Stephane Sueur

Dicopper(II) complexes of novel polyfunctional pyridazines: crystal structure and magnetic properties of bis[µ-pyridazine-3,6-dicarbaldehyde dioximato(1–)-κN1,N′:N2,N″]-bis[aqua(perchlorato-κO)copper(II)]

Two novel pyridazine ligands with 3,6-CRNOH (R = H, H2L1; Ph, H2L2) oxime side chains were synthesised. The related copper(II) dinuclear complexes [Cu2(HL1)2(ClO4)2(H2O)2]1 and [Cu2(HL2)2(ClO4)2(MeOH)n]2 were obtained subsequently. The crystal structure of 1 was determined: space group P21/n, a= 12.031(6), b= 9.517(4), c= 9.973(5)A, β= 100.16(4)° and Z= 2. The copper(II) ions of the binuclear unit are bridged by the two diazine fragments of the two essentially planar tetradentate ligands with the oxime nitrogen atoms completing the equatorial co-ordination. Two intra-complex hydrogen bridges link the terminal oximato moieties to give dinucleating macrocyclic complexes. In complexes 1 and 2 the copper(II) is in a classical 4 + 2 environment. The magnetic properties of those compounds revealed a spin-singlet ground state in each case. The singlet-triplet energy gaps were found to be –536(2) for 1 and –545(4) cm–1 for 2. The low-lying states of the complexes are discussed in relation to the nearly planar structure of the macrocyclic complexes.

Influence reciproque des coordinats nitrosyle et violurate dans les bis(dihydrogenoviolurato)chloronitrosylruthenium et tris(dihydrogenoviolurato)nitrosylruthenium. Echanges protoniques, interconversion nitrosyle-nitrite

Abstract The study of protonation equilibria in the complexes bis(dihydrogenoviolurato)chloronitrosylruthenium and tris(dihydrogenoviolurato)nitrosylruthenium demonstrates the mutual effects of nitrosyl and violurate ligands in the coordination sphere of ruthenium. The very important increasing of the acidity of the deprotonation sites in the coordinated heterocycles is explained by the coordination of the nitrosyl to ruthenium(II). Shifts of metal-to-ligand charge transfer transition bands which give informations about the energy of the molecular orbitals in the ligand violurate accompany the successive deprotonations. Reciprocally, the deprotonated species of coordinated heterocycle constitute as much different coordination environments for the nitrosyl ligand and determine its affinity for nucleophilic agents in general and especially for OH − .

15 N–13C coupling constants and 15N/14N isotope effects on 13C n.m.r. chemical shifts of pyrimidine-2(1H),4(3H),5(6H), 6-terone 5-oximato complexes

15 N-Labelling of the oxime function of pyrimidine-2(1H),4(3H),5(6H), 6-terone 5-oximato iron and ruthenium complexes has enabled the measurement of one- and two-bond 13C–15N coupling constants and upfield isotopic shifts in the 13C n.m.r. spectra.

Ketoximato-complexes. Part 3. Structure and properties of tris chelates of cobalt(III), iron(II), and ruthenium(II)

A number of tris chelates derived from dihydrogenviolurate (H2va–) and 1,3-dimethylviolurate (dmva–) have been synthesized. Complexes of general formula [ML3]n–(M = CoIII, n= 0; M = FeII or RuII, n= 1; L = H2va or dmva) are described and characterized by i.r., u.v.–visible, and 1H n.m.r. spectra. Infrared data support the assumption of the same fac co-ordination structure for all the complexes in the solid state. The 1H n.m.r. spectra are in accordance with an octahedral arrangement in the fac configuration in solution. The 1H n.m.r. shifts are a probe of electron-density changes at the N(1) and N(3) sites of the co-ordinated heterocycle. Measurements of pKa for the [M(H2va)3]n– complexes are presented and are consistent with the n.m.r. data. The energies of the π→π* and d→π* electronic transitions of the protonated and deprotonated species provide information about the energies of the molecular orbitals of the violurate ligand. The results are interpreted in terms of Lewis-acid charge withdrawal and π-back bonding.

Novel ruthenium nitrosyl complexes formed by nitrosating the tris(violurato)- and tris(1,3-dimethylviolurato)-ruthenate(II) anions

The salt Na2[Ru(NO)(NO2)4(OH)] reacts with barbituric acid in water to give Na[Ru(H2va)3](H2va–= bidentate violurate), and with 1,3-dimethylbarbituric acid to give Na[Ru(dmva)3](dmva–= bidentate 1,3-dimethylviolurate). The complexes react with Na[NO2] in acidic aqueous solutions to afford a series of novel diamagnetic nitrosylruthenium complexes of the general type cis-[Ru(L–L)2(NO)X](L–L = bidentate H2va– or dmva–; X–= Cl–, Br–, or unidentate H2va– or dmva–). In water, acetomtrile, or dimethyl sulphoxide. the complexes cis-[Ru(L–;L)3(NO)] release the co-ordinated nitrosyl lirgand owing to the intramolecular transformation: cis-[Ru(L–L)2(NO)(unidentate L–L)]→[Ru(L–L)2(bidentate L–L)]–+[NO]+. On the basis of the i.r. and 1H n.m.r. spectra, the most probable structures of the complexes are given and the high electrophilicity of co-ordinated NO is shown to result from the strong π-backbonding properties of the bidentate violurate ligands.