93Nb, NMR

In the absence of water molecules in the system, similar compositions of fluoride complexes of tantalum and niobium are expected. An analysis of the 19F and 93Nb NMR spectra of solutions based on anhydrous hydrogen fluoride, performed by Buslaev et al., revealed the presence of NbF6 and NbF72 complexes [57]. 

The almost certainly regular octahedron proposed for [M(PF3)6], (M = Cr, Mo, and W) and [VH(PF3)6], based on spectroscopic data, has not yet been substantiated by X-ray or electron diffraction methods however, the well-resolved 51V and 93Nb NMR spectra of the anions [M (PF3)6] (M = V, Nb), and the 95Mo NMR spectrum of [Mo(PF3)6] indicate that the metal atoms are certainly in a high symmetrical environment. 

V. Korovin, S. Randarevich, and Y. Shestak, Niobium extraction hy TBP and TVEX-TBP from hydrochloric media based on 31P, 93Nb NMR data, Rus. J. Inorg. Chem., 36, 3167-3171 (1991). 

Madhu et al. proposed the use of two consecutive RAPT pulse trains to obtain signal enhancement in spin-5/2 nuclei, such as 27Al and 170 [72]. In their scheme, the saturation of population achieved for the outermost ( 5/2) — 3/2)) transitions was followed by saturation of the 3/2) —> l/2) populations before detection of the CT NMR signal. Kwak et al. used similar RAPT pulse trains to obtain significantly improved signal enhancement on 27Al and 93Nb [73],... 

Nb(PF3)6] has been prepared by photolysis of [Nb(CO)6]- under PF3 and studied by multinuclear NMR. The 93Nb chemical shifts suggest weaker Nb-PF3 than Nb-CO interactions.722... 

In this section, we will be concentrating mainly on the use of NMR technique based literature on dipolar glasses and the information obtained from them. The NMR nuclei studied in dipolar glasses are 1H, 2H and 87Rb and 31P. 207Pb, 45Sc and 93Nb are other nuclei which are studied in relaxor materials. 

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