Complexes of heteroscorpionate trispyrazolylborate ligands. Part XII. Variable hapticity of hydrobis (3-phenyl-5-isopropylpyrazolyl)(3,5-dimethylpyrazolyl) borate in its rhodium(I) complexes with COD and NBD

摘要

The structure of Tp"Rh(NBD) complex was determined by X-ray crystallography (Tp" = hydrobis(3-phenyl-5-isopropylpyrazolyl)(3,5-dimethylpyrazolyl)borate, NBD = 2,5-norbornadiene). The Tp" was found to be kappa(3) coordinated to rhodium(I). Two independent molecules of Tp"Rh(NBD) were found in triclinic crystals with Rh-N(pz) distances in the region of 2.113(3)-2.307(3) Angstrom. On the other hand the same Tp" ligand was demonstrated to be coordinated in kappa(2) fashion in Tp"Rh(COD) (COD = 1,5-cyclooctadiene) by variable temperature 1-D and 2-D H-1 NMR measurements. The intramolecular exchange between coordinated and uncoordinated 3-phenyl-5-isopropylpyrazolyl residues occurs with DeltaG(not equal) = 42.2 kJ/mol as it was calculated from the H-1 NMR studies. (C) 2003 Elsevier Ltd. All rights reserved.