SYNTHESES AND STRUCTURES OF BIS(TRICARBONYLCHROMIUM)-SUBSTITUTED ALPHA,OMEGA-DIPHENYLHEXATRIENE COMPLEXES

Treatment of several (4-substituted benzaldehyde)chromium tricarbonyl complexes with bisphosphoranes provides the first examples of (4,4'-su bstituted alpha, omega-diphenylhexatriene)bis(chromium tricarbonyl) co mplexes in good yield. Systems containing both donor and acceptor subs tituents may be prepared. The structures of three examples, E,E,E-eta( 6)-4-R-C6H4-(CH=CH)(3)-eta(6)-C6H4-4'-R] [Cr(CO)(3)](2), (R = Me(2)N, 1; R = Me(3)Si, 3; R = F3C, 4) have been determined by single crystal X-ray diffraction. The results demonstrate that the olefinic portions of the molecules adopt the all trans E,E,E conformation, and that the tricarbonylchromium groups adopt anti orientations on each face of the organic plane. Compounds 3 and 4 are soluble enough to allow acquisit ion of H-1 NMR spectra of sufficient quality to allow the accurate sim ulation of the resonances corresponding to the olefinic protons. The s imulations suggest that the hexatriene moiety behaves as three indepen dent double bonds, in accord with the structural results.