C-F and C-C bond activation by transition metals in low energy atomic ion/surface collisions

The transition metal ions, Cr+., Mo+., W+. and Re+, abstract one or more fl uorine atoms or CmFm groups (m = 1,2; n = 1-5) in collisions with fluorocar bon self-assembled monolayers (F-SAMs). The number of atoms abstracted incr eases with collision energy, and with W+. and Re+ it is possible to maximiz e a specific scattered product ion by selecting the appropriate collision e nergy. The collision energy dependence suggests that dissociation of the pr oducts of multiple abstractions is not an important source of, any of the o bserved ion/surface reaction products. The ions W+. and Re+ activate and in sert into C-C as well as C-F bonds. In Re+ collisions, products of C-C bond activation are of comparable intensity to the C-F activation products. The reactivity of the ions towards fluorine abstraction is observed to be Cr+. < Mo+. < W+. < Re+. The data are interpreted in terms of reaction at the s urface and are rationalized by considering three factors (i) the electronic structures of the ions, (ii) the thermochemistry of fluorine abstraction, and (iii) the degree of orbital overlap of the metal ion and the F-SAM subs trate. Copyright (C) 1999 John Whey & Sons, LM.