CRYSTAL AND MOLECULAR-STRUCTURE OF O-PHENYLDIBENZOFURANIUM TETRAFLUOROBORATE

The crystal and molecular structure of O-phenyldibenzofuranium tetrafl uoroborate, a representative of triaryloxonium compounds, was determin ed by the direct method (a = 7.001(2), b, = 13.865(5), and c = 16.352( 5) Angstrom; gamma = 93.71(2)degrees; Z=4; sp.gr.P2(1)/n; and R = 0.08 1) 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 folde d 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 Angstrom the plane through the adjacent alpha-C atoms. The BF 4- ion occupies two sites (with probabilities of 0.8 and 0.2), which a re related by a rotation about an F-F edge. One of the F atoms has a s hort contact (2.883 Angstrom) with the O atom. Moreover, all the F ato ms form hydrogen bonds with the C atoms of the six-membered rings.