A nearly symmetric trinuclear chromium(III) oxo carboxylate assembly: preparation, molecular and crystal structure, and magnetic properties of [Cr3O(O2CPh)6(MeOH)3](NO3) · 2MeOH

Complex [Cr3O(O2CPh)6(MeOH)3](NO3) · 2MeOH (1 · 2MeOH) has been synthesized from the one-pot reaction between Cr(NO3)3 · 9H2O and NaO2CPh in MeOH. The structure of the complex has been solved by single-crystal X-ray crystallography. It crystallizes in the monoclinic space group P21/n with a=14.716(6) Å, b=22.569(8) Å, c=15.755(6) Å, β=95.02(1)°, V=5212.5(4) Å3 and Z=4. Although the cation does not possess any crystallographically imposed symmetry element, its {Cr3(μ3-O)} core is nearly symmetric. Each CrIII…CrIII vector is further bridged by two η1:η1:μ2 benzoates, with a terminal MeOH molecule completing octahedral coordination at each metal ion. The crystal structure consists of layers that are parallel to (0 1 0) crystallographic plane and are formed through π–π stacking interactions and hydrogen bonds. Variable-temperature magnetic susceptibility and solid-state 1H NMR studies indicate that the total spin value of the ground state is 1/2. EPR experiments reveal the existence of a distribution of trimers with axial anisotropy in the g tensor.