Structural Characterization of a Series of N5‐Ligated Mn^IV‐Oxo Species

Abstract

Analysis of extendedX -ray absorption fine structure (EXAFS) data for the Mn IV -oxo complexes [Mn IV (O)( DMM N4py)] 2+ + ,[ Mn IV (O)(2pyN2B)] 2+ + ,a nd [Mn IV (O)(2pyN2Q)] 2+ + ( DMM N4py = N,N-bis(4-methoxy-3,5-dimethyl-2-pyridylmethyl)-N-bis(2-pyridyl)methylamine; 2pyN2B = (N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2pyridylmethyl)amine, and 2pyN2Q = N,N-bis(2-pyridyl)-N,Nbis(2-quinolylmethyl)methanamine) afforded Mn=Oa nd MnÀNb ond lengths.T he Mn=Od istances for [Mn IV (O)( DMM N4py)] 2+ + and [Mn IV (O)(2pyN2B)] 2+ + are 1.72 and 1.70 ,r espectively.I nc ontrast, the Mn=Od istance for [Mn IV (O)(2pyN2Q)] 2+ + was significantly longer( 1.76 ). We attribute this long distance to sample heterogeneity, which is reasonable given the reduced stability of [Mn IV (O)(2pyN2Q)] 2+ + .T he Mn=Od istances for [Mn IV (O)( DMM N4py)] 2+ + and [Mn IV (O)(2pyN2B)] 2+ + could only be well-reproduced using DFT-derived modelst hat included strong hydrogen-bonds between second-sphere solvent 2,2,2-trifluoroethanol molecules and the oxo ligand. These results suggesta ni mportantr olef or the 2,2,2-trifluoroethanol solvent in stabilizing Mn IV -oxo adducts. The DFT methods were extended to investigate the structure of the putative [Mn IV (O)(N4py)] 2+ + ·(HOTf) 2 adduct. These computations suggest that aM n IV -hydroxos pecies is most consistentw ith the availablee xperimental data.[a] Dr.

The most reactive iron and manganese complexes with N-pentadentate ligands for dioxygen activation—synthesis, characteristics, applications

“…Moreover, complexes [(N4Py)Fe IV = O] 2+ and [(Bn-TPEN)Fe IV = O] 2+ can replace oxygen atom in reaction with H 2 O [ 79 ], and with derivatives of p -benzoquinone as a plastoquinone counterpart, has been successfully used in the photodriven reaction of water oxidation [ 4 ]. Both N4Py and Bn-TPEN ligands produced highly reactive Fe IV = O complexes [ 63 ], with weaker solvent-interactions, and the Mn IV -oxo units seems to be more basic than its Fe IV -oxo analogues [ 11 ]. For the Mn IV = O adducts, DFT computations predicted that ( 5 ) has a larger barrier for H-atom abstraction from cyclohexane than ( 5′ ) [ 80 ].…”

“…Recently, synthesis of low-valent iron and manganese complexes capable of stabilizing intermediates produced in the oxygenation cycles, which show similarity to natural systems, is of great interest. Within the last two decades, a number of mononuclear complexes with oxoiron(IV) [ 3 – 20 ] and oxomanganese(IV) [ 9 , 11 , 18 , 21 ] units supported by polydentate non-heme ligands have been investigated. These complexes serve as models for high-valent intermediates in the catalytic cycles of enzymes that carry out a series of oxidative modifications.…”

Oxygen Transfer from Trimethylamine N‐Oxide to CuI Complexes Supported by Pentanitrogen Ligands

“…The axial elongation of the Cu1-N7 bond in [L1CuII(H2O)](NO3)2, may be attributed to the methylene-C-N angles in the metallacycles formed with benzimidazole groups compared to the quinoline analogs. [4], [13], [14] The wider C-C-N angles of 124.1(2)° and 123.2(2)° may cause the elongation to reduce the strain in the five-membered rings of [L1CuII(H2O)](NO3)2, which contrasts with the 117.2(3)° and 120.6(3)° C-C-N angles in [L2Cu(NO3)]NO3. This is also reflected in the elongated vs compressed octahedral deformations observed, which may also be reflected in the higher reactivity of the quinoline-based [L2CuI(CH3CN)]OTf (see below).…”

Differences in chemoselectivity in olefin oxidation by a series of non-porphyrin manganese(iv)-oxo complexes

“…Previously our group reported a series of Mn IV -oxo species bound to neutral pentadentate derivatives of the N4py scaffold. 25 These N 5 ligands differ in electronic and steric properties by virtue of substitution of two pyridyl groups with quinolinyl (N2py2Q), benzimidazolyl (N2py2B), or 3,4-dimethyl-5-methoxypyridyl ( DMM N4py) moieties (Fig. 2).…”