Carbon cyanide complexes

By studying the NMR spectra of the products, Jensen and co-workers were able to establish that the alkylation of (the presumed) [Co (DMG)2py] in methanol by cyclohexene oxide and by various substituted cyclohexyl bromides and tosylates occurred primarily with inversion of configuration at carbon i.e., by an 8 2 mechanism. A small amount of a second isomer, which must have been formed by another minor pathway, was observed in one case (95). Both the alkylation of [Co (DMG)2py] by asymmetric epoxides 129, 142) and the reduction of epoxides to alcohols by cobalt cyanide complexes 105, 103) show preferential formation of one isomer. In addition, the ratio of ketone to alcohol obtained in the reaction of epoxides with [Co(CN)5H] increases with pH and this has been ascribed to differing reactions with the hydride (reduction to alcohol) and Co(I) (isomerization to ketone) 103) (see also Section VII,C). 

Kruper WJ, Swart DJ (1985) Carbon dioxide oxirane copolymers prepared using double metal cyanide complexes. US Patent 4500704... 

Robertson NJ, Qin Z, Dallinger GC, Lobkovsky EB, Lee S, Coates GW (2006) Two-dimensional double metal cyanide complexes highly active catalysts for the homopolymerization of propylene oxide and copolymerization of propylene oxide and carbon dioxide. Dalton Trans 5390-5395... 

Cadmium carbonate forms a cyanide complex ion, Cd(CN)42+ in cyanide solutions. It dissolves in concentrated aqueous solutions of ammonium salts forming ammonium complexes. 

The problem of the stability of the complexes of the transition metals was for many years a puzzling one. Why is the cyanide group so facile in the formation of complexes with these elements, whereas the carbon atom in other groups, such as the methyl group, does not form bonds with them Why do the transition metals and not other metals (beryllium, aluminum, etc.) form cyanide complexes In the ferro-... 

Prominent among the carbon donor complexes are the cyanides, principally compounds of [Zn(CN)4]2, although [Zn(CN)3] is also known. Other carbon donor complexes are the triethyl and tetraethyl complexes, which are readily electrolyzed. 

Fig. 8. Absorption spectra of the cyanide complex of bovine Co(II) carbonic anhy-drase (solid curve) and the pseudotetrahedral complex, Co[(C6Hs)3PO]2(SCN)2 (broken curve). From Lindskog and Ehrenberg (58) and Cotton et al. (19), respectively...

Cyanide complexes have long been written as normal cyanides (e. g. Hofmann, 1900) but this structure has been accepted for many compounds without compelling experimental evidence. Several accurate x-ray studies indicate metal-carbon bonding in Ag(CN)2 (Hoard, 1933) Mo(CN)8-4 (Hoard and Nordsieck, 1933) and Fe(CN)6 4 (Powell and Bartindale, 1945). This early x-ray evidence deserves re-evaluation in view of the fact that recent structure determinations on cyanide compounds, performed with modern instrumentation and computers, have not afforded clear distinction of the N and C ends. With neutrons, the relative scattering factors of carbon vs. nitrogen are appreciably different. Curry and Runciman (1959) took advantage of this to demonstrate the normal cyanide formulation for Co(CN)6 3. 

Professor J. L. Hoard (private communication) has collected new x-ray data on K4Mo (CN) 8 2H2O (see section TIB, 1) which demonstrate that coordination is through carbon. The relative sizes of low spin trivalent metal ions in cyanide complexes, which was discussed in section IIB, 2, has been investigated by Chadwick and Sharpe (private communication) who find a decrease in the order, Cr(III) > Nn(IlI) > Fe(III) > Co(III). 

Concentrated sulphuric acid Heat a little of the solid salt with concentrated sulphuric acid carbon monoxide is evolved which may be ignited and burns with a blue flame. All cyanides, complex and simple, are decomposed by this treatment. 

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