Abstract
A Series of rhodium (III) cyclometallated complexes of the type (RhHCl(NC5H2C=N Ar (PPh3)2} (Ar=Substituted aryl), have been synthesized and characterized. Schiff bases derived from a substituted benzaldehyde and 2-amino pyridine substituents were allowed to react with [RhCl(PPh3)3] or [Rh(μ-Cl)(COD)]2 in the presence of 4 equivalents of PPh3 (or Ph2BzP) to give Rh(III) Cyclometallated complexes, in which the imine C-H bond was added oxidatively to the rhodium metal to give (H-M-C). The complexes were characterized using IR and NMR spectroscopy confirmed by elemental micro-analysis. The absorption of the hydride ligand was inferred as trans to N-donar ligand.
Highlights
The Cyclometallation of aromatic and to a lesser extent aliphatic C-H groups is widely recognized [1,2], these are relatively little known concerning with the cyclometallation of aldehydes [3] and imine functions [4,5,6]
In most recent application for ruthenium, rhodium and iridium complexes have been used as therapeutic agents and a number of kinetically inert ruthenium(II), iridium(III) and rhodium(III) complexes have been reported as inhibitors of protein kinases [11,12,13,14,15]
The main futures in the infrared of the complexes is the shift of the stretching frequencies of the azomethine (-C=N-) group of the transition metal complexes to lower frequencies
Summary
The Cyclometallation of aromatic and to a lesser extent aliphatic C-H groups is widely recognized [1,2], these are relatively little known concerning with the cyclometallation of aldehydes [3] and imine functions [4,5,6]. The synthesis and characterization of a variety of new rhodium (III) complexes of {N-benzylideneamino} pyridines, in which the imine C-H bond has undergone oxidative addition to the metal, are reported here. The Schiff bases were prepared by mixing equivalent amount of substituted benzaldehydes and 2-amino pyridine derivatives in methanol solution. This mixture was boiled under reflux with stirring for 8h, at 80oC in an oil bath, and the mixture was concentrated by rotary evaporation to give yellow precipitate. 20 ml of dry THF was boiled under reflux for 1 hr addition of n-hexane induced precipitation of the product, which was filtered off (the product could be recrystallized form CH2Cl2/hexane (Table 2, Scheme 2) A solution of {Rh (μ-C1)(COD)}2 (200 mg, 0.28 mmol) Schiff base (0.56 mmol) and PPh3 (293 mg, 1.12 mmol) in ca. 20 ml of dry THF was boiled under reflux for 1 hr addition of n-hexane induced precipitation of the product, which was filtered off (the product could be recrystallized form CH2Cl2/hexane (Table 2, Scheme 2)
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