Selected-ion flow tube studies of reactions of C-60(n+) (n=1, 2, 3) with chlorinated ethylenes

The chlorination of singly and multiply charged C-60 cations has been inves tigated using the selected-ion flow tube (SIFT) technique with chlorinated ethylenes as possible chlorinating agents. Observations are reported for th e reactions of C-60(+), C-60(2+), and C-60(.3+) with CH2=CHCl, CH2CCl2, tra ns-CHCl=CHCl, cis-CHCl=CHCl, CHCl=CCl2 and CCl2=Cl-2 at room temperature (2 95 +/- 2 K) in helium at a total pressure of 0.35 +/- 0.02 Torr. The result s generally are consistent with previous studies of the reactivities of the se three ionized states of C-60 under SIFT conditions. C-60(+) was observed not to react in any way and C-60(3+) reacted exclusively by rapid electron transfer, k > 1.0 x 10(-9) cm(3) molecule(-1) s(-1). C-60(2+) was observed to be less reactive with values of k in the range from 1.5 x 10(-12) to 1. 6 x 10(-10) cm(3) molecule(-1) s(-1) and exhibited three different types of reaction channels: electron transfer, adduct formation, sand (Cl)(2) trans fer. The latter channel was the only chlorination channel observed and occu rred exclusively with the cis and trans isomers of 1,2-dichloroethylene, bu t in competition with adduct formation. The variation observed in the occur rence of these three channels with charge state is consistent with what is now known about the role of charge state in promoting bond formation with t he C-60 surface and the role of coulombic repulsion between product ions in preventing electron transfer. A bimolecular reaction of the C-60 (trans-HC lC=CHCl)(2+) adduct ion with trans-1,2-dichloroethylene was observed leadin g to the elimination of acetylene or chlorine. Higher-order sequential addi tions to C-60(2+) were seen with vinyl chloride, 1,1-dichloroethylene, and trichloroethylene and these are proposed to proceed by "ball-and-chain" pol ymerization. (C) 1999 Elsevier Science B.V.