Ruthenium Complexes Bearing Unsymmetric CNC′ Pincer Ligands: Molecular Structures and Electronic Properties

Cationic ligands - from monodentate to pincer systems

For a long time, the small group of cationic ligands stood out as obscure systems within the general landscape of coordinative chemistry. However, this situation has started to change rapidly during the last decade, with more and more examples of metal-coordinated cationic species being reported. The growing interest in these systems is not only of purely academic nature, but also driven by accumulating evidence of their high catalytic utility. Overcoming the inherently poor coordinating ability of cationic species often required additional structural stabilization. In numerous cases this was realized by functionalizing them with a pair of chelating side-arms, effectively constructing a pincer-type scaffold. This comprehensive review aims to encompass all cationic ligands possessing such pincer architecture reported to date. Herein every cationic species that has ever been embedded in a pincer framework is described in terms of its electronic structure, followed by an in-depth discussion of its donor/acceptor properties, based on computational studies (DFT) and available experimental data (IR, NMR or CV). We then elaborate on how the positive charge of these ligands affects the spectroscopic and redox properties, as well as the reactivity, of their complexes, compared to those of the structurally related neutral ligands. Among other systems discussed, this review also surveys our own contribution to this field, namely, the introduction of sulfonium-based pincer ligands and their complexes, recently reported by our group.

Crystal structure of 3,3′-(pyridine-2,6-diylbis(methylene))bis(1-propyl-1H-imidazol-3-ium) ditetrafluoroborate, C19H27B2F8N5

C19H27N5, orthorhombic Pbca (no. 61), a = 9.8515(12) Å, b = 16.508(2) Å, c = 29.817(3) Å, β = 90°, V = 4849.3(10) Å3, Z = 8, R gt (F) = 0.0409, wR ref(F 2) = 0.1082.

Ruthenium bistridentate complexes with non-symmetrical hexahydro-pyrimidopyrimidine ligands: a structural and theoretical investigation of their optical and electrochemical properties

The optical and electronic properties of six Ru complexes with non-symmetrical tridentate ligands have been investigated and, as corroborated by electrochemical data, the presence of the hpp ligand strongly affects the oxidation potential of the metal ion.

Platinum complexes bearing normal and mesoionic N-heterocyclic carbene based pincer ligands: syntheses, structures, and photo-functional attributes

Platinum complexes featuring pyridine bis-N-heterocyclic imidazol-2-ylidene/triazol-5-ylidene donors are prepared and screened for vapo/mechanochromic attributes.

Bidentate NHC^pyrozolate ligands in luminescent platinum(ii) complexes

The tuning of luminescence from blue to yellow was achieved with platinum complexes containing NHC^pyrozolate and functionalized-phenyl-pyridine or triazole-pyridine ligands.