Nitrosyl cyano

K4Ni(CN)4 is a yellow solid which is extremely sensitive to oxygen and moisture. It can be prepared by reducing K2Ni(CN)4 in liquid NH3 with an excess of potassium17 and decomposes in water with H2 evolution. CN ions can be easily replaced by ligands with greater jt acceptor properties such as CO, NO and phosphines. Mixed carbonyl and nitrosyl cyano complexes have been prepared by direct reactions (equations 1 and 2).18,19... 

The Regioselectivity ofHetero Diels-Alder Reactions. In a few cases, carbonyl, nitrosyl, cyano, and other double bonds with one or more electronegative heteroatoms have acted as dienophiles in Diels-Alder reactions. The carbonyl group has a HOMO and a LUMO as shown in Fig. 1.51. The energies of both orbitals are relatively low, and most of their Diels-Alder reactions will therefore be guided by the interaction between the HOMO of the diene and the LUMO of the carbonyl compound. This explains the regioselectivity in the cycloaddition of dimethylbutadiene 6.176 and formaldehyde, and between 1-substitituted butadienes 6.177 and nitrosobenzenes. 

Nitrosyl Cyano Complexes. Although they are not basically different from other nitrosyl complexes, [M(CN)5NO] 1- species have generally received special attention. Those studied by X-ray crystallography have octahedrally coordinated metal atoms and linear MNO groups. These... 

Before reviewing the other physical data on organometallic nitrosyls we now summarize the purely chemical information on the compounds. For convenience the material has been divided into three main categories (a) nitrosyl carbonyls and nitrosyl isocyanides (b) nitrosyl cyano species and (c) cyclopentadienyl and miscellaneous organometallic nitrosyls. 

Only a limited number of cyano and isocyano complexes and mixed carbonyl, nitrosyl and phosphine cyano complexes of nickel(O) have been described so far.16... 

Dicarbonyl(nitrosyl)triphenyl-phosphinecobalt, 101 Dilithium acyl(alkyl)(cyano)cuprates, 209... 

Direct preparation of the gas is potentially hazardous, and explosive decomposition of the impure gas in the condensed state (below —20°C) has occurred. A safe procedure involving isolation of the 1 1 adduct with 9,10-dimethylanthracene is preferred. The impure gas contains nitrogen oxide and it is known that nitrosyl cyanide will react with the latter to form an explosive compound [1], The need to handle this compound of high explosion risk in small quantities, avoiding condensed states, is stressed [2]. See other CYANO COMPOUNDS, NITROSO COMPOUNDS... 

Formation of Ni(CO)4 or Co(CO)4- by the cyanide method depends upon the stepwise substitution of the anion of the cyano complex by the iso-electronic carbon monoxide molecule. By treating Co2(CO)8 with potassium cyanide we obtained cyanocarbonyls of cobalt of low oxidation number (83). In reactions of the nitrosyl carbonyls of iron and cobalt, Behrens (86) substituted all the CO groups with CN to give K3[Co(NO)(CN)3] or... 

The only compound to be noted here is the recently described14 cyano nitrosyl K3[Mn(CN)2(NO),]. This green compound has been made by the reduction of the dimeric species K4[Mn2(CN)4(NO)4] with potassium in liquid ammonia. The IR spectrum suggests a tetrahedral structure similar to the isoelectronic [Fe(CN)2(NO)2]2. ... 

More recently Behrens and co-workers15 were able to prepare the series of monocyano nitrosyl carbonyls by reactions such as equation (1). The Mn° compounds obtained in this work are listed in Table 6. Na[Mn(CN)(CO)3(NO)] dissolves readily in polar solvents such as water, ethanol, acetone or THF, but the solutions, even in the absence of light and air, are unstable. Crystalline salts, which are air stable, were obtained by adding such a solution to an excess of the appropriate cation. The related isonitrile species were prepared by alkylation of the cyano anions with R304. ... 

The cyano complexes of cobalt(—I) are restricted to nitrosyl and carbonylnitrosyl mixed ligand complexes, all of which obey the 18-electron rule. 

Irradiation of the Cr complexes [CrCCNlg] and [Cr(CN)6-x(OH),] (where x = 1, 3, or 6) in alkaline media has been described. Ligand photosubstitution by OH and oxidation to Cr both occur and in the case of [Cr(CN)s(H20)] and [Cr(CN)3(H20)3], photoaccelerated aquation is ob-served. " [CrL(CN)2(H20)]"- (where H4L = EDTA) also undergoes CN photoaquation, probably because labilization of other ligands is blocked or alternatively is not observable under the experimental conditions. This finding should be contrasted with the behaviour of cyano-ammine complexes which show primarily NH3 photoaquation.A complex photosubstitution occurs in the case of the nitrosyl complex [Cr(CN)5NO] and is followed by secondary thermal transformations to produce hydroxo-complexes of Cr . In the presence of oxygen, Cr04 ions are also formed. ... 

Related reactions include the formation of the 2-cyano compounds (190) when 1,2-dimethyl-5-nitroimidazole is heated with nitrosyl chloride or an AT-oxide, and when 2-methyl-l-(o-nitrophenyl)imidazoles (191) cyclize under the influence of iron(II) oxalate (Scheme 98) (74JCS(P1)1970). The last reaction product is contaminated by a large amount of amine reduction product ( 64%) but there is also some cyclization with the 4-methyl isomer of (191). In the presence of trimethylamine, 2-cyanomethylbenzimidazole condenses with acetone to give the unsaturated derivative (192 Scheme 99) (77CPB3087). Neither 2-methylimidazole nor 2-methylbenzimidazole reacts with formamide in the presence of phosphoryl chloride. 

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