Synthesis of mono- and geminal dimetalated carbanions of bis(phenylsulfonyl)methane using alkali metal bases and structural comparisons with lithiated bis(phenylsulfonyl)imides

Abstract

The α,α′-stabilized carbanion complexes [(PhSO₂)₂CHLi·THF] 1, [(PhSO₂)₂CHNa·THF] 2 and [(PhSO₂)₂CHK] 3 were prepared by the direct deprotonation of bis(phenylsulfonyl)methane I in THF with one molar equivalent of MeLi, BuNa and BnK respectively. The geminal dianionic complexes [(PhSO₂)₂CLi₂·THF] 4, [(PhSO₂)₂CNa₂·0.55THF] 5 and [(PhSO₂)₂CK₂] 6 were similarly prepared by the reaction of I with two molar equivalents of MeLi, BuNa and BnK respectively in THF. NMR and MS solution studies of 1–3 are consistent with the formation of charge-separated species in DMSO media. Solutions studies of 4–6, in conjunction with trapping experiments, indicate that the dianions deprotonate DMSO and regenerate the monoanions 1–3. Crystallographic analysis of 1 revealed a 1D chain polymer in which the metal centers are chelated by the bis(sulfonyl) ligands and connect to neighboring units through Li–O(S) interactions. An unexpected feature of 1 is that the polymeric chains are homochiral, since the chelating ligands of the backbone adopt the same relative configuration. Also, the phenyl substituents of each chelate in 1 are oriented in a cisoid manner. The sodium derivative 2 adopts a related solid-state structure, where enantiomeric pairs of chains combine to give a 1D ribbon motif. The lithium bis(phenylsulfonyl)imides [(PhSO₂)₂NLi·THF] 9 and [(PhSO₂)₂NLi·Pyr₂] 10 were also prepared and structurally characterized. In the solid state 9 has a similar connectivity to that found for 1 but with heterochiral chains. In comparison, the more highly solvated complex 10 forms a 1D polymeric arrangement without chelation of the ligands and with the phenyl substituents oriented in a transoid fashion.