Iron coordination chemistry of phenylpyruvate: An unexpected κ³-bridging mode that leads to oxidative cleavage of the C2-C3 Bond

One mononuclear iron(II)-phenylpyruvate complex [Tp^Ph2Fe ^II(PPH)] (1) of the tridentate face-capping Tp^Ph2 ligand and two dinuclear iron(II)-phenylpyruvate enolate complexes [(6-Me ₃-TPA)₂Fe^II₂(PP)]²⁺ (2) and [(6-Me₃-TPA)₂Fe^II₂(2-NO ₂-PP)]²⁺ (3) of the tetradentate 6-Me₃-TPA ligand are reported to demonstrate two different binding modes of phenylpyruvate to the iron(II) centers. Phenylpyruvate binds in a κ²-(O,O) manner to the mononuclear Fe^II(Tp^Ph2) center of 1 but bridges in a κ³-(O,O,O) fashion to the two Fe ^II(6-Me₃-TPA) centers of 2 and 3. Mononuclear complex 1 reacts with O₂ to undergo oxidative decarboxylation and ortho-hydroxylation of one of the aromatic rings of the Tp^Ph2 ligand. In contrast, dinuclear complexes 2 and 3 react with O₂ to undergo oxidative cleavage of the C2-C3 bond of phenylpyruvate.