Tris(pyrazolyl)methanes (tpms) are a versatile class of tripodal ligand that consist of a central carbon atom bonded to one nitrogen atom on each of three pyrazole moieties.  By including chiral pyrazoles derived from menthone or camphor into the synthetic procedures for tpms, chiral ligands were produced.  In each case, one or three chiral pyrazoles were incorporated into the ligand to produce a variety of enantiomerically pure ligands. The tpm ligands thus formed were isolated by chromatography or crystallization and were characterized through 1H NMR spectroscopy and, in several instances, X-ray crystallography.  In some cases the new ligands formed 2:1 complexes with Fe(II). The iron complexes were characterized by X-ray crystallography and NMR.  Both techniques confirmed that the complexes could have either a high-spin (HS) or a low-spin (LS) electronic configuration depending on the steric bulk of the chiral tpm ligand and the orientation of the chiral appendages within the complex.

Chiral tris(pyrazolyl)methane scorpionate ligands and their iron(II) complexes

247th National Meeting (2014)

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