A new class of Lewis acidic hosts is described. The hosts are macrotricyclic species containing four tin atoms that serve as the bridgeheads of the macrotricycle and contain an electron withdrawing group to impart Lewis acidic character. Variable length polymethylene chains link the tin atoms. The preparation of two macrotricyclic host precursors and one macrotricyclic host, 1,7,13,19-tetrachloro-1,7,13,19-tetrastann-(17,5,5,.5) tetratriacontane (7), are described. Tin II9 NMR studies of host 7 binding chloride ...
The preparation of eight symmetrical, macrobicyclic hosts containing two chloride or bromide substituted tin atoms at the bridgehead positions and linking chains of 6, 7, 8, 10, 12 methylene groups are described. In solution, the smaller members exist as one isomer with the halogens outside of the cavity (out-out isomer), but the larger members exist as a mixture of the major out-out isomer and a minor in-out isomer that contains ...
Crystalline complexes of 1,10-dichloro-1,10-distannabicyclo.8. 8hexacosane and benzyltriphenylphosphonium chloride (complex 3) and of 1,8- dichloro-1,8-distannabicyclo-6.6.6eicosane and tetrabutylammonium fluoride (complex 4) have been studied by X ray crystallography and solid state 119 Sn NMR spectroscopy. The halide ions are encrypted within the cavities of the bicyclic hosts in both complexes. Complex 3 is a stannates stannane species wherein one of the Lewis acidic tins binds the chloride strongly and the other interacts ...
The binding of halide ions by host 1 (1, 8-dichloro-1,8-distanna- bicyclo(6.6.6)eicosane) in solution have been studied Nuclear Magnetic Resonance (NMR) spectroscopy. In CDCl3 solutions, host 1 maintains its structural integrity in the presence of tetraalkylammonium halides. Host 1 shows no binding properties towards chloride, bromide or iodide ions. Molecular recognition of anionic guests by multidentate, Lewis acidic hosts in organic media has been observed in only limited cases. Further, neutral, ...
The preparation of macrobicyclic hosts 1,8-dichloro-1,8- distannabicyclo eisocane (1a), 1,10-dichloro-10-distannabicyclo hexacosane (1b), 1,12-dichloro-1,12-distannabicyclo dotriacontane (1c) and 1, 12-dichloro-1,12- distannabicyclo octatriacontane (1d) are reported. Complexation of chloride ion in CDCl3 solutions by these hosts was studied by Sn-119 NMR spectroscopy, and kinetics and equilibrium constants for 1b-d were determined by line shape analysis. Selective chloride binding was observed; hosts 1b and 1c bind chloride more strongly than does host 1d, and ...
This report updates and corrects information in Technical Report No. 6 (September 15, 1985). New data includes concentration effects on tin-119 chemical shifts, measurements of chemical shifts of dibutyltin dichloride (5) plus chloride ion at low concentrations, direct determination of relative complexing strengths of acyclic model 5 against macrocyclic hosts and modified calculations of host-guest binding energies in acetonitrile. Three macrocyclic Lewis acidic hosts containing two symmetrically disposed dichlorostanna moieties ...
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