Oxo-Centered Trinuclear Chromium(III) Complexes with Both Carboxylate and Amidoximate Ligands

Abstract

Compounds [Cr 3 III (μ3-O)(O2CPh)5(H2N-sao)(EtOH)2]·EtOH (1·EtOH) and [Cr 3 III (μ3-O)(O2CPh)3(H2N-pao)3]NO3·H2N-paoH·EtOH (2·NO3·H2N-paoH·EtOH) have been obtained either in a sequential one-pot, two-step procedure in which Cr(NO3)3·9H2O is first reacted with sodium benzoate in ethanol under reflux, followed by the addition of salicylamidoxime (H2N-saoH2) or pyridine-2-amidoxime (H2N-paoH), or in a one-step protocol starting from [Cr 3 III (μ3-O)(O2CPh)6(EtOH)3]NO3. They were characterized by single-crystal X-ray diffraction, magnetometry and EPR spectroscopy. Complexes 1 and 2 are derived from the parent complex [Cr 3 III (μ3-O)(O2CPh)6(EtOH)3]+ by replacement of one and three benzoate ligands, respectively, by oximate ligands. The salicylamidoximate and pyridine-2-amidoximate ligands display a tridentate coordination mode with the N–O oximate group bridging a pair of Cr atoms and the additional ligating atom substituting for an ethanol ligand of the parent complex. In both cases susceptibility, magnetization and EPR data reveal a S T = 1/2 ground state with a nearly isotropic g-tensor.