Synthesis and Structural Systematics of First-Row Transition Metal Complexes with 2-[Bis(benzimidazol-2-ylmethyl)amino]ethanol
2014
Takahashi, Kazuhiro | Nishida, Yuzo
A nickel(II) complex with (bbimae) (= 2-[bis(benzimidazol-2-ylmethyl)amino]ethanol), [Ni(bbimae)(NCS)₂] · H₂O (1) and an oxovanadium(IV) complex, [VO(bbimae)(NCS)₂] · dma (dma = N.N-dimethylacetamide) (2) have been prepared and their crystal structures determined by X-ray diffraction. Crystal data for 1 at 293 K: a = 13.334(2). b = 17.048(2), c = 10.3829(9) Å, space group P2₁2₁2₁, Z = 4, and dcₐₗcd = 1.41 gcm⁻³. Crystal data for 2 at 293 K: a = 14.099(2). b = 14.998(4), c = 14.051(2) Å, β = 107.634(9)°, space group P2₁/c, Z = 4, and dcₐₗcd = 1.36 gcm⁻³. In the nickel(II) complex, (bbimae) functions as a tetradentate ligand, and the geometry around Ni(II) ion is best described as distorted octahedral. The structure is very similar to those of the corresponding Co(II) and Mn(II) complexes. In the case of 2, which is also distorted octahedral, (bbimae) is a tridentate ligand without the coordination of the alcohol group. The M-N (benzimidazole) distances are in the range of 1.95-2.18 Å, and also observed for other first-row transition metal complexes with (bbimae). and differ in the order V(IV) < Mn(II) > Co(II) > Ni(II) > Cu(II). consistent with effective ionic radii of the metal ions. Comparison of the structural parameters of these complexes with those of the metal ions in biological systems has supported the usefulness of the tripod-like ligands to synthesis model compounds for biological systems.
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