Thermodynamics of metal-ligand bond formation: XVI. Base adducts of some organotin compounds

Thermodynamic data have been obtained by calorimetric titration in benzene solution at 30° for reaction of organotin compounds with Lewis bases; data are reported for forty acid/base systems.Ph₃SnCl forms $\text{1}\text{1}$ adducts of low stability with pyridine (py) or 4-methyl-pyridine (4-mepy). Ph₂SnCl₂, Me₂SnCl₂, Bu₂SnCl₂ and Bu₂Sn(NCS)₂ form simultaneously $\text{1}\text{1}$ and $\text{1}\text{2}$ adducts with py or 4-mepy and $\text{1}\text{1}$ adducts with 2,2′-bipyridine or 1,10-phenanthroline (phen); the enthalpies of formation of the phen adducts are similar to those of $\text{1}\text{2}$ adducts with 4-mepy. With BuSnCl₃ and PhSnCl₃ it was not possible to obtain data for each step in addition of pyridine or 4-mepy. Adduct stabilities increase with increasing chloride substitution and in the order Bu < Me < Ph; adducts of Bu₂Sn(NCS)₂ are more stable than those of Bu₂SnCl₂.Tributylphosphine does not react with Ph₃SnCl but gives $\text{1}\text{1}$ adducts with the other tin compounds; only PhSnCl₃ adds a second molecule of this base. The $\text{1}\text{1}$ adducts are more stable than those with heterocyclic bases. Tributylamine brings about disproportionation of the compounds R₂SnX₂ to R₄Sn and SnX₄NBu₃.