D. S. Bolotin, V. Burianova, A. Novikov
Oct 5, 2016
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Organometallics
Abstract
Three types of oxime species, i.e., 4-morpholylcarbamidoxime (hydroxyguanidine), phenylacetamidoxime and benzamidoxime (amidoximes), and cyclohexanone oxime and benzophenone oxime (ketoximes), react at room temperature with the 2-nitrilium closo-decaborate clusters, leading to 2-iminium closo-decaborates (14 examples; 57–94%). These species were characterized by ICPMS-based boron elemental analysis, HRESI–-MS, molar conductivity, IR, 1H{11B}, and 11B{1H} NMR spectroscopies, and additionally by single-crystal X-ray diffraction (for six compounds). On the basis of kinetic data, ΔH⧧, ΔS⧧, and ΔG⧧ of the additions were determined, showing a 4 order-of-magnitude decrease in reactivity from the hydroxyguanidine to the aromatic ketoxime as entering nucleophiles. The results of DFT calculations indicate that the mechanism for these reactions is stepwise and is realized through the formation of the orientation complex of the nitrone form, R2R3C═N+(H)O–, of oximes with [B10H9NCEt]−, giving further an acyclic interm...