Tetraborane(10), B4H10: structures in gaseous and crystalline phases

Abstract

Supplementing gas-phase electron-diffraction data with restraints derived from a graded series of ab initio calculations makes possible refinement of all geometrical parameters and amplitudes of vibration. By avoiding the need to fix some parameters, this technique yields structures which are more completely refined and thus have more reliable standard deviations than procedures used previously. It has been applied to the gas-phase structure of the urachno boron hydride tetraborane( lo), B,H,,. Salient structural parameters (rt structure) were found 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( 1 5), r[B(2)-H( 1,2)] 14 1.7( 8), r[B( 1 )-H( 1 )] 119.8(8), r[B(2)-H(2)Iendn] 121.0(8) and r[B(2)-H(2),,,] 120.5(8) pm; butterfly angle 117.2( 4)". 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. ~ ~~ ~~ ~~~~3 We use the term 'uncertainty' for the estimated possible error in a supplementary observation, and 'estimated standard deviation' for the error in a parameter derived in the least-squares refinements. The uncertainties, which give the weights assigned to additional observations, are, in the case of additional experimental data, the estimated standard deviations of those data. 9 'Restraint' is used for any additional information which is applied flexibly, 'constraint' for one which is applied rigidly, such as a fixed parameter or molecular symmetry.

Aluminium Atoms at High Connectivity Sites in Polyhedral Polyborane Analogous Clusters: From Aluminaboranes to Carbaalanes

“…formation is quite similar to that of tetraborane(10), [22] although the inner BϪB bond is lengthened. The AlϪB disIn contrast to these well-established classes of polyhedral cluster compounds, no comparable chemistry has been de-tance of the AlϪHϪB three center bonds was found to be 231.6 pm which, as expected, is much longer than the AlϪB veloped with aluminium which is the next heavier homologue of boron in the third main group.…”

Molecular Structure of 1,2-Bis(trifluoromethyl)-1,1,2,2-tetramethyldisilane in the Gas, Liquid, and Solid Phases: Unusual Conformational Changes between Phases

“…17,18 All independent geometric parameters were refined using a least-squares method and restraints were applied, using the SARACEN method, [5][6][7] to five parameters that could otherwise not be refined (Table 4). The restraints were based on values calculated at the MP2/6-311++G** level.…”

“…[5][6][7] The structure of 1,2-ditert-butyldisilane 1 was found to be anti with C 2 symmetry at room temperature, while 1,2-ditert-butyltetrachlorodisilane 2 returned a transoid conformation by both GED and ab initio methods. Both of these systems displayed evidence of steric crowding, with larger than average bond angles observed about the silicon atoms.…”

Gas-phase structures of 1-adamantylphosphines, PH n (1-Ad)3−n (n = 1–3)

“…For each of 1-3 a series of quantum mechanical calculations, employing different levels of theory and basis sets, were performed using the Gaussian 03 suite of programs [14]. As well as providing insights into the structures of the compounds, the graded series of calculations for 1 provided the values and uncertainties for the SARACEN restraints [15][16][17] used in the GED structure refinement.…”