Ligand Field Spectra Research Articles

Ligand field spectra of some metals in their unfamiliar oxidation states—IV. Bivalent rhenium

Abstract The absorption spectra of three tetra co-ordinated complexes of bivalent silver have been measured. The visible absorption bands, which could be resolved into three Gaussian component, have been associated with the ligand field spectra. It has been concluded that in these complexes bivalent silver is in a square planar configuration.

Ligand field spectra of some metals in their unfamiliar oxidation states—II: Trivalent silver and copper

Ligand field spectra in a Ag(III) and a Cu(III) complex have been located and characterized. The polarized crystal spectra measurements on Cu(III) complex indicates that the assignment of d-orbital configuration from the study of solvent effect on the electronic spectra may not be always reliable.

Ligand field spectra of some metals in their unfamiliar oxidation states—III: Tetravalent manganese

The ligand field bands in the absorption spectra of a biguanide complex of dihydroxo manganese (IV) hydroxide have been located and characterized. The following values were experimentally obtained for the ligand field parameters; Dq = 1592 cm −1, F 2 = 1007 cm −1 and F 4 = 146 cm −1.

Ligand field parameters of Mo(III) complexes

Spectral absorption data of some octahedral chromophores of Mo3+ are reported, together with values of Δ and β 55 parameters, whenever experimentally attainable. For complexes with sufficiently electronegative ligands, almost complete ligand field spectra can be observed, whereas in other complexes intense charge transfer bands occur; with ligands of low electronegativity, charge transfer bands from the central ion to the ligands are frequently encountered.

Structural Interconversions of Octahedral, Planar, and Tetrahedral Nickel(II) Complexes

A series of bis-(N-R-salicylaldimine(Ni(II) complexes has been prepared in which the R group contains a site capable of coordination. Complexes with R=CH2CHCH2OCH3 but differing in the extent and position of chelate ring substitution have been thoroughly studied. For these complexes it has been shown from measurement of ligand field spectra amd piton contact shifts that in the temperature range —40 to 50° in chloroform solution discrete octahedral, planar and tetrahedral stereoisomers are present in equilibrium. At low temperatures the octahedral form predominates; at higher temperatures the equilibrium is displaced toward the planar and tetrahedral forms. For two complexes the temperature dependence of the distribution of stereoisomers has been estimated from spectral data. The spectra of the octahedral complexes were found to be quite similar to those of associated paramagnetic bis(salicylaldimine)nickel(II)+. suggesting quasi-octahedral coordination in the latter. The spin density distributions in the coordinated ligand systems were shown to be similar in sign in the octahedral and tetrahedral stereoisomers.

Studies on Nickel(II) Complexes. VI. The Conformational Equilibria of Bis(o-hydroxynaphthaldimine) Complexes

The existence of a planar ⥨ tetrahedral structural equilibrium in solutions of three isomeric groups of bis(o-hydroxynaph-thaldiminej—Ni(II) complexes has been established from studies of magnetic susceptibilities, ligand field spectra, and proton magnetic resonance spectra. Like the related salicylaldimine complexes, 1 these naphthaldimine complexes manifest isotropic hyperfine contact shifts in their proton resonance spectra. The assignment of these spectra is discussed. The sign of the contact shifts and spin densities are shown to be in agreement with a qualitative valence bond model of spin delocalization. The use of the contact shift effect in obtaining cis spin-spin coupling constants is illustrated for one o-hydroxynaph-thaldimine system.

Ligand field spectra of some metals in their unfamiliar oxidation states—I: Bivalent silver

The absorption spectra of three tetra co-ordinated complexes of bivalent silver have been measured. The visible absorption bands, which could be resolved into three Gaussian component, have been associated with the ligand field spectra. It has been concluded that in these complexes bivalent silver is in a square planar configuration.

Ligand Field Spectrum of Vanadium(II) Hexaquo Ions.

Ligand Field Spectrum of Vanadium(II) Hexaquo Ions.