Reactions of [closo-B 12 H 12 ] 2with ArI(OAc) 2 in aqueous AcOH in the presence of [NEt 4 ] + or [NHEt 3 ] + give [closo-B 12 H 11-1-IAr]-(1) in 74-95% yield as a white precipitate. The zwitterions decompose in CD 3 CN solutions with rates k = 3.30±0.04×10-4 s-1 (Ar = Ph, 1a[NEt 4 ]) and k = 1.96±0.01×10-4 s-1 (Ar = C 6 H 4 OMe-4, 1b[NEt 4 ]) at 0 o C. Reactions of the zwitterion with Me 2 NCHS and pyridine gave the corresponding products [closo-B 12 H 11-1-SCHNMe 2 ]-(2) and [closo-B 12 H 11-1-NC 5 H 5 ]-(3) isolated in 25-27% and up to 44% yield, respectively. The former anion is a protected thiol derivative, which was transformed to the sulfonium derivative [closo-B 12 H 11-1-S(CH 2) 5 ]-(8). The molecular structure and spectroscopic properties of pyridinium zwitterion 3 were analyzed experimentally and computationally (B3LYP), and results compared with those for the [closo-B 10 H 9-1-NC 5 H 5 ]-(4) analogue. Mechanisms of formation of 2-4 from appropriate aryliodonium zwitterions were analyzed with the M06-2x computational method.

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Succinimides are among the most studied compounds due to their wide profile of biological activities. It is well-known that succinimides undergo ring-opening reactions under alkaline conditions. This feature limits the formation of 3-substituted succinimides from maleimides by an oxa-Michael reaction, for which basic conditions are required. Herein, we report the synthesis, characterization, and crystal structure of metallocarbonyl (Fe, Ru) complexes bearing 3-substituted succinimide ligands. These complexes were obtained in oxa-Michael reactions of CpM­(CO)2(η1-maleimidato) (M = Fe, Ru) with alcohols (MeOH, EtOH) in the presence of K2CO3. During the crystallographic studies of an iron complex bearing the 3-methoxysuccinimide ligand, we also identified unexpected crystals of free 3-methoxysuccinimide. We performed some additional experiments and theoretical calculations to determine the mechanism of formation of the obtained N-nonsubstituted succinimide. We demonstrate that 3-methoxysuccinimide resulted from light-induced degradation of CpFe­(CO)2(η1-3-methoxysuccinimidato). On the basis of these findings, we propose an indirect route leading to 3-substituted succinimides starting from maleimide via the light-induced degradation of iron metallocarbonyl succinimidato complexes. The proposed methodology prevents ring opening of succinimide under alkaline conditions and gives N-nonsubstituted succinimide products. To confirm the effectiveness of the described method, CpFe­(CO)2(η1-maleimidato) was allowed to react with several aliphatic alcohols and phenol, affording the oxa-Michael reaction products in the case of primary alcohols. The irradiation of the obtained compounds with daylight gave the N-nonsubstituted 3-alkoxysuccinimides.

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