Synthesis, Crystal Structure and Magnetic Properties of Three {CrIIIMnII} Heterodimetallic Complexes Based on Heteroleptic Cyanido‐Bearing CrIII Building Blocks

Abstract

The use of the heteroleptic [CrIII(AA)(CN)4]– complexes as ligands towards the preformed [MnII(tptz)]2+ and [MnII(pyim)2]2+ species afforded the heterometallic compounds of formula [MnII(tptz)(H2O)(NO3)(µ‐NC)CrIII(ampy)(CN)3]·CH3CN (1), [MnII(tptz)(H2O)(NO3)(µ‐NC)CrIII(phen)(CN)3]·H2O (2) and {[MnII(pyim)2][(µ‐NC)Cr(phen)(CN)3]2}·3H2O (3) [AA = 2‐aminomethylpyridine (ampy) and 1,10‐phenanthroline (phen), tptz = 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine and pyim = 2‐(1H‐imidazol‐2‐yl)pyridine]. 1 and 2 are neutral heterodinuclear complexes, where the [CrIII(AA)(CN)4]– building block acts as a monodentate ligand through one of its four cyanido groups towards a manganese(II) ion with seven coordination sites completed by a tridenate tptz molecule, a bidentate nitrate anion and a water molecule. Compound 3 is a neutral heterotrinuclear complex made up by two peripheral [CrIII(AA)(CN)4]– units acting as monodentate ligands through one of their cyanido groups towards an inner [MnII(pyim)2]2+ entity. Each manganese(II) ion in 3 is six‐coordinate with two cyanido nitrogen atoms and two bidentate pyim molecules, building a distorted octahedral surrounding. The values of the CrIII–MnII distance across the bridging cyanido ligand are 5.3766(7) (1), 5.3194(6) (2) and 5.3245(8) and 5.4538(7) Å (3). The magnetic properties of 1–3 were investigated in the temperature range 1.9–300 K. Overall antiferromagnetic behaviour is observed for all three compounds, with the antiparallel alignment of the local spins leading to either a ground‐state spin triplet (1 and 2) or a spin doublet (3). The values of the magnetic coupling between the CrIII and MnII ions across the single cyanido bridges are J = –7.40(2) (1), –6.65(2) (2) and –6.41(2) and –4.65(2) cm–1 (3), with the spin Hamiltonian being defined as H = –J(SCr1·SMn1) (1 and 2) and H = –J1(SCr1·SMn1) – J2(SCr2·SMn2) (3). These values could be correlated with the Mn–N–Ccyanido angle, and they agree with those reported for this exchange pathway in other magneto‐structural studies.