Dicyano metal complexes

Several methods have typically been used to prepare cyanide complexes. - Representative examples of these processes are shown in Equations 3.51-3.53. As shown in Equations 3.51 and 3.52, the oxidative addition of HCN or cyanogen (NC-CN) to a transition metal forms hydridometal cyanide complexes or dicyano metal complexes. Although less common, the oxidative addition of nitriles has even been shown to form organometal cyanide complexes. " These reactions have been observed for Ni(0) species, as shown in Equation 3.53. 

Consequently, we will centre our attention on the main type of acceptors according to their different molecular nature. Thus, we will focus on derivatives of the parent molecules TCNQ, dicyano-p-quinonediimine (DCNQI), other polycyano derivatives, dithiolene metal complexes (l,3-dithioIe-2-thione-4,5-dithiolate, dmit) and some interesting cases in the emerging chemistry of fullerene [13] derivatives as shown in Figure 1.1. 

Anomalous behavior is exhibited by the tricarbonylruthenium complex of 1-methoxycar-bonyl-1//-azepine in that at room temperature with TCNE, perfluoropropanone or l,l-dicyano-2,2-bis(trifluoromethyl)ethylene, exo-2,5-adducts, e.g. (143), are obtained. Deuteration studies reveal that the addition is non-concerted and involves an initial electrophilic attack by the 2u--system at the uncoordinated double bond of the azepine-metal carbonyl complex <77JCS(D)204). 

Cocyclization of 3,4-dicyano-l,2,5-selenodiazole 81 and alkene 234 by reaction with Mg(OBu)2 in BuOH, and subsequent demetalation by trifluoroacetic acid and metalation with MnCl2, led to a porphyrazine containing one 1,2,5-selenodiazole ring Mn complex 235 in 59% yield (Equation 29) <2003AGE462, 2003JOC1665>. 

Structures of type XVIII or XIX as proposed for the diazodicyanomethane complex (Table 12) may also apply to the complexes of diphenyldiazomethane and 9-diazo-fluorene. The formation of the ketenimine complex (45) from the reaction of (CN)2CN2 and Ni(t-BuNC)4 probably occurs via attack of the complexed dicyano-methylene carbene on the isocyanide ligand113 The observation that these complexes112 113 catalyze the formation of ketenimines from isocyanides and diazo compounds, a reaction which does not proceed under same conditions without the transition metal, may be of preparative value 113 ... 

Dihydropyridines are inherently unstable and rapidly isomerize to other dihydropyridine isomers many also rapidly eliminate H2 to form pyridines. The exceptions are 3,4-dihydropyridines substituted at the 2- and 5-positions with electron-donating groups. However, even stable 3,4-dihydropyridines can be oxidized to the corresponding pyridine by the use of 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) <1995T7161>. An example of the stability of these substituted 3,4-dihydropyridines is in the unexpected formation of 2-methoxy-3,4-dihydropyridine 45 rather than the expected pyridine 46 from the [3+3] cyclization of 4-amino-l-azabutadiene 44 with Fischer alkynylcarbene complex 43 (Equation 1) <2001NJC8>. The 2-methoxy group was proposed to stabilize an intermediate and result in elimination of the metal without aromatization. 

The cyanogen molecule, N=C—C=N, is linear. It dissociates into CN radicals, and, like RX and X2 compounds, it can oxidatively add to lower-valent metal atoms giving dicyano complexes, for example,... 

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