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Evidence for Bidirectional Noninnocent Behavior of a Formazanate Ligand in Ruthenium Complexes

, , , , and . Inorganic Chemistry, 54 (16): 8126--8135 (2015)
DOI: 10.1021/acs.inorgchem.5b01408

Abstract

Redox series of the complexes Ru(L)(L')2n, L = 1,5-diphenyl-3-(4-tolyl)-formazanate and L' = 2,4-pentanedionate (acac-), 2,2'-bipyridine (bpy), or 2-phenylazopyridine (pap), were studied by cyclic and differential pulse voltammetry and by TD-DFT-supported spectroelectrochem. (UV-visible-NIR, EPR). The prepd. complexes are Ru(L-)(acac)2 (1), Ru(L-)(bpy)2(ClO4) (2) , and Ru(L-)(bpy)2(ClO4) (3). The precursors RuIII(L-)(acac-)2, RuII(L-)(bpy)2ClO4, and RuII(L-)(pap)2ClO4 were identified in their indicated oxidn. states by x-ray crystal structure detn. The six-membered formazanato-ruthenium chelate rings have an envelope conformation with puckering of the metal. DFT calcns. indicate a pronounced sensitivity of the N-N bond lengths toward the ligand oxidn. state. Several electrochem. accessible charge states were analyzed, and the derived oxidn. nos. RuII, RuIII, or RuIV, L' or (L').bul.-, and L-, L.bul.2-, or the new formazanyl ligand L.bul. for the two-way noninnocent formazanate reflect the increasing acceptor effect of the ancillary ligands L' in the series acac- \textless bpy \textless pap. on SciFinder(R)

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