Triple‐Decker Transition‐Metal Complexes (C n H n )M(B 6 C)M(C n H n ) (M = Fe, Ru, Mn, Re; n = 5, 6) Containing Planar Hexacoordinate Carbon Atoms

A density functional theory investigation is presented in this work on a new class of triple‐decker complexes (C n H n )M(B 6 X)M(C n H n ) (M = Fe, Ru, Mn, Re; X = B, C, N; n = 5, 6) containing almost perfect planar hexacoordinate carbon atoms and other planar hexacoordinate nonmetals at the centers of the B 6 X middle‐deckers. Effective d–π coordination interactions between the partially filled 3d orbitals of the transition‐metal center and the delocalized π orbitals of the three parallel ligands maintain the stabilities of these triple‐decker complexes. The strong IR absorption peaks of (C n H n )M(B 6 X)M(C n H n ) complexes mainly originate from the in‐plane and off‐plane vibrations of their planar hexacoordinate nonmetal centers. The results obtained in this work provide a possible new approach to characterize planar hexacoordinate carbon‐containing systems in future experiments and expand the structural domain of transition‐metal complexes by introducing inorganic B 6 X middle‐deckers into traditional sandwich‐type structures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)