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 1 H, 13 C, and 73 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 6 H 4 ) 3 GeY and (XC 6 H 4 ) 4 Ge, where X = o-, m-, and p-OCH 3 , o-, m-, and p-OC 2 H 5 , m-and p-CF 3 , H, p-C(CH 3 ) 3 , p-Cl; and Y = Cl and H. Chemical shifts and X-ray data are also reported for o-CH 3 and o-OCH 3 tetrakis(phenoxy)-((XC 6 H 4 O) 4 Ge) and thiophenoxygermanes ((XC 6 H 4 S) 4 Ge). For tetrakis derivatives, 73 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 73 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.

Solid‐State 73Ge NMR Spectroscopy of Simple Organogermanes

“…and that reported by Yoder et al. (−27.1 ppm) 20. We were unable to acquire a static spectrum at 21.1 T in a reasonable period of time, excluding the possibility of measuring the CSA.…”

“…The isotropic shift found for 2 (À20 ppm) lies between the reported solution-state values of À11.3 ppm reported by Takeuchi et al [9] and that reported by Yoder et al (À27.1 ppm). [20] We were unable to acquire a static spectrum at 21.1 T in a reasonable period of time, excluding the possibility of measuring the CSA.…”

G73e Nuclear Magnetic Resonance Spectroscopy of Germanium Compounds

“…Similarly, the 73 Ge NMR spectra for series of arylsubstituted germanes were obtained to investigate the effects of hyperconjugation in these systems, and the data are collected in Table 7 [9]. These findings indicate that the amount of hyperconjugation occurring in this series of compounds is not as significant as in the alkoxy and thioalkoxy species 14-24.…”

Synthetic, Structural, and Physical Aspects of Organo-Oligogermanes

“…By 1999, data for 16 germanium compounds having germaniumgermanium single bonds had been reported. [91][92][93] In addition, 73 Ge NMR data for compounds having other types unusual environments for germanium, including hypervalent systems, [94,95] have been recently described. We have investigated several of our oligogermanes using this method and the resulting data is collected in Table 5.…”