Chrom(III)- und Chrom(IV)-Komplexe der π-Aromaten-Reihe: Präparative und strukturchemische Aspekte

Abstract

The dinuclear, paramagnetic organochromium(III) complex [(η 5-C 5Me 5)Cr(μ-Cl)CH 3] 2 ( 2) containing bridging chloro and terminal methyl ligands (X-ray diffraction study) can be obtained from thf-solvated methylchromium dichloride ( 1a) or from chromium trichloride ( 1b) with common transfer reagents of the C 5Me 5-group in 40 and 65% yield, respectively, thus constituting a convenient starting material in organochromium chemistry of intermediate metal oxidation states. Treatment of 2 with trimethylphosphane effects cleavage of the chloro-bridged structure to give the mononuclear complex (η 5-C 5Me 5)CrCl(CH 3)(PMe 3) ( 3), whereas reaction with sodium phenoxide involves substitution of the bridge ligand with formation of [(η 5-C 5Me 5)Cr(μ-OC 6H 5)CH 3] 2 ( 4). Oxidation of 2 with bromine gives (chiral) (η 5-C 5Me 5)CrCl(Br)(CH 3) ( 5) selectively as a pair of enantiomers, which can then be converted into the diamagnetic Cr IV alkoxide complex (η 5-C 5Me 5)Cr(CH 3-(OC 6H 5) 2 ( 6). By contrast, no chromium oxidation occurs when 2 is treated with iodine; rather the mixed chloroiodo derivative of net composition [(η 5-C 5Me 5)Cr-Cl 1/2I 3/2] 2·I 2 ( 7) is formed, and is a polymer with bridging iodine (I 2) in the crystal.