Unusual reactivity of methylene group adjacent to pyridine-2-carboxamido moiety in iron(III) and cobalt(III) complexes.
The Fe(III) and Co(III) complexes of the ligand N-(2-picolyl)picolinamide (pmpH; H represents the dissociable amide hydrogen), namely, [Fe(pmp)(2)]BF(4) (1) and [Co(pmp)(2)]ClO(4) (2), have been synthesized and structurally characterized. The [bond]CH(2)[bond] moiety of pmp(-) in [M(pmp)(2)](+) (M = Fe, Co) is very reactive and is readily converted to carbonyl (C[double bond]O) group upon exposure to dioxygen. Such conversion results in [M(bpca)(2)]ClO(4) complexes (M = Fe (3), Co (5); bpcaH = bis(2-pyridylcarbonyl)amine) which have been characterized by spectroscopy and X-ray diffraction. The structure of 5 is reported here for the first time. The reactivity of the [bond]CH(2)[bond] moiety of pmp(-) has so far precluded the isolation of 1 although other metal complexes of pmp(-) have been reported years ago. The CH(2) --> C[double bond]O transformation arises from the tendency of the coordinated pmp(-) ligand to achieve further conjugation in the ligand framework and provides a better way to synthesize the metal complexes of bpcaH ligand. Reaction of 3 with NaH affords Fe(II) complex [Fe(bpca)(2)] (4) without any reduction of the ligand frame.
Rowland
John M
JM
Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA.
Olmstead
Marilyn M
MM
Mascharak
Pradip K
PK
D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D006838:Hydrocarbons; D008024:Ligands; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010084:Oxidation-Reduction; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship
D005290:Ferric Compounds; D006838:Hydrocarbons; D008024:Ligands; C465084:N-(2-picolyl)picolinamide; D009942:Organometallic Compounds; D011725:Pyridines; C465085:bis(2-pyridylcarbonyl)amine; C030011:carbene; D003035:Cobalt; D008697:Methane