Deprotonation of the carbaborane nido-7-NH2But-7-CB10H12: Crystal structures of nido-7-NH2But-7-CB10H12 and [NEt3(CH2Ph)][nido-7-NHBut-7-CB10H12]

The crystal structure of nido-7-NH2But-7-CB10H12 1 has been determined by X-ray diffraction. The compound crystallises in the orthorhombic space group Pbca [a = 10.507(5), b = 13.805(6), c = 18.093(9) Angstrom]. The nido-icosahedral structure was established with two endo-B-H-B and two NH2 hydrogen atoms located in Fourier-difference maps and refined. The structure determination is also supported by B-11-{H-1}-B-11-{H-1} correlation NMR spectroscopy. A molecular orbital calculation and frontier density analysis of 1 indicated that deprotonation should initially occur at the exo-nitrogen atom. Treatment of 1 with 1 equivalent of LiBun, followed by addition of [NEt3(CH3Ph)]Cl, gave [NEt3(CH3Ph)][nido-7-NHBut-7-CB10H12] 2 as the only product and single crystals were grown for an X-ray diffraction study. The salt crystallises in the monoclinic space group P2(1)/n [a = 10.651(2), b = 11.652(2), c = 20.926(3) Angstrom, beta = 101.77(2)degrees]. The H-1, C-13-{H-1} and B-11-{H-1} NMR spectra of 1 and 2 have also been recorded.