Further Adventures in Germanium NMR

Abstract

The acoustic ring signal that dominates NMR spectra of low gyromagnetic ratio nuclei has always been a problem when trying to observe signals from weak samples. This work looks at some ways of improving the observability o f 7 3 G e -one such nucleus.

G73e Nuclear Magnetic Resonance Spectroscopy of Germanium Compounds

“…As part of our extensive investigations on the chemistry of discrete oligogermanes [13][14][15][81][82][83][84][85][86][87][88][89], we recently reported an investigation of the 73 Ge NMR spectra of several oligogermanes [13], which furthers the studies conducted by Wilkins et al [2] and Thomson et al [11]. The data from these three studies are shown in Table 9.…”

“…In this case, nitrogen is a stronger donor than oxygen and the ISRN Spectroscopy 7 corresponding linewidth of the germane 8 is larger than that observed for 7 which contains only oxygen atoms as potential donors. Similarly, in the triaryl-substituted germanes 9-11 (Scheme 7), the strength of the donor interaction is expected to decrease with the identity of the donor atom in the order N > O > S [53], and the order of ν 1/2 values of these compounds follows the expected trend, measuring 900 Hz (9), 350 Hz (10), and 270 Hz (11). In addition, the steric bulk of the substituent in the oxygen substituted species has little effect on the observed ν 1/2 values in these compounds, as the ν 1/2 values for 9, 12, and 13 are all 350 Hz [53].…”

“…In the more highly methyl substituted oligogermane Me 2 HGeGeH 3 (30) the resonance for the -GeHMe 2 atom appears at δ −127 ppm and in Me 3 GeGeH 3 (31) the resonance for the -GeMe 3 atom appears at δ −48 ppm [2]. Only one resonance was observed in the 73 Ge NMR spectrum of Me 2 ClGeGeH 3 (33) at δ −281 ppm arising from the -GeH 3 atom [11]. No resonance was observed for the -GeMe 2 Cl atom due to the presence of the single chlorine atom that results in excessive broadening of the signal for the germanium atom to which it is attached.…”

“…The 73 Ge NMR spectrum of Ph 3 GeEt using a one-pulse experiment (top), the RIDE sequence (middle), and the EXSPEC sequence (bottom). Reprinted [11] with permission. Copyright 1999 Taylor & Francis.…”

“…The presence of aryl substituents in place of alkyl substituents also affects an upfield shift of the 73 Ge NMR resonance, albeit to a significantly lesser extent than what is observed for hydrogen substituents. The single resonance for the permethyl-and perethyl-substituted digermanes Ge 2 Me 6 (34) [11] and Ge 2 Et 6 (35) [12] was observed at δ −59 and −35 ppm (resp.) while that for Ge 2 Ph 6 (36) [11] was observed upfield at δ −67 ppm.…”