Syntheses and structures of bis(tricarbonylchromium)-substituted α,ω-diphenylhexatriene complexes

Abstract

Treatment of several (4-substituted benzaldehyde)chromium tricarbonyl complexes with bisphosphoranes provides the first examples of (4,4′-substituted α,ω-diphenylhexatriene)bis(chromium tricarbonyl) complexes in good yield. Systems containing both donor and acceptor substituents may be prepared. The structures of three examples, [ E, E, E-, η 6-4-R-C 6H 4-(CHCH) 3- η 6-C 6H 4-4′-R][Cr(CO) 3] 2, (R = Me 2N, 1; R = Me 3Si, 3; R = F 3C, 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 acquisition of 1H NMR spectra of sufficient quality to allow the accurate simulation of the resonances corresponding to the olefinic protons. The simulations suggest that the hexatriene moiety behaves as three independent double bonds, in accord with the structural results.