Synthesis and structure of tricarbonylchromium mono-complexes, bis-complexes and tris-complexes of 10-methyltribenzotriquinacene

Complexation of 10-methyltribenzotriquinacene (MTBT) a bent triarene of C3v symmetry afforded six mono-, bis- and tris-Cr(CO)3 complexed isomers which have been isolated and identified. The results of various synthetic experiments indicate that complexation at the convex side of a free benzene ring is favoured, probably for steric reasons. As compared with the isomer complexed at the convex face (anti), that complexed at the concave one (syn) is less stable. The H-1 and C-13 NMR spectral data together with the X-ray structures of the two bis- and one tris-complexes account for the lower stability of the syn isomers.