organic compounds
ꢀ
60.0 (2) and 359.8 (2) for atoms B1 and B2, respectively.
Another monoclinic polymorph of the title compound, (Ib),
Acta Crystallographica Section C
Crystal Structure
3
Communications
has been described at 190 K in the P2 /c space group, with cell
parameters a = 12.378 (5) A, b = 8.019 (2) A, c = 19.180 (7) A,
1
Ê Ê Ê
3
= 100.89 (3) and V = 1869.51 A (Lange et al., 2002). The
ISSN 0108-2701
ꢀ
Ê
ꢀ
only similarity between the cell parameters of the two poly-
morphs is that the c axis of (Ia) and the b axis of (Ib) differ by
A new polymorph of tetraphenyl-
diboroxane
Ê
just 0.1 A. Since the cell parameters are otherwise completely
different, the setting in P2 /n has been selected for polymorph
1
(
Ia). A least-squares ®t of the two polymorphs shows that the
Linda Kaufmann, Hans-Wolfram Lerner and Michael
Bolte*
orientations of the phenyl rings attached to atom B2 are
almost identical in (Ia) and (Ib), while the orientations of the
phenyl rings attached to atom B1 differ signi®cantly (Fig. 2).
This difference can also be illustrated by a comparison of the
corresponding torsion angles (Table 1); only the torsion angles
about the B1ÐC1 and B1ÐC7 bonds differ signi®cantly.
An analysis of short intramolecular distances for both
polymorphs reveals two somewhat shorter XÁ Á ÁH distances in
polymorph (Ib), which might be the reason for the different
Institut f uÈ r Anorganische Chemie, J. W. Goethe-Universit aÈ t Frankfurt, Max-von-Laue-
Strasse 7, 60438 Frankfurt/Main, Germany
Received 13 August 2007
Accepted 21 August 2007
Online 22 September 2007
Ê
orientations of the phenyl rings [B2Á Á ÁH10 = 2.63 A in (Ib)
A new polymorph of tetraphenyldiboroxane [or oxybis-
(
Ê
Ê
versus 2.74 A in (Ia), and C2Á Á ÁH6 = 2.71 A in (Ib) versus
diphenylborane)], C H B O, (Ia), has been found. It is
2
Ê
Ê
2
4
20
2.79 A in (Ia); all CÐH distances are 0.93 A in both poly-
morphs]. A molecular mechanics calculation with the mol-
ecular modelling program MOMO (Beck et al., 1991) shows
that the conformation of polymorph (Ia) is more stable
monoclinic, like the already known form, (Ib), and can be
re®ned in the same space group, namely P2 /c, or in the
equivalent setting P2 /n. The molecular conformations of the
1
1
�
1
� 1
two polymorphs differ in the rotations of two of the phenyl
rings about the BÐC bonds, leading to markedly different
packing patterns and cell dimensions.
than that of polymorph (Ib) by 4.2 kcal mol [1 kcal mol =
�
1
4
.184 kJ mol ].
The packing motifs of the two polymorphs are quite
different, presumably due to the different orientations of two
of the four aromatic rings. The orientations of the packing
diagrams (Figs. 3 and 4) have been chosen so that one mol-
ecule (shown with dashed bonds) has approximately the same
orientation in both ®gures. Comparison of the diagrams shows
that the orientation of the remaining molecules differs
markedly.
Comment
Recently, we have synthesized the anionic [1,1]diborata-
+
ferrocenophane, (II), which represents a highly ef®cient Li
scavenger (see scheme below) (Scheibitz et al., 2003), and
anionic ferrocene derivatives such as the ferrocenyl borate,
(
IV) (Kaufmann et al., 2007). The ferrocene derivative, (III),
represents a versatile starting material for the synthesis of a
broad range of ferrocenyl-substituted polyborates. In an
attempt to synthesize the borane, (III), from FcHgCl (Fc =
C H FeC H ) and Ph BBr, we obtained the title compound,
5
4
5
5
2
tetraphenyldiboroxane, Ph BÐOÐBPh , (I), as a side-
2
2
product in a new polymorph, (Ia).
Figure 1
A perspective view of the title polymorph, showing the atom-numbering
scheme [identical to that used for (Ib)]. Displacement ellipsoids are
drawn at the 50% probability level and H atoms are shown as small
spheres of arbitrary radii.
Both B atoms in polymorph (Ia) are in trigonal±planar
environments (Fig. 1). The sums of the bond angles are
o588 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107041352
Acta Cryst. (2007). C63, o588±o590