Abstract
The absorption spectra of ten organotin compounds were measured in the infrared region 2.5-15.3 mum (4000-650 cm-1) and in the ultraviolet region 200-400 mum. The compounds used were: the homologous series PhnSnCl4-n (n=1, 2, 3, and 4), tetrabonzyltin, tribenzyltin chloride, tetra-p-tolyltin, tetrakis-p-chlorophenyltin, triethyltin phenoxide and N:triethyltin phthalimide. The results have been analysed and discussed in detail and a tentative assignment of many of the normal vibrational frequencies carried out. Some of the vibrational fine structures of the electronic absorption bands has been tentatively assigned. The spectral measurements were carried out on samples in the liquid or the solid state and in solutions. The effect of the tin atom on the normal vibrational frequencies of the phenyl, benzyl and ethyl groups seems to be negligible and most of the normal frequencies fall within the range expected for hydrocarbons. Certain variations in some of the normal frequencies of the homologous series phnSncl4-n are correlated to the number of chlorine atoms attached to tin. No interaction between phenyl, benzyl or ethyl groups attached to the some tin atom was observed. Evidence from both vibrational and electronic absorption spectra of the phenyltin compounds confirms the formation of d-p-bond between the electronic cloud of the benzene nucleus and the empty outermost d-orbital of tin; and that the electronegativity of tin increases in the phenyl compounds in the following order: Ph4Sn < Ph3sncl < Ph2Sncl2 < PhSncl3 The following electronic configuration may participate appreciably in determining the electronic structure of the phenyltin compounds. An equation derived from the electrostatic theory for the effect of the interaction between the substituent and the ortho-hydrogens of monosubstituted benzenes on the gamma-C-H vibrations was developed which leads to the calculation of group dipole moments which are in good agreement with the accepted values from other methods. Tetraphenyltin and tetrabenzyltin were prepared by an improved method and a new method for the preparation of tetra-p-tolyltin is described.