Synthesis of an Organogallium(I) Compound Ga(CH2CMe2Ph)n with EPR spectral Evidence for Gallium Clusters

摘要

The organogallium(I) compound Ga(CH2CMe2Ph)n has been prepared by the reduction of Ga(CH2CMe2Ph)2 Cl by using either sodium or lithium with naphthalene in THF. The yellow dihydronaphthalene gallium(III) intermediate M2 C10H8 Ga(CH2CMe2Ph)2Cl2 initially formed at -78 deg C but then decomposed at higher temperatures to form Ga(CHeCM2Ph)n, Ga(CH2CMe2Ph)3 and MCl. EPR spectra, which were recorded as the two yellow intermediates Na2 C10H8Ga(CH2CMe2R)2Cl2 (R = Ph, Me) decomposed, indicated the presence of radicals. The first and second derivatives of the EPR signals, line-widths, g-values and hyperfine coupling constants are consistent with the radicals being clusters of organogallium species. The experimental spectra were simulated by the superposition of two spectra, a single Gaussian shaped line with a peak-to-peak width of 14 mT (92%) with the spectrum of 5 equivalent gallium nuclei, A = mT (8%). The even number of lines observed in the experimental spectra indicate an odd number of gallium nuclei with at least five being required to give the number of observed lines.