Discussion
73Ge is an esoteric nucleus as far as NMR spectroscopy is concerned, chiefly because of its large quadrupolar moment, which tends to cause excessive broadening of signals, and there are many fewer reported data than for other Group IVB elements.' So far, to our knowledge, no attempt has been made to determine the 73Ge NMR spectra of germacyclohexanes, regardless of the fundamental importance of this class of compounds in relation to their carbon analogues.
As part of an extensive study of the NMR spectra of organogermanium compounds2 we have prepared and determined the 73Ge and 13C NMR spectra of germacyclohexane (l), 1-, 3and 4-methyl-1-germacyclohexane (2-4, respectively), 1, l-dimethyl-l-germacyclohexane (5), transand cis-174-dimethyl-l-germacyclohexane (6) as a mixture and 1,1,3-and 1,1,4trimethyl-1-germacyclohexane (7 and 8, respectively). The 73Ge chemical shifts in ppm relative to external tetramethylgermane [ SC3Ce)], together with the halfwidths ( A V ~, ~ in Hz), are listed in Table 1. One-bond Table 1. 73Ge chemical s h i of germacyclohexanes" of Ma HnGe) J(GeWb A v , , ~~ S('3C)" None (1) -131.2 92.8 16.4 26.6 1-(2) -65.3 90.8 22.3 33.1 3-(3) -131.2 26.6 4-(4) -134.3 94.0 21.0 26.4 1.1-(5) ~ 13.7 15.6 30.1 1,4-(eld -61.5, -73.4 30.2(c), 32.7(t) 1,1,3-(7) -12.2 30.8 1.1.4-(8) -17.2 18.3 29.8 a In ppm relative to tetramethylgermane. Negative values correspond to upfield shifts. cThe corresponding 13C shifts of the carbon analogues of 1-8. Data taken from Ref. 7. * A mixture of trans and cis isomers. Position Hz.