Synthesis, Characterization and Redox Behaviour of Mono‐ and Dicarbonyl Phosphane Rhenium(I) Complexes Bearing N‐, N,N‐ and N,O‐Type Ligands

Unexpected Redox Chemistry of P∩N- and As∩N-Rhenium(I) Tricarbonyl Complexes in the Presence of CO2 Acting as an Acid

This study reports on Re tricarbonyl complexes bearing 8-(diphenylphosphanyl)quinoline, P∩N, and 8-(diphenylarsanyl)quinoline, As∩N, as bidendate ligands. We studied the reactivity of these complexes in comparison with fac-Re(N∩N)(CO)3Cl (with N∩N = 2,2'-bipyridine or 4,4'-dimethyl-2,2'-bipyridine). We used a combination of electrochemical and spectroelectrochemical methods with time-resolved spectroscopy over 10 orders of magnitude (100 ps-1 s) to investigate the peculiar reactivity of one-electron-reduced Re(CO)3(P∩N)Cl and Re(CO)3(As∩N)Cl complexes also in the presence of protons.

Characterization of a Mixed-Valence Ru(II)/Ru(III) Ion-Pair Complex. Unexpected High-Frequency Electron Paramagnetic Resonance Evidence for Ru(III)-Ru(III) Dimer Coupling

In this contribution, we report the synthesis and full characterization of the first mixed-valence Ru(II)/Ru(III) ion-pair complex, [Ru^II(bipy)₂(pic)]⁺[cis-Ru^IIICl₂(pic)₂]^-, in the solid state and in aqueous solution, where bipy = 2,2'-bipyridine and pic^- = picolinate. In addition, unexpected high-frequency electron paramagnetic resonance evidence for interactions between two neighboring Ru(III) ions, resulting in a triplet state, S = 1, was found.

Pyridine-2,6-Dicarboxylic Acid Esters (pydicR2) as O,N,O-Pincer Ligands in CuII Complexes

The pyridine-2,6-carboxylic esters pydicR2 with R = Me or Ph form the unprecedented mononuclear CuII complexes [Cu(pydicR2)Cl3]− in one-pot reactions starting from pyridine-2,6-carboxychloride pydicCl2, CuII chloride, and NEt3 in MeOH or PhOH solution under non-aqueous conditions. The triethylammonium salts (HNEt3)[Cu(pydicR2)Cl3] were isolated. The methyl derivative could be crystallized to allow a XRD structure determination. Both structures were optimized using DFT calculations in various surroundings ranging from gas phase and the non-coordinating solvent CH2Cl2 to the weakly coordinating acetone and well-coordinating solvents acetonitrile (MeCN) or dimethylformamide (DMF), while detailed calculation showed the charge distribution, dipole moments, and HOMO–LUMO gap energies changing upon solvation. According to these calculations, the ion pairs and the anionic CuII complexes were stable, which shows only Cu–Cl bond elongation and weakening of the charge transfer between the anionic complex and the cation as solvents become polar. Synthesis attempts in the presence of water yielded the CuII complexes [Cu(pydic)(OH2)2]n and [Cu(OH2)6][{Cu(pydic)}2(µ-Cl)2], which results from pydicCl2 hydrolysis. Alternatively, the new pydic(IPh)2 (IPh = 2-iodo-phenyl) ester ligand was synthesized and reacted with anhydrous CuCl2, which yields the new binuclear complex [{Cu(pydic(IPh)2)Cl}2(µ-Cl)2]. EPR spectroscopy of the solid compounds reveals typical axial spectra in line with the observed and DFT calculated geometries. Cyclic voltammetry and UV–vis absorption spectroscopy in solution are in line with un-dissociated complex species [Cu(pydicR2)Cl3]−.

Rhenium and technetium bi- and tricarbonyl complexes in a new strategy for biomolecule incorporation using click chemistry

A versatile strategy to prepare fac-[M(I)(CO)3](+) and cis-[M(I)(CO)2](+) (M = Re, (99m)Tc) complexes was developed using Huisgen click chemistry and monodentate phosphine ligands to readily incorporate biomolecules and tailor the chemical properties.