2,2 -Bipyridine niobium complex

Numerous complexes of niobium(IV) and niobium(V) halides with various nitrogen-donor ligands have been reported in the literature. The products obtained from these reactions are critically dependent upon the reaction conditions. " Tetrakis(isothiocyanato)bis(2,2 -bipyridine)niobium(IV) can be prepared directly from the hexakis(isothiocyanato)niobate(IV) complex or by the reduction of the hexakis(isothiocyanato)niobate(V) ion according to the published method. This method can also be extended to the preparation of other analogous complexes. 

Tetrakis(isothiocyanato)bis(2,2 -bipyridine)niobium(IV) is a medium-brown crystalline solid. It is only very slightly soluble in 1,2-dichloroethane, dichlo-romethane, and acetonitrile. These extremely dilute solutions of the complex readily decompose in the presence of oxygen or moisture however, in the solid state the complex appears to be air-stable. It does not melt or decompose below ca. 275°. The infrared spectrum, ultraviolet spectrum, magnetic moment, and x-ray powder diffraction pattern of the product obtained by this procedure are essentially identical to those obtained for the product prepared by the reduction of the hexakis(isothiocyanate)niobate(V) complex. ... 

Niobium (continued) complexes, 6 5 with bipy and phen, 12 179 homoleptic, 2,2 -bipyridine, 34 14 compounds... 

The method described above has been found suitable for the synthesis of Nb(NCSe)4(CioH8N2)2, Nb(NCS)4(dmbipy)2, and Nb(NCSe)4(dmbipy)2, where dmbipy is4,4 -dimethyl-2,2 -bipyridine. These niobium (IV) compounds can also be prepared from the hexakis(isothiocyanate)niobate(V) complex. The sensitivity of the materials to air and moisture makes the method somewhat more time-consuming, but the use of niobium tetrachloride as a starting material is avoided. The tantalum(V) complexes, Ta(NCS)6(CioH8N2)... 

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