Synthesis, structure and NMR spectroscopy of some rhodium(III) cyclometallated Schiff's base complexes derived from 2-benzylidene-3-methylpiridines. Crystal structure of (PPh3)2>

Article abstract of DOI:10.1016/S0022-328X(00)99413-0

The Schiff's base derived from 2-amino, 3-methylpiridine and an aryl aldehyde reacts with either RhCl(PPh3)3 or 2 in the presence of four equivalents of L (L=PPh3, P(4-ClC6H4)3, P(cyclohexyl)3, AsPh3, SbPh3) to give a Rh^III cyclometallated complex (2), in which the imine C-H bond has oxidatively added to metal.The complexes 2 react with reagents such as Br^-, CN^-, CH3I, C<*>NR (R = cyclohexyl, t-butyl), P(OCH3)3, CO, to give substitution products (3), in which the Cl has been replaced.The complexes 2 and 3, as well as some few Ir^III analogs (4), have been isolated and characterized using 1H, 31P, and (occasionally) 13C NMR spectroscopy.The crystal structure of the complex RhHI<2-(3-nitrobenzylidene)-3-methylpiridine>(PPh3)2 (3b) has been determined by X-ray diffraction.The complex shows a distorted octahedral structure with the following bond distances (Angstroem) and angles (deg): Rh-I, 2.771(2); Rh-N(1), 2.15(1); Rh-C(7'), 1.98(2); Rh-P(1), 2.326(5); Rh-P(2) 2.332(5); P-Rh-P, 159.7(2), N(1)-Rh-C(7'), 78.5(6).In the light of the NMR and X-ray data, it is suggested that the -C(R)=N- moiety exerts a large trans influence