Reaction of ethynediyl, butadiynediyl and ethynyl iron complexes, (η5-C5R5)(CO)2Fe-(CC)n-X [X = Fe(η5-C5R5)(CO)2, H;: R5 = Me5, Me4Et; n = 1, 2], with Fe2(CO)9 leading to polynuclear C2 and C4 complexes

Polynuclear C-2 and C-4 cluster compounds are prepared by treatment of the iron complexes containing mu-C-2 (ethynediyl), mu-C-4 (butadiynediyl) and C2H (ethynyl) ligands with Fe-2(CO)(9). The ethynediyl complex (eta(5)-C5Me5)(CO)(2)Fe-CC=C-Fe(eta(5)-C5Me5) (CO)(2) gives the tetrairon dicarbide complex, (mu(4)-C-2)Fe-4(eta(5)-C5Me5)(2)(CO)9, which shows dynamic behavior by way of reversible scission and recombination of the Fe-Fe bonds. Reaction of the butadiynediyl complex, (eta(5)-C5Me5)(CO)(2)Fe-C=C-C=C-Fe(eta(5)-C5Me5)CO2, affords tetranuclear nona- and decacarbonyl cluster compounds depending on the reaction conditions. The nonacarbonyl cluster compound formed exclusively in benzene adopts a normal acetylide cluster type structure and one of the two C=C functional groups remains unreacted, but the decacarbonyl cluster isolated as a minor product from the reaction in THF consists of a mu(3)-eta(3)-propargylidene diiron core and a ketene functional group, which should be formed by addition of an Fe-2 unit followed by migration of CO to the terminal carbon atom of the C-4 bridge. In contrast, reactions of polyynyl complexes are found to be less selective. Reaction of (eta(5)-C5Me5)(CO)(2)Fe-C=C-H results in the formation of a low yield mixture of products, of which the p-quinone complex, c-2,5-[Fe(eta(5)-C5Me5)(CO)(2)](2)-C6H2O2, has been isolated and characterized by X-ray crystallography, though (eta(5)-C5Me5)(CO)(2)Fe-C=C-C=C-H merely gives an intractable reaction mixture. (C) 1998 Elsevier Science S.A. All rights reserved.