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Heterobimetallic Cr−Mn Complexes of Fused Arenes: Chromium-Templated Benzannulation of a Cymanthrene-Type Metal Carbene and Haptotropic Metal Migration along a Dibenzo[c,e]indene Platform

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posted on 25.05.2009, 00:00 by Julien Dubarle Offner, Roland Fröhlich, Olga Kataeva, Françoise Rose-Munch, Eric Rose, Karl Heinz Dötz
The chromium-templated benzannulation of the chromium cymanthrene-type carbene 3 with 3-hexyne affords the heterobimetallic chromium−manganese hydroquinoid dibenzo[c,e]indene complexes anti-4 and syn-5, in which the chromium entities are coordinated regioselectively to the hydroquinoid ring. Both diastereomers undergo a thermoinduced haptotropic migration of the chromium moiety to give their haptotropomers anti-6 and syn-7 in comparable yields, independent of the relative configuration of both metal centers, while the manganese fragment remains coordinated to the cyclopentadienyl ring. The molecular structures of all heterobimetallic complex structures were established by X-ray analysis. A kinetic NMR study of the chromium migration revealed first-order kinetics for the anti complex 4, supporting the intramolecular nature of the metal rearrangement.