Interaction of the [GaH₄]⁻ Anion with Weak XH Acids − A Spectroscopic and Theoretical Study

Abstract

Abstract The dihydrogen bonding (DHB) between the hydride atom of the [Bu 4 N][GaH 4 ] salt and different XH acids, namely CF 3 CH 2 OH, FCH 2 CH 2 OH, i PrOH, MeOH, indole and 4‐O 2 NC 6 H 4 NH 2 , has been investigated for the first time by low‐temperature IR spectroscopy. The DHB spectroscopic and thermodynamic parameters in solvents of low polarity and high basicity ( E j = 1.37) were obtained. The nature, structures, energies and electron distributions of the model DHB complexes of GaH 4 − with H 2 O, MeOH, CF 3 OH, H 2 NCF 3 or NO 2 C 6 H 4 NH 2 were studied by DFT calculations and compared with those of the analogous complexes of BH 4 − with H 2 O, MeOH or CF 3 OH. Two types of DHB structures with monodentate and symmetric chelate coordination were found. The lengthening of the X−H and Ga−H bonds, electron polarization and overlap population of the H ··· H bond are greater in the first type of structure. A comparative analysis of experimental data demonstrates that the spectroscopic and thermodynamic characteristics, e.g. ν(XH) and ν(GaH) band shifts, ν(XH) bonded integral intensities, formation enthalpies and E j of all the DHB complexes increase down the group (BH 4 − ·HX < GaH 4 − ·HX). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)