Structures of polyfluoroaromatic compounds. II. Crystal structure of 2,3,5,6-tetrafluorobiphenyl

Abstract

The mean P-C bond lengths for the sulphide and selenide are almost exactly the same (~1.812 A) but are noticeably longer in the phosphine (1.835/k). The lengths do not vary significantly from those observed in the o-tolyl derivatives and it would seem, therefore, that the position of substitution of the methyl group has no direct effect upon them. The length of the P-C bonds seems to be influenced by two factors only: the valence state of the P atom and, for individual bond lengths, the degre~ of intermolecular steric hindrance.Thanks are due to the SRC for a studentship to KDH; to the Computing Centres at Oxford and Coleraine for facilities and to Dr C. K. Prout for providing the diffractometer.

Structures of polyfluoroaromatic compounds. V. Crystal structure of perfluorodiphenylacetylene

“…The set of four short C-F bonds are comparable with the shorter than average C-F bonds in 2-nitrononafluorobiphenyl where the range is 1.331-1.348 A (mean 1.342 A). The remaining C-F bonds are nearer in length to those found in 2,3,5,6-tetrafluorobiphenyl (Goodhand & Hamor, 1978), range 1.357-1.364 A (mean 1.360 A). It does not seem possible to rationalize these differences in the present structure.…”

“…The small endocyclic angles at C(1) and C(I'), mean 116.4 °, are consistent with some double-bond character in C(1)-C(A) and C(I')-C(B). They are, however, also explainable, as in tetrafluorobiphenyl (Goodhand & Hamor, 1978), by the presence of the electronegative F substituents.…”

Structure of 4'-butyl-2,3,5,6-tetrafluorobiphenyl-4-carbonitrile

“…The butyl group lies at 13.4 (4) ° to the phenyl group and there is an angle of 40.8 (4) ° between the tetrafluorophenyl and phenyl groups. This latter angle is substantially smaller than the 57.9 ° in 2,3,5,6-tetrafluorobiphenyl (TFB) (Goodhand & Hamor, 1978) and the 52.9 ° in 2,3,4,…”

“…Non-H-atom coordinates are listed in Table 2 4'-BUTYL-2, 3,5,6-TETRAFLUOROBIPHENYL-4-CARBONITRILE '6penta u°r° ip eny aae Goodhand & Hamor, 1978) but is similar to the ~.~~ 40.5° in 4'-n,butylbiphenyl-4-carbonitrile (Vani, ~ t 1983). These results suggest that the inter-ring tor~g~~..~S'~.…”