Radicals metal carbonyls

Bimolecular substitution and oxidation reactions of 17-electron pentacoordinate metal carbonyl radicals. A. Poe, Transition Met. Chem. (Weinheim, Ger.), 1982,7, 65-69 (41). 

Some metal carbonyl radical ions have been generated from neutral carbonyls, in situ in... 

V(CO)6 is the only homoleptic metal carbonyl radical, comparable with Re(CO)j and Mn(CO)3L2 radicals, which however are more difficult to study. For the substitution reaction in hexane solution ... 

In dinuclear complexes containing a metal-metal single bond, the major consequence of irradiation is homolytic cleavage to form reactive metal-carbonyl radicals. Many simple substitutions can be explained by a mechanism involving thermal substitution of these radicals. This mechanism is especially helpful in explaining the formation of a disubstituted product ... 

Most of the photoreactions of dimeric Co carbonyls involve cluster formation or cross coupling with other dimers. Compared to other metal-carbonyl radicals, Co(CO) is much less reactive COjCCO) is inert to irradiation in the presence of IC,H,. Even if the expected ICo(CO) were formed, its thermal instability would lead to problems. Irradiation in chlorocarbons produces Co3(CO),CCl in low yield. Under conditions where CO can be removed from solution, irradiation of COjCCO), in inert solvents leads to Co fCO) A likely mechanism involves CO loss from Co(CO) fragments that recombine to yield a transient, unsaturated dimer, which reacts with Co fCO), to give tetramer and CO. 

The chemistry of metal carbonyl radicals dates back to the discovery of "V (CO)6 in 1959.9 The electronic structure and reactions of this complex continue to be investigated.10 The rate of ligand substitution of V(CO)6 would be shown 15 years later to occur at a rate 1010 times faster than that in Cr(CO)6 and was ascribed to associative rather than dissociative pathways occurring for the radical complex ... 

In a theoretical study of bimolecular nucleophilic substitutions, at six-, five-, and four-coordinate metal carbonyl radicals, Walsh diagrams, contour maps, and the atomic character and energies of the frontier MO s derived from SCF-discrete varlatlonal-Xa calculations were employed to deduce the most favorable mode of attack of PH3 at the 17-electron complexes... 

Dinuclear Carbonyls.—Substitution reactions of [Mn2(CO)io] do not occur by CO dissociation or by associative reaction with incoming ligand, but by thermal or photochemical formation of [Mn(CO)5 ]. Rapid substitution of metal carbonyl radicals has been frequently noted but the mechanisms of these substitutions are... 

Studies reported in 1983 on the mechanism of CO substitution in metal carbonyl radicals have been continued. CO substitution by phosphines in V(C0)s is a second-order process with the rate of reaction dependent upon the basicity and size of the ligand. The kinetics and mechanism of 0- and N-Lewis base induced disproportionation of the same metal carbonyl and its phosphine substituted derivatives have also been examined, as have the mechanisms of redox reactions of V(C0)s with metal carbonylates. At low... 

Papers on the identification, magnetic properties and substitution behaviour of several metal carbonyl radicals have been published. " E.s.r. measurements on matrix isolated carbonyls M(C0)f, (M = Cu or Ag, n = 1 or 3 and M = Au, n = 1) have been used to infer structural and bonding data. " Spectra of Ag(C0)3 recorded under differing conditions have been interpreted in terms of two... 

Metal-carbonyl radicals M(CO)n (M being a metal with an odd number of valence electrons), MCp(CO)n (M being a metal with an even number of valence electrons)... 

An attempt has been made to order the reactivity of metal carbonyl radicals generated by the photoinduced cleavage of metal-metal bonds by determining the relative rate of reaction of M and with organic halides RX in the reaction (37),... 

Basolo and co-workers recently studied CO substitution in [V(CO)6], which is the only stable homoleptic metal carbonyl radical. With phosphine and phosphite nucleophiles (L) reaction (1) follows a strictly second-order... 

The mechanisms involve the formation of extremely reactive metal carbonyl radicals as a result of photolysis. The radicals are oxidized in a dark reaction by the organic disulphide, accompanied by formation of thiolate... 

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