Synthesis and Characterization of Novel Oxo-Bridged Dinuclear and Hydroxo-Bridged Trinuclear Chromium(III) Assemblies
journal contributionposted on 08.10.1997, 00:00 by Anthony Harton, Katisha Terrell, John C. Huffman, Chris MacDonald, Alicia Beatty, Sichu Li, Charles J. O'Connor, John B. Vincent
The structural and spectroscopic properties of a novel dinuclear chromium−oxo and a trinuclear chromium−hydroxo complex are reported. The dinuclear assembly, [Cr2(μ-O)2(μ-O2CMe)(bpy)2(H2O)2]ClO4·bpy·[bpyH]ClO4 (1), crystallizes in the monoclinic space group Cc with a = 16.8259(8) Å, b = 21.9622(11) Å, c = 14.6056(8) Å, β = 122.1830(10)°, V = 4568.0(4) Å3, and Z = 4. The structure was refined with 4378 observed reflections having F > 2.0σ(F), giving final R factors of 0.0721 and 0.1305 for R and Rw2, respectively. The [Cr2(μ-O)2(μ-O2CMe)]+ core is structurally akin to those of recently reported isoelectronic [Mn2(μ-O)2(μ-O2CMe)]3+ complexes. The trinuclear assembly, [Cr3(μ-OH)2(μ-O2CMe)4(O2CMe)2(bpy)2]ClO4 (2)·5CHCl3 crystallizes in the triclinic space group P1̄ with a = 16.104(5) Å, b = 17.623(5) Å, c = 12.236(3) Å, α = 93.33(1)°, β = 92.81(1)°, γ = 64.84(1)°, V = 3136.68 Å3, and Z = 2. The structure was refined with 6732 observed reflections having F > 2.33σ(F), giving final R factors of 0.0602 and 0.0616 for R and Rw, respectively. Results of electronic, 1H and 2H NMR, and EPR spectroscopy, fast atom bombardment mass spectrometry, and variable-temperature magnetic susceptibility studies of these materials and the use of Cr−oxo assemblies as isoelectronic models of the photosynthetic manganese assembly in high-S states are discussed.