Contributions to the chemistry of halosilane adducts: XVIII. On the nature of compounds of trimethylhalosilanes with 1,1,3,3-tetramethylguanidine and 2-trimethylsilyl-1,1,3,3-tetramethylguanidine: preparation and characterization of mono- and bis-(2-trimethylsilyl)-1,1,3,3-tetramethylguanidinium halides |
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| Affiliation: | 1. G. K. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation;2. Novosibirsk State University, 630090 Novosibirsk, Russian Federation;3. N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation;1. Department of Organic Chemistry, Cracow University of Technology, Warszawska 24, 31-155, Cracow, Poland;2. Faculty of Chemistry, University of Opole, Oleska 48, 45-052, Opole, Poland;3. Institute of Heavy Organic Synthesis “Blachownia”, Energetyków Str. 9, 47-225, Kędzierzyn-Koźle, Poland;1. Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Silesian University of Technology, B. Krzywoustego 4, 44-100 Gliwice, Poland;2. Biotechnology Centre of Silesian University of Technology, B. Krzywoustego 8, 44-100 Gliwice, Poland;3. Department of Chemical Organic Technology and Petrochemistry, Silesian University of Technology, B. Krzywoustego 4, 44-100 Gliwice, Poland |
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| Abstract: | 1,1,3,3-Tetramethylguanidine (TMG) and 2-(trimethylsilyl)-1,1,3,3-tetramethylguanidine (TMSTMG) react with trimethylhalosilanes Me3SiHal in equimolar ratio with ionization of the Sihalogen bond to give the stable guanidinium salts [(Me2N)2CNHSiMe3]Hal (Hal Cl (1), Br (2)) and [(Me2N)2CN(SiMe3)2]Hal (Hal Cl (3), Br (4), I (5)), respectively, involving tetracoordinate silicon. No reaction occurs with Me3SiF. The same ionic species are present in CHCl3 or CH3CN solutions (IR, 1H, 29Si NMR), thus establishing for the first time, the formation of an ionic solid derivative of Me3SiCl stable towards dissociation. Reaction with an excess of TMG gives an equilibrium mixture of TMSTMG and TMG · HHal. The bis(silyl)guanidinium salts are less stable towards dissociation than the mono(silyl) derivatives, the stability sequence being Cl− < Br− < I− within the series. The reactions of both types of compound have been investigated. The implications of the present and earlier results for the mechanisms of racemization and nucleophilic substitution at silicon are discussed. |
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