Some Recent Problems on the Field of Organometallic Compounds of Transition Metals

Abstract

Since the discovery of ferrocene by Pauson and Miller in 1951 and the discovery of the coordinated polymerization catalysts by Ziegler and Natta, the chemistry of organic derivatives of transition metals has developed rapidly and is now extending its range. There have been extensive research activities concerning the syntheses, structure and the nature of bonding of various organotransition metal compounds including, for example, metal carbonyls; r-complexes having olefins, di-olefins, acetylenes and aromatic nuclei as ligands; and generally unstable cr-bonded alkyl and aryl transition metals, and many others. The investigation of the reactivities of the organic part attached to the transition metal and the investigation of the catalytic activities of this sort of complexes have also been made.The author and his coworkers have been continuing researches on thisorganometallic field since several years. He wishes to mention about some of the recent results of their work. Interaction of Cumulene Systems with Transition MetalsMuch interest has been focused in the recent years on the field of organometallic n-complexes of mono-and polyolefins. However, interaction of cumulene systems with organic derivatives of transition metals has not been investigated extensively. It is interesting to see whether cumulene type double bonds in a straight chain form stable r-complexes or not. Investigation of this interaction would be also important in connection with the catalytic action of metal carbonyls in the known polymerization and carbonylation of allenic compounds.At the outset, we have found that the cumulene systems yield stable r-cornplexes with iron. In the course of our study, allene has been reported by Green and Ariyaratnel to be in a .rr-complexed form in a cation: [C5H5Fe(C0)2(C3H4)]+. In this cation, the iron is probably coordinated through one double bond of allene as in ordinary olefin complexes.Tetraphenylallene-and tetraphenylbutatriene-iron carbonyl c~r n p l e x e s .~.~ We have found that reaction of iron pentacarbonyl with tetraphenylallene or tetraphenylbutatriene gave red crystals according to Equation 1 or 2, respectively.The products, I and 11, were quite stable in air and found to be monomeric and diamagnetic. The pyrolysis and the substitution reaction of these complexes showed that the tetraphenylallene and tetraphenylbutatriene retained its skeletal structure on the v-complex formation.The bondings and structures of I and I1 are interesting ones to discuss. The presence of three carbonyl groups in I prefers the idea that the two double bonds 98