(η-Cycloheptatriene)- and (η-cycloheptatrienylium)-(η-cyclopentadienyl)manganese. Formation of cyclic triene complexes by photochemical displacement of three carbonyl groups from tricarbonyl-(η-cyclopentadienyl)manganese

Abstract

Cycloheptatrienes react photochemically with tricarbonyl(η-cyclopentadienyl)manganese or its derivatives to give neutral diamagnetic (η-cycloheptatriene)(η-cyclopentadienyl)manganese compounds via dicarbonyl(1–2-η-cycloheptatriene) intermediates. Trityl salts convert the cycloheptatriene derivatives into (η-cycloheptatrienylium)-(η-cyclopentadienyl) manganese salts which may be reduced back by lithium tetrahydridoaluminate. 7-Substituted cycloheptatrienes yield predominantly the exo-substituted complexes which resist such hydride abstraction but are convertible into other isomers by hydrogen migration on heating. (η-Cyclo-octatriene)- and (1–6-η-cyclo-octa-tetraene)-(η-cyclopentadienyl)manganese may be obtained similarly but are much less stable than their cycloheptatriene analogues.