Synthesis, solution and solid-state structure of Pd(II), Pt(II), Ir(III) and Zn(II) complexes with 5-pyridyl substituted N-methyl isoxazolidines

Pd(II), Pt(II), Zn(II) and Ir(III) complexes with 5-pyridine substituted N-methyl isoxazolidines (4-(2-methyl-3-phenylisoxazolidin-5-yl)-pyridine (L1), 2-(2-methyl-3-phenylisoxazolidin-5-yl)-pyridine (L2), 2-(2-methyl-3-ferrocenylisoxazolidin-5-yl)-pyridine (L3)) have been prepared and characterized by 1H, 13C, and 31P NMR. The configurations of coordinated isoxazolidines have been assigned by the analysis of NMR coupling constants and by nuclear Overhauser measurements through 2D-ROESY experiments. The molecular structures of [Cp*Ir(L2)Cl][BPh4] (6) (Cp*-pentamethylcyclopentadienyl) and trans-[PdCl2(L3)PEt3] (8) have been established by means of X-ray crystallography. The crystal structure of 6 consists of piano stool geometry with respect to the Ir(III) center with N,N-bidentate coordinated ligands. The six-membered chelate ring formed by Ir(1), N(1), C(5), C(6), O(1), N(2) possesses a ‘twist-tub’ conformation. The crystal structure of 8 consists of neutral square planar Pd(II) complexes. L3 is coordinated in a monodentate manner via the pyridine nitrogen atom. The isoxazolidine fragment of both compounds has an envelope conformation. NMR data are consistent with an O,N-bidentate coordination of L2 for [Zn(L2)Cl2] (5), while L1 act as a monodentate ligand through the nitrogen atom of the pyridine in [Zn(L1)2Cl2] (4).