Synthesis, Structure, and Characterization of a Novel Manganese(IV) Monomer, [MnIV(Me3TACN)(OMe)3](PF6) (Me3TACN = N,N‘,N‘‘-Trimethyl-1,4,7-triazacyclononane), and Its Activity toward Olefin Oxidation with Hydrogen Peroxide
- 1 January 1996
- journal article
- research article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 35 (22) , 6461-6465
- https://doi.org/10.1021/ic951522w
Abstract
A novel manganese(IV) monomer, [MnIV(Me3TACN)(OMe)3](PF6), has been synthesized in methanol by the reaction of MnCl2 with the ligand, N,N‘,N‘‘-trimethyl-1,4,7-triazacyclononane (Me3TACN), in the presence of Na2O2. The resulting product was isolated as the red/brown crystalline hexafluorophosphate salt. The compound crystallizes in the space group P2/c with the cell dimensions a = 15.652(2) Å, b = 8.740(1) Å, c = 15.208(2) Å, β = 108.81(1)°, V = 1969.4(4) Å3, and Z = 4. The structure was solved by the heavy-atom method and was refined by full-matrix least-squares techniques to a final value of R = 0.067 (Rw = 0.097) based upon 3087 observations. The manganese atom in the molecule is six-coordinate in an N3O3 ligand environment with the triazacyclononane facially coordinated. Pertinent average bond distances and angles are as follows: Mn−O, 1.797(5) Å; Mn−N, 2.116(5) Å; O−Mn−O, 97.8(2)°; N−Mn−N, 81.4(2)°; O−Mn−N, 167.8°(2); O−Mn−N, 86.8(2)°; O−Mn−N, 92.8(2)°. The complex was further characterized by UV−vis and EPR spectroscopies, solution magnetic susceptibility measurements, FAB-MS, and electrochemistry. [MnIV(Me3TACN)(OMe)3](PF6) was found to catalyze the oxidation of water-soluble olefins using hydrogen peroxide as the oxidant in an aqueous medium. The catalyzed rates of oxidation of these olefins indicate at least a 12-fold rate enhancement over oxidant alone. The unusual stability of the catalytic species was demonstrated by the repeated additions of substrate and oxidant while maintaining a constant catalytic rate of oxidation.Keywords
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