Heteronuclear Bonds between Transition Metals

Photolysis of mixtures of [ M(CO)3Cp 2l (M = Mo or W) and [ 02(00)3] or [ Fe(CO)2Cp 2] gives heteronuclear species such as [Cp(CO)aMoCo(CO)4], photoexcitation of which causes metal-metal bond cleavage.  

Raverdino, S. Aitne, L. Milone, and E. Sappa, Inorg. Chim. Acta., 1978,30,9. 

Heteronuclear Bonds between Transition Metals.— Table 3 contains details of X-r y structural studies carried out this year on heteronuclear metal-metal-bonded compounds and follows the same format as in last year s Report. 

Davidson, L. Manojlovic-Muir, K. W. Muir, and A. Kieth, J. Chem. Soc., Chem. Commun., 1980, 749. 

Marinetti, E. Sappa, A. Tiripicchio, and M. Tiripicchio Camellini,/. Organomet. Chem., 1980, 197, 335. 

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Robert D.A., Geoffroy G.L. Compounds with heteronuclear bonds between transition metals. In Comprehensive Organometallic Chemistry, Wilkinson G., Stone F.G.A., Abel E.W. Eds., Perga-mon, Oxford, UK, 1982 Vol. 6, pp. 821-877 and references therein Rogovin, M., Neumann, R. Silicate xerogels containing cobalt as heterogeneous catalysts for the side-chain oxidation of alkyl aromatic compounds with tert-butyl hydroperoxide. J. Mol. Catal. A Chem. 1999 138 315-318... 

A rational, and general, approach to complexes containing heteronuclear bonds between Ni or Pt and a second transition metal is by addition of a complex containing a metal-carbon or metal-metal multiple bond to a coordinatively unsaturated Ni(0) or Pt(0) species, thus producing a di- or tri-metallacyclopropane or -propene. These reactions proceed in good yield under mild conditions, and the products are quite predictable. Reactions (l)-(n) give some examples ... 

Silicon-transition metal chemistry is a relatively new area. The work of Hein and his associates (1941) on Sn—Co derivatives established the possibility of forming bonds between a Group IVB metal and a transition element 139), but it was another fifteen years before CpFe(CO)2SiMej 203), the first of many silyl derivatives, was synthesized. The interest in these compounds derives from (1) comparison with the corresponding alkyl- and Ge-, Sn-, and Pb- transition metal (M) complexes, including the role of ir-back-bonding from filled d orbitals of M into empty d orbitals on Si (or other Group IVB metal), and (2) expectation of useful catalytic properties from such heteronuclear derivatives. 

The subject of heteronuclear cluster compounds of the transition metals remains an active area of research interest, and was reviewed in the early 1980s by Geoffroy el al. (1,2). Clusters with novel architectures, exemplified by the star clusters of Stone and co-workers (5), continue to be synthesized. Whereas there is undoubtedly strong academic interest in the structure, bonding, and chemical reactivity of heteronuclear clusters in their own right, additional impetus to this field is given by the important relationship between heteronuclear clusters and bimetallic alloy catalysts. This relationship was the subject of a published symposium (4). 

The term Zintl phase is applied to solids formed between either an alkali- or alkaline-earth metal and a main group p-block element from group 14, 15, or 16 in the periodic table. These phases are characterized by a network of homonuclear or heteronuclear polyatomic clusters (the Zintl ions), which carry a net negative charge, and that are neutralized by cations. Broader definitions of the Zintl phase are sometimes used. Group 13 elements have been included with the Zintl anions and an electropositive rare-earth element or transition element with a filled d shell (e.g. Cu) or empty d shell (e.g. Ti) has replaced the alkali- or alkaline-earth element in some reports. Although the bonding between the Zintl ions and the cations in the Zintl phases is markedly polar, by our earlier definition those compounds formed between the alkali- or alkaline-earth metals with the heavier anions (i.e. Sn, Pb, Bi) can be considered intermetallic phases. 

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