Trinuclear mixed-valence complexes with the linear [Rh3]4+ core

Abstract

The complexes [Rh₃(µ₃-L)₂(CO)₄(PPh₃)₂][BF₄][1⁺; L = 1,8-naphthyridin-2-onate (napyo) or 5,7-dimethyl-1,8-naphthyridin-2-onate (dmnapyo)] and [Rh₃(µ₃-L)₂(CO)₂(µ⁴-cod)₂][BF₄](2⁺; cod = cyclo-octa-1,5-diene) undergo two reversible one-electron oxidations at a platinum bead electrode in CH₂Cl₂. Chemical oxidation of (1⁺) or (2⁺) with [N(C₆H₄Br-p)₃][BF₄] in CH₂Cl₂, or electrolytic oxidation at a platinum electrode, gave the mixed-valence dications [Rh₃(µ₃-L)₂(CO)₄(PPh₃)₂]²⁺(1²⁺; L = napyo or dmnapyo) and [Rh₃(µ₃-L)₂(CO)₂(η⁴-cod)₂]²⁺(2²⁺; L = napyo or dmnapyo), isolated as the violet bis(tetrafluoroborate) salts, and characterised by i.r., visible, and e.s.r. spectroscopy and by cyclic voltammetry.