Synthesis and Structural Systematics of First-Row Transition Metal Complexes with 2-[Bis(benzimidazol-2-ylmethyl)amino]ethanol

A nickel(II) com plex with (bbim ae) ( — 2-[bis(benzimidazol-2-ylmethyl)amino]ethanol), [Ni(bbim ae)(NCS)2] • FLO (1) and an oxovanadium (IV) complex, [VO (bbim ae)(NCS)2] -dma (dma = N,N-dim ethylacetam ide) (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) Ä , space group P 2 ,2 ,21, Z = 4, and dcalcd = 1.41 g em “3. Crystal data for 2 at 293 K: a = 14.099(2), b = 14.998(4), c — 14.051(2) A , ß = 107.634(9)°, space group P2,/c, Z = 4, and dca!cd = 1.36 gem “3. In the nickel(II) com plex, (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 correspond­ ing Co(II) and M n(II) com plexes. 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 .9 5 -2 .1 8 Ä , and also observed for other first-row transition metal com plexes with (bbim ae), and differ in the order V (IV ) < M n(II) > Co(II) > Ni(II) > Cu(II), consistent with effective ionic radii o f the metal ions. Comparison of the structural parameters of these complexes with those of the metal ions in biological systems has supported the usefullnessof the tripod-like ligands to synthesis m odel compounds for biological systems.