Crystal and molecular structure of O-phenyldibenzofuranium tetrafluoroborate

The crystal and molecular structure of O-phenyldibenzofuranium tetrafluoroborate, a representative of triaryloxonium compounds, was determined by the direct method (a=7.001(2), b=13.865(5), and c=16.352(5) A; γ=93.71(2) deg.; Z=4; sp. gr. P21/n; and R=0.081) for 2078 unique nonzero reflections. Both benzene rings A and B of the dibenzofuran fragment and the phenyl ring D are planar; the furan cycle C adopts the envelope conformation. The A and B cycles are folded to the same side of the plane of the furan cycle. The oxonium moiety of the cation C3O+ is essentially nonplanar: the O atom is displaced by 0.323 A the plane through the adjacent α-C atoms. The BF4- ion occupies two sites (with probabilities of 0.8 and 0.2), which are related by a rotation about an F-F edge. one of the F atoms has a short contact (2.883 A) with the O atom. Moreover, all the F atoms from hydrogen bonds with the C atoms of the six-membered rings