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 copounds were prepared as part of a study of the synthesis of organometallic complexes with potential nonlinear optics applications. For Z-(4-Me₂N–C₆H₄–CH=CH–C₆H₄-4-NO₂)Cr(CO)₃,1, triclinic, ,a=7.214 (3) Å,b=7.340 (3) Å,c=17.238 (9)Å, =88.23 (5)°, =88.76 (4)°, =87.66 (3) °,Z=2. For Z-(C₆H₅–CH=CH–C₆H₄-4-NO₂)Cr(CO)₃,2, monoclinic, P2₁/C,a=12.255 (3) Å,b=9.415 (1) Å,c=13.579 (4) Å, =105.60 (2)°,Z=4. For Z-(4-F₃C–C₆H₄–CH=CH–C₆H₄-4-NO₂)Cr(CO)₃,3, triclinic, ,a=7.094 (2) Å,b=8.057 (5) Å,c=17.295 (9) Å, =87.95 (5)° =85.94 (4)°, =64.24 (5)°,Z=2. The structural data show that the Z isomers exhibit bond lengths and angles similar to those observed in the E isomers, but the stilbene fragment is considerably more nonplanar. As a consequence, these molecules are unlikely to behave as NLO materials.