IR STUDY OF METALLOTROPIC REARRANGEMENTS AND ION-PAIR INTERACTIONS IN CHROMIUM TRICARBONYL COMPLEXES WITH POLYCYCLIC AROMATIC LIGANDS
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Date
1998
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Publisher
Ohio State University
Abstract
Metallotropic rearrangements (itramolecular rearrangements involving the displacement of the transition metal atom) in chromium tricarbonyl $\pi$-complexes with polycyclic aromatic ligands were studied by FTIR spectroscopy. A novel $\eta^{6} \eta^{5}$ rearrangements have been found and studied for anions $\eta^{6}$-phenalenyl- (I) and $\eta^{6}$-(9- hydroanthracenyl) (II) tri***ar-bonychromium generated by deprotonation of corresponding neutral $\eta^{6}$-complexes with various bases (BuLi, $Ph_{3}P=CH_{2}$, proton sponges or t-BuOM, where $M=K, Cs$) at low temperatures. IR spectra in the $\nu(CO)$ range of the $\eta^{6}$- and $\eta^{6}$-anions with various counter-ions $(Li^{+}_{+} K^{+}$, and $Cs^{+}$) in THF and dimethoxyethane solutions and in the presence of the solvating additive, dibenzo-18-crown-6, in a temperature region between -70 to $20^{\circ}C$ showed that anionic complexes exist in solution as tight and solvent separated ion pairs or as their equilibrium mixture. The factors that influence the ion-pair equilibrium (solvent, the excess of the base, temperature, the nature of the counter-ion) have been studied. The results are compared with the NMR data. The work was supported by the Russian Foundation for Basic Research (grants 96-03-3241a and 96-03-34082a).
Description
Author Institution: A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences; Department of Chemistry, M.V. Lomonosov Moscow State University