SYNTHESIS, SPECTROSCOPIC (MOSSBAUER, IR AND NMR) AND X-RAY STRUCTURALSTUDIES OF DIORGANOTIN COMPLEXES OF 2,2'-BIPYRIMIDINE AND FURTHER NMR-STUDIES OF DIORGANOTIN-PYRAZINE AND DIORGANOTIN-2,2'-AZOPYRIDINE COMPLEXES

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)bip ym, R(2)SnCl(2)bipym . bipym and (R(2)SnCl(2))(2)bipym were synthesize d and studied by H-1 and C-13 NMR spectroscopy in solution, and by IR and Mossbauer spectroscopy in the solid state and frozen solutions. Th e 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 bi pym. The second complex is a centrosymmetric binuclear species that ha s the ligand lone-pairs bound to two Et(2)SnCl(2) units, whereas the f irst has one Et(2)SnCl(2) species bound to the ligand and one ligand u ncoordinated. The data obtained by Sn-119 Mossbauer spectroscopy for t he solids and for frozen solutions indicate the presence of quadrivale nt tin in an octahedral environment with trans alkyl groups, in keepin g with the X-ray structures. The NMR spectra, however, reveal ligand l ability in solution, and the C-Sn-C angles calculated from coupling co nstants suggest a coordination number of between 5 and 6. These result s 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 complexe s may have a potential antitumour activity.