TETRABORANE(10), B4H10 - STRUCTURES IN GASEOUS AND CRYSTALLINE PHASES

Supplementing gas-phase electron-diffraction data with restraints deri ved from a graded series of ab initio calculations makes possible refi nement of all geometrical parameters and amplitudes of vibration. By a voiding the need to fix some parameters, this technique yields structu res which are more completely refined and thus have more reliable stan dard deviations than procedures used previously. It has been applied t o the gas-phase structure of the arachno boron hydride tetraborane(10) , B4H10. Salient structural parameters (r(alpha)(o) structure) were fo und to be: r[B(1)-B(2)] 186.6(2), r[B(1)-B(3)] 173.7(5), r[B(1)-H(1,2) ] 123.0(15), r[B(2)-H(1,2)] 141.7(8), r[B(1)-H(1)] 119.8(8), r[B(2)-H( 2)](endo)] 121.0(8) and r[B(2)-H(2)(exo)] 120.5(8) pm; butterfly angle 117.2(4)degrees. The crystal structure was also redetermined at 100 K . All gas-phase, crystallographic and ab initio structural parameters were found to be in good agreement.