Cobalt nitrosyl

Carbonyl Nitric Oxides. Another group of metal-carbonyl complexes, worthy of investigation as CVD precursors, consists of the carbonyl nitric oxides. In these complexes, one (or more) CO group is replaced by NO. An example is cobalt nitrosyl tricarbonyl, CoNO(CO)3, which is a preferred precursor for the CVD of cobalt. It is a liquid with a boiling point of 78.6°C which decomposes at 66°C. It is prepared by passing NO through an aqueous solution of cobalt nitrate and potassium cyanide and potassium hydroxide. ... 

CONC304 COBALT NITROSYL TRICARBONYL -2295.1356 4.3067E+04 1.0148E+03 -1.4317E+00 7.7031E... 

Enemark, J. H., Feltham, R. D., Riker-Nappier, J., and Bizot, K. F. (1975). Stereochemical control of valence. IV. Comparison of the structures and chemical reactivities of five-and six-coordinate diarsine complexes of the cobalt nitrosyls CoNO) group. Inorg. Chem. 14, 624-632. 

This potassium salt, K4Ni2(CN)6, may be further reduced by potassium in liquid ammonia to yield a yellow substance, K4Ni(CN)4. This has nickel in the zero-valent state and is thus comparable to the metal carbonyls, Fe(CO)5 and Ni(CO)4 (p. 157), to cobalt nitrosyl carbonyl Co(CO)4NO, and to the metal ammoniates Ca(NH3)6 and Pt(NH3)2. However, K4Ni(CN)4, and the closely related acetylene derivative, K4Ni(C=CH)4, are especially unusual, for in them, the zero-valent metal has been incorporated into an anion, whereas in the carbonyls and metal ammoniates, the zerovalent metals are present as uncharged species. 

Redox Potential for Iron and Cobalt Nitrosyl Dithiolene Complexes, [M(NO)(S—S)2]z ... 

Table 11 Preparations Cobalt-Nitrosyl Complexes (Non-phosphine Containing)... 

General accounts of the reactivity of coordinated nitrosyls are available.106 121 124 A metal ion or metal complex is unable to generate the reactivity of ionic NO+ towards nucleophiles (i.e. OH-, RS-, RHN-) or of NO- towards electrophiles (i.e. H+, PhCH2X), but it can present NO in a less reactive form under conditions inappropriate to the free ion. Thus linear coordination with vNO > 1886 cm 1 may promote nucleophilic reactions at N, and bent coordination with the higher electron density on N (vNO < 1700cm-1) may promote electrophilic attack by H+, 02, NO and PhCHjBr.125 No cobalt nitrosyl is known to undergo nucleophilic attack on the nitrosyl group. Normally linear coordination is associated with four or five coordination and the nucleophile adds to the unsaturated metal instead. However a number of electrophilic reactions are known (Table 13). A recent discussion of these is recommended.124... 

Table 13 Electrophilic Reactions of Cobalt-Nitrosyl Complexes... 

Optically active organometallic complexes have been used to study stereochemical reactions. Substituted cobalt nitrosyl complexes are interesting chiral see Chiral) complexes because they exhibit tetrahedral structures, whereas most optically active organometallic complexes are half-sandwich structmes with octahedral geometries. Diastereomeric cobalt complexes of the type Co(CO)(NO)(L)( L) (L = phosphite or phosphane L = optically active phosphane or isocyanide) have been synthesized from (4) via substitution (Scheme 6). ... 

The cobalt nitrosyl complex is a deep-violet crystalline solid which is stable in air but decomposes rapidly in solution in the presence of oxygen. It is soluble in chloroform and dichloromethane but insoluble in ether and alcohols. Its chemistry has been studied recently. ... 

PtG. 20. The proposed mechanism for the reaction of 5-coordinate cobalt nitrosyl complexes with oxygen. 

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