Synthesis and Structures of Mixed‐Valence Oxido‐Bridged Diruthenium Complexes Bearing Ethylbis(2‐pyridylmethyl)amine

Abstract

Trihalogenoruthenium(III) complexes bearing an ethylbis(2‐pyridylmethyl)amine (ebpma) ligand, fac‐[RuIIIX3(ebpma)] (X = Cl, Br), were reduced by zinc in acetone that contained halogeno acid to afford a reddish‐orange solution. Two kinds of dinuclear complexes were synthesized from the solution. After removing the remaining zinc and adding counterions such as PF6– and BF4– with water, the solution was allowed to stand under air until the color of the solution changed. New oxido‐bridged dinuclear complexes of mixed‐valence RuIII–RuIV [{RuIII,IVX2(ebpma)}2(μ‐O)]Y (X = Cl, Y = PF6, [1]PF6; Y = BF4, [1]BF4; X = Br, Y = PF6, [2]PF6; Y = BF4, [2]BF4), which showed a similar framework to the reported water oxidation catalysts, were obtained as deep‐colored solids. In the reaction without addition of extra water, a different mixed‐valence dinuclear complex of RuII–RuIII [{RuII,III(ebpma)}2(μ‐Cl)3]2+, for which the metal centers were triply bridged by three chlorides, was formed. The synthetic procedures are useful for the development of multinuclear frameworks that function as molecular catalysts for redox reactions such as water oxidation.

A Pyrazolate‐Bridged Bis(pentadentate) Ligand and Its Dinuclear Ruthenium Complex

“…Starting from the known 3,5-bis[6-(hydroxymethyl)-2-pyridyl]-1H-pyrazole (I) [7] the dibromide II is synthesized, which is then coupled with two di(2-picolyl)-amine side arms (see Supporting Information for details). HL bis5 is obtained in good purity and has been characterized by 1 H, 13 C and 2D NMR spectroscopy as well as by ESI mass spectrometry (see Figures S1-S5 , the sixth coordination site, which is filled by labile MeCN in 1 but potentially available for substrate binding, is relatively exposed: the angles N4-Ru1-N1 (199.2°) and N8-Ru2-N2 (198.7°), if viewed from the MeCN ligands' side, are much larger than 180°, indicating significant distortion from a perfect octahedral environment of the metal ions. Furthermore, the Ru···Ru distance in 1 (ca.…”

“…This result is in agreement with the findings for the A + and B 2+ complexes, which also generated mainly CO 2 and produced poor values in terms of turnover number (TON) because of complex degradation. [1,3] Ligands containing relatively weak benzylic-type C-H bonds are often found susceptible to metal-mediated fragmentation under strongly oxidizing conditions, usually by C-H activation by high-valent metal-oxo intermediates.…”

“…A representative example in the field of catalytic water oxidation is the tridentate ligand in A + (Figure 1), [1] which is a further development from the so-called "blue dimer" complex, [(bipy) 2 …”

“…While the peak separation of pairs of exchanging protons in the absence of exchange cannot be determined in the available temperature range, the rate constant for the interconversion of the two forms in the slow exchange regime (viz. spectra at 188 and 198 K in Figure 3) was estimated by using Equation (1), where k T is the rate constant at a given temperature and Δv 1/2 is the line width of the analyzed NMR signal at the same temperature. [17] In case of fast exchange above the coalescence temperature (viz.…”

Crystal structure ofcis,fac-{N,N-bis[(pyridin-2-yl)methyl]methylamine-κ3N,N′,N′′}dichlorido(dimethyl sulfoxide-κS)ruthenium(II)

“…The complex can be represented as the cis,fac-isomer to indicate the cis-geometry of the dmso ligand to the aliphatic N atom and the facial coordination mode of bpma. A literature survey of Ru II complexes of bpma and those of closely related bis(pyridin-2-ylmethyl)alkylamine ligands reveals that an overwhelming majority of the complexes contain facially coordinated tridentate ligands (Dakkach et al, 2013;Fischer et al, 2009;Mishra et al, 2009;Matsuya et al, 2009;Mola et al, 2006Mola et al, , 2007Mola et al, , 2009Rodriguez et al, 2001;Sala et al, 2008;Serrano et al, 2006;Shimizu et al, 2008;Suzuki et al, 2014). cis,fac-isomer is the thermodynamically favored (Mola et al, 2007), and therefore the more frequent occurrence of this isomer is unsurprising.…”