A study of two geometric isomers of 1,1 '-bi-3-cyanocyclohex-2-enylidene

The preparation, separation, crystal structure and H-1 NMR spectra are repo rted for the two geometrical isomers of 1,1'-bi-3-cyanocyclohex-2-enylidene . The E-isomer crystallized as thin plates in the monoclinic space group P2 (1)/n with a = 5.3980(5), b = 7.0757(7), c = 15.300(2) Angstrom, beta = 94. 571(2)degrees and Z = 2. The structure has symmetry C-2h. The Z-isomer crys tallized as needles in the triclinic space group P (1) over bar with a = 7. 0790(6), b = 11.3155(9), c = 15.386(1) Angstrom, alpha = 104.943 degrees be ta = 90.164(2)degrees, gamma = 99.494(2)degrees, and Z = 4. The compound cr ystallized with two molecules per asymmetric unit. In C6D6, H-1 NMR Signals of the 2-vinyl protons appear almost identical. However, in a mixture of C 6D6 and pyridine-d(5), the 2-vinyl protons can be distinguished. The struct ures compare favorably with MM2 calculations.