This research focuses on the synthesis and structural characterization of three new Ru^II polypyridyl com­plexes containing α-di­imine ligands with one PF₆⁻ counter-ion. The investigation employs a combination of spectroscopic and X-ray diffraction methods to characterize the com­plexes.

The structure of a CO₂ reduction photo­catalyst prototype, the first cis-dicarbonyl ruthenium(II) tetra­pyrrole complex, has been determined by X-ray and electron diffraction to have an unprecedented seesaw-coordinated biladiene ligand.

The structure of the title compound exhibits disorder around a axis. The 4-meth­oxy­pyridine ligands have a propeller-like arrangement around the ruthenium at 52.01° from the RuN₄ plane.

The crystal structures of five compounds in the Al–Ru–Si system with approximate compositions ∼Ru₁₆(Al_0.78Si_0.22)₄₇ (I), ∼Ru₉(Al_0.70Si_0.30)₃₂ (II), ∼Ru₁₀(Al_0.67Si_0.33)₄₁ (III), ∼Ru(Al_0.57Si_0.43)₅ (IV) and ∼Ru₂(Al_0.46Si_0.54)₉ (V) are presented. Notably, the crystal structure of (I) can be related to that of a cubic rational crystalline approximant to an icosa­hedral quasicrystal through crystallographic shear and then unit-cell twinning.

The title compound, [Ru(C₁₂H₁₄NO₂)Cl(η⁶-C₆H₆)], exhibits a half-sandwich tripod stand structure and crystallizes in the ortho­rhom­bic space group P2₁2₁2₁. The arene group is η⁶ π-coordinated to the Ru atom with a centroid-to-metal distance of 1.6590 (5) Å, with the (S)-2-(4-isopropyl-4,5-di­hydro­oxazol-2-yl)phenolate chelate ligand forming a bite angle of 86.88 (19)° through its N and phenolate O atoms.

The title compound is a ruthenium–gallium metal cluster. The ruthenium and gallium have a direct metal–metal bond with a length of 2.4575 (2) Å.

The propensity for the central amine N atom in tris­(pyridin-2-yl)amine [or (2-py)₃N] to remain sp²-hydridized allows the isolation of complexes containing either κ²- or κ³-(2-py)₃N, or both, as in [RuCl{κ²-(2-py)₃N}{κ³-(2-py)₃N}][SbF₆].

cis-[RuCl₂{2-(4-meth­oxy­phen­yl)-1,8-naphthyridine-κN⁸}₂(CO)₂] and the 2-meth­oxy­phen­yl derivative exhibit moderate catalytic activity with 100% selectivity for the hydrogen-transfer reaction to aceto­phenone in the presence of a base.

Two concomitant polymorphs of a ruthenium complex were crystallized. The colour of both crystals was orange but the shapes, as well as the crystal structures, were different. The Hirshfeld surface and fingerprint plot analysis of both isomers satisfactorily explained the difference in melting points.

In the crystal structure of the title compound, the ruthenium(II) metal center is surrounded by two bidentate 2,2′-bi­pyridine, an isonicotinamide ligand, and a water in a distorted octa­hedral geometry. Hydrogen bonding is present between counter-ion and ligand.