Niobium pentamethoxides

The lithium compound was heated at about 520 K and niobium pentamethoxide at 470 K in a stream of argon containing oxygen. Lithium niobate was deposited on the reaction vessel which was heated to 720 K. 

Riess, J. G., and Hubert-Pfalzgraf, L. G., Niobium pentamethoxide, a multi-faced study of an early transition metal alkoxide, Chimia, 30, 481 (1976). 

Apart from the monomeric methoxides of the metalloids (B, Si, Ge, As, and Te) which are very volatile and soluble in organic solvents, most of the metal methoxides (except niobium and tantalum pentamethoxides and uranium hexamethoxide) are comparatively nonvolatile and insoluble in common organic solvents. Attempts have been made to... 

The pentavalent niobium and tantalum alkoxides are reasonably volatile and can be distilled unchanged in the pressure range 0.05-10mm, e.g. pentamethoxides of niobium" and tantalum" have been distilled at 153°C/0.1 or 200°C/5.5 and 130°C/0.2 or 189°C/10.0 mm pressures, respectively. The data in Table 2.12 indicate that the boiling points are dependent on chain length furthermore, the methoxides and ethoxides of tantalum are more volatile than the niobium analogues whereas for higher n-alkoxides, the reverse is... 

Riess and Hubert-Pfalzgraf " measured the temperature and concentration dependence of the NMR spectra of niobium and tantalnm pentamethoxides in nonpolar solvents like toluene, carbon disulphide, and octane at ambient temperature and at low temperatures (-11 to -74°C) and at different concentrations and confirmed that at low temperatures and higher concentrations methyl protons having peak intensity ratio 2 2 1 are obtained. This is consistent with the X-ray structure of [(MeO)4Nb(/r-OMe)2Nb(OMe)4]. The coalescence of these peaks occurs at higher temperature (10°C) and low concentration (0.01 m). 

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