O-(TRIFLUOROMETHYL)ARYL INTERACTIONS AND STABILIZATION IN HYPERVALENTGERMINATION COMPOUNDS

A series of o-(trifluoromethyl)phenyl-substituted germanes have been s ynthesized to study the potential for weak Ge-F bonding interactions. H-1-F-19 coupling constants in these compounds range between 2 and 5 H z. These coupling magnitudes are consistent with previously reported l iterature examples in F-19 and multinuclear NMR spectra for derivative s of the [2,4,6-(CF3)(3)C6H2]- ligand. Solid-state structural characte rization of these germanes consistently reveals Ge-F contacts at 2.8-2 .9 Angstrom, midway between the longest single bond and the longest ex pected van der Waals contact. For the simple unsymmetrical catenate, - (CF3)(2)C6H3](2)Ge(H)Ge(H)[2,4,6-(CF3)(3)C6H2](2) (4), there are close contacts to both germanium atoms from the ortho-CF3 groups. 4 is not otherwise sterically constrained to force distal, intramolecular conta cts, and thus a weak Ge-F bonding interaction is invoked for the entir e series of o-(trifluoromethyl)aryl-substituted tetravalent Ge compoun ds. The synthetic approaches to these germanes make extensive use of G e(II) precursors, employing both catalytic hydrogenation and insertion reactions of germylenes.