THEORETICAL-STUDY OF ME2S.B11H13 COMPLEX AND INTERMEDIATE STRUCTURES OF B11H15 DERIVATIVE

In this paper we have theoretically studied different isomers of the M e2S . B11H13 complex using the AM1 semi-empirical SCF-MO calculations. The calculated geometries were in good agreement with those determine d by using X-ray diffraction. The comparison of heats of formation for the three isomers showed that the 2-Me2S . B11H13 conformation (-12.4 7 kcal mol(-1)) is more stable than 7-Me2S . B11H13 (-7.64 kcal mol(-1 )) and 7-Me2S . B11H13 (-7.20 kcal mol(-1)). However, the discussion o f a suggested mechanism of their formation, using intermediate structu res of B11H13 permitted us to conclude that the 7-Me2S . B11H13 confor mation is kinetically favoured. The interaction between the H-2 molecu le and B11H13 is more important at the B-1 and B-2 centres than at the B-7 centre, so the H-2 elimination from B11H13 structures to form B11 H13 is easier at the last of these. (C) 1998 Elsevier Science B.V.