Mesitylpseudohalogermanes Mes(2)Ge(CN)(2) and Mes(3)GeX (X = CN, NCS, N-3,NCO and OH; Mes=2,4,6-trimethylphenyl): syntheses, crystal and molecular structures

The crystal and molecular structures of the mesitylpseudohalogermanes, Mes( 2)Ge(CN)(2) (Mes =2,4,6-trimethylphenyl) and Mes(3)GeX (X = CN, NCS, N-3, N CO, or OH), have been determined by X-ray diffraction methods; the isocyana te and hydroxide crystallise as a 1:1 hydrogen-bonded complex. All are cova lent monomers free from pseudohalogen bridging, and all except the cyanides and hydroxide are N-bonded to germanium. Each Ge atom is four-coordinate i n a distorted tetrahedral geometry, as evident from (mes)-Ge-(mes) angles b etween 112 and 120 degrees, which are attributed to the sterically demandin g mesityl groups. The greatest distortion is displayed by Mes(2)Ge(CN)(2), for which the NC-Ge-CN angle of 97.8(3)degrees and (mes)-Ge-(mes) angle of 119.8(3)degrees are also consistent with the bulky mesityl groups and the s mall steric requirements of the cyano groups. The Ge-N-Y angles show a dist inctive trend, decreasing from 173.3(5)degrees for the isothiocyanate (Y = CS), through 153.5(5)degrees for the isocyanate (Y = CO), to 119.0(7)degree s for the azide (Y = NN), an effect attributed to differences in electronic structure of the pseudohalo ligands. The geometries of the compounds exami ned here are compared with those of some other tri- and dimesityl-Group 14 metal derivatives as well as related phenylgermanium compounds. (C) 2000 El sevier Science S.A. All rights reserved.