Synthesis of 10-Methylsulfide and 10-Alkylmethylsulfonium nido-Carborane Derivatives: B–H···π Interactions between the B–H–B Hydrogen Atom and Alkyne Group in 10-RC≡CCH2S(Me)-7,8-C2B9H11

5 years ago

Synthesis of 10-Methylsulfide and 10-Alkylmethylsulfonium nido-Carborane Derivatives: B–H···π Interactions between the B–H–B Hydrogen Atom and Alkyne Group in 10-RC≡CCH2S(Me)-7,8-C2B9H11

Ivan A. Godovikov, Igor B. Sivaev, Kyrill Yu. Suponitsky, Vladimir I. Bregadze, Sergey A. Anufriev

The 10-dimethylsulfonium derivative of nido-carborane 10-Me2S-7,8-C2B9H11 was prepared by reaction of the protonated form of nido-carborane with dimethylsulfide in toluene. Its partial demethylation with sodium amide in toluene gave the corresponding 10-methylsulfide derivative [10-MeS-7,8-C2B9H11]–. This 10-methylsulfide derivative was alkylated with various alkylating agents to produce a series of 10-alkylmethylsulfonium derivatives 10-R(Me)S-7,8-C2B9H11 (R = Et, Pr, Bu, CH2CH=CH2, CH2Ph, CH2C≡CH, CH2C≡CPh, CH2C≡CSiMe3). The 11B NMR spectra of the latter three compounds containing an acetylene group demonstrate unusually strong signal splitting that can be explained by strong intramolecular B–H···π(C≡C) interactions. The existence of such interactions in the solid state was supported by the X-ray crystal structure of 10-HC≡CCH2(Me)S-7,8-C2B9H11 with a short B–H···C(C≡C) distance of 2.658 Å. This is the first example of B–H···π(C≡C) hydrogen bonding.Reaction of the protonated nido-carborane with SMe2 gives the 10-dimethylsulfonium derivative 10-Me2S-7,8-C2B9H11. Its demethylation-alkylation produces a series of 10-alkylmethylsulfonium derivatives 10-R(Me)S-7,8-C2B9H11. The compounds containing an alkyne group (R = CH2C≡CH, CH2C≡CPh, CH2C≡CSiMe3) demonstrate strong intramolecular B–H···π(C≡C) interactions both in the solid state and in solution.

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DOI: 10.1002/ejic.201700785