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 intermediate (the rate-determining step), followed by proton migration, leading to the addition product. The calculated overall activation barrier for these transformations is consistent with the experimental kinetic observations. This work provides, for the first time, a broad nucleophilicity series of oximes, which is useful to control various nucleophilic additions of oxime species.

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Three types of N(H)-nucleophiles were used to study the nucleophilic addition to the CN group of the 2-propanenitrilium closo-decaborate cluster giving N-closo-decaborato amidrazones.

The reactions of salts of the anion [2 B 10 H 9 (N≡CMe)] -with aliphatic alcohols ROH (R = C n H 2n+1 (n = 1-6) CH 2 CH 2 (OEt), Pr i , Bu i , Bu t , i C 5 H 11 ) are studied. These reactions result in hydrolytically stable imidates [2 B 10 H 9 {NH=C(OR)Me}] -. Their structures were con firmed by the data from mass spectrometry, IR, 1 H, 11 B, and 13 C NMR spectroscopy. The molecular geometry of [2(Z) B 10 H 9 {NH=C(OBu)Me}] -, which formed in nucleophilic addi tion reaction of n butyl alcohol to [2 B 10 H 9 (N≡CMe)] -, was established by X ray diffrac tion analysis.

The Z-configured nitrones − O + N(Me)C(H)C 6 H 4 R 2p (R 2 = OMe (2a), Me (2b), NO 2 (2c)) react with the nitrile functionality of the closo-decaborate clusters [Bu n4 N][B 10 H 9 (NCR 1 )] (R 1 = Me (1a), Et (1b), Bu t (1c), Ph (1d)) in CHCl 3 solution under mild conditions (20−25 °C, 16−18 h) to afford the products of cycloaddition: viz., the borylated 2,3-dihydro-1,2,4-oxadiazoles. This reaction represents the first example of boron-mediated 1,3dipolar cycloaddition of allyl anion type dipoles, i.e. nitrones, to the nitrile group. Alteration of the lipophilic [Bu n4 N] + counterion with the hydrophilic Na + via the metathetical reaction with NaBPh 4 in 3a,b,e,f allows the modification of their hydrophilic−lipophilic properties and, consequently, solubility. Compounds 3a−j and 5a−d were characterized by high-resolution ESI-MS, IR, and 1 H, 13 C{ 1 H}, and 11 B{ 1 H} NMR spectroscopy. The structures of 3a,e,f were determined by single-crystal X-ray diffraction.