Triorganotin cations stabilized by intramolecular SnN coordination; synthesis and characterization of {C,N,N′-2,6-bis[(dimethylamino)methyl]phenyl}diorganotin bromides {A figure is presented}

The synthesis of {2,6-bis[(dimethylamino)methyl]phenyl}diorganotin bromides, 2,6-(Me₂NCH₂)₂C₆H₃SnRR′⁺ Br^- is described. The compounds in which R = R′ = Me or Et and R = Me, R′ = Ph are extremely soluble in water and other polar solvents and insoluble or slightly soluble (R = R′ = Et) in apolar solvents. The diphenyl compounds shows the opposite solubility behaviour. The dimethyl compound is completely dissociated in water in to a triorganotin of 84.8 ohm^-1 cm^-1 (1/1 electrolyte). NMR spectroscopy reveals that the triorganotin cation has a TBP structure in which the N atoms occupy axial sites. Dynamic NMR spectra of the methylphenyl compound show that above -90°C ratedetermining SnN dissociation occurs and that above 5°C second process, involving rate-determining rotation of the substituted aryl group around the (N₂)CSn bond begins. An X-ray investigation of single crystals of the dimethyl compound, which is unstable towards X-rays, establishes the ionic structure of the triorganotin halide in the solid (shortest SnBr 4.99 Å) as well as the molecular geometry of the triorganotin cation. Crystals are monoclinic, space group P2₁/n with Z = 4 in a unit cell of dimensions: a = 11.13(1), b = 16.73(2), c =10.10(1) Å, and β 114.2(1)°.