The Ambivalent Bonding of the 3(5)‐Isopropylpyrazolyl Moiety in Homo‐ and Heteroscorpionate Hydrobis(3‐R1‐5‐R2‐pyrazolyl)(y‐isopropylpyrazolyl)boratocobalt(II) Complexes (y = 3 or 5)

Abstract

AbstractThe synthesis of hydrotris(pyrazol‐1‐yl)borate ligands (Tpx) by condensation of sodium borohydride with 3(5)‐isopropylpyrazole and either 5(3)‐methyl‐3(5)‐phenylpyrazole or 3,5‐diphenylpyrazole gave the novel heteroscorpionate ligands hydrobis(5‐methyl‐3‐phenylpyrazolyl)(5‐isopropylpyrazolyl)borate and hydrobis(3,5‐diphenylpyrazolyl)(5‐isopropylpyrazolyl)borate, respectively. These were converted into CoTpx(NCS) complexes as well as CoTpx2 in the case of the former ligand. In an attempted synthesis of heteroscorpionates bearing two y‐isopropylpyrazolyl moieties (y = 3 or 5) formation of the homoscorpionate hydrotris(3‐isopropylpyrazolyl)borate along with the above‐mentioned heteroscorpionates was noticed; no formation of the desired heteroscorpionates could be detected. The bis[hydrobis(5‐methyl‐3‐phenylpyrazolyl)(5‐isopropylpyrazolyl)borato]cobalt(II) and tetrahydrofuranothiocyanatobis[hydrobis(5‐methyl‐3phenylpyrazolyl)(5‐isopropylpyrazolyl)borato]cobalt(II) tetrahydrofuran solvate complexes were studied by X‐ray crystallography. Two Tpx ligands provide six nitrogen donors from pyrazol‐1‐yl residues to form a Tpx2Co complex in which two 5‐isopropylpyrazolyl rings are placed in a plane of symmetry, whereas the same Tpx ligand is bound in an η3 fashion in the pentacoordinate [CoTpx(NCS)(THF)]·THF complex, in which a nitrogen atom from thiocyanate and an oxygen atom from THF complete the coordination sphere of the central metal ion. These compounds as well as the complexes thiocyanatohydrobis(3,5‐diphenylpyrazolyl)(5‐isopropylpyrazolyl)boratocobalt(II) and thiocyanatohydrotris(3‐isopropylpyrazolyl)boratocobalt(II) were characterized by 1H NMR and IR spectroscopy. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2003)