Treatment of anhydrous NbCl4(4-tBupy)2 with three equivalents of potassium 3,5-di-tert-butylpyrazolate afforded a Nb(V) complex by oxidative cleavage of a N-N bond of one pyrazolate ring, along with hydrogen abstraction. The other two pyrazolate ligands are intact, and a chloride ion completes the coordination sphere. The analogous Ta(V) compound was obtained in a similar fashion from TaCl4(4-tBupy)2. Similar treatment of NbCl3(4-tBupy)2 with three equivalents of potassium 3,5-di-tert-butylpyrazolate afforded a Nb(V) complex that contains two intact pyrazolate ligands and one new ligand in which a pyrazolate ligand has undergone two electron oxidative addition to the Nb(III) metal center. These complexes were characterized by X-ray crystallography and NMR. The potential aromaticity of these metallapyrimidine and metallapyridinium complexes was probed by nucleus-independent chemical shift (NICS) calculations.

Metallopyrimidines and metallopyrimidiniums from oxidative addition of pyrazolate N-N bonds to Nb(III), Nb(IV), and Ta(IV) metal centers and assessment of their aromatic character

244th National Meeting (2012)

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