Rhenium oxide cluster anions in a molecular beam

The formation of rhenium oxide cluster anions is studied in a pulsed molecular beam experiment as a function of source conditions and oxygen content (0.1‐10%) in the carrier gas. RenOm clusters are formed directly in plasma reactions in the laser vaporization cluster source. With both increasing oxygen content and stagnation pressure, larger oxide clusters are formed (m^n) and the distribution is dominated by certain mass peaks of high intensity indicating a high stability. At lower pressure and less oxygen content, a large variety of oxides is observed. Most stable clusters contain Re atoms with a formal oxidation state of 17 and oxygen in the 22 oxidation state. Oxygen rich clusters can be attributed to a series (ReO 4)l(Re2O7)m(O)n with l50 ‐1, m50 ‐ 4, and n50 ‐1. The results are explained by the nature of the Re‐O bond which is important for the alkene metathesis reaction mechanism. (Int J Mass Spectrom 209 (2001) 1‐ 4) © 2001 Elsevier Science B.V.