204141-52-6Relevant articles and documents
High-spin molecules: Hexanuclear Mn(III) clusters with [Mn6O4X4]6+ (X = Cl-, Br-) face-capped octahedral cores and S = 12 ground states
Aromí, Guillem,Knapp, Michael J.,Claude, Juan-Pablo,Huffman, John C.,Hendrickson, David N.,Christou, George
, p. 5489 - 5499 (2007/10/03)
Reaction of R2dbmH (R = H, Me, Et; dbmH is dibenzoylmethane) with MnCl3 (generated in situ from MnCl2 and MnO4-) in MeCN yields the five- coordinate, square-pyramidal complexes [MnCl(R2dbm)2] (R = H, 1; Me, 4; Et, 7). The same reaction with MnBr2 yields [MnBr(R2dbm)2] (R = H, 2; Me, 5; Et, 8). Slow hydrolysis of 4 or 7 in CH2Cl2/MeCN over two weeks gives [Mn6O4Cl4(R2dbm)6] (R = Me, 9; Et, 11); the crystal structure of 9 reveals a novel [Mn6(μ3-O)4(μ3-Cl)4]6+ core comprising an Mn6/(III) octahedron whose faces are capped by O2- or Cl- ions. Similar slow hydrolysis of 5 or 8 gives [Mn6O4Br4(R2dbm)6] (R = Me, 10; Et, 12); the crystal structure of 10 is identical with that of 9 except for the Br--for- Cl- substitution. The 1H NMR spectra of 1-12 in CDCl3 show paramagnetically shifted and broadened R2dbm resonances. The spectra are as expected for retention of the solid-state structures, the Mn6 complexes exhibiting effective T(d) solution symmetry with no evidence of fragmentation to [MnX(R2dbm)], [Mn(R2dbm)3], or any other species. The effective magnetic moment (μ(eff)) per Mn6 for 9/12 slowly increases from 16.01/16.73 μ(B) at 320/300 K to a maximum of 24.37/24.60 μ(B) at 30.1/40.0 K, and then decreases to 13.69/13.86 μ(B) at 2.00 K. Fitting of the data to the theoretical equation derived for a Mn6/(III) octahedron gives (for 9/12) J(cis) = 8.6/8.5 cm-1 and g = 1.97/1.98 with J(trans) and TIP held fixed at 0 cm-1 and 1200 x 10-6 cm3 mol-1, respectively. These values indicate a S = 12 ground state. Fitting of magnetization vs field data collected in the 2.00-15.0 K and 0.500-50.0 KG ranges confirmed S = 12 ground states with D ? 0 cm-1.
