Synthesis, molecular structure, and stereochemical nonrigidity of bis(3-(dimethylamino)propyl)difluorostal dihydrate, {[Me(2)N(CH2)(3)]2SnF2 center dot 2H(2)O}, and enhanced reactivity of its fluoride adduct {[Me(2)N(CH2)(3)]2SnF3}(-)Bu(4)N(+) toward dichloromethane

The X-ray diffraction analysis of crystals of {[Me(2)N(CH2)(3)]2SnF2 . 2H(2)O (3a) obtained by reaction of [Me(2)N(CH2)(3)]2SnR(2) (R = Me, Ph) with Pr3SnF reveals a six-coordinate, distorted octahedral geometry at tin with the pairs of fluorine, nitrogen and carbon atoms bound to the metal atom being all in a mutual trans configuration. Room-temperature Sn-119, F-19, H-1, and C-13 NMR spectra of 3a reveal exchange averaging with loss of the (1)J(Sn-119-F-19) coupling on the Sn-119 and F-19 NMR time scales. Below -50 degrees C, Sn-119 and F-19 NMR coupling data evidence the existence of only two isomers among the five a priori possible ones, a major (ca. 80%) and a minor species (ca. 20%). The methyl C-13 resonance as well as the (1)J(Sn-119-F-19), (1)J(Sn-119-C-13), and (2)J(F-19-C-13) coupling patterns reveal the major species to have the same all-trans structure as in the crystal state, while the minor species has a cis arrangement felt its fluorine and nitrogen atoms and the trans one for its carbon atoms. Gradient assisted H-1-Sn-119 HMQC spectroscopy establishes (3)J(Sn-119-H-1) correlations through the Me(2)N-->Sn bond to exist in both slow- and fast-exchange ranges. Together with the loss of the (1)J(Sn-119-F-19) coupling at high temperature, this evidences the Me(2)N-->Sn coordination to be maintained during the cis-trans isomerization and the latter to occur through a dissociative mechanism involving tin-fluorine bond rupture. Addition of Bu(4)N(+)F(-) . 3H(2)O in CH2Cl2 yields under quaternization of one nitrogen zwitterionic {[Me(2)(ClCH2N+ (CH2)(3)][Me(2)N(CH2)(3)]SnF3-}. H2O (3b).