Trinuclear cobalt complex

The quasi-reversible character of these redox reactions indicates that some geometrical changes are taking place without changing the clathrochelate framework. As in the case of trinuclear cobalt complexes, macrobicyclic nickel dioximates are characterized by a high oxidation state stabilization in comparison with other nickel complexes. For example, for Ni(HDm)2 bis-dioximate, two processes (oxidation and reduction) were observed for nickel(II) ion [80],... 

In contrast to iron and manganese, the number of trinuclear cobalt complexes is comparatively small. The reaction of [Co2(CO)s] with 2-propane thiolate or with C3H7SSC3H7 in methanol under solvothermal conditions afforded the electroneutral complex (Co3(SC3H7)s(CO)4], which contains a triangle of cobalt atoms. Its structure is shown in Fig. 16. 

These trinuclear cobalt complexes can be protonated by HBF4, whereby the following equihbrium is established [435] ... 

An imusual class of trinuclear cobalt complexes prepared by reaction of oxygen with solutions of bis(triphenylphosphine) cobalt(II) chloride in allylamine, AA, in the presence of benzotriazole, BT, have been shown to exhibit catalytic activity. Complex VIII, for example, weakly catalyzes the oxidation of triphenylphosphine at room temperature (80% after 3 days, 20 turnovers) the process being accelerated by UV light. 

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... 

CpCo(MeEt2C3B2Et2)Ni(8-Me-2,3,5-C3B7H9) Trinuclear C3B2 complexes (tetradecker sandwiches) Cobalt S, X, H, B, MS 41... 

The circular dichroism (CD) spectra of optically active di-, tri-, and tetranuclear complexes of chromium(III) and cobalt(III) have been reported and used to establish the complexes absolute configurations (55 59, 111, 115, 116, 152-157). The changes in circular dichroism resulting from ion pairing have been studied for the tetranuclear hexol Co j(OH)2Co(NH,)4J, h+ and have been shown to be attributable to the vicinal effect of the chiral oxygen centers produced stereospecifically by the ion-pair formation (56). For a series of trinuclear cobalt (III) amine complexes, cis-Co(CN)2[(OH)2Co(N4)2 J3 +, it was shown that the main CD contributions due to the two chiral Co(OH)4(CN)2 and Co(N4)(OH)2 centers are additive (155). In the case of the related tetranuclear complex Co((OH)2Co(en)2J,< + this postulate of additivity of CD spectra proved unsatisfactory (57). 

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... 

Cyclic voltammetric data (mV) for the trinuclear cobalt NsSs-complexes in AN (0.1 moM-i ((7i-C4H9)4N)BF4) [129]. 

Cyclic voltammograms for clathrochelate and semiclathrochelate trinuclear cobalt NsSs-complexes demonstrated one quasi-reversible... 

In 1966, [Co(en)3] Bfj was separated into its optically active enantiomers on a colunm of anion-exchange resin, which was in advance loaded with tartrate or anti-monyltartrate ions. The resolution was partial. In the same year, Brubaker et al. achieved the total resolution of a trinuclear cobalt(III) complex, hexakis(2-amino-ethanethiolato)tricobalt(III) bromide on a column of a cation-exchange cellulose (Bio-Rad Cellex CM) by eluting with 0.1 mol/dm NaCl. 

The mechanisms of the oxidation of phosphines and arsines by chromium(VI) have been examined both in solution and on a diatomite support. Kinetic parameters are presented for both supported and solution reactions. A ruthenium complex of 1,4,8,1 l-tetramethyl-l,4,8,ll-tetraazacyclotetradecane has been utilized to oxidize triphenylphosphine in acetonitrile. Although a limited temperature range was utilized, a AH value of 8.7 0.8 kcal mor and a A5 value of -20 2 cal K mor were calculated. The secondary phosphine oxides, HP(0)R (R = n-butyl, isobutyl, cyclohexyl) and 9H-9-phosphabicyclononane-9-oxide, react with cobaltocene to yield dihydrogen and cobalt(I) compounds. With the less bulky phosphorus ligands at elevated temperatures trinuclear cobalt(III, II) complexes may be obtained. Arsenious acid may be utilized to catalyze the oxygen atom... 

The so-formed mononuclear cobalt species has been used further as a tridentate ligand in the synthesis of a series of trinuclear heterometallic complexes of the following type [404,435] ... 

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. 

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. 

The bridge-forming proclivity of the neutral cobalt (III) complex, CoL3, has also been demonstrated (6). Two trinuclear compounds of the formula [M(CoL3)]Xn, where M is Ni(II) or Co (III), have been isolated in pure form. Detailed study of these substances indicates that the complex CoL3 forms three mercaptide bridges to the third metal ion, thus providing octahedral coordination of the six sulfur atoms about that ion. Data on these unusual compounds are also included in Tables I and II. 

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