STRUCTURES OF Z-(NITROSTILBENE)CHROMIUM TRICARBONYL COMPLEXES - THE EFFECT OF METAL COORDINATION ON THE NONPLANARITY OF THE STILBENE SYSTEM

The structures of the nitrostilbene complexes Z-(4-R-C6H4-CH=CH-C6H4-4 '-NO2)Cr(CO)3 (R = Me2N, 1; H, 2; F3C, 3), are reported. The compounds were prepared as part of a study of the synthesis of organometallic c omplexes with potential nonlinear optics applications. For Z-(4-Me2N-C 6H4-CH=CH-C6H4-4'-NO2)Cr(CO)3, 1, triclinic, P1BAR, a = 7.214 (3) angs trom, b = 7.340 (3) angstrom, c = 17.238 (9) angstrom, alpha = 88.23 ( 5)-degrees, beta = 88.76 (4)-degrees, gamma = 87.66 (3)-degrees, Z = 2 . For Z-(C6H5-CH=CH-C6H4-4'-NO2)Cr(CO)3, 2, monoclinic, P2(1)/c, a = 1 2.255 (3) angstrom, b = 9.415 (1) angstrom, c = 13.579 (4) angstrom, b eta = 105.60 (2)-degrees, Z = 4. For Z-(4-F3C-C6H4-CH=CH-C6H4-4'-NO2)C r(CO)3, 3, triclinic, P1BAR, a = 7.094 (2) angstrom, b = 8.057 (5) ang strom, c = 17.295 (9) angstrom, alpha = 87.95 (5)-degrees, beta = 85.9 4 (4)-degrees, gamma = 64.24 (5)-degrees, Z = 2. The structural data s how that the Z isomers exhibit bond lengths and angles similar to thos e observed in the E isomers, but the stilbene fragment is considerably more nonplanar. As a consequence, these molecules are unlikely to beh ave as NLO materials.