New derivatives of trovacene (heta7-C7H7)V(heta5-C5H5): studies of redox splitting, exchange coupling and hydrogen bonding
The strategy followed in this work is based on the utilization of hydrogen bonds, master key interaction in crystal engineering, between adequately functionalised organometallic molecules. Exchange interactions mediated by hydrogen bridges, i.e. O-H---O, in paramagnetic complexes can be studied empl...
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|Zusammenfassung:||The strategy followed in this work is based on the utilization of hydrogen bonds, master key interaction in crystal engineering, between adequately functionalised organometallic molecules. Exchange interactions mediated by hydrogen bridges, i.e. O-H---O, in paramagnetic complexes can be studied employing EPR spectroscopy. Hence, a study of selective metalation of trovacene, in the five-membered ring, in both rings, and in the seven-membered ring obtained employing (heta7-cyclo-heptatrienyl)(heta5-pentamethylcyclopentadienyl)vanadium, was undertaken and subsequent reactions of carboxylation and formylation were performed. Distortion of the molecular geometry, such as ring tilting or deviations of the individual rings from the planarity can be studied spectroscopically to furnish understanding of the bonding in tilted sandwich complexes. Strained, ring-tilted sila-metallocenophanes are of interest because of the fact that these species readily undergo thermally induced ring-opening polymerisation (ROP). For this purpose, via dilithiation of trovacene, monosila- and disila-trovacenophanes were synthesized, and, thermal or catalytic ring-opening polymerisation was attempted. In organometallic carboxylic acids the hydrogen bonding capacity of the COOH groups can be combined with the topology of the ligand coordination about the metal centers. In this study the chromium sandwich complex of benzoic acid, [Cr(h6-C6H5COOH)2], was used as such as well as in the oxidized form, containing CrI as the central metal and in the deprotonated, zwitterionic form. The different packing modes, governed by hydrogen bonding, have been elucidated by means of X-ray diffraction.|