Carbon–fluorine bond activation in perfluorobenzonitrile by LiN(SiMe₃)₂. Synthesis of (Me₃Si)₂NC₆F₄CN-4 and crystal structure of LiN(C₆F₄CN-4)₂·2C₄H ₈O

Abstract

The reaction of C₆F₅CN with the dimeric lithium salt [Li(NSiMe₃)·Et₂O]₂ yielded a 11∶9 mixture of (Me₃Si)₂NC₆F₄CN-4 1 and LiN(C₆F₄CN-4)₂·2thf, respectively (thf = tetrahydrofuran). The compounds were characterized spectroscopically and complex 2 by crystal structure determination. The central lithium forms a distorted trigonal bipyramid the apical position of which is filled by a nitrile nitrogen of an adjacent molecule, inducing chains running parallel to the b-direction of the crystal. The driving force for the production of 1 and 2 is the elimination of LiF and SiMe₃F, respectively. The calculated enthalpy for formation of 2 is more favourable compared to that for formation of 1, although the similar yields indicate that similar enthalpies of activation apply to both systems.

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