Tin(IV) Complexes Based on Diimines and 3,5-Di- Tert -Alkyl Substituted Pyrocatechols

New tin(IV) complexes based on various pyrocatechols containing tert -butyl and tert -octyl substituents in the aromatic ring are synthesized and structurally characterized. Reduction of spatially hindered o -quinones with tin amalgam in tetrahydrofuran allows the preparation of compounds with the trans -position of catecholate ligands in the metal coordination sphere. In the further reaction of synthesized tin(IV) biscatecholates with N-donor ligands (pyridine (Py), α,α′-dipyridyl (dipy), 1,10-phenanthroline (phen), pyrazino-[2,3- f ][1-10]-phenanthroline (DPQ), dipyrido-[3,2- a :2′3′- c ]-phenazine (DPPZ)) the respective six-coordinated complexes are obtained. The introduction of bidentate ligands naturally results in the cis -position of dioxolene ligands in the tin coordination sphere. The possibility of intramolecular ligand–ligand charge transfer (LL′CT) between catecholate and diimine moieties in the synthesized octahedral metal derivatives is shown by electronic absorption spectroscopy. The effect of substituents in catecholate ligands and acceptor properties of diimines on the shift of a long-wave absorption band is determined. The electronic transition corresponding to LL′CT is revealed to undergo a bathochromic shift in the electronic absorption spectrum with a decrease in the polarity of the solvent used.