Identification of the Dinuclear and Tetranuclear Air-Oxidized Products Derived from Labile Phenolate-Bridged Dimanganese(II) Pyridyl-Chelate Compounds
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.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 914195
- Report Number(s):
- BNL-78763-2007-JA; EJICFO; TRN: US200804%%590
- Journal Information:
- Eur. J. Inorg. Chem., Vol. 2006; ISSN 1434-1948
- Country of Publication:
- United States
- Language:
- English
Similar Records
Structural and photophysical properties of lanthanide complexes with planar aromatic tridentate nitrogen ligands as luminescent building blocks for triple-helical structures
Synthesis and characterization of gallium and indium thiolate complexes. Crystal and molecular structures of [M(SC{sub 5}H{sub 4}N){sub 3}] (M = Ga, In), [In(SC{sub 5}H{sub 3}N-3-SiMe{sub 3}){sub 3}], and [M{sub 2}(OC{sub 2}H{sub 4}){sub 2}(SC{sub 5}H{sub 4}N){sub 4}] (M = Ga, In)