Metal compounds with complexes containing

REACTIONS OF LOW VALENT METAL COMPOUNDS WITH COMPLEXES CONTAINING METAL—METAL MULTIPLE BONDS. 

It is also relevant to record that several iron-carbonyl complexes with bridging, and in one case terminal, aryltellurol ligands have been prepared by reaction of Fe(CO)5, Fe(CO)12 or [ji-CpFe(CO)2]2 with diaryl ditellurides and which, together with complexes containing other transition metal carbonyls, e.g, ruthenium, osmium and manganese, provide a substantial number of interesting compounds.2... 

The chemistry of technetium is quite complex especially because of its numerous oxidation states (4-7 to -1). In the higher oxidations states (Tc(IV) to Tc(VII)), the metal behaves as a hard Lewis acid and its chemistry is dominated by multiple-bonded oxo ligands. The lower oxidation states ions can be classified as soft metals and will form stable compounds with hgands containing the following donor atoms P, As, S, Se, X (except F ), N, and itt-acceptors such as CO, NO, and isonitriles. 

Similar behavior is observed for calix[4]arene (see Calixarenes) complexes of the type (89). Moreover, the oxygen donor atoms are particularly appropriate for the oxophilic early transition metals. A rich chemistry has been developed with complexes containing zirconium - carbon bonds. In this area, aryne zirconocene compounds can be thermally generated and isolated withont trimethylphosphane additional coordination. Zirconium-bntadiene chemistry has been explored as well and constitutes a source of zircoiuum complexes. 

The mass spectra of bimetallic carbonyl metal compounds with cyclic arsine ligands have been discussed (Table 10). Molecular ion peaks are present for the pentamethyl-cyclopentaarsine containing complexes of chromium and tungsten, (AsMe)5[M(CO)]2 (186,188). Their decomposition includes CO and/or M(CO)5 loss giving rise to the ions (AsMe)sM2(CO) + (n = 0-9), (AsMe)sM(CO)/ (n = 0-5), M As Me-" and MAs Me+ (m = 2-4), MjAs Me, M AsMe -" (m = 2-4), MAs (w = 2-5), MAsjCH and AsMOj The latter is the most abundant in the mass spectra . ... 

The catalysts are usually prepared in hydrocarbon solvents, essentially in the absence of air or moisture and are mixtures of ill-defined composition. In many instances dark-coloured precipitates are formed of variable stoichiometry containing complexes of the organo-metal compound with the transition metal in a lower valence state. Natta [5] showed that pure lower valence transition metal compounds, such as titanium or vanadium trichloride, when treated with organo-metal compounds were effective catalysts, and were particularly suitable for the preparation of crystalline high melting point polyolefins. The close identity of these two classes of catalyst has led to their description as... 

BX3 compounds are Lewis acids, with acceptor strength in the order BI3>BBr3> BC13>BF3. B203 and the very weak acid B(OH)3 give rise to a wide range of metal borates with complex structures containing both three- and four-coordinate boron. 

Since silicon is an analog of carbon in the Periodic System, it is important to survey reactions of Si-H compounds with complexes of metals in low oxidation states. Similar to C-H compounds, derivatives containing Si-H bonds easily react with low-valent metal complexes via oxidative addition mechanism to afford hydridosilyl or silyl compounds. Typical examples of such reactions [70] are shown below. 

This chapter is devoted to reactions of hydrocarbons and other C-H containing compounds with complexes of metals in a high oxidation state [I]. Section VIII. I describes reactions which lead to isolable or detectable organo-metaUic compounds. However, many known processes of hydrocarbon oxidation by high-valent metal complexes either do not involve a step of a-organyl derivative formation at all or the formation of such intermediates is only suspected. High-valent metal intermediates have been proposed to take part in certain biological oxidation processes (see Chapter XI). 

Compounds of the complex ion [Co(CN)g] have no unpaired electrons, for example, but compounds of the [CoFg] ion have four unpaired electrons per metal ion. Both complexes contain Co(III) with a 3d electron configuration. — (Section 7.4) Clearly, there is a major difference in the ways in which the electrons are arranged in these two cases. Any successful bonding theory must explain this difference, and we present such a theory in the next section. 

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