TRI-N-BUTYLTIN 2,6-DIFLUOROBENZOATE, A UNIQUE MACROCYCLIC TETRAMER CONTAINING A 16-MEMBERED SN4C4O8 RING, AND OTHER RELATED-COMPOUNDS

The X-ray crystal structure determination of tri-n-butyltin 2,6-difluorobenzoate, compound 4, revealed the compound to exist as a macrocyclic tetramer with 4BAR symmetry. The five-coordinated tin atoms have distorted trigonal bipyramidal geometries with the three butyl groups occupying equatorial positions and the carboxylate ligands bridging the tin atoms as bidentate ligands in apical positions. Crystals of the compound 2,6-F2C6H3CO2SnBu3, M(r) = 447.12, are tetragonal, space group I4BAR, with Z = 8 in a unit cell of dimensions a = 15.631(3) angstrom, c = 16.882(1) angstrom with R = 0.037 for 3151 unique reflections. In the cyclotetramer, each tin atom exhibits one strong and one weak Sn-O bond. The synthesis and spectral characterization of eight other related tri-n-butyltin carboxylates are presented. As for compound 4, its solution structure is monomeric, with a tetrahedral tin atom.