INTERACTIONS IN MOLECULAR-CRYSTALS, 144 - ORTHO-BENZENE DERIVATIVES WITH MESHED COGWHEEL TRIMETHYLSILYL SUBSTITUENTS - STRUCTURAL COMPARISON WITH BENZENE-1,2-DISULFONATE SALTS AND ROTATION ENTHALPY HYPERSURFACES

ortho-Benzene derivatives with adjacent bulky propeller substituents a re well-suited model compounds to investigate their potentially couple d rotations. To approach the molecular dynamics of 1,2-bis(trimethylsi lyl)benzene, a liquid at room temperature and containing heteroelement substituents, an advantageous starting point are the crystal structur es of the stereochemically correspondent benzene-1,2-disulfonate diani on salts. For both the rotations of the synperiplanar three-bladed rot or-groups -SO3- and -Si(CH3)(3), PM3-enthalpy hypersurfaces are presen ted, which suggest only weak interdentate interaction and, concomitant ly, only partly coupled intermolecular substituent rotation dynamics. Additional data from the Cambridge Structural Database for silicon org anic compounds fit into the contour lines of the enthalpy surface calc ulated for 1,2-bis(trimethylsilyl)benzene, and the structure correlati on with varying distances Si Si between the heteroelement centers can be discussed in more general terms of the substituent propeller blade length vs. thickness ratio.