Pt. Brain et al., MOLECULAR-STRUCTURE OF TRIFLUOROPHOSPHINE TETRABORANE(8), B4H8PF3, ASDETERMINED IN THE GAS-PHASE BY ELECTRON-DIFFRACTION AND AB-INITIO COMPUTATIONS, Inorganic chemistry, 36(6), 1997, pp. 1048-1054
The molecular structure of trifluorophosphine tetraborane(8), B4H8PF3,
has been studied in the gas phase by electron diffraction. The experi
mental data can be fitted using a model which represents the gas as co
nsisting solely of the endo conformer with C-s symmetry, the PF3 group
staggered with respect to the B(I)-H(1) bond. Important experimental
structural parameters (r(alpha)degrees) are r[B(1)-B(2)] (hinge-wing)
= 184.7(9) pm, r[B(1)-B(3)] (hinge-hinge)= 172.2(12) pm, r[B(2)-B(3)]
= 179.9(10) pm, r[B(1)-P] = 179.8(9) pm, and r(P-F) (mean) = 152.8(1)
pm; B(3)B(1)P = 131.6(11)degrees, and the dihedral (''butterfly'') ang
le between the planes B(1)B(2)B(3) and B(1)B(4)B(3) is 133.9(23)degree
s. These values agree well with the ab initio (MP2/TZP level) optimize
d molecular geometry for the endo conformer; at the MP2/TZP//MP2/TZP ZPE(HF/6-31G) level, the exo conformer is predicted to represent ca.
2% of the compound vapor, consistent with the experimental B-11 NMR s
olution spectrum. The experimental and theoretical geometries are supp
orted by comparison of the calculated (IGLO) B-11 NMR chemical shifts
with the experimental NMR data.