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Fluorinated weakly coordinating anions [M(hfip)6]– (M = Nb, Ta): syntheses, structural characterizations and computations
U. Preiss, G. Steinfeld, H. Scherer, A. M. T. Erle, B. Benkmil, A. Kraft, I. Krossing.
ZAAC - Journal of Inorganic and General Chemistry, 19, 714-721, (2013)
Abstract
The synthesis, spectroscopic and structural characterisation of a series of [M(hfip)6]– (M = Nb, Ta; hfip = O–C(H)(CF3)2) salts that are the typical starting materials to introduce these weakly coordinating anions by metathesis reactions into a given system is described. The salts Li[Nb(hfip)6] and Li[Ta(hfip)6] formed in 65 to 77 % yield from freshly sublimed MCl5 and Li[hfip]. By contrast, several attempts to synthesize Li[Sb(hfip)6] on the similar route (replace NbCl5 by SbCl5) failed to yield a pure product. Upon metathesis of the Li-niobate with AgF in CH2Cl2, the pure Ag[Nb(hfip)6] formed. Mixing Li[Nb(hfip)6] with an equimolar amount of Cl–CPh3 in CH2Cl2 gave the yellow [CPh3][Nb(hfip)6]. Several of the compounds were characterized by X-ray analysis. Thus, the crystal structures of the Li+-
and Ag+-solvates 1,2-C6H4F2{LiNb(hfip)6}2, [Li(H2O)][Ta(hfip)6], and [Ag(C6H5F)][Nb(hfip)6] as well as that of [CPh3][Nb(hfip)6] were solved and are described in this work.
Keyword(s): weakly coordinating anions; niobium; tantalum; lithium; silver; density funcional calculations
DOI: 10.1002/zaac.201300027
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