The formation of yttrium-carbon cluster ions and their reactivities toward CH,Br, H,O and NH, were examined by using a Fourier transform ion cyclotron resonance mass spectrometer equipped with a Smalley supersonic expansion ion source. A broad range of yttrium-carbon cluster ions can be generated. Unlike other metal-carbon systems, such as titanium-arbon and vanadiuwarbon where Mac:, (termed metallo-carbohedrene) species show 'magic' character in the mass spectra in that their intensities dominate neighboring peaks, Y&: , is not observed to be the most abundant Y,C,+ ion. One peak that stands out as being relatively intense under various conditions is Y,CT. The collision-induced dissociation and reactivity of this ion were therefore chosen for study and compared with those of Y, C: * and Y,C; to see the effect of added yttrium and carbon. The major fragmentation pattern of Y,C,+ and Y4Cx+ species is via loss of metal. YC,+ and Y,C,+ (x = 4, 5) are also produced. Unlike the metal-carbon cluster ions, Nb,C,+, M, C: , (M = V, Ti and Nb) and V, , C:, .
studied previously, simple attachment reactions with small neutral molecules such as H,O and NH, were not observed. Instead, Y4C,+ dehydrogenates H,O and NH, , while Y,C; react with H,O in a sequential fashion to yield yttrium-oxide cluster ions and neutral acetylene. Y,CT-, ions abstract bromine from CH,Br. This reaction is believed to result from the odd number of electrons in these cluster ions, in which a single electron can pair with that of Br to form a u bond. Supporting this are the reactions of the even-electron species Y,CT with CH,Br, where bromine abstraction does not occur.