REACTIONS AND THERMOCHEMISTRY OF SMALL CLUSTER IONS - FE(CS2)N(+) (N=1, 2)

Thermal reactions of Fe(CS2)(n+) (n = 1, 2) with a series of ligand mo lecules, L, have been studied by using a selected ion flow tube. Prima ry reactions observed include ligand association, ligand switching, an d charge transfer. Fe(CS2)(+) favors association while Fe(CS2)(2)(+) u ndergoes mainly switching reactions. The bond dissociation energy D de grees(Fe+-CS2) = 39.6 +/- 2.5 kcal/mol was determined by the measureme nt of forward and backward ligand switching rate constants. This value was verified by the observation of the onset of switching for a serie s of reactions Fe(CS2)(+) + L --> FeL(+) + CS2 as a function of D degr ees(Fe+-L). Consecutive reactions in the flow tube tend to produce end products having a maximum coordination number of four, e.g., Fe(CS2)L (3)(+) and Fe(L)(4)(+), where L is a monodentate ligand such as NH3 or Fe(L)(2)(+) with polydentate ligands such as C6H6. The interactions o f Fe(CS2)(+) and Fe(CS2)(2)(+) with Xe were studied using a guided ion beam apparatus. Collision-induced dissociation (CID) thresholds gave bond dissociation energies of D-0 degrees(Fe+-CS2) = 39.7 +/- 1.1 kcal /mol in excellent agreement with the SIFT result and D-0 degrees(CS2Fe +-CS2) = 45.0 +/- 1.4 kcal/mol. Additional higher energy products in t he Fe(CS2)(+) system observed are FeXe+ and FeS+.