Niobium complexes cyanides

Niobium, tris(diethyldilhiocarbamato)oxy-stereochemistry, 1,82 structure, 1, 83 Niobium, tris(oxa ato)oxy-stereochcmistry, 1, 82 Niobium, tris(phcnylcncdirhio)-structure, 1, 63 Niobium alanate, 3, 685 Niobium complexes alkyl alkoxy reactions, 2, 358 amides, 2,164 properties, 2, 168 synthesis, 2, 165 applications, 6,1014 carbamicacid, 2, 450 clusters, 3, 672,673,675 hexamethylbenzene ligands, 3, 669 cyanides synthesis, 2, 9 p-dinitrogen, 3, 418 fluoro... 

The A-trimethylsilylimines 68 (R = t-Bu, Ph, 2-MeCgH4 or 2-BrC6H4), which are prepared by the reaction of non-enolizable aldehydes with lithium bis(trimethylsilyl)amide, followed by trimethylsilyl chloride, undergo pinacolic coupling induced by NbCLt 2THF to yield the vicinal diamines 69 as mixtures of dl- and meso-isomers, in which the former predominate. Another method for the preparation of 1,2-diamines is by the combined action of the niobium tetrachloride/tetrahydrofuran complex and tributyltin hydride on cyanides RCN (R = /-Hu. Ph, cyclopentyl or pcnt-4-en-l-yl) (equation 32)82. 

Even fewer complexes with nitrogen donor ligands have been reported and all are methyl cyanide adducts (Tables X and XI). Protactinium pentabromide forms a soluble 1 3 complex in contrast to the 1 1 complexes formed by niobium and tantalum pentahalides (46). Other actinide pentahalide-methyl cyanide complexes are still unknown. Protactinium tetrachloride, tetrabromide, and tetraiodide react with anhydrous, oxygen-free methyl cyanide to form slightly soluble 1 4 complexes (44, 48) which are isostructural with their actinide tetrahalide analogs. 

The full report of the preparation and properties of two octacyanoniobates has appeared (Vol. 4, p. 75). Impure K5[Nb(CN)8] can be obtained from the reaction of an excess of aqueous potassium cyanide with an electrolytically reduced solution of niobium pentachloride in methanol. Oxidation of the product by air or H2O2 gives orange K4[Nb(CN)8],2H20 (see p. 73). Solutions of this salt are stable in the dark but disproportionate photolytically to the Nb complex, Nb20s, and HCN. M5[Nb-... 

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