Syntheses and electrochemistry of bimetallic complexes containing cyclohexanediolate or cyclopentanediolate bridges

Abstract

The bimetallic complexes [(ML(NO)Cl}, (l,x-OzCnHzn~z)] [L = HB(3,5-Me,C,HN2),; n = 6, x = 2-4, M = Mo; n = 5, x = 3, M = Mo or W-J, in which parts of cyclohexyl or cyclopentyl groups link two redoxactive { 0-ML(NO)] moieties, have been synthesized and found to exhibit two one-electron reduction processes separated by a potential difference, AE,, which increases with decreasing through-bond metal-metal separation. The value AE, for [ ( ~o ~( ~~) ~~) , ( ~, ~-~, ~6 ~~o ) ]is only slightly less (67 mV) than that of its aryl-bridged counterpart, [(MoL(NO)Cl},( 1 ,3-0,C6H,)]. However, AEf for [(MoL(NO)Cl),( 1 ,4-0,C6HlO)] is ca. 300 mV smaller than for [(MoL(NO)CI},(I ,4-0,C6H4)] which contains a mesomeric link between the metal centres.

Coordination and Organometallic Chemistry of Metal−NO Complexes

“…By utilization of metathesis reactions of its dihalo precursors, the redox-active Tp*M(NO)X moiety (M = Mo or W; X = Cl, Br, or I) has been appended in monometallic [Tp*M(NO)(X)(Y)] or bimetallic [Tp*M(NO)(X)(μ-Y)(X)(ON)MTp*] complexes to entities Y such as an arylamino derivative of retinal, protected and unprotected monosaccharides, various alkoxides, amides, and β-diketonates, − , bipyridine and bipyridylpolyene bridges, − extended polypyridyl-type bridging ligands, extended diphenol bridging ligands, glucofuranoside and galactopyranoside derivatives, asymmetric bridging ligands containing a pyridyl and a phenolate donor, − a bridging S−S group, a bridging O atom, − stilbenamide ligands carrying long-chain alkoxy substitutents, stilbazoles, ligands based on 4-hydroxyphenylalkanols, a variety of mono- and bifunctional O- and N-donor ligands, − thiolates, redox-active fluorenone-based ligands, Schiff bases, diolates, and pyrazine. , On occasion, the related Tp*M(NO)(Y) derivatives of the systems listed in this paragraph have also been prepared and characterized during the above-cited studies.…”

Mixed-valence dinuclear molybdenum complexes with benzenediamido and dianilido bridges: comparison with related phenolato and dipyridyl species, and with their pentammineruthenium analogues

“…These reduction processes were mostly quasi-reversible, presumably as a result of gradual dissociation of X or slow electrode kinetics, as has been observed before in this type of complex. 24 In general, the first reduction potentials are ca. 300 mV more positive and the second ca.…”