Structurally characterized terminal manganese(iv) oxo tris(alkoxide) complex

Abstract

A Mn(IV) complex featuring a terminal oxo ligand, [Mn^IV(O)(ditox)₃][K(15-C-5)₂] (3; ditox = ^tBu₂MeCO⁻, 15-C-5 = 15-crown-5-ether) has been isolated and structurally characterized. Treatment of the colorless precursor [Mn^II(ditox)₃][K(15-C-5)₂] (2) with iodosobenzene affords 3 as a green free-flowing powder in high yields. The X-ray crystal structure of 3 reveals a pseudotetrahedral geometry about the central Mn, which features a terminal oxo (d(Mn–O_term = 1.628(2) Å)). EPR spectroscopy, SQUID magnetometry, and Evans method magnetic susceptibility indicate that 3 consists of a high-spin S = 3/2 Mn(IV) metal center. 3 promotes C–H bond activation by a hydrogen atom abstraction. The [Mn^IV(O)(ditox)₃]⁻ furnishes a model for the proposed terminal oxo of the unique manganese of the oxygen evolving complex of photosystem II.