HIGHLY SOLUBLE COMPLEXES OF [FEH6](4-) AND ION-PAIRING INTERACTIONS

The complex hydride, [FeH6][MgX(THF)(2)](4) (1), (X = Br0.88Cl0.12) se rves as a model for the influences affecting the solubility of polyhyd ridic complex hydrides. (1) is converted to [FeH6][MgOR(THF)(n)](4) . 4LiX (2) and (3) (R = Bu-t and Et, respectively) upon treatment with L iOR in benzene solution. The solubilities in THF are 6 x 10(-3) and >0 .5 M for (1) and (2), respectively. H-1 NMR lineshape and electronic s pectra suggests the presence of the ion pairing reaction: [FeH6][MgY(T HF)(2)](4) = [FeH6][MgY(THF)(2)](3)(-) + [MgY(THF)(n)](+) (Y = halide and alkoxide). The species with alkoxides coordinated to magnesium sho w a ligand-to-metal charge transfer (LMCT) band which shows the corres ponding hypsochromic shift with increasing solvent polarity. (C) 1998 Elsevier Science S.A. All rights reserved.