Complexes of heteroscorpionate trispyrazolylborate anionic ligands - Part I. The crystal structure and reactivity of thiocyanato[hydrobis(3-phenylpyrazolyl)(3-tert-butylpyrazolyl)-borato]cobalt(II) complex

The high-spin cobalt(II) complexes with homoscorpionate hydrotris(3-phenylp yrazolyl)borate (Tp(Ph)) and heteroscorpionate hydrobis(3-phenylpyrazolyl)( 3-tert-butylpyrazolyl)Borate {HB(3-Phpz)(2)(O-t-Bupz)} anionic ligands (Tp' ) of the general formula Tp'Co(X) were studied. The former tripodal ligand prov ides intermediate steric hindrance for the central metal ion, which is able to adopt two additional donors from thiocyanate and neutral ligands l ike pyrazole (pzH) and methanol. or two oxygen donors from the lactate anio n. Replacement of one of three 3-phenyl substituents in Tp(Ph) by the tert- butyl one produces a ligand of high steric hindrance which gave tetracoordi nate Tp'Co(X) complexes, where X = thiocyanate or monodentate lactate. The complexes were studied by the H-1 NMR spectroscopic method in solution and two of them, Tp(Ph)'Co(NCS)(pzH) and [HB(3-Phpz)(2)(3-t-Bupz)]Co(NCS), were characterized structurally by X-ray crystallography. (C) 2000 Elsevier Sci ence B.V. All rights reserved.