Trinuclear cobalt clusters

All other trinuclear cobalt clusters contain triply-bridging ligands. Most of these belong to the structural type 91, which is similar to the methinyl tricobalt enneacarbonyls. Structure 91 is realized with X = S or Se 368) (see [27] in Chapter 2.3.),... 

Arene-capped trinuclear cobalt clusters have been briefly mentioned in COMC (1995) as this field of cobalt cluster chemistry started in the early 1990s. ... 

Fachinetti el at. have proposed that a trinuclear hydroxymethylidyne cobalt cluster could possibly be an intermediate in CO hydrogenation (61-63). Evidence for the equilibrium... 

Te were isolated. Their structures [2S] (366, 368) are similar to those of the ECo3(CO)9 clusters [27] and thus offer the possibility for the experimental bonding investigation mentioned in Chapter 2.3. Of SFeCo2(CO)9CO substitutions by isonitriles have been observed (304). Other trinuclear iron-cobalt clusters include CpCoFe2(CO)9 obtained from CpCo(CO)2 and Fe2(CO)9, for which structure [92] was made plausible (272), and CpFeCo2(CO)g(C=CPh), for which structure [94] was suggested (403). 

Phenylthio ketones, asymmetric hydrogenation, 10, 47 Phenylthiourea, with trinuclear Os clusters, 6, 747 Phenyltris(A r/-butylthio)methylborato ligands, in cobalt(II) complexes, 7, 18... 

A trinuclear cobalt(I) complex, PhCCo3(CO)9, can also catalyse the reduction of nitro compounds in the presence of hydroxide ion at room temperature under a normal pressure of CO [49]. Satisfactory results were obtained under phase transfer conditions. The catalyst and the aromatic nitro compounds were dissolved in benzene under carbon monoxide and an aqueous solution of sodium hydroxide containing cethyltrimethylammonium bromide was added. At a substrate/cat =10 ratio, ca. 60-80 % of amine was obtained in a 18 h reaction. The reaction also proceeded in a homogeneous phase (methanol-water, methanol, dioxane-water) but with lower conversions (less than 45 %). Cobalt complexes such as MeCCo3(CO)9 and MeCo(CO)4 were also active, but less effective. At the end of the reaction, the catalyst was recovered only in part (ca. 15 %). In the organic phase, an IR absorption at 1891 cm, attributable to [Co(CO)4] anion, was observed. Strangely enough, the preformed [Co(CO)4] anion has not been tested as catalyst. The active species was supposed to be the hydride cluster anion reported in Scheme 6. 

In organometallic systems in particular, clusters with bridging alkylthiolates are well known, as exemplified by Co2(Cp)2(/i-SCH3)2, which undergoes reactions with alkyne-cobalt complexes to yield trinuclear clusters.170... 

The tetranuclear and trinuclear clusters will only be observed at low pressures [8], but all other species are very common under hydroformylation conditions. Complex 4 is an ionic complex that is formed in polar solvents [9] and even hexa-solvated, divalent cobalt species may form as the cation. Under practical conditions both the dimers and the hydrides are observed, thus depending on the hydrogen pressure there will be more or less of the hydride present. 

Indoline, in trinuclear Ru and Os clusters, 6, 725 Indolizidine, via cyclization-hydrosilylation, 11, 389-390 Industrial processes, in Ziegler-Natta polymerizations, 4,1040 Inflammation, drugs for, 12, 460 Infrared spectroscopy applications, 1, 501 cobalt complexes, 1, 488... 

A hexanuclear chalcogen/carbonyl compound of cobalt containing no thiolate ligands, [Co6E2(E2)(CO)i4] (E = S, Se), is shown in Fig. 27 for E = The cluster complex is assembled from two identical trinuclear Co3S(CO)vS2 sub-units which share the S atoms of the disulfide ligand. They possess principle features already known from the [Fe3E(CO)9]- (E = S, Se, Te) series of complexes (see Fig. 9, Section 1.10.5). 

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