(Ni2), (Ni3), and (Ni2 + Ni3): A Unique Example of Isolated and Cocrystallized Ni2 and Ni3 Complexes

摘要

Structural and magnetic characterization of compound {[Ni_2(L)_2(0Ac)_2][Ni_3(L)_2(0Ac)_4]}_2CH_3CN (3) (HL = the tridentate Schiff base ligand, 2-[(3-methylamino-propylimino)-methyl]-phenol) shows that it is a rare example of a crystal incorporating a dinuclear Ni(II) compound, [Ni_2(L)_2(0Ac)_2], and a trinuclear one, [Ni_3(L)_2(0Ac)_4]. Even more unusual is the fact that both Ni (II) complexes, [Ni_2(L)_2(0Ac)_2] (1) and [Ni_3(L)_2(0Ac)_4(H_2O)_2] _ CH_2Cl_2. 2CH_3OH (2), have also been isolated and structurally and magnetically characterized. The structural analysis reveals that the dimeric complexes [Ni_2(L)_2(0Ac)_2] in cocrystal 3 and in compound 1 are almost identical-in both complexes, the Ni(II) ions possess a distorted octahedral geometry formed by the chelating tridentate ligand (L), a chelating acetate ion, and a bridging phenoxo group with very similar bond angles and distances. On the other hand, compound 2 and the trinuclear complex in the cocrystal 3 show a similar linear centrosymmetric structure with the tridentate ligand coordinated to the terminal Ni(II) and linked to the central Ni(II) by phenoxo and carboxylate bridges. The only difference is that a water molecule found in 2 is not present in the trinuclear unit of complex 3; instead, the coordination sphere is completed by an additional bridging oxygen atom from an acetate ligand. Variable-temperature (2-300 K) magnetic susceptibility measurements show that the dinuclear unit is antiferromagnetically coupled in both compounds (2J= _36.18 and _29.5 cm~(-1) in 1 and 3, respectively), whereas the trinuclear unit shows a very weak ferromagnetic coupling in compound 3 (2J= 0.23 cm~(-1)) and a weak antiferromagnetic coupling in 2 (2J= _8.7(2) cm~(-1)) due to the minor changes in the coordination sphere.