On the Structural Dichotomy of Cationic, Anionic, and Neutral FeS(2).
Structural and thermochemical aspects of the FeS(2)(+) cation are examined by different mass spectrometric methods and ab initio calculations using density functional theory. Accurate threshold measurements provide thermochemical data for FeS(+), FeS(2)(+), and FeCS(+), i.e., D(0)(Fe(+)-S) = 3.06 +/- 0.06 eV, D(0)(SFe(+)-S) = 3.59 +/- 0.12 eV, D(0)(Fe(+)-S(2)) = 2.31 +/- 0.12 eV, and D(0)(Fe(+)-CS) = 2.40 +/- 0.12 eV. Fortunate circumstances allow a refinement of the data for FeS(+) by means of ion/molecule equilibria, and the resulting D(0)(Fe(+)-S) = 3.08 +/- 0.04 eV is among the most precisely known binding energies of transition-metal compounds. The present results agree with previous experimental findings and also corroborate the computed data for FeS(+) and FeS(2)(+). Ab initio calculations predict a sextet ground state ((6)A(1)) for FeS(2)(+) with a cyclic structure. The presence of S-S and Fe-S bonds accounts for the fact that not only reactions involving the disulfur unit but also sulfur-atom transfer can occur. In contrast, the FeS(2)(-) anion is an acyclic iron disulfide. In the gas phase, neutral FeS(2) may adopt either acyclic or cyclic structures, which are rather close in energy according to the calculations.
Schröder
Detlef
D
Department of Chemistry, University of Utah, Salt Lake City, Utah 84112.
Kretzschmar
Ilona
I
Schwarz
Helmut
H
Rue
Chad
C
Armentrout
P. B.
PB