Chromium(III) and Chromium(II) Phenolate Complexes with Bulky Alkylcyclopentadienyl Ligands

Abstract

The chromium(II) tricarbonyl methyl complex [Cp′′′Cr(CO) 3 CH 3 ] (1, Cp′′′ = η 5 -C 5 H 2 tBu 3 -1,2,4) was obtained from chromium hexacarbonyl, NaCp′′′, and methyl iodide. 1 was found to establish an equilibrium with the dicarbonyl acetyl isomer [Cp′′′Cr(CO) 2 (COCH 3 )] in solution via reversible, slightly endothermic methyl migration from chromium to a carbonyl ligand with ΔH ca. 3.6 kJ/mol and E a ca. 49.5 kJ/mol. Phosphorus pentachloride oxidized 1 to the green, dinuclear tetrachloro complex [Cp′′′CrCl(μ-Cl)] 2 (2), which was crystallized as the blue-green chromium(III) half sandwich complex [Cp′′′CrCl 2 -(THF)] (3) in the presence of tetrahydrofuran vapor. Attempted sublimation of the known chromium(II) iodo complex [ 4 CpCr-(μ-I)] 2 resulted in a redox reaction with formation of the chromium(III) iodo dimer [ 4 CpCrI(μ-I)] 2 , whose tri(tert-butyl)-[a] FB Chemie der TU Kaiserslautern

Supported Organochromium Ethylene Oligomerization Enabled by Surface Lithiation

“…In Cr/LTO , the local environment of chromium has a trigonal bipyramidal structure with a coordination number of five. − This includes a Cr–C bond (2.034 Å), two Cr–O bonds (1.940 and 1.944 Å) where the oxygen atoms originate from terminal hydroxyl groups, and two Cr–O bonds (1.944 and 2.271 Å) resulting from interactions with lattice oxygen atoms from the LTO support. Similar five-coordinate chromium­(II) complexes exhibiting trigonal bipyramidal geometry have been previously reported but are generally uncommon. − …”

Organozinc Fluoride and Trifluoromethyl Compounds Supported by the Bis(2-pyridylthio)methyl Ligand

“…To place these observations in more context, the M–CF 3 and M–CH 3 bond lengths in structurally related metal complexes are presented in Table . − In addition, average M–CF 3 and M–CH 3 bond lengths for elements that possess structurally characterized trifluoromethyl compounds are summarized in Table . Examination of these data indicate that the notion that M–CF 3 bonds are shorter than corresponding M–CH 3 bonds is not universally observed.…”