Use of73Ge NMR Spectroscopy and X-ray Crystallography for the Study of electronic interactions in substituted tetrakis(phenyl)-, -(phenoxy)-, and -(thiophenoxy)germanes
Abstract
NMR chemical shifts of H, C, and Ge, molecular modeling, and single-crystal X-ray diffraction results are reported for a series of substituted tris- and tetrakis(phenyl)germanes of the type (XC H ) GeY and (XC H ) Ge, where X = o-, m-, and p-OCH , o-, m-, and p-OC H , m- and p-CF , H, p-C(CH ) , p-Cl; and Y = Cl and H. Chemical shifts and X-ray data are also reported for o-CH and o-OCH tetrakis(phenoxy)- ((XC H O) Ge) and thiophenoxygermanes ((XC H S) Ge). For tetrakis derivatives, Ge resonances are observed for all but the o-methoxyphenoxy compound, for which the inability to detect a resonance is attributed to rapid quadrupolar relaxation caused by intramolecular interactions of the methoxy oxygen with the central atom. The observation of a relatively broad, slightly upfield Ge resonance in the analogous phenyl and thiophenoxy derivatives suggests, as do the results of molecular modeling, that in these compounds there is some hypercoordination. The solid-state structures show bond angles at the aromatic carbon bearing the alkoxy group that suggest an interaction of the alkoxy oxygen with germanium. Oxygen-germanium bond distances are about 17% shorter than the sum of the van der Waals radii. © 2010 American Chemical Society. 1 13 73 73 73 6 4 3 6 4 4 3 2 5 3 3 3 3 3 6 4 4 6 4 4
