%0 Journal Article
%T Nuclear Magnetic Resonance Spectroscopy of Germanium Compounds
%A Charles S. Weinert
%J ISRN Spectroscopy
%D 2012
%R 10.5402/2012/718050
%X The field of NMR spectroscopy is reviewed in this paper, from early developments in the 1950s to present day research. Specific attention is paid to recent investigations, including the observation of fluxional behavior of hypervalent germanium species having five or six attached ligands by 73Ge NMR spectroscopy, the spectral properties of linear and branched oligogermanes that contain single germanium-germanium bonds, and the relatively new field of solid-state germanium-73 NMR. 1. Introduction The use of nuclear magnetic resonance (NMR) spectroscopy to characterize and probe the nuclei of the group 14 elements is highly useful, with the notable exception of the central element germanium. Carbon-13 NMR spectroscopy is invaluable for the characterization of organic compounds, and silicon-29 NMR spectroscopy can provide a wealth of structural information for organosilicon compounds [17¨C20], and allows direct observation of the silicon nucleus itself rather than gaining information regarding the silicon centers indirectly by probing the attached organic substituents. Tin has two NMR-active nuclei, tin-117 and tin-119, which, like carbon-13 and silicon-29, are both spin 1/2 nuclei. These two nuclei have also been extensively used for the characterization of organotin compounds, and 117Sn¨C119Sn coupling between the two nuclei can also be readily observed [21]. Lead-207 is the only NMR-active nucleus for this element, and it is also spin 1/2 and has been regularly used to characterize organolead compounds [22]. The relevant NMR parameters for the group 14 nuclei are summarized in Table 1. Table 1: Nuclear magnetic resonance data for the group 14 elements. In terms of germanium, the only NMR-active nucleus this element possesses is 73Ge [23, 24], which has a spin of 9/2 and a relatively large quadrupole moment of £¿19.6£¿fm2 [25]. This large quadrupole moment leads to the observation of broad lines if the germanium nucleus being observed is not disposed in a symmetric environment. To further complicate matters, the gyromagnetic ratio of all other observable nuclei in group 14 render them sensitive enough to be observed without considerable difficulty. However, the gyromagnetic ratio for the 73Ge nucleus is 0.9332 ¡Á 107£¿rad T£¿1 s£¿1 [26¨C28] which results in an inherent lack of sensitivity despite the fact that the natural abundance of the 73Ge nucleus is 7.7% which is seven times that of 13C (1.1%). At a magnetic field strength of 11.74 T, the 73Ge nucleus resonates at 17.44£¿MHz and therefore requires a dedicated low-band probe for its observation. In fact, the
%U http://www.hindawi.com/journals/isrn.spectroscopy/2012/718050/