The chemical and electrochemical one-electron oxidation of diamidonaphthalene-bridged complexes; paramagnetic [Rh2]3+-containing A-frames

Abstract

The complexes [Rh₂L₄{µ-2,3-(NH)₂C₁₀H₆}][1; L₂=(CO)(PPh₃) or η⁴-cod (cyclo-octa-1,5-diene)] and [Rh₂L₄{µ-1,8-(NH)₂C₁₀H₆}][2; L₂=(CO)(PPh₃), η⁴-cod, η⁴-nbd (norbornadiene), or η⁴-tfbb (tetrafluorobenzobarrelene)] undergo two sequential one-electron oxidations at a platinum bead electrode. At –78 °C, the chemical oxidation of compound (1; L₂=η⁴-cod) or (2; L₂=η⁴-cod) in thf, with [CPh₃][BF₄] in CH₂Cl₂, gives the [Rh₂]³⁺-containing salts [Rh₂(η⁴-cod)₂(η-L¹)][BF₄][1⁺; L¹= 2,3-(NH)₂C₁₀H₆ or 2⁺; L¹= 1,8-(NH)₂C₁₀H₆] which, in tetrahydrofuran (thf)-CH₂Cl₂ mixtures at –196 °C, show solvent-dependent e.s.r. spectra implying thf co-ordination at one axial site. The irreversible one-electron reduction of [Rh₂(NO)(η⁴-cod)₂{µ-1,8-(NH)₂C₁₀H₆}][PF₆](3), prepared from (2;L₂=η⁴-cod) and [NO][PF₆] in CH₂Cl₂, leads to the loss of NO and the regeneration of (2; L₂=η⁴-cod).