(TRIFLUOROETHYLIDYNE)SULFUR TRIFLUORIDE, F3CCSF3 - 2 SOLID-STATE STRUCTURES AND REACTIVITY AS A CARBENE

The known solid-state structure of F3CC=SF3 (phase I) is revised (a = 629.4 (6), b = 755.1 (6), c = 569.2 (7) pm, beta = 105.25 (10)-degrees, Z = 2, P2(1)/m). The C-C-S angle is found to be 171.4 (3)-degrees. A second solid-state structure with very different packing (phase II) was observed (a = 948.2 (7), b = 694.6 (5), c = 890.3 (7) pm, beta = 118.47 (2)-degrees, Z = 4, P2(1)/n) with a C-C-S angle of 162.9 (2)-degrees. In connection with the gas-phase structure (C-C-S angle of 155-degrees), these data show the bending force constant to be very small (nonclassical molecular structure). These findings are explained in terms of a low-lying carbene state, F3CCSF3. The dimerization reaction of F3CC=SF3 is first order with an activation energy of 55 kJ mol-1. Beside the E dimer F3C(SF3)C=C(SF3)CF3, a linear trimer is formed over very long reaction times. Reaction of F3CC=SF3 and F5SC=SF3 with fluorinated isonitriles yields alkylidenesulfur difluorides. For C6F5N=CFC(SF5)=SF2 the structure was established by single-crystal X-ray investigation as the Z isomer with respect to the CS double bond (a = 730.4 (1), b = 740.6 (2), c = 1202.5 (4) pm, alpha = 85.53 (3)-degrees, beta = 86.08 (2)-degrees, gamma = 71.03 (2)-degrees, Z = 2, P1BAR).