Pentafluorophenylarsines. The crystal and molecular structures of tetrakis(pentafluorophenyl)diarsine, (C6F5)2AsAs(C6F5)2, tetrakis(pentafluorophenyl)diarsenic(III) oxide, (C6F5)2AsOAs(C6F5)2, and tris(pentafluorophenyl) arsine

Article abstract of DOI:10.1016/0022-328X(89)87173-6

Crystalline materials from a high-boiling fraction obtained as by-products in the preparation of C6F5AsCl2, or from subsequent reaction with elemental mercury, have been crytallographically identified as consisiting primarily of secondary and tertiary substituted pentafluorophenylarsenic compounds.The crystal and molecular structures of three of these products are reported: (C6F5)2AsAs(C6F5)2 (1), (C6F5)2AsOAs(C6F5)2 (2), and (C6F5)3As (3). 1: C24F20As2, tetragonal, P42₁c, a 13.253(3), c 42.584(10) Angstroem, V 7479 Angstroem³, Z=12 (three independent half-molecules), R(F) 6.54percent. 2: C24F20As2O, monoclinic, C2/c, a 16.676(5), b 7.755(2), c 22.266(6) Angstroem, β 117.13(2) deg, V 2563 Angstroem³, Z=4 (one-half molecule), R(F) 4.85percent. 3: C18F15As, triclinic, P1, a 8.902(2), b 10.888(2), c 11.185(2) Angstroem, α 109.59(2), β 103.12(2), γ 106.95 deg, V 911.3(4) Angstroem³, R(F) 4.50percent. 1 is twisted 16.5 deg from a trans conformation and contains the longest As-As bond reported for any organoarsenic compound, 2.479(4) Angstroem.However, non-bonded F...F contact distances fail to support steric reasons for these distortions. 2 has an As-O-As angle of 116.2(3) deg determined primarily by lattice packing effects. 3 is pyramidal with As-C distances and C-As-C angles typical of triarylarsines.