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Multiple bonding between atoms is of ongoing fundamental and applied interest. Here, we report a multinuclear (1H, 13C, and 71Ga) solid-state magnetic resonance spectroscopic study of digallium compounds which have been proposed, albeit somewhat controversially, to contain single, double, and triple Ga−Ga bonds. Of particular relevance to the nature of these bonds, we have carried out two-dimensional 71Ga J/ D-resolved NMR experiments which provide a direct measurement of J(71Ga,71Ga) spin-spin coupling constants across the gallium−gallium bonds. When placed in the context of clear-cut experimental data for analogous singly, doubly, and triply bonded carbon spin pairs or boron spin pairs, the 71Ga NMR data clearly support the notion of a different bonding paradigm in the gallium systems. Our findings are consistent with an increasing role across the purported gallane-gallene-gallyne series for classical and/or slipped π-type bonding orbitals. [ABSTRACT FROM AUTHOR]

Direct insight into the elusive nature of multiple bonding between gallium atoms in molecular solids is obtained with ultrahigh ‐ field two ‐ dimensional 71Ga NMR spectroscopy. The gallium – gallium J couplings offer a novel perspective on the electronic structure of these bonds, and the intriguing results are discussed in the context of analogous data for carbon−carbon and boron−boron spin pairs. Cover designed by L. Kobera; background photograph courtesy of V. Terskikh. More information can be found in the Full Paper by D. L. Bryce et al. on page 9565 ff. [ABSTRACT FROM AUTHOR]

Abstract: While the synthetic utility and reactivity of the so-called “GaI” species is reasonably well established, its exact composition remains unknown. Using primarily multinuclear magnetic resonance techniques (and supported with powder X-ray diffraction measurements), we offer some new insights into the composition of “GaI”. Using 127I nuclear quadrupole resonance (NQR) experiments, it is clearly demonstrated that gallium diiodide (GaI2) is a significant component of this material, while GaI3 is not. This finding is in contrast with a prior literature account, which noted that Ga2I3 (i.e., one equivalent of GaI3 per equivalent of Ga metal) was present in significant amounts. Additional solid-state nuclear magnetic resonance (SSNMR) experiments using the 69/71Ga probe nuclei in multiple magnetic fields clearly establish, via its diagnostic Knight-shifted resonance, the presence of Ga0 metal, which is in agreement with prior literature. Taken together, a composition may be tentatively offered: that “GaI” is, to a large extent, two equivalents of Ga0 metal with two equivalents of GaI2, where the latter is composed of Ga+ and ions. This composition may be represented as [Ga0]2[Ga]+[GaI4]−. [Copyright &y& Elsevier]