Nickel compounds transition metal electronic structure

Asymmetric Synthesis by Homogeneous Catalysis Cyanide Complexes of the Transition Metals Electronic Structure of Organometallic Compounds Hydride Complexes of the Transition Metals Mechanisms of Reaction of Organometallic Complexes Nickel Organometallic Chemistry P-donor Ligands. 

What are the most common valence states of the transition metals shown in their compounds Give the electronic structures of iron, cobalt, and nickel in these valence states. 

In a sense the tr-allyl compounds of the transition metals can be regarded as the simplest of the sandwich molecules. Bis(jr-allyl)nickel, the best known of such complexes, has been shown by x-ray crystallography (104,105) to have a staggered arrangement of tr-allyl moieties and hence a C2h molecular conformation. The electronic structure of the ground state of bis(jr-allyl)nickel has been investigated by both semiempirical (47) and ab initio (274,275) methods, and a semiempirical computation has been performed on bis(7r-allyl)palladium (47). 

Ferrocene is only one of a large number of compounds of transition metals with the cyclopentadienyl anion. Other metals that form sandwich-type structures similar to ferrocene include nickel, titanium, cobalt, ruthenium, zirconium, and osmium. The stability of metallocenes varies greatly with the metal and its oxidation state ferrocene, ruthenocene, and osmocene are particularly stable because in each the metal achieves the electronic configuration of an inert gas. Almost the ultimate in resistance to oxidative attack is reached in (C5H5)2Co , cobalticinium ion, which can be recovered from boiling aqua regia (a mixture of concentrated nitric and hydrochloric acids named for its ability to dissolve platinum and gold). In cobalticinium ion, the metal has the 18 outer-shell electrons characteristic of krypton. 

The A2 metals and the elements of the earlier B subgroups (Bj metals) form the electron compounds already discussed. With the metals of the later B subgroups the A2 metals, like the Aj, tend to form intermetallic phases more akin to simple homopolar compounds, with structures quite different from those of the pure metals. The nickel arsenide structure has, like typical alloys, the property of taking up in solid solution a considerable excess of the transition metal. From Table 29.12... 

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