solution. Stereospecific dimerization of bhd is not observed during formation or thermal decomposition of its complexes. Electrophiles attack the unique bridging carbonyl group, but not the dienyl ring, of the cp derivatives.