SPECTROSCOPIC STUDIES FOR ADDUCTS OF 2-AMINOPYRIMIDINE WITH TIN(IV) HALIDES AND TIN(II) CHLORIDE - CIS-TRANS ISOMERISM IN TETRABROMOBIS(2-AMINOPYRIMIDINE)TIN(IV)

The complexes [SnCl4(Apyrim)(2)], 1, [SnBr4(Apyrim)(2)], 2 and [SnCl2( Apyrim)](2), 3, have been prepared and structurally characterized in, the solid state by means of Sn-119 Mossbauer spectroscopy, determinati on of lattice dynamics by temperature-dependent Sn-119 Mossbauer spect roscopy, and by vibrational studies. Conductivity measurements and UV spectra in solution are also reported. A cis octahedral structure (C-2 ) is proposed for [SnCl4(Apyrim)(2)] while for [SnBr4(Apyrim)(2)] both cis (C-2) and trans (C-2h) isomers are proposed to be present in the solid state, in an 1:1 molar ratio. An asymmetrically bridged dimer st ructure is proposed for [SnCl2(Apyrim)](2). From the variable-temperat ure Mossbauer effect, the Debye temperature for 1-3 were determined to be 150, 139 and 117, respectively. A computational study was attempte d, utilizing a PM3 Hamiltonian in order to investigate the prevailing isomer of each of the studied species both in the gas phase and in sim ulated solvent bulk (COSMO model). (C) 1998 Elsevier Science B.V. All rights reserved.