CARBON-FLUORINE BOND ACTIVATION IN PERFLUOROBENZONITRILE BY LIN(SIME3)(2) - SYNTHESIS OF (ME3SI)(2)NC6F4CN-4 AND CRYSTAL-STRUCTURE OF LIN(C6F4CN-4)(2)CENTER-DOT-2C(4)H(8)O

The reaction of C6F5CN with the dimeric lithium salt [Li(NSiMe3). Et2O ](2) yielded a 11:9 mixture of (Me3Si)(2)NC6F4CN-4 1 and LiN(C6F4CN-4) (2) . 2thf, respectively (thf = tetrahydrofhran). The compounds were c haracterized spectroscopically and complex 2 by crystal structure dete rmination. The central lithium forms a distorted trigonal bipyramid th e apical position of which is filled by a nitrile nitrogen of an adjac ent molecule, inducing chains running parallel to the b-direction of t he crystal. The driving force for the production of 1 and 2 is the eli mination 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 activ ation apply to both systems.