A proposed mechanism for the O–O bond formation in the oxygen-evolving complex (OEC) of Photosystem II (PSII) involves a terminal Mn–oxo intermediate. Thus, synthesizing multi-metallic clusters containing such a terminal oxo group is expected to provide further mechanistic insight for the catalytic water oxidation reaction. Here we report the synthesis and characterization of a series of tetranuclear complexes LM3OM(L')(PhNHPz)3 (L = 1,3,5-tris(2-(di(2-pyridyl)hydroxymethyl)phenyl)benzene; M = Mn, Fe; L' = OH, Cl; PhNHPz = 3-phenylamino-pyrazolate). Three metal centers are coordinated by a previously reported ligand, based on three dipyridyl-alkoxide units on a 1,3,5-triarylbenzene motif. The fourth metal center is site-differentiated, and is supported by three PhNHPz ligands and a µ4–oxo. The PhNHPz bridging ligands were found to provide a hydrogen-bonding network which interacts with terminal ligands bound to the site-differentiated metal. The effect of the second coordination sphere interactions on structure and reactivity will be discussed.

Toward the synthesis of tetrametallic terminal oxo complexes supported by aminopyrazole ligands

251st National Meeting (2016)

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