title: MoF6 and WF6: nonrigid molecules?
abstract: Calculations reveal that the octahedral-trigonal prismatic-octahedral rearrangement has particularly low-energy barriers for MoF6, WF6, and (hypothetical) CrF6. Experimental evidence is obtained from the dynamic 19F NMR spectra of the derivatives CF3-CH2-O-MoF5, CF3-CH2-O-WF5, C6F5-O-MoF5, C6F5-O-WF5, and (CF3)3C-O-WF5. The ground-state structure of all these compounds is octahedral; at elevated temperatures the nonequivalent metal-bound fluorine atoms undergo an intramolecular exchange. The exchange mechanism could be a 3+3 or a 2+4 twist; calculations favor the 3+3 twist.
authors.affiliation: Freie Universität Berlin, Institut für Chemie, Anorganische und Analytische Chemie, Fabeckstrasse 34-36, 14195 Berlin, Germany.
authors.forename: Gustavo Santiso
authors.initials: GS
authors.lastname: Quiñones
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hägele
authors.forename: Konrad
authors.initials: K
authors.lastname: Seppelt