Tetracobalt complex

Indole N-substituted diyne tetracobalt complexes 1467 undergo a Lewis acid-mediated dimerization-cyclization reaction through the indole 3-position to afford indolophanetetrayne cobalt complexes 1468 (Scheme 280) <20030L1003>. 

D. Solooki, J. D. Bradshaw, C. A. Tessier and W. J. Youngs, Synthesis and characterization of trithienocy-clotriyne (TTC) and its tetracobalt complex. The first example of a dehydroannulene containing thiophene rings, Organometallics, 13, 451-455 (1994). 

The planar trithienocyclotriyne (TTC) has been synthesised and its reaction with [Co2(CO)g] shown by X-ray crystallography to afford l a tetracobalt complex in which only two of the three alkynes of TTC bind to a Co2(CO)g moiety. 

An analogous type of lithium-induced zipper cyclization was observed with PAM 5, affording the mesolDL pair of helicenes (Scheme 11) [34]. PAM 5 also reacted with dicobaltoctacarbonyl to give a tetracobalt cluster in which only two of the triple bonds have been complexed [35]. 

After extraction the catalyst remains in the olefin phase as shown by IR analysis either as an acyl complex, as dicobalt octacarbonyl, or (at low CO pressure) as tetracobalt dodecacarbonyl. 

A tetracobalt anionic complex, viz. [In Co(CO)4 4] (27) (37,37a), has been briefly described together with the thallium analogue (28) (37a), both formed by addition of [Co(CO)4] to either 25 or 26. No structural details have been reported although the indium and thallium centers are presumably tetrahe-drally coordinated by the four cobalt atoms. Mention is also made (37a) of the facile heterolytic bond dissociation (In—Co or Tl—Co) observed in polar solvents. Little has been reported about the reactivity of these complexes, although a discussion on the use of 25 as a catalyst in the dimerization of norbornadiene has appeared (58). 

In the report that described the synthesis of 108 (777), Whitmire also observed that the reaction between NaBi03 and methanolic [Fe(CO)s] in the presence of hydroxide afforded the trianionic species [Bi Fe(CO)4 4]3, 110, which was subsequently characterized by X-ray crystallography (775). Cluster 110 contains a central bismuth atom tetrahedrally coordinated by four Fe(CO)4 fragments and is isoelectronic with the anionic tetracobalt-indium complex, 27, and the neutral tetracobalt-germanium, - tin, and -lead complexes, 68, 71, and 72. Oxidation of 110 affords 108 (777), while acidification (772) yields the hydride-containing cluster [BiFe3(CO)9(/i-H)3], 111, which also contains a tetrahedral BiFe3 core. Johnson and Lewis (114) have... 

Note that tetracobalt dodecacarbonyl is a catalyst precursor for reaction at 150 and 10 atm CO. Only 0.01 equiv of the cobalt cluster is required. Actually catalytic amount of Co2(CO)g of high purity is sufficient to complete the intramolecular P-K reaction, also the hexacarbonyldicobalt complex of 2-methyl-3-butyn-2-ol can be decomposed with triethylsilane to generate an active cobalt carbonyl catalyst. ... 

The structure of the dodecaamminehexa-/i-hydroxo-tetracobalt(III) ion has been established by an X-ray crystal structure analysis of the racemic chloride," and several investigations of the optical activity of the resolved isomers and related hexa-/i-hydroxo-tetracobalt(III)-type complex ions have been made. ... 

Schaming D, Costa-Coquelard C, Sorgues S, Ruhlmann L, Lampre I (2010) Photocatalytic reduction of Ag2S04 by electrostatic complexes formed by tetracationic zinc porphyrins and tetracobalt Dawson-derived sandwich polyanion. Appl Catal A 373(1-2) 160-167... 

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