Triorganotin cations stabilized by intramolecular Sn-N coordination: Synthesis and characterization of {C,N,N-2,6-bis[(dimethylamino)methyl]phenyl}diorganotin bromides R'R'R''-Sn+Br

Abstract

The synthesis of {2, 6-bis[(dimethylamino)methyl]phenyl}diorganotin bromides, 2,6-(Me{2}NCH{2}){2}C{6}H{3}SnRR'}+{ 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}o{C ratedetermining Sn@?N dissociation occurs and that above 5}o{C second process, involving rate-determining rotation of the substituted aryl group around the (N{2})C@?Sn 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 Sn@?Br 4.99 @9) as well as the molecular geometry of the triorganotin cation. Crystals are monoclinic, space group P2{1}/n with Z = 4 in a unit cell of dimensions: a = 11.13(1), b = 16.73(2), c =10.10(1) @9, and @b 114.2(1)}o{.