Five-coordinate metal(II) complexes based pyrazolyl ligands

The reactions of pyrazole based ligands with M(II) perchlorate hexahydrate in the presence of NH4NCS afforded the mononuclear complexes [Co(Bzbedmpza)(NCS)2]·¾CH3COCH3 (1), [Ni(Bzbedmpza)(NCS)2] (2), [Cu(Bzbedmpza)(NCS)2] (3) and [Cu(Mebedmpza)(NCS)2] (4), and in the presence of NaN3, the complex [Cu(tedmpza)(N3)]ClO4 (5) was isolated where Bzbedmpza = N-benzyl-bis(3,5-dimethyl-2-(pyrazol-1H-yl)ethyl)amine, Mebedmpza = N-methyl-bis(3,5-dimethyl-2-(pyrazol-1H-yl)ethyl)amine and tedmpza = tris(2,5-dimethyl-ethyl-pyrazol-1H-yl)amine. The complexes were structurally characterized by elemental microanalyses, IR and UV–Vis spectroscopy and by single crystal X-ray crystallography. The complexes 2–5 display distorted SP geometry, whereas the cobalt(II) complex 1 has a distorted TBP. Also, all the thiocyanato complexes 1–4 are coordinated to the central metal ions through N-terminal thiocyanate. The stability of any of the two possible limiting geometries (SP versus TBP) including nature of the central metal ion and the structural parameters of the amine coligands (steric effect, nature of chelate ring sizes and skeleton of the coligand) are analyzed as a function of τ values.

Five new mononuclear five-coordinate N-thiocyanato and azido Co(II), Cu(II) and Ni(II) complexes based on pyrazolyl ligands are synthesized and structurally characterized. The role of metal ion and structural parameters of the amine coligands in stabilizing the square pyramidal versus trigonal bipyramidal geometry are discussed.Figure optionsDownload as PowerPoint slide