6533b82dfe1ef96bd12912dc

RESEARCH PRODUCT

Synthesis, spectroscopic (Mössbauer, IR and NMR) and X-ray structural studies of diorganotin complexes of 2,2′-bipyrimidine and further NMR studies of diorganotin-pyrazine and — 2,2′-azopyridine complexes

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Abstract The ligand 2,2′-bipyrimidine (bipym) was reacted with diorganotins R 2 SnCl 2 (R = methyl, ethyl) and complexes of the types R 2 SnCl 2 bipym, R 2 SnCl 2 bipym · bipym and (R 2 SnCl 2 ) 2 bipym were synthesized and studied by 1 H and 13 C NMR spectroscopy in solution, and by IR and Mossbauer spectroscopy in the solid state and frozen solutions. The complexes Et 2 SnCl 2 bipym · bipym and (Et 2 SnCl 2 ) 2 bipym were characterized by X-ray diffraction methods. In both complexes the tin environment is octahedral with chloro atoms in a cis disposition, the ethyl groups in a trans disposition and two N atoms from the ligand bipym. the second complex is a centrosymmetric binuclear species that has the ligand lone-pairs bound to two Et 2 SnCl 2 units, whereas the first has one Et 2 SnCl 2 species bound to the ligand and one ligand uncoordinated. The data obtained by 119 Sn Mossbauer spectroscopy for the solids and for frozen solutions indicate the presence of quadrivalent tin in an octahedral environment with trans alkyl groups, in keeping with the X-ray structures. The NMR spectra, however, reveal ligand lability in solution, and the CSnC angles calculated from coupling constants suggest a coordination number of between 5 and 6. These results together with the long SnN bond distances in crystals of Et 2 SnCl 2 bipym · bipym and (Et 2 SnCl 2 ) 2 bipym suggest that these complexes may have a potential antitumour activity.