Methylenetriimidosulfate H2CS(NtBu)32−—The First Dianionic Sulfur(VI) Ylide

Through isoelectronic replacement of the oxygen atoms in SO42− ions by one CH2 and three NtBu groups one arrives formally at the dianion H2CS(NtBu)32−, which has been isolated for the first time in the form of the sulfur(VI) ylide complex [(tmeda)2Li2{CH2S(NtBu)3}] (see structure). Deprotonation of the S-bonded methyl group in the triimidosulfonate MeS(NtBu)3− ion provides facile access in good yields. Hydrolysis favors the formation of the triimidosulfate [{(tmeda)Li2[OS(NtBu)3]}3] and methane, and not, as one might expect, diimidomethylenesulfate and the amine. tmeda=Me2NCH2CH2NMe2.