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Issue 1, 2012
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Silylation products of cyclic tri-aminal carbanions and their lithiation

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Abstract

The structure of 1,3,5-trimethyl-1,3,5-triaza-cyclohexane (TMTAC) was determined by single crystal X-ray diffraction and compared with earlier gas-phase data. It shows a preference for an aee-conformation in all phases. Lithiated TMTAC, [(RLi)2·(RH)] (1) (R = 2,4,6-trimethyl-2,4,6-triaza-cyclohex-1-yl), was reacted with Et3SiCl, Ph3SiCl and PhMe2SiCl to afford the substituted silanes Et3SiR (1), Ph3SiR (2) and PhMe2SiR (3) in moderate yields. They were characterised by NMR spectroscopy (1H, 13C, 29Si). 1 reacts with Me2SiCl2 and Ph2SiCl2 to give Me2SiR2 (5) and Ph2SiR2 (6) which were characterised by NMR spectroscopy. 5 was also identified by crystal structure determination. Analogous triple substitution could not be observed by employing trichlorosilanes. Quantumchemical calculations explain this by sterical overcrowding of the silicon atom. The reaction of 1 with SiCl4 did not yield fourfold substitution but a formal insertion product of SiCl2 into a C–N bond of the TMTAC ring (2,4,6-trimethyl-2,4,6-triaza-1,1-dichloro-1-sila-cycloheptane, 7) in very small quantities. It was identified by X-ray crystallography and shows an intramolecular Si⋯N dative bond. The reactions of (3) and (5) with n-butyl lithium afforded lithiation of the silicon bound methyl groups in both cases. The products, 8 and 9, were characterised by NMR spectroscopy (1H, 13C, 29Si), 8 was also characterised by X-ray crystallography.

Graphical abstract: Silylation products of cyclic tri-aminal carbanions and their lithiation

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Publication details

The article was received on 19 May 2011, accepted on 15 Sep 2011 and first published on 10 Nov 2011


Article type: Paper
DOI: 10.1039/C1DT10943J
Citation: Dalton Trans., 2012,41, 104-111
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    Silylation products of cyclic tri-aminal carbanions and their lithiation

    C. Sicking, A. Mix, B. Neumann, H. Stammler and N. W. Mitzel, Dalton Trans., 2012, 41, 104
    DOI: 10.1039/C1DT10943J

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