Syntheses and electrochemistry of bimetallic complexes containing cyclohexanediolate or cyclopentanediolate bridges

Abstract

The bimetallic complexes [{ML(NO)Cl}₂(1,x-O₂C_nH_{2n– 2})][L = HB(3,5-Me₂C₃HN₂)₃; n= 6, x= 2–4, M = Mo; n= 5, x= 3, M = Mo or W], in which parts of cyclohexyl or cyclopentyl groups link two redoxactive {O–ML(NO)} moieties, have been synthesized and found to exhibit two one-electron reduction processes separated by a potential difference, ΔE_f, which increases with decreasing through-bond metal–metal separation. The value ΔE_f for [{MoL(NO)Cl}₂(1,3-O₂C₆H₁₀)] is only slightly less (67 mV) than that of its aryl-bridged counterpart, [{MoL(NO)Cl}₂(1,3-O₂C₆H₄)]. However, ΔE_f for [{MoL(NO)Cl}₂(1,4-O₂C₆H₁₀)] is ca. 300 mV smaller than for [{MoL(NO)Cl}₂(1,4-O₂C₆H₄)] which contains a mesomeric link between the metal centres.