1H NMR Studies of Some Pyrazole Ligands Coordinated to Co(III)

Proton  chemical shifts  of pyrazole ligands   coordinated  to Co(III)   move downfieldas   the  total  charge  of complex   increases.  However   1H   chemical  shifts   of pyrazole   ring  in[Co(NH3)3(pyzH)]3+  and  [Co(NH2)3(pyz)]2+  compare  to  those  of pyz H,+    with  one  positive charge    move   upfield.    These unexpected   phenomena  together   with   facile    nitration  and bromination  of [Co(NH3)3(pyzH)]3+ compare to  nitration and  bromination of free pyrazole   or its   protonated form  under feroing   conditions could   be  related  to  more  electron releasing of Co(NH3)33+grouprelativetoH+.

N FORUGHIFAR ,A MOBINIKKHALEDI ,K H ZAMANI ,B HOGABRY ,