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Title: Identification of the Dinuclear and Tetranuclear Air-Oxidized Products Derived from Labile Phenolate-Bridged Dimanganese(II) Pyridyl-Chelate Compounds

Abstract

Dioxygen-sensitive dinuclear manganese complexes of the phenoxo-hinged dinucleating ligand 2,6-bis{l_brace}[N,N{prime}-bis(2-picolyl)amino]methyl{r_brace}-4-tert-butylphenolato (bpbp{sup -}) containing exogenous labile THF, water and perchlorato ligands are described. The manganese(II) complexes [Mn{sub 2}(bpbp)(ClO{sub 4}){sub 2}(THF)]{sup +} (1) and [Mn{sub 2}(bpbp)(ClO{sub 4})(H{sub 2}O){sub 2}]{sup 2+} (2) have been isolated as the salts 1{center_dot}ClO{sub 4}{center_dot}THF{center_dot}3H{sub 2}O, 1{center_dot}B(C{sub 6}H{sub 5}){sub 4}{center_dot}4THF and 2{center_dot}(ClO{sub 4})2{center_dot}H{sub 2}O. Complexes 1 and 2 are spontaneously oxidised in air in solution and the solid state. The reaction products of the air oxidation in THF, water and methanol solutions are labile dinuclear Mn{sup II}-Mn{sup III}, Mn{sup III}{sub 2} and Mn{sup III}-Mn{sup IV} complexes containing water- and methanol-derived exogenous ligands. In addition, a Mn{sub 4} complex has been isolated. Magnetic susceptibility data confirm the Mn{sup II}-Mn{sup III} oxidation state assignment with an S = 2/S = 5/2 model with weak antiferromagnetic coupling (J = -3.7 cm{sup -1}) in [Mn{sub 2}(bpbp)(CH{sub 3}O){sub 2}(H{sub 2}O){sub 2}](ClO{sub 4}){sub 2} [3{center_dot}(ClO{sub 4}){sub 2}]. A tetranuclear complex, [Mn{sub 4}(O){sub 4-n}(OH){sub n}(bpbp){sub 2}](ClO{sub 4}){sub 4} [n = 1 or 2; 7{center_dot}(ClO{sub 4}){sub 4}], recovered from THF shows a Mn{sub 4}O{sub 6} adamantane-type core with the O bridges furnished by the two phenolato groups and four hydroxide/oxide bridges. We have arrived at twomore » feasible formulations for the core metal oxidation states and oxo-bridge protonation states, namely [Mn{sup III}{sub 4}(O){sub 2}(OH){sub 2}(bpbp){sub 2}]{sup 4+} and [Mn{sup III}{sub 3}Mn{sup IV}(O){sub 3}(OH)(bpbp){sub 2}]{sup 4+}, for 7, on the basis of a bond valence sum analysis of the crystal structure, elemental analysis and XANES. Thus, complex 7 is at least two oxidation state levels lower than known complexes with the Mn{sub 4}O{sub 6} adamantane core structure. The magnetism of 7 was fitted well to an MnIII4 three-J model. Complex cations related to 3 by homology, and to 7 by hydration/solvation, have been identified by ESI mass spectrometry. The [Mn{sub 2}(bpbp)(OH){sub 2}(H{sub 2}O){sub 2}]{sup 2+} ion (4) present in aqueous solutions on dissolution of 1{center_dot}ClO4{center_dot}THF{center_dot}3H2O in air or by simple dissolution of 3 in water-containing solvent is isoelectronic to 3. In the presence of significant amounts of water the Mn{sup II}-Mn{sup III} complexes 3 and 4 are susceptible to further metal oxidation and concomitant aquo ligand deprotonation to give ions assignable to [Mn{sup III/IV}{sub 2}(bpbp)O(OCH{sub 3}){sub 2}(H{sub 2}O)]{sup 2+} (5) and [Mn{sup III}{sub 2}(bpbp)(OH){sub 3}(H{sub 2}O)]{sup 2+} (6). ESI mass spectra of water or methanol solutions of 1, 2, 3 and 7 show predominantly an ion assignable to the oxide [Mn{sub 2}(bpbp)(O)]{sup 2+} (8). Cation 8 is most likely not present in solution. Using mild source conditions and MS-MS techniques, the gas-phase fragmentation pathways to generate 8 have been mapped.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914195
Report Number(s):
BNL-78763-2007-JA
Journal ID: ISSN 1434-1948; EJICFO; TRN: US200804%%590
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Eur. J. Inorg. Chem.; Journal Volume: 2006
Country of Publication:
United States
Language:
English
Subject:
10 SYNTHETIC FUELS; 36 MATERIALS SCIENCE; AIR; AQUEOUS SOLUTIONS; CRYSTAL STRUCTURE; MAGNETIC SUSCEPTIBILITY; MANGANESE COMPLEXES; MASS SPECTRA; MASS SPECTROSCOPY; METHANOL; OXIDATION; WATER; national synchrotron light source

Citation Formats

Larsen,F., Boisen, A., Berry, K., Moubaraki, B., Murray, K., McKee, V., Scarrow, R., and McKenzie, C. Identification of the Dinuclear and Tetranuclear Air-Oxidized Products Derived from Labile Phenolate-Bridged Dimanganese(II) Pyridyl-Chelate Compounds. United States: N. p., 2006. Web. doi:10.1002/ejic.200600488.
Larsen,F., Boisen, A., Berry, K., Moubaraki, B., Murray, K., McKee, V., Scarrow, R., & McKenzie, C. Identification of the Dinuclear and Tetranuclear Air-Oxidized Products Derived from Labile Phenolate-Bridged Dimanganese(II) Pyridyl-Chelate Compounds. United States. doi:10.1002/ejic.200600488.
Larsen,F., Boisen, A., Berry, K., Moubaraki, B., Murray, K., McKee, V., Scarrow, R., and McKenzie, C. Sun . "Identification of the Dinuclear and Tetranuclear Air-Oxidized Products Derived from Labile Phenolate-Bridged Dimanganese(II) Pyridyl-Chelate Compounds". United States. doi:10.1002/ejic.200600488.
@article{osti_914195,
title = {Identification of the Dinuclear and Tetranuclear Air-Oxidized Products Derived from Labile Phenolate-Bridged Dimanganese(II) Pyridyl-Chelate Compounds},
author = {Larsen,F. and Boisen, A. and Berry, K. and Moubaraki, B. and Murray, K. and McKee, V. and Scarrow, R. and McKenzie, C.},
abstractNote = {Dioxygen-sensitive dinuclear manganese complexes of the phenoxo-hinged dinucleating ligand 2,6-bis{l_brace}[N,N{prime}-bis(2-picolyl)amino]methyl{r_brace}-4-tert-butylphenolato (bpbp{sup -}) containing exogenous labile THF, water and perchlorato ligands are described. The manganese(II) complexes [Mn{sub 2}(bpbp)(ClO{sub 4}){sub 2}(THF)]{sup +} (1) and [Mn{sub 2}(bpbp)(ClO{sub 4})(H{sub 2}O){sub 2}]{sup 2+} (2) have been isolated as the salts 1{center_dot}ClO{sub 4}{center_dot}THF{center_dot}3H{sub 2}O, 1{center_dot}B(C{sub 6}H{sub 5}){sub 4}{center_dot}4THF and 2{center_dot}(ClO{sub 4})2{center_dot}H{sub 2}O. Complexes 1 and 2 are spontaneously oxidised in air in solution and the solid state. The reaction products of the air oxidation in THF, water and methanol solutions are labile dinuclear Mn{sup II}-Mn{sup III}, Mn{sup III}{sub 2} and Mn{sup III}-Mn{sup IV} complexes containing water- and methanol-derived exogenous ligands. In addition, a Mn{sub 4} complex has been isolated. Magnetic susceptibility data confirm the Mn{sup II}-Mn{sup III} oxidation state assignment with an S = 2/S = 5/2 model with weak antiferromagnetic coupling (J = -3.7 cm{sup -1}) in [Mn{sub 2}(bpbp)(CH{sub 3}O){sub 2}(H{sub 2}O){sub 2}](ClO{sub 4}){sub 2} [3{center_dot}(ClO{sub 4}){sub 2}]. A tetranuclear complex, [Mn{sub 4}(O){sub 4-n}(OH){sub n}(bpbp){sub 2}](ClO{sub 4}){sub 4} [n = 1 or 2; 7{center_dot}(ClO{sub 4}){sub 4}], recovered from THF shows a Mn{sub 4}O{sub 6} adamantane-type core with the O bridges furnished by the two phenolato groups and four hydroxide/oxide bridges. We have arrived at two feasible formulations for the core metal oxidation states and oxo-bridge protonation states, namely [Mn{sup III}{sub 4}(O){sub 2}(OH){sub 2}(bpbp){sub 2}]{sup 4+} and [Mn{sup III}{sub 3}Mn{sup IV}(O){sub 3}(OH)(bpbp){sub 2}]{sup 4+}, for 7, on the basis of a bond valence sum analysis of the crystal structure, elemental analysis and XANES. Thus, complex 7 is at least two oxidation state levels lower than known complexes with the Mn{sub 4}O{sub 6} adamantane core structure. The magnetism of 7 was fitted well to an MnIII4 three-J model. Complex cations related to 3 by homology, and to 7 by hydration/solvation, have been identified by ESI mass spectrometry. The [Mn{sub 2}(bpbp)(OH){sub 2}(H{sub 2}O){sub 2}]{sup 2+} ion (4) present in aqueous solutions on dissolution of 1{center_dot}ClO4{center_dot}THF{center_dot}3H2O in air or by simple dissolution of 3 in water-containing solvent is isoelectronic to 3. In the presence of significant amounts of water the Mn{sup II}-Mn{sup III} complexes 3 and 4 are susceptible to further metal oxidation and concomitant aquo ligand deprotonation to give ions assignable to [Mn{sup III/IV}{sub 2}(bpbp)O(OCH{sub 3}){sub 2}(H{sub 2}O)]{sup 2+} (5) and [Mn{sup III}{sub 2}(bpbp)(OH){sub 3}(H{sub 2}O)]{sup 2+} (6). ESI mass spectra of water or methanol solutions of 1, 2, 3 and 7 show predominantly an ion assignable to the oxide [Mn{sub 2}(bpbp)(O)]{sup 2+} (8). Cation 8 is most likely not present in solution. Using mild source conditions and MS-MS techniques, the gas-phase fragmentation pathways to generate 8 have been mapped.},
doi = {10.1002/ejic.200600488},
journal = {Eur. J. Inorg. Chem.},
number = ,
volume = 2006,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}