D. Hnyk et al., MOLECULAR-STRUCTURE OF 2,4-ETHANOTETRABORANE(10), B4H8(CH2)2, AS DETERMINED BY GAS-PHASE ELECTRON-DIFFRACTION AND AB-INITIO COMPUTATIONS, Inorganic chemistry, 33(12), 1994, pp. 2572-2578
The structure of gaseous 2,4-ethanotetraborane(10), B4H8(CH2)2, more c
ommonly referred to as dimethylene-tetraborane, has been determined by
electron diffraction and ab initio computations. The results confirm
that the molecule consists of a tetraborane(10) cage substituted at th
e ''wing'' boron atoms, B(2) and B(4), by a bridging ''ethene'', C2H4,
moiety. The molecular symmetry is C2v, the conformation about the C-C
bond being eclipsed. Salient structural parameters (r(a)) of the expe
rimental geometry are r[B(1)-B(2)] (hinge-wing) = 189.5(3), r[B(1)-B(3
)](hinge-hinge) = 172.9(17), r(B-C) = 159.8(3), and r(C-C) = 156.8 (fi
xed) pm; B(1)B(2)B(3) = 54.2(5)degrees, and the dihedral (''butterfly'
') angle between the planes B(1)B(2)B(3) and B(1)B(4)B(3) is 100.8(2)d
egrees. These values agree well with the ab initio (MP2/6-31G) optimi
zed molecular geometry and are supported by comparison of the calculat
ed (IGLO) H-1, B-11, and C-13 NMR chemical shifts, using both the MP2/
6-31G and GED geometries, with the experimental NMR data.