Orbital Populations and π Backbonding in Some Organohalostannanes: The Interpretation of Tin Mössbauer and Ligand NQR Data

Tin Mössbauer isomer shifts and quadrupole splittings are reported for 23 compounds. Equations are derived and applied which enable the tin hybrid orbital populations for tetravalent tin compounds of the type AmSnB4−m to be determined from the above data. Critical tests of the theory are proposed. A minimum value of 5.8 mm sec−1 is obtained for the quadrupole splitting due to one p electron by comparing Mössbauer-derived with ligand NQR-derived populations. The two sets of populations are also used to obtain π backbonding orbital populations in organohalostannanes. The results show that tin sp3 orbitals are more important than d orbitals for π backbonding.