The molecular structure of tetra-tert-butyldiphosphine: an extremely distorted, sterically crowded molecule

Abstract

The molecular structure of tetra-tert-butyldiphosphine has been determined in the gas phase by electron diffraction using the new DYNAMITE method and in the crystalline phase by X-ray diffraction. Ab initio methods were employed to gain a greater understanding of the structural preferences of this molecule in the gas phase, and to determine the intrinsic P-P bond energy, using recently described methods. Although the P-P bond is relatively long [GED 226.4(8) pm; X-ray 223.4(1) pm] and the dissociation energy is computed to be correspondingly small (150.6 kJ mol(-1)), the intrinsic energy of this bond (258.2 kJ mol(-1)) is normal for a diphosphine. The gaseous data were refined using the new Edinburgh structure refinement program ed@ed, which is described in detail. The molecular structure of gaseous P(2)Bu(t)(4) is compared to that of the isoelectronic 1,1,2,2-tetra-tert-butyldisilane. The molecules adopt a conformation with C(2) symmetry. The P-P-C angles returned from the gas electron diffraction refinement are 118.8(6) and 98.9(6) degrees, a difference of 20 degrees, whilst the C-P-C angle is 110.3(8) degrees. The corresponding parameters in the crystal are 120.9(1), 99.5(1) and 109.5(1) degrees. There are also large deformations within the tert-butyl groups, making the DYNAMITE analysis for this molecule extremely important.

The Molecular Structure of Hexamethyldigermane Determined by Gas-Phase Electron Diffraction with Theoretical Calculations for (CH3)3M−M(CH3)3 Where M = C, Si, and Ge

“…5 Data analysis was carried out using the program "ed@ed". 6 The experimental intensity curves are shown in Figure 1. Radial distribution (RD) curves for the final models of the molecule are presented in Figure 2.…”

Equilibrium Gas-Phase Structures of Sodium Fluoride, Bromide, and Iodide Monomers and Dimers

“…Further data reduction and the least-squares refinements were then carried out using the ed@ed v2.4 refinement program 49 using the scattering factors of Ross et al. 50 As is generally the case in electron diffraction studies, inelastic scattering was not included explicitly on the basis that it is typically non-oscillatory (especially at wider scattering angles) and is, therefore, removed with the background in this kind of analysis.…”

Structures of Energetic Acetylene Derivatives HC≡CCH2ONO2, (NO2)3CCH2C≡CCH2C(NO2)3 and Trinitroethane, (NO2)3CCH3

“…The data were reduced to total intensities using PIMAG (version 040827) [74] in connection with a sector curve, which was based on experimental xenon scattering data and tabulated scattering factors of xenon. Further data reduction yielding molecular intensity curves was performed using the ED@ED program (Version 3.0) [75] and scattering factors [76]. For both compounds the ratio of the electron wavelength to the nozzle-to-plate distances was checked using benzene data and the widely accepted r a value of 1.397Å for the C-C distance in benzene.…”