Date: March 24, 2005
Creator: Sydora, Orson L.; Wolczanski, Peter T.; Lobkovsky, Emil B.; Buda, Corneliu & Cundari, Thomas R., 1964-
Description: This article discusses low-coordinate chromium siloxides. Abstract: Treatment of CrCl2(THF)2 with NaOSitBu3 afforded the tetrameric "box" [Cr(μ-OSitBu3)]4 (1,X-ray). THF cleaved 1 to provide trans-(silox)ClCr(THF)2 (2), whereas degradation of 1 with 4-picoline caused disproportionation and the generation of trans-Cl2Cr(4-pic)2 and trans-(silox)2 Cr(4-pic)x (n=2,3; 3,3-4-pic). Chromous centers in 1 were antiferromagnetically coupled, and density functional calculations on the high-spin (multiplicity = 17) model [Cr-(μ-Cl)(μ-OH)]4 (1') revealed that its singly occupied 3d orbitals spanned an energy range of ͠2 eV. The addition of 8 equiv of Na(silox) to 1 yielded [(tBu3SiO)Cr(μ-OSitBu3)2] Na·C6H6 (4, Y shaped, ∠OCrO(Na) = 91.28(7)°), and treatment of 4 with dibenzo-18-crown-6 produced [(silox)(3)Cr] [Na(dibenzo-18-crown-6)] (5, ∠OCrO = ͠120°, (120 + α)°, (120 - α)°). Calculations of [((t)Bu(3)SiO)Cr(mu-OSi(t)Bu(3))(2)]Na (4') and Cr(silox)(3)(-) (5') provided reasonable matches with the experimental geometries (X-ray). The trigonal chromic derivative (silox)(3)Cr(6) was synthesized from CrCI(3)(THF)(3) for structural and calculational comparisons to the chromous derivatives.
Contributing Partner: UNT College of Arts and Sciences