Cobalt anion

Before addition of the benzyl halide, the only carbonyl adsorption peak is found at 1900 cm, indicative of the cobalt tetracarbonyl anion. After addition, this band immediately disappears and peaks at 2000 cm l are observed. These most likely represent the corresponding acyl complex. Reaction with methoxide yields the product and regenerates the cobalt anion. In the absence of sufficient methoxide, the reaction requires attack by the much... 

The autoxidation of hydrocarbons catalyzed by cobalt salts of carboxylic acid and bromide ions was kinetically studied. The rate of hydrocarbon oxidation with secondary hydrogen is exactly first order with respect to both hydrocarbon and cobalt concentration. For toluene the rate is second order with respect to cobalt and first order with respect to hydrocarbon concentration, but it is independent of hydrocarbon concentration for a long time during the oxidation. The oxidation rate increases as the carbon number of fatty acid solvent as well as of cobalt anion salt are decreased. It was suggested that the cobalt salt not only initiates the oxidation by decomposing hydroperoxide but also is responsible for the propagation step in the presence of bromide ion. 

Table II, Effect of Cobalt Anion and of Solvent Acid on Oxidation Rate of 4.07M Ethylbenzene with 2 X 10"2M Cobalt and 4 X 10"2M NaBr in Acetic Acid at 65°C.

Yb(5d)(H20)3]Cl, and [Yb(5d)(CoP] (fig. 12) where CoP is the cyclopentadienyl-tris(dieth-ylphosphito)cobaltate(I) anion (see fig. 13) for which the luminescence intensity increases in the proportions 1 22 36 62 271, upon excitation at 512 nm (Meng et al., 2000). The effect of coordinated water molecules on the metal-centered fluorescence intensity is clearly seen in the more than four-fold enhancement obtained by replacing the three water molecules in [Yb(5d)(H20)3 ]C1 by CoP the 2F5/2 lifetime of the latter complex (40 ps) is also much longer than lifetimes reported for other Ybm porphyrinates. In addition, the cobaltate anion rigidities the molecule, which results in a much finer structure of the ligand-field split electronic levels. 

A catalyst combining a Lewis-acidic Cr(m) with a tetracarbonyl cobalt anion promotes the carbonylation of epoxides at pressures as low as 1 atm CO (Equation 50) <20060L3709>. Sn2 ring opening by the Co(CO)4 anion generates a... 

The basic steps of the catalytic cycle with the cobalt catalyst are shown in Fig. 4.3. The tetracarbonyl cobalt anion 4.7 is formed from cobalt iodide, by reactions 4.5-4.7. 

Borole (IV in Figure 14) has been used to synthesize a plethora of sandwich and half-sandwich stmctures it is the bora analog of cyclopentadiene. Borole is an antiaromatic system see Antiaromatic Compound), and only the blue pentaphenyl derivative has been prepared. The general route to borole complexes consists of complexation under dehydrogenation of 2- or 3-borolenes, which are prepared from [Mg(butadiene)]x and RBX2. Thus, the heating of either isomer of borolene with Co2(CO)g produces [(borole)Co(CO)2]2 (47) (equation 60) from which further cobalt borole complexes are prepared (equation 61). CpCo(borole) (48) can be made from (47) by Cp transfer from the labile 20-electron nickelocene (equation 61). Pyrolysis of (48) at 160-180 °C gives a triple-decker complex (49) in nearly quantitative yield, which in turn can be cleaved by Cp into (48) and the bis(borole)cobaltate anion (50 ) (Scheme 34). 

Recent elegant studies using deuterated solutions of vitamin Bi2 are also inconsistent with a Co—H system in the reduced solutions (62). Further, the reactions in Fig. 10 may be interpreted in terms of a complex cobalt anion [compare Co(CO)4-], and therefore it must be concluded that the presence of a Co—H system in vitamin Bi2, is not proven and that the evidence is rather against the postulate. 

The technetium-cobalt carbonyl TcCo(CO)9]° was prepared in a similar procedure by reacting [Tc(CO)5Br with the tctracarbonyl cobaltate anion [Co(CO)4] in THF ... 

With the same concept, but using the more reactive Ti(III) cationic radical [Cp2TiCl(THF)2] or a cationic salphen aluminum complex in combination with the cobalt anion [Co(CO)4] , Coates et al. succeeded to make the epoxide or aziridine carbonylative ring expansion reaction catalytic (Scheme 60) [149]. For both substrates, it is proposed a nucleophilic attack of the cobalt anion at the least-substituted carbon atom of the three-membered ring, the latter being activated by the Lewis acidic part of the catalyst. Of note, catalysts 106 and 107 used in this reaction are described as ion pairs rather than M-Co bond containing complexes. 

R. Hammer and H.F. Klein, The tetrakis(triphosphine)cobalt anion. 

The first trialkylpalladiumflV) complex stabilised by oxygen donors has been reported addition of methyl, benzyl, or allyl halides to [Pd(CH3)2(bipy)] at -20 C produces [Pd(CH3)2(R)(X)(bipy)] which can be reacted with the silver salt of the cobalt anion [Co(n -C5H5)(PR2=0)3]. ... 

The basic organometallic reactions of the cobalt catalyst are shown on the right-hand side of Figure 4.1. On the left-hand side are shown the organic reactions that are an integral part of the overall catalytic cycle. The tetracarbonyl cobalt anion 4.1 (same as 2.60) is formed from cobalt iodide by Reactions 4.2.1.1 and 4.2.1.2. 

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