Formation and reactivity of yttrium—carbon cluster ions in the gas phase: Y4C+7-9 and Y3C+7,8

The formation of yttrium-carbon cluster ions and their reactivities toward CH 3 Br, H 2 O and NH 3 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-carbon and vanadium-carbon where M 8 C 12 + (termed metallo-carbohedrene) species show 'magic' character in the mass spectra in that their intensities dominate neighboring peaks, Y 8 C 12 + is not observed to be the most abundant Y 8 C x + ion. One peak that stands out as being relatively intense under various conditions is Y 4 C 7 + . The collision-induced dissociation and reactivity of this ion were therefore chosen for study and compared with those of Y 4 C 8,9 + and Y 3 C 7,8 + to see the effect of added yttrium and carbon. The major fragmentation pattern of Y 3 C x + and Y 4 C x + species is via loss of metal. YC 2 + and Y 2 C x + (x = 4, 5) are also produced. Unlike the metal-carbon cluster ions, Nb 4 C 4 + , M 8 C 12 + (M = V, Ti and Nb) and V 14 C 12,13 + studied previously, simple attachment reactions with small neutral molecules such as H 2 O and NH 3 were not observed. Instead, Y 4 C 7 + dehydrogenates H 2 O and NH 3 , while Y 3 C 7,8 + react with H 2 O in a sequential fashion to yield yttrium-oxide cluster ions and neutral acetylene. Y 4 C 7-9 + ions abstract bromine from CH 3 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 σ bond. Supporting this are the reactions of the even-electron species Y 3 C 7,8 + with CH 3 Br, where bromine abstraction does not occur