Spectroscopic and structural studies of tin complexes
Several hexachlorostannate (IV) and hexabromostannate (IV) salts have been prepared and studied by halogen n.q.r. spectroscopy. Correlations were found to exist between the (^35)cl or (^79)Br n.q.r. frequencies and the respective Sn-Cl and Sn-Br bond lengths in the hexahalo tannate ions. A similar correlation was also found for some trichlorostannate (II) ions. An approximate relationship between cation size and average n.q.r. frequency was deduced for the hexahalostannates. Crysta~ structure determinations by Dr. J.C. Halfpenny of (pyH)(_2)SnBr(_6) and (Me(_2)NH(_2))(_2)SnBr(_6) are reported in this context. These two compounds were also studied by variable temperature n.q.r., together with Me(_3)NHSncl(_3) and seven hexachlorostannates, which revealed the existence of a number of structural phase changes between 77K and 300K. (^119)Sn n.m.r. spectroscopy has been used to study the concentration behaviour of several stannous halides in solution, and a relationship between the chemical shift at infinite dilution and the dielectric constant of the solvent was noted. The effect of halide ions on the chemical shifts of some stannous halides and some preliminary investigations into tin (II) cyanide complexes are described. Pairwise interaction theory has been used extensively in the interpretation of the results of exchange reactions in solution between octahedral tin complexes containing chloride, bromide, fluoride, azide, cyanide and thiocyanate ligands, and has enabled isomeric configurations to be assigned to many of the observed species. This theory was also used in analysing the chemical shifts of exchange products between some stannic halides in carbon disulphide, methanol and ethanol. In addition, the behaviour of SnCL(_4), SnBr(_4) and SnP(_4) individually in aqueous media has been followed by (^119)Sn n.m.r. measurements. The solid state (^119)Sn n.m.r. spectra of several tin (II) and tin (IV) compounds have been recorded and these are believed to be the first reports of such measurements.