Electrochemical Oxidation and Cation Radicals of All-Five and All-Six 1-Substituted Metallatranes (M = Si, Ge). Spectroelectrochemical Study

摘要

Electrooxidation of all-five and all-six membered metallatranes (M = Si, Ge) derivatives of triethanolamine, and those with aryl-fused lateral chains (derivatives of 2,2',2"-nitrilotriphenol and 2,2',2"-nitrilotris(methylene) triphenol) was studied by cyclic voltammetry and EPR-spectroelectrochemistry supported by DFT B3LVP/ LANL2DZ calculations. Phenyl and vinyl metallatranes form distonic cation radicals which are more stable than those of triorganyl amino precursors, and can be observed in acetonitrile already at 250 K. EPR-spectroelectrochemistry revealed that spin density in these species is mainly localized on the axially directed and pointed inside the atrane cage p-z orbital of nitrogen. Both EPR and Fermi contact coupling from DFT B3LYP/LANL2DZ calculations have shown zero contribution from the metal in the spin delocalization in these species. DFT calculations suggest that the N atom in these cation radicals is practically planar; Ge atom configuration flattens approaching trigonal bipyramid or, like Si, adopts closer to tetrahedral configuration, the trends depending on the substituent.