Electronic configuration of five-coordinate high-spin pyrazole-ligated iron(II) porphyrinates.
Pyrazole, a neutral nitrogen ligand and an isomer of imidazole, has been used as a fifth ligand to prepare two new species, [Fe(TPP)(Hdmpz)] and [Fe(Tp-OCH(3)PP)(Hdmpz)] (Hdmpz = 3,5-dimethylpyrazole), the first structurally characterized examples of five-coordinate iron(II) porphyrinates with a nonimidazole neutral ligand. Both complexes are characterized by X-ray crystallography, and structures show common features for five-coordinate iron(II) species, such as an expanded porphyrinato core, large equatorial Fe-N(p) bond distances, and a significant out-of-plane displacement of the iron(II) atom. The Fe-N(pyrazole) and Fe-N(p) bond distances are similar to those in imidazole-ligated species. These suggest that the coordination abilities to iron(II) for imidazole and pyrazole are very similar even though pyrazole is less basic than imidazole. Mössbauer studies reveal that [Fe(TPP)(Hdmpz)] has the same behavior as those of imidazole-ligated species, such as negative quadrupole splitting values and relative large asymmetry parameters. Both the structures and the Mössbauer spectra suggest pyrazole-ligated five-coordinate iron(II) porphyrinates have the same electronic configuration as imidazole-ligated species.
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China. cjhu@suda.edu.cn
Chuanjiang
C
Hu
Bruce C
BC
Noll
Charles E
CE
Schulz
W Robert
WR
Scheidt
D018360:Crystallography, X-Ray; D004583:Electrons; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D011166:Porphyrins / Q000138:chemical synthesis / Q000737:chemistry*; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry*
D005296:Ferrous Compounds; D011166:Porphyrins; D011720:Pyrazoles; C031280:pyrazole