Organotin halide equilibria. Part III. Comparison of the stability constants of 2,2′-bipyridyl adducts of diorganotin di-isothiocyanates and dichlorides in benzene and toluene solutions

Abstract

Stability constants have been obtained for dialkyltin di-isothiocyanate–2,2′-bipyridyl adducts, R₂Sn(NCS)₂,bipy (R = Bu, octyl), and dioctyltin dichloride–2,2′-bipyridyl adducts, octyl₂SnCl₂,bipy, in benzene solution at 30, 35, and 40 °C. Some values in toluene solution are also reported. Comparisons of these stability constants show that the di-isothiocyanates are considerably better acceptors than the dichloride (by factors of ca. 500). The enthalpy (–ΔH/kcal mol^–1) and entropy of formation (–ΔS/cal mol^–1 K^–1) of the adducts were for Bu₂Sn(NCS)₂, bipy, octyl₂Sn(NCS)₂,bipy, and octyl₂SnCl₂,bipy in benzene solution 16·8, 38·2; 17·2, 38·4; and 12·7 and 34·8, respectively. The values for octyl₂SnCl₂ in toluene were 12·6 and 35·1. Spectral indications of [R₂Sn(NCS)₂]₂,bipy adducts in solution were obtained.