Gas - phase reactions of fullerene cations C 60 x 1 ( x 5 1 – 3 ) with pyrrolidine and piperidine : sequential reactions with C 60 1

Results of selected-ion flow tube experiments are reported that explore the nucleophilic interaction of pyrrolidine and piperidine with C60 1 , C60 , C60 31 at 294 6 2 K in helium buffer gas at a pressure of 0.35 6 0.01 Torr. Two efficient sequential addition reactions were observed with C60 1 in analogy with previous results obtained with acyclic amine nucleophiles. Multicollision-induced dissociation experiments suggest the formation and conversion of two isomers of the second adduct ion. As a first step C–N bond formation is proposed to occur with the C60 cage with or without ring opening. Subsequent bonding may involve hydrogen bonding or, if ring opening occurs, further C–N bond formation at the terminus of the first substituent. Nucleophilic attack of C60 21 and C60 31 by pyrrolidine leads to ring cleavage and formation of C60(NH3) n1 (n 5 2,3) accompanied by loss of what is likely to be 1,3-butadiene. C60(NH3) n1 effectively donates a proton to pyrrolidine. The ring-cleavage channel dominates competing channels leading to electron transfer and nucleophilic addition. However, ring cleavage is not observed with piperidine which reacts with C60 21 and C60 31 exclusively by electron transfer because of its lower ionization potential. Further reactions of the proton-transfer product lead to the formation of “mixed” adducts of the type (NH2)C60(C4H8NH) n1 (n 5 1,2) that may involve two C–N bonds with the C60 surface or, alternatively, proton bonding to protonated aziridine. (Int J Mass Spectrom 195/196 (2000) 401–409) © 2000 Elsevier Science B.V.