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

A Mn(iv) complex featuring a terminal oxo ligand, [MnIV(O)(ditox)3][K(15-C-5)2] (3; ditox = t Bu2MeCO-, 15-C-5 = 15-crown-5-ether) has been isolated and structurally characterized. Treatment of the colorless precursor [MnII(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-Oterm = 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 [MnIV(O)(ditox)3]- furnishes a model for the proposed terminal oxo of the unique manganese of the oxygen evolving complex of photosystem II.