Probing valence and spin situations in selective ruthenium–iminoquinonoid frameworks. An experimental and DFT analysis

Bidirectional non-innocence of the β-diketonato ligand 9-oxidophenalenone (L-) in [Ru([9]aneS3)(L)(dmso)]n, [9]aneS3 = 1,4,7-trithiacyclononane

The new compound [Ru(II)([9]aneS3)(L)(dmso)]ClO4 ([]ClO4) ([9]aneS3 = 1,4,7-trithiacyclononane, HL = 9-hydroxyphenalenone, dmso = dimethylsulfoxide) has been structurally characterised to reveal almost equal C-O bond distances of coordinated L(-), suggesting a delocalised bonding situation of the β-diketonato ligand. The dmso ligand is coordinated via the sulfur atom in the native (1+) and reduced states (1 and 1-) as has been revealed by X-ray crystallography and by DFT calculations. Cyclic voltammetry of 1+ exhibits two close-lying one-electron oxidation waves at 0.77 V and 0.94 V, and two similarly close one-electron reduction processes at -1.43 V and -1.56 V versus SCE in CH2Cl2. The electronic structures of 1n in the accessible redox states have been analysed via experiments (EPR and UV-vis-NIR spectroelectrochemistry) and by DFT/TD-DFT calculations, revealing the potential for bidirectional non-innocent behaviour of coordinated L(˙/-/˙2-). Specifically, the studies establish significant involvement of L based frontier orbitals in both the oxidation and reduction processes: [([9]aneS3)(dmso)Ru(III)-L˙](3+) (1(3+)) ⇌ [([9]aneS3)(dmso)Ru(III)-L(-)](2+)/[([9]aneS3)(dmso)Ru(II)-L˙](2+) (1(2+)) ⇌ [([9]aneS3)(dmso)Ru(II)-L(-)](+) (1(+)) ⇌ [([9]aneS3)(dmso)Ru(II)-L(˙2-)] (1) ⇌ [([9]aneS3)(dmso)Ru(II)-L(3-)](-)/[([9]aneS3)(dmso)Ru(I)-L(˙2-)](-) (1-).

Sensitivity of the valence structure in diruthenium complexes as a function of terminal and bridging ligands

The compounds [(acac)2Ru(III)(μ-H2L(2-))Ru(III)(acac)2] (rac, 1, and meso, 1') and [(bpy)2Ru(II)(μ-H2L(•-))Ru(II)(bpy)2](ClO4)3 (meso, [2](ClO4)3) have been structurally, magnetically, spectroelectrochemically, and computationally characterized (acac(-) = acetylacetonate, bpy = 2,2'-bipyridine, and H4L = 1,4-diamino-9,10-anthraquinone). The N,O;N',O'-coordinated μ-H2L(n-) forms two β-ketiminato-type chelate rings, and 1 or 1' are connected via NH···O hydrogen bridges in the crystals. 1 exhibits a complex magnetic behavior, while [2](ClO4)3 is a radical species with mixed ligand/metal-based spin. The combination of redox noninnocent bridge (H2L(0) → → → →H2L(4-)) and {(acac)2Ru(II)} → →{(acac)2Ru(IV)} or {(bpy)2Ru(II)} → {(bpy)2Ru(III)} in 1/1' or 2 generates alternatives regarding the oxidation state formulations for the accessible redox states (1(n) and 2(n)), which have been assessed by UV-vis-NIR, EPR, and DFT/TD-DFT calculations. The experimental and theoretical studies suggest variable mixing of the frontier orbitals of the metals and the bridge, leading to the following most appropriate oxidation state combinations: [(acac)2Ru(III)(μ-H2L(•-))Ru(III)(acac)2](+) (1(+)) → [(acac)2Ru(III)(μ-H2L(2-))Ru(III)(acac)2] (1) → [(acac)2Ru(III)(μ-H2L(•3-))Ru(III)(acac)2](-)/[(acac)2Ru(III)(μ-H2L(2-))Ru(II)(acac)2](-) (1(-)) → [(acac)2Ru(III)(μ-H2L(4-))Ru(III)(acac)2](2-)/[(acac)2Ru(II)(μ-H2L(2-))Ru(II)(acac)2](2-) (1(2-)) and [(bpy)2Ru(III)(μ-H2L(•-))Ru(II)(bpy)2](4+) (2(4+)) → [(bpy)2Ru(II)(μ-H2L(•-))Ru(II)(bpy)2](3+)/[(bpy)2Ru(II)(μ-H2L(2-))Ru(III)(bpy)2](3+) (2(3+)) → [(bpy)2Ru(II)(μ-H2L(2-))Ru(II)(bpy)2](2+) (2(2+)). The favoring of Ru(III) by σ-donating acac(-) and of Ru(II) by the π-accepting bpy coligands shifts the conceivable valence alternatives accordingly. Similarly, the introduction of the NH donor function in H2L(n) as compared to O causes a cathodic shift of redox potentials with corresponding consequences for the valence structure.

Tris-[4-(di-methyl-amino)-pyridine][tris(pyra-zol-1-yl)methane]--ruthenium(II) bis-(hexa-fluorido-phosphate) diethyl ether monosolvate

In the title compound, [Ru(C₁₀H₁₀N₆)(C₇H₁₀N₂)₃](PF₆)₂·C₄H₁₀O, the Ru^II cation is coordinated by one tris­(1-pyrazol­yl)methane (Tpm) and three dimethylaminopyridine (dmap) ligands in a slightly distorted octa­hedral geometry. The asymmetric unit consists of one complex cation, two hexa­fluorido­phosphate anions and one diethyl ether solvent mol­ecule in general positions. Although quite a large number of ruthenium complexes of the facially coordinating tridentate Tpm ligand have been structurally characterized, this is only the second one containing three pyridyl co-ligands. The average Ru—N(Tpm) distance is 2.059 (12) Å, while the average Ru—N(dmap) [dmap = 4-(di­methyl­amino)­pyridine] distance is somewhat longer at 2.108 (13) Å. The orientation of the dmap ligands varies greatly, with dihedral angles between the pyridyl and opposite pyrazolyl rings of 14.3 (2), 23.2 (2) and 61.2 (2)°.