Cluster compounds containing a linear carbon chain derived from polyynediyl and polyynyl complexes, Fp*-(CC)n-X [X = Fp*, H; Fp* = Fe(η5-C5Me5)(CO)2]

Our studies on polynuclear complexes containing a one-dimensional carbon chain derived from polyynyl [Fp*-(CdropC)(n)-H 1(n)] and polyynediyl complexes [Fp*-(CdropC)(n)-Fp*2(n) ; Fp* = FeCp*(CO)(2)] are reviewed. Reaction of 1(n) and 2(n) with di- and trinuclear metal carbonyl species produces polycarbon-polymetal systems with a variety of coordination structures including eta(2)-alkyne, mu-acetylide, mu-cumulenylidene, mu(3)-alkylidyne and mu(3)-propargylidene structures. In addition to the cluster formation reactions as usually observed for acetylide and alkyne cluster compounds, the unique cluster transformations such as valence isomerization of the conjugated carbon chain, metal migration along the carbon rod and CdropC cleavage reaction are observed. These transformations are realized by the flexible electronic structure of the pi-conjugated carbon chain (polyynyl<---->cumulenic), which fits the electronic structure of the attached metal fragments. (C) 2002 Elsevier Science B.V. All rights reserved.