Abstract
The first dinuclear and trinuclear chromium(III) and dinuclear vanadium(III) complexes ofN(4)-R-substituted-3,5-di(2-pyridyl)-1,2,4-triazole (Rdpt) ligands have been prepared by solvothermal complexations under inert atmospheres, and characterized. The reactions of Cr(III)and V(III)withadpt(R= amino) resulted in deamination of the ligand and yielded the dinuclear doubly-triazolate bridged complexes [V-2(III)(dpt(-))(2)Cl-4] (1) and [Cr-2(III)(dpt(-))(2)Cl-4] (2). In the case of the Cr(III)complex2this bridging results in a rare example of ferromagnetic coupling for a dinuclear Cr(III)compound. DFT studies confirm that in2the ferromagnetic coupling pathways dominate over the antiferromagnetic pathways, whereas in1the reverse occurs, consistent with the observed overall antiferromagnetic coupling in that case. It was also found that the use of different additives in the reaction allows the nuclearity of the Cr(III)product to be manipulated, giving either the dinuclear system, or the first example of a trinuclear circular helicate for aRdptcomplex, [Cr-3(III)(dpt)(3)Cl-6]center dot 13/4MeCN center dot 1/4DCM (3). Reaction ofN(4)-pydpt (R= 4-pyridyl) with V(III)led to an unusual shift of the pyridyl substituent from N-4 to N-1 of the triazole, forming the ligand isomerN(1)-pydpt, and giving a dinuclear doubly-triazole bridged complex, [V-2(III)(N-1-pydpt)(2)Cl-6]center dot 2MeCN (4). Reaction with Cr(III)results in loss of the 4-pyridyl ring and a mixture of the di- and trinuclear complexes, 2 and 3. Interestingly, partial oxidation of the V(III)in dinuclear complex 4 to vanadyl V-IV=O was identified by crystallographic analysis of partially oxidized single crystals, [((VO)-O-IV)(0.84)(V-III)(1.16)(N-1-pydpt)(2)Cl-5.16]center dot 0.84H(2)O center dot 1.16MeCN (5).