Conformational Analysis and Assignments of Relative Stereocenter Configurations in Fluoroalkyl-Iridium Complexes Using 19F{1H} HOESY Experiments. Comparison with...

Solution conformations about the metal-carbon bond of the secondary fluoroalkyl ligands in iridium complexes [IrCp*(PMe3)(RF)X] [Cp* = C5Me5 RF = CF(CF3)2, X = I (1), CH3 (2); RF = CF(CF3)- (CF2CF3), X = I (4), CH3 (5)] have been determined using 19F{¹H} HOESY techniques. The molecules adopt the staggered conformation with the tertiary fluorine in the more hindered sector between the PMe3 and X ligands, with CF3 (and CF2CF3) substituents lying in the less hindered regions between PMe3 and Cp* or X and Cp*. In molecules containing the CF(CF3)2 ligand, these conformations are identical to those adopted in the solid state. For compound 4, containing the CF(CF3)(CF2CF3) ligand, two diastereomers are observed in solution. Solution conformations and relative stereocenter configuration assignments have been obtained using 19F{¹H} HOESY and correlated with the X-ray structure for the major diastereomer of 4, which has the (Slr, Sc) or (Rlr, Rc) configuration. Relative stereocenter configurations of analogue 5, for which no suitable crystals could be obtained, were assigned using 19F{¹H} HOESY and proved to be different from 4, with 5 preferring the (Slr, Rc) or (Rlr, Sc) configuration. [ABSTRACT FROM AUTHOR]