A THEORETICAL-STUDY OF ZNCH2 AND ZNSNH2 ELECTRONIC-STRUCTURE AND THE ZNCH2-HZNCH PHOTOLYTIC REARRANGEMENT

A theoretical study of the electronic structure of the prototypical zi nc carbenes and zinc stannylenes ZnXH(2) (X = C, Sn) as well as their monopositive and dipositive ions ZnXH(2)(+) and Z(n)XH(2)(2+) is repor ted. Based on ab initio Hartree-Fock calculations and introducing elec tron correlation through second-order Moller-Plesset perturbation theo ry (MP2), the molecular structures of ground and some excited states o f these complexes have been examined. Special attention has been devot ed to the analysis of the bond mechanisms between zinc and carbon or t in and how the charge modifies these bonds. Zn-X stretch force constan ts and dissociation energy profiles are also reported. In the last par t of the work an approach to the ZnCH2-HZnCH photolytic rearrangement has been performed. Based on complete active space self-consistent-Fie ld (CASSCF) calculations a saddle point on the potential energy hypers urface has been located. A careful analysis of the nature of the wave functions for the 10 lowest states suggests a mechanism involving an e xcitation toward the first B-3(1) excited state lying at 33000 cm(-1) in agreement with experiment (<35700 cm(-1)).