Bis(acetylacetonato)ruthenium Complexes of Noninnocent 1,2‐Dioxolene Ligands: Qualitatively Different Bonding in Relation to Monoimino and Diimino Analogues

Abstract

Coordination compounds [Ru(acac)(2)(Q)] (acac=acetylacetonate; Q=o-benzoquinone) were prepared as complexes 1 (Q=o-benzoquinone), 2 (Q=3-methoxy-o-benzoquinone), 3 (Q=4-methyl-o-benzoquinone), and 4 (Q=3,5-di-tert-butyl-o-benzoquinone). The structures of 1 and 2 were determined to reveal a Ru(III)/o-benzosemiquinone formulation, supported by analysis of experimental data (spectroscopy, magnetism of 1) and by DFT calculations. The S=1 ground state calculated for 1 stands in contrast to the spin-paired analogues with arylimino-o-benzosemiquinonato and diimino-o-benzoquinone ligands. The close contacts of about 5.3 Å possible between semiquinone O atoms of different molecules in the crystal allow for intermolecular spin-spin interactions and an overall complex magnetic behavior. One quasireversible oxidation and two reversible one-electron reductions yielded the corresponding molecular ions, which were characterized by UV-visible-NIR and EPR spectroelectrochemistry in terms of [Ru(III)(acac)(2)(Q(0))](+) , [Ru(III)(acac)(2)(Q(2-))](-), and [Ru(II)(acac)(2)(Q(2-))](2-) descriptions in agreement with DFT results. The use of acceptor-substituted 1,2-dioxolenes resulted in the isolation of ionic species Na[Ru(acac)(2)(Q)] (Na(5); Q=4-chloro-o-benzoquinone) and Na(6) (Q=4-nitro-o-benzoquinone), which were similarly investigated as compounds 1-4. Magnetic susceptibility and EPR results confirm an S=1/2 ground state based on ruthenium(III). The combined studies reveal a remarkable substituent sensitivity, and in comparison to recently analyzed Ru(acac)(2) complexes with o-benzoquinone monoimine and diimine ligands, the all-O-donor-containing new systems are distinguished by a qualitatively different metal-ligand interaction based on closer intermolecular radical-radical contacts and on weaker intramolecular dπ-π* interactions.

Tris(β-ketoiminato)ruthenium(III) complexes: Electrochemical and computational chemistry study

“…In order to determine whether the electronic energy of these complexes also was accurate, the possible spin states, S = ½, 3/2 and 5/2, were calculated for the d 5 complex 2, see Table 2. The results were in agreement with experimental observation [ 18,19 ], clearly showing that the neutral tris(β-ketoiminato)ruthenium(III) complexes 1 -5 of this study were all low-spin with S = ½.…”

“…The synthesis of ligand 3 described below. The five ruthenium complexes of the corresponding ligands were synthesized by using literature methods of related complexes as a guide [19,12].…”

“…3H2O) with the corresponding ketoimine ligands [12], or by stirring a mixture of RuCl3 . 3H2O and the relevant ketoimine ligand at room temperature [19].…”

“…containing the O,O-bidentate ligand acac = acetylacetonato = (CH3COCHCOCH3) -) [20]. This observation also agrees with literature results obtained for [Ru(O,O-BID)3-n(N,O-BID)n] (n = 1 or 2), where it was observed that when one of the two O,O bidentate ligands was substituted with a N,O bidentate ligand from [Ru(acac)3] (acac = acetylacetonato = (CH3COCHCOCH3) -), both the Ru(III)/Ru(II) reduction and the Ru(III)/Ru(IV) oxidation occurred at a lower potential[19].…”

Mixed Donor–Acceptor‐Derived N,N′‐Diarylpyrazine‐2,5‐dicarboxamido‐Bridged Diruthenium Systems: Structures, Magnetic Properties, and Electronic Forms in Multiredox States

“…As expected, the magnetic properties of ruthenium compounds containing two {Ru III (acac) 2 } fragments connected by O‐ or N‐donor‐based bridging ligands are strongly dependent on the nature of the bridge. Thus, similar antiferromagnetic coupling constants ( J ) are usually observed,[3c], [6a], but some dependence of the magnetic properties on the magnetic field has also been noted . However, for 1 , the bridging ligand (L 1 2– ) favors only intramolecular antiferromagnetic interactions, and the magnetic properties are independent of the applied magnetic field.…”