Formation of a carbonato bridged Ni4-complex by atmospheric CO2 fixation: Crystal structure and magnetic properties

Abstract

Reaction of NiCl2·6H2O with a simple N2O donor tridentate reduced Schiff base ligand, 2-[(3-methylamino-propylamino)-methyl]-4-nitro-phenol (HL) yielded a tetranuclear complex, [Ni4L4Cl2(µ4-CO3)(CH3CN)2]·0.5CH3CN·H2O (1) which was structurally characterized. Complex 1 is an example of atmospheric CO2 fixation model with uniqueness in a new µ4-κ2:κ2:ƞ1:ƞ1-carbonato coordination mode to Ni(II). Involvement of this type of NNO donor ligands for the synthesis of carbonato bridged polynuclear compounds by spontaneous atmospheric CO2 fixation is very rare. All Ni(II) ions are in octahedral environment in 1 with phenoxido and hexadentate µ4-carbonato bridging. Variable temperature magnetic measurements showed overall antiferromagnetic coupling between Ni(II) centers with J1 = −60.32 cm−1, J2 = −19.52 cm−1, J3 = 2.6 cm−1 and J4 = 3.3 cm−1. The magnetic behavior of the complex has been explained considering the carbonato and phenoxido bridging angles.