Struktur-Reaktivitäts-Beziehungen bei koordinativ ungesättigten Chelatkomplexen. I. Spektrophotometrische Gleichgewichtsuntersuchungen zum Einfluß der äquatorialen Ligandsubstitutuenten auf die Adduktbildung planarer Bis (3-oxo-1-enaminato)-nickel(II)-chelate mit Pyridin

Structure Reactivity Correlations in Coordinatively Unsaturated Chelate Complexes. I. Spectrophotometric Equilibrium Investigations on the Effect of the Equatorial Ligand Substituents on the Adduct Formation of Planar Bis(3-oxo-l-enaminato)nickel(II) Chelates with Pyridine . The effect of the equatorial ligand substituents R, R¹, and R² on the ability of the diamagnetic planar nickel(II) chelates I, II , and III to form paramagnetic, octahedral bis(adducts) with pyridine is examined by determination of equilibrium constants (and thermodynamic data) for the equilibrium (1) using spectrophotometric and (in part) magnetic methods. Several new compounds of the types I and II are synthesized and characterized by visible and ¹HNMR spectra. Some different methods for computing the photometric measurements of simple equilibria are compared. The K values vary from <10^?4 to > 10⁵ l² mol^?2 in dependence on the ligand substituents. The distinct influence of the peripherhal substituents R¹/R² correlates with their inductive effect. The N-substituents R act mainly on the field strength of the equatorial ligands.