The 119Sn and 15N NMR spectral study of the chelate formation in the triphenyltin(IV) oxinate

The 119 Sn and 15 N NMR spectra of triphenyltin(IV) oxinate and (therewith isoelectronic compound) 1-naphthoxide have been measured in the media of a non-coordinating solvent - deuteriochloroform - and two coordinating solvents - pyridine and hexamethylphosphoramide - in the temperature region from 240 to 370 K. The values of parameters of the 119 Sn and 15 N NMR spectra and their temperature dependences and comparison of the parameters of the 119 Sn NMR spectra of the two isoelectronic compounds indicate that, in the non-coordinating solvent (deuteriochloroform), the triphenyltin(IV) oxinate forms a chelate complex with bidentate function of the oxinate ligand and with cis -trigonally bipyramidal geometry around the penta-coordinated central tin atom, whereas the triphenyltin(IV) 1-naphthoxide forms a simple compound with pseudo-tetrahedral arrangement of the substituents around the tetra-coordinated central tin atom. In both coordinating solvents chemical reactions take place which produce complexes of triphenyltin(IV) compounds with one molecule of the solvent and with trans -trigonally bipyramidal structure around the penta-coordinated central tin atom. The temperature dependences of δ( 119 Sn) chemical shifts have been used for estimation of the basic thermodynamic parameters of formation of these complexes which confirm that the formation of the complexes with coordinating solvents is - in the case of triphenyltin(IV) oxinate - connected with an exchange equilibrium consuming the original cis -chelate complex (the coordination number 5 of the central atom does not change), whereas with the 1-naphthoxide the reaction consists in a simple formation of the complex with an increase in the coordination number of the central atom (from 4 to 5).