Comparison of two MnIVMnIV-bis-μ-oxo complexes {[MnIV(N4(6-Me-DPEN))]2(μ-O)2}2+ and {[MnIV(N4(6-Me-DPPN))]2(μ-O)2}2+

Abstract

The addition of tert-butyl hydroperoxide ( t BuOOH) to two structurally related MnII complexes containing N,N-bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine (6-Me-DPEN) and N,N-bis(6-methyl-2-pyridylmethyl)propane-1,2-diamine (6-Me-DPPN) results in the formation of high-valent bis-oxo complexes, namely di-μ-oxido-bis{[N,N-bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine]manganese(II)}(Mn—Mn) bis(tetraphenylborate) dihydrate, [Mn(C16H22N4)2O2](C24H20B)2·2H2O or {[MnIV(N4(6-Me-DPEN))]2(μ-O)2}(2BPh4)(2H2O) (1) and di-μ-oxido-bis{[N,N-bis(6-methyl-2-pyridylmethyl)propane-1,3-diamine]manganese(II)}(Mn—Mn) bis(tetraphenylborate) diethyl ether disolvate, [Mn(C17H24N4)2O2](C24H20B)2·2C4H10O or {[MnIV(N4(6-MeDPPN))]2(μ-O)2}(2BPh4)(2Et2O) (2). Complexes 1 and 2 both contain the `diamond core' motif found previously in a number of iron, copper, and manganese high-valent bis-oxo compounds. The flexibility in the propyl linker in the ligand scaffold of 2, as compared to that of the ethyl linker in 1, results in more elongated Mn—N bonds, as one would expect. The Mn—Mn distances and Mn—O bond lengths support an MnIV oxidation state assignment for the Mn ions in both 1 and 2. The angles around the Mn centers are consistent with the local pseudo-octahedral geometry.