AN UNSYMMETRIC TRINUCLEAR CHROMIUM(III) OXO CARBOXYLATE ASSEMBLY - STRUCTURE AND CHARACTERIZATION OF CR3O(O(2)CPH)(4)(8-HQN)(3)CENTER-DOT-1.25 CH2CL2

The structural and spectroscopic properties of a series of unsymmetric trinuclear chromium-oxo complexes are reported. One example, Cr3O(O(2 )CPh)(4)(8-hqn)(3) (1). 1.25CH(2)Cl(2) crystallizes in the triclinic s pace group P (1) over bar (No. 2) with a 11.901(2) Angstrom, b = 19.41 0(4) Angstrom, c = 11.701(1) Angstrom, alpha = 96.58(1)degrees, beta = 95.66(1)degrees, gamma = 101.21(1)degrees, V = 2614(1) Angstrom 3, an d Z = 2. The structure was refined with 4869 reflections having I > 3. 00 sigma(I) giving final values of 0.057 and 0.069 for R and R(w), res pectively. The [Cr3O](7+) core of the complex is distinctly unsymmetri c with Cr- - -Cr separations of 2.909(1), 3.235(1), and 3.466(2) Angst rom and Cr-O-Cr angles of 94.4(2), 118.1(2), and 130.2(2)degrees. The magnetic susceptibility of complex 1 was measured in the range 8-300 K . The effective moment per molecule decreases from 6.36 mu(B) at 300 K to 4.0 mu(B) at 15 K, which is appropriate for a system with a spin 3 /2 ground state. Below 15 K, the magnetic moment varies little with te mperature. The significance of these results in terms of the molecule' s structure is discussed. Results of H-1 and H-2 NMR, ERR, and mass sp ectral studies are presented.