Study of a novel hepta-coordinated FeIII bimetallic complex with an unusual 1,2,4,5-tetrazine-ring opening

Reaction of Fe(NO3)3 with 3,6-di(pyrimidin-2-yl)-1,2,4,5-tetrazine (BPymTz) in acetonitrile gives a hepta-coordinated FeIII complex (1) with the bridging unit 1,2-diiminohydrazido (1,2-dih2−: −HNC(R) NNC(R)NH−) generated in situ from the tetrazine ring-opening of BPymTz. DFT calculations, X-ray diffraction studies and SQUID magnetometry measurements were successfully performed on 1. The crystallography measurement confirms the ring-opening and the substituent’s contribution to the rare pentagonal bipyramidal coordination geometry of the metal ions. Magnetic susceptibility measurements on 1 reveal an S = 0 ground state, arising from the antiferromagnetic interaction between the two FeIII centers (J = −3.02 cm−1) within the molecule.

Graphical abstractA new FeIII complex, [FeIII2(1,2-dih2−)(NO3)2(H2O)4](NO3)2 was prepared by reaction of BPymTz with FeNO3·9H2O. The formation of a new bridging ligand, generated in situ from the tetrazine ring opening of BPymTz, was observed. DFT calculations, X-ray diffraction studies and SQUID magnetometry measurements were performed on the FeIII complex.Figure optionsDownload full-size imageDownload as PowerPoint slide