Search results for "Cyclopentadienyl ligands"
showing 4 items of 4 documents
A Dysprosium Metallocene Single-Molecule Magnet Functioning at the Axial Limit
2017
Abstraction of a chloride ligand from the dysprosium metallocene [(Cpttt)2DyCl] (1Dy Cpttt=1,2,4‐tri(tert‐butyl)cyclopentadienide) by the triethylsilylium cation produces the first base‐free rare‐earth metallocenium cation [(Cpttt)2Dy]+ (2Dy) as a salt of the non‐coordinating [B(C6F5)4]− anion. Magnetic measurements reveal that [2Dy][B(C6F5)4] is an SMM with a record anisotropy barrier up to 1277 cm−1 (1837 K) in zero field and a record magnetic blocking temperature of 60 K, including hysteresis with coercivity. The exceptional magnetic axiality of 2Dy is further highlighted by computational studies, which reveal this system to be the first lanthanide SMM in which all low‐lying Kramers doub…
Diene-Containing Half-Sandwich MoIII Complexes as Ethylene Polymerization Catalysts: Experimental and Theoretical Studies
2001
International audience; Seventeen-electron compounds of Mo III having the general formula [(h 5-C 5 R 5)Mo(h 4-diene)X 2 ] (R H, Me; diene butadiene, iso-prene, or 2,3-dimethylbutadiene; X Cl, CH 3) are a new class of ethylene polymerization catalysts. The polyethy-lene obtained shows a bimodal distribution , the major weight fraction being characterized by very long (M around 10 6) and highly linear polymer chains. The newly prepared pentamethylcyclo-pentadienyl (Cp*) derivatives are more active than the cyclopentadienyl (Cp) derivatives, but much less active than previously investigated niobium III compounds having the same stoichiometry. On the other hand, the turnover frequency of the a…
Cyclopentadienylmolybdenum(VI) and molybdenum(V) oxo chemistry: New synthetic and structural features
2002
International audience; Convenient syntheses for Cp, Cp*, and related cyclopentadienyl derivatives (4Cp = C5HiPr4; Cp′′′ = C5H2tBu3-1,2,4) of formula [(Ring)2Mo2O5] are described. Compound [Cp2Mo2O5] was produced in good yields by the rapid oxidation of red [CpMoO2]4 with PhIO in CH2Cl2. [Cp*2Mo2O5] was obtained by CH3COOH acidification of aqueous solutions of [Cp*MoO3]−Na+, the latter being generated in a single step from [Cp*MoCl4] and more than 5 equiv. of aqueous NaOH in air. Minor quantities of [Cp*MoO2]2 were also isolated from this reaction, although the formation of this by-product may be reduced by using a two-step basic hydrolysis procedure. Extension of the latter strategy also a…
Synthesis of new half sandwich tetrachloro derivatives of molybdenum(V) and tungsten(V). X-ray structures of (C5HPri4)W(CO)3(CH3) and (C5Et5)WCl4
2002
International audience; The new synthetic intermediates (Ring)MCl4 [Ring=C5HPri4 or 4Cp, M=Mo, 2; Ring=C5Et5 or VCp, M=W, 4, Ring=4Cp, M=W, 6] containing sterically protecting cyclopentadienyl ligands have been synthesized. Along the synthetic pathway to 2, it was found that the treatment of [4CpMo(CO)3]− with an aqueous ferric solution according to the well established Manning procedure affords the hydride compound 4CpMo(CO)3H (1) by hydrolysis rather than the expected neutral dimer by oxidation. Compound 1 could be converted, however, to 2 upon oxidation with PhICl2 in good yields. Compound 4 is shown by a single crystal X-ray analysis to adopt a monomeric four-legged piano stool structur…