The stereoselective synthesis of cis- and trans-F2TePh3Cl (phenyl substituents adopt a mer arrangement) via 5-coordinate cations Ph3TeFCl+ and [Formula: see text] is described. trans-F2TcPh3Cl isomerizes to the thermodynamically more stable cis isomer, and cis -F2TePh3Cl has non-equivalent fluorines which undergo stereoselective fluorine exchange, as confirmed by 19F and l25Te nmr spectroscopy. These results are consistent with an intermolecular mechanism of isomerization and fluorine exchange involving Te—F bond cleavage.The coordination model of reaction mechanisms provides a unified description of stereochemical rearrangements, ligand exchange processes, and chemical reactions in these, and related, octahedral and trigonal bipyramidal compounds. Keywords: synthesis of cis- and trans-F2TcPh3Cl, isomerization of octahedral Te compounds, fluorine exchange in cis-F2TePh3Cl, synthesis of Ph3TeF, coordination model of reaction mechanisms.
