New complexes of transition metal ions, (Pd(II), Pt(II), Au(III)), and terrae rare, (Y(III), La(III) , Sm(II)), with N-heterocyclic aromatic ligands

Several palladium(II), platinum(II) and gold(III) complexes with general formula [M(Ln)(X)(Y)] [M = Pd, X = Y = Cl, X = Y = OAc; M = Pt, X = Y =Cl; M = Pd, X = Cl, Y = CH3; M = Pt, X = Cl, Y = CH3 or X = Y = CH3] and [M(Ln)(X)(Y)]+ [M=Au, X = Y = Cl, X = Cl Y = OH, X = Y = OH], have been synthesized by reaction of different Pd(II), Pt(II) and Au(III) derivatives with the corresponding ligands based on a imidazo[1,5-a]pyridines skeleton. Ln is 3-substituted (pyridin-2-yl)imidazo[1,5-a]pyridines; 1-substituted 3-(pyridin-2-yl)imidazo[1,5-a]pyridines and bis-imidazo[1,5-a]pyridin-3-yl)benzenes; and they act as N,N-bidentate chelating ligands. Detailed spectroscopic investigation (including IR, mono- and two-dimensional 1H NMR) and elemental analysis has been performed for all these species, allowing their complete characterization. The X-ray structural analysis performed on two of Pd(II), three Pt(II) and one of Au(III) complexes confirmed spectroscopic and analytical data. A computational analysis for complexes of Pt(II) was performed to explain the lack cyclometalation reaction. Also yttrium(III), lanthanum(III) and samarium(II) complexes have been synthesized by reaction of different Y(III), La(III) and Sm(II) derivatives with the same ligands. Finally, a series of Pt(II) cyclometalated rollover complexes have been studied with two substituted bipyridines: 6-ethyl-2,2′-bipyridine and 6-methoxy-2,2′-bipyridine in comparison with previously studied 2,2’-bipyridine complexes.