Theoretical study of metallasilatranes; Bonding nature and prediction of new metallasilatrane

The new bond between Pt atom and hypervalent six-coordinate Si species in platinum-silatrane reported recently was theoretically investigated mainly with DFT method and in part with MP2 method. The DFT method with B3PW91 and M06 functionals reproduces well the Pt–Si, Pt–Cl and Si–N bond distances. Though the Si–Cl distance is overestimated by all functionals employed here when one d polarization function is added to each of Si and Cl, the M06-optimized Si–Cl distance is close to the experimental value when two d polarization functions are added to each of Si and Cl, suggesting that the functional and basis sets must be carefully employed in theoretical calculation of hypervalnet six-coordinate Si species. Population analysis clearly indicates that the Pt–Si bond is formed by the charge-transfer (CT) from the occupied dσ orbital of Pt to the empty p orbital of Si, which enhances the CT from the S atoms and Cl ligand to the Pt center. Besides platinum- and palladium-silatranes, no metallasilatrane has been reported so far. Based on the knowledge of bonding nature, we presented theoretical prediction that iridium(I) can form a similar metallasilatrane. Actually, the DFT calculation indicates that iridium-silatrane has essentially the same equilibrium geometry and bonding nature as those of platinum-silatrane.