Strength and directionality of the C(sp(3))-H center dot center dot center dot S(sp(3)) interaction. An ab initio study using the H2S center dot center dot center dot CH4 model complex

Using the MP2 and MP4 methods and extended basis sets. the potential energy surface of the H2S ... CH4 complex was examined to locate all its minimum energy conformations. Two minima. are found, characterized by C-H ... S and S-H ... C intermolecular contacts: at the MP2 level, the basis-set superposition error-corrected interaction energy is -0.42 and -0.84 kcal/mol, respectively, similar to the MP2 values previously found for the C-H ... S interactions (-0.49 and -0.72 kcal/mol). The anistropy of the C-H ... S interaction is also studied. (C) 1997 Elsevier Science B.V.