119445-90-8Relevant articles and documents
Preparation des complexes (M=Ti, Zr; X=Cl, alkyl, aryl, CO). Etude par RMN dynamique de la gene sterique a la rotation des groupements aryle lies au metal
Courtot, P.,Labed, V.,Pichon R.,Salauen, J. Y.
, p. C9 - C13 (1989)
The new ligand C5Me4H reacts with or to afford the dichloro complexes (M=Ti, Zr) and trichloro complex .Treatment of these complexes with RLi, or their reduction under CO, gives the derivatives (R=CH3, C6H5, p-C6H4CH3, CO).The preparation of the new series of compounds, , is also described.The electronic effects of the C5Me4H ligand resemble closely those of C5Me5.The coalescence of the 1H and 13C NMR aromatic signals indicates that rotation of the aromatic nucleus around the metal-carbon bond is restricted owing to the large size of the C5Me4H ligand in the aryl complexes.The activation parameters of this rotation have been determined for .
Dinitrogen functionalization with terminal alkynes, amines, and hydrazines promoted by [(η5-C5Me4H) 2Zr]2(μ2,η2, η2-N2): Observation of side-on and end-on diazenido complexes in the reduction of N2 to hydrazine
Bernskoetter, Wesley H.,Pool, Jaime A.,Lobkovsky, Emil,Chirik, Paul J.
, p. 7901 - 7911 (2005)
Functionalization of the N2 ligand in the side-on bound dinitrogen complex, [(η5-C5Me4H) 2Zr]2-(μ2,η2, η2-N2), has been accomplished by addition of terminal alkynes to furnish acetylide zirconocene diazenido complexes, [(η5-C5Me4H)2Zr(C≡CR)] 2(μ2,η2,η2-N 2H2) (R = nBu, tBu, Ph). Characterization of [(η5- C5Me4H) 2Zr(C≡CCMe3)]2(μ2, η2,η2-N2H2) by X-ray diffraction revealed a side-on bound diazenido ligand in the solid state, while variable-temperature 1H and 15N NMR studies established rapid interconversion between η1,η1 and η2,η2 hapticity of the [N2H 2]2- ligand in solution. Synthesis of alkyl, halide, and triflato zirconocene diazenido complexes, [(η5-C 5Me4H)2ZrX]2(μ2, η1,η1-N2H2) (X = Cl, I, OTf, CH2Ph, CH2SiMe3), afforded η1,η1 coordination of the [N2H 2]2- fragment both in the solid state and in solution, demonstrating that sterically demanding, in some cases π-donating, ligands can overcome the electronically preferred side-on bonding mode. Unlike [(η5-C5Me4H)2ZrH] 2(μ2,η2,η2-N 2H2), the acetylide and alkyl zirconocene diazenido complexes are thermally robust, resisting α-migration and N2 cleavage up to temperatures of 115 °C. Dinitrogen functionalization with [(η5-C5Me4H)2Zr] 2(μ2,η2,η2-N 2) was also accomplished by addition of proton donors. Weak Bronsted acids such as water and ethanol yield hydrazine and (η5-C 5Me4H)2Zr(OH)2 and (η5-C5Me4H)2-Zr(OEt) 2, respectively. Treatment of [(η5-C 5Me4H)2Zr]2(μ2, η2,η2-N2) with HNMe2 or H2NNMe2 furnished amido or hydrazido zirconocene diazenido complexes that ultimately produce hydrazine upon protonation with ethanol. These results contrast previous observations with [(η5-C 5Me5)2Zr(η1-N2)] 2(μ2,η1,η1-N 2) where loss of free dinitrogen is observed upon treatment with weak acids. These studies highlight the importance of cyclopentadienyl substituents on transformations involving coordinated dinitrogen.
Influence electronique et sterique du ligand tetramethylcyclopentadienyle sur les proprietes physiques et sur la reactivite de complexes du titane et du zirconium
Courtot, P.,Pichon, R.,Salaun, J. Y.,Toupet, L.
, p. 661 - 672 (2007/10/02)
The complexes (C5Me4H)2MR1R2 (M=Ti, Zr) and (C5Me4H)(C5H5)MR1R2 (M=Ti) have been prepared (R1=R2=Cl, CH3, C6H5, p-C6H4CH3, CO; R1=Cl, R2=CH3, C6H5, p-C6H4CH3).The NMR and IR spectra of these complexes indicate that C5Me4H exhibits an electron-donor effect more important than C5H5 and a little bit weaker than that of C5Me5.A structural investigation of the complex (C5Me4H)2Zr(C6H5)Cl and the study of the 1H or 13C dynamic NMR properties of the compounds (C5Me4H)2MR1R2 (M=Ti, Zr; R1=R2=C6H5, p-C6H4CH3; R1=Cl, Br, R2=C6H5, p-C6H4CH3) show clearly that C5Me4H has a steric effect intermediate between C5H5 and C5Me5.The steric or electronic effects of C5Me4H have been used to induce specific isomerization reactions of various alkenes by using (C5Me4H)2Ti(CH3)2 as catalyst. --- Key words: zirconium, titanium, tetramethylcyclopentadienyl, photo-assisted, isomerization.
