The molecular structure of tetra-tert-butyldiphosphine: an extremely distorted, sterically crowded molecule.
The molecular structure of tetra-tert-butyldiphosphine: an extremely distorted, sterically crowded molecule.
复制标题
四叔丁基二膦的分子结构：一种极度扭曲、空间拥挤的分子。
作者：
S. L. Hinchley;H. Robertson;K. B. Borisenko;A. Turner;Blair F. Johnston;D. Rankin;M. Ahmadian;J. N. Jones;A. Cowley
用电子衍射法和X射线衍射法测定了四叔丁基双膦在气相和晶相中的分子结构。从头算方法被用来更好地了解该分子在气相中的结构择优，并利用最近描述的方法确定了本征P-P键能量。虽然P-P键相对较长[GED 226.4(8)PM；X射线223.4(1)PM]，并且解离能相应地很小(150.6 kJ摩尔(-1))，但对于双膦来说，这个键的内禀能(258.2 kJ摩尔(-1))是正常的。用新的爱丁堡结构修正程序ed@ed对气体数据进行了修正，并对其进行了详细描述。对气态P(2)Bu(T)(4)的分子结构与等电子的1，1，2，2-四叔丁基二硅烷的分子结构进行了比较。分子采用C(2)对称性构象。由气体电子衍射精修得到的P-P-C角为118.8(6)度和98.9(6)度，相差20度，而C-P-C角为110.3(8)度。晶体中的相应参数为120.9(1)、99.5(1)和109.5(1)度。叔丁基内部也有很大的变形，这使得对这种分子的炸药分析变得极其重要。
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.