The method for synthesis of 2-sulfanyl closo -decaborate anion and its S -alkyl and S -acyl derivatives

A two-stage method for preparation of the sulfanyl derivative of closo-decaborate anion (n-Bu4N)2[2-B10H9SH]2- (1) is worked out. At the first stage, the [2-B10H9SC(NMe2)2]- (2) or the [2-B10H9SCHNMe2]- (3) derivative is obtained by the reaction of [B10H11]- with tetramethylthiourea or thiodimethylformamide, respectively. Further reducing of (2) and (3) with hydrazine results in (1). This procedure surpasses those described earlier in yield and simplicity. It is found that (1) enters into exhaustive alkylation reactions with alkyl halides forming S,S-disubstituted sulfonium salts. The following derivatives are synthesized: [2-B10H9S(n-Bu)2]- (4), [2-B10H9S(CH2Ph)2]- (5), [2-B10H9S(CH2CHCH2)2]- (6), [2-B10H9S(CH2COOEt)2]- (7), and [2-B10H9S(CH2CONH2)2]- (8). The reactions of 1 with acetyl chloride and benzyl chloride result in the formation of thioethers [2-B10H9SС(O)CH3]2- (9) and [2-B10H9SС(O)Ph]2- (10), respectively. Salts of 1–10 are characterized by NMR and IR spectroscopy, and salts of derivatives 1–3, 5–9 are studied by single-crystal X-ray diffraction. Compared to organic sulfonium salts and thioethers, compounds 1–10 are much more resistant to nucleophiles and bases.