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MoF 6 and WF 6 : Nonrigid Molecules?
Author(s) -
Quiñones Gustavo Santiso,
Hägele Gerhard,
Seppelt Konrad
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400095
Subject(s) - octahedron , intramolecular force , crystallography , chemistry , twist , molecule , trigonal prismatic molecular geometry , fluorine , metal , ground state , trigonal crystal system , stereochemistry , crystal structure , physics , atomic physics , geometry , organic chemistry , mathematics
Calculations reveal that the octahedral–trigonal prismatic–octahedral rearrangement has particularly low‐energy barriers for MoF 6 , WF 6 , and (hypothetical) CrF 6 . Experimental evidence is obtained from the dynamic 19 F NMR spectra of the derivatives CF 3 CH 2 OMoF 5 , CF 3 CH 2 OWF 5 , C 6 F 5 OMoF 5 , C 6 F 5 OWF 5 , and (CF 3 ) 3 COWF 5 . 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.