On the stabilities of the complex anions of carbon and silicon XH 4− and XH 5−

Abstract

The hydride attack at CH 3 leads to a C 2v complex, which, in analogy to the polar van der Waals' anions NH 4 − and H 3O −, is a minimum on the potential energy surface, whereas SiH 3 suffers proton abstraction to yield SiH 2 − and H 2, which can form only a very loosely bound complex. CH 4 and SiH 4 can both attach an H − ion leading to a “bond-on” ( C 3v) CH 5 − and to the H 3 “face-on” ( C 3v) SiH 5 − complexes, respectively. The D 3h isomers of both CH 5 − and SiH 5 − are minima on the potential energy surfaces, and turn out to be the least stable of the investigated CH 5 − and the most stable of the investigated SiH 5 − species.