SYNTHESIS AND CHARACTERIZATION OF POLYNUCLEAR CHROMIUM CARBONYL TETRAANIONS
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Polynuclear chromium carbonyl complexes of the general formula [Cr4(CO)12(3-OR)4]4- (R = H, C6H5) have been prepared as their Et4N+ salts. Reaction of Cr(CO)6 with excess hydroxide ion in aqueous THF solution yields [Cr4(CO)12(3-OH)4]4-. The X-ray structure of [Et4N]4[Cr4(CO)12(M3-OH)4] has been determined. The structural features of the tetraanion consist of a cubane-like A4B4 (A = chromium, B = oxygen) arrangement with triply bridging 3-hydroxide groups and Cr(CO)3 units. The Cr-Cr distance within the Cr4O4 core is nonbonding (3.33 (5) (average)), consistent with a closed-shell metal configuration. The crystals are monoclinic (space group I2/a) with cell constants a = 21.827 (7) , b = 12.236 (2) , c = 22.899 (4) , = 116.49 (2), V = 5474 (5) 3, and Z = 8. The, 3-phenoxide derivative, [Et4N]4[Cr4(CO)12(3-OC6H5)4], has been prepared by treatment of Cr(CO)3(CH3CN)3 with [Et4N] [OC6H5] in equimolar concentrations and characterized by spectroscopic methods. 1985, American Chemical Society. All rights reserved.