New heptacoordinated organotin(IV) complexes derivatives of 2,6-diacetylpyridinebis(2-furanoylhydrazone), H(2)dapf, and 2,6-diacetylpyridinebis(2-thenoylhydrazone), H(2)dapt. Crystal and molecular structure of [Me2Sn(Hdapt)]Br.H2O

The reaction of the ligands H(2)dapf and H(2)dapt, with R4-mSnXm (m = 2, 3; R = Me, Ph and X = CI, Br) led to the formation of eight new heptacoordina ted organotin(Ii) complexes, which were studied by microanalysis, IR, NMR a nd Mossbauer spectroscopy to investigate their structural properties. The m ethyl derivative [Me2Sn(Hdapt)]Br . H2O was also studied by single crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P2 (1)/c, with a = 21.920(3), b = 7.4470(5), c = 16.805(2) Angstrom, beta = 11 0.18(1)degrees, Z = 4. The structure determination revealed a monocationic complex of Sn(IV) in a distorted bipyramidal geometry [Me2Sn(Hdapf)](+), wi th Pr as counter ion and one molecule of water helping the crystal packing. Mossbauer parameters of the complex [Me2Sn(Hdapf)](2)[Me2SnCl4] have evide nced two Sn(IV) sites, as observed in the crystal structure determination. Also a correlation between Mossbauer and X-ray data based on the point-char ge model is discussed.