Crystal structure of phenyl-substituted cyclopentenes

The crystal structures of two stereoisomers of tetraphenyl- and pentaphenyl -substituted cyclopentenes 1 and 2 have been determined by X-ray analysis. An envelope conformation E-1 has been ascertained for the cis isomer 1a, wh ereas the cis, cis isomer 2a, which crystallizes in two different space gro ups, P1, and P2(1)/n, displays a twisted T-2(1) conformation. The phenyl su bstituents are all tilted with respect to the cyclopentene ring in both str uctures. Compound 1a crystallizes in the space group P2(1)/a with a = 18.55 3(3), b = 6.006(2), c = 19.355(5), beta = 102.67(4)degrees, and V = 2104.2( g) Angstrom 3 for Z = 4; compound 2a(1) crystallizes in P21/n with a = 10.0 64(2), b = 20.756(5), c = 12.245(3) Angstrom, beta = 95.21(2)degrees, and V = 2547(1) Angstrom(3) for Z = 4; compound 2aII crystallizes in P1 with a = 10.117(3), b = 11.750(2), c = 12.359(2) Angstrom, alpha = 111.25(2), beta = 94.84(2), gamma = 108.78(2)degrees, and V = 1262.3(6) Angstrom(3) for Z = 2.