Zirconocene hydrochloride

The alkenylboronic esters were synthesized according to a literature procedure [56], Hydrozirconation of alkenylboronic esters with zirconocene hydrochloride, Cp2Zr(H)Cl, prepared by Buchwald s procedure [57], took place smoothly in CH2C12, providing in each case the corresponding borazirconocene 1,1-alkane 18 [34], Addition of propargyl bromide and a catalytic amount of copper(I) cyanide was accompanied by the disappearance of the yellow color associated with these compounds and by carbon—carbon bond... 

The zirconocene complex, CpCp Zr—GePh3(Cl) undergoes hydrogenolysis of the Zr—Ge bond, giving zirconocene hydrochloride and triphenylgermane. The reaction is slow in comparison with the hydrogenolysis of the Zr—Si bond in an analogous complex (equation 47)41. 

Zirconocene hydrochloride was prepared according to Buchwald s procedure2 and stored in a Schlenk filter flask under argon in a freezer at -20°C or obtained from Aldrich Chemical Company, Inc., and used without further purification. 

Zirconocene hydrochloride aldrich Zirconocene chloride hydride Zirconium, chlorodi-ji-cyclopentadienylhydro- (8) Zirconium, chlorobis(r 5-2,4-cyclopentadien-1-yl)hydro- (9) (37342-97-5)... 

Generation of organozirconium species 18 follows the hydrozirconation of the triple bond using zirconocene hydrochloride (Schwartz reagent) 16. This 16-electron, d° Zr(IV) complex is coordinatively unsaturated, so alkyne 15 coordinates to the electrophilic Zr center followed by insertion of the triple bond into the Zr-H bond. The resulting a-vinyl-Zr(lV)-species 18 is formed with a high cA-selectivity and regioselectivity, such that the bulky zirconocene moiety always adds end-on to the terminal multiple bond. 

Fernandez-Megia, E. Zirconocene hydrochloride, "Schwartz reagent". Synlett 999, 1179. 

Among transition metals, zirconium is the most important for hydrometallation of alkynes. The available 16 electron complex Cp2ZrHCl (Cp = cyclopentadienyl) 122 (zirconocene hydrochloride) adds stereoselectively syn to alkynes to give the -vinyl zirconium species 126. The initial interaction is the donation of two electrons by the triple bond 123 to make the reasonably stable 18-electron n-complex (or r 2-complex) 124. Typically for a transition metal Ji-complex, a ligand is now transferred from the metal to one end of the tr-bond 125 while the metal itself forms a stable 16-electron o-complex at the other 126. The H transfer is intramolecular so the metal and H atoms must add to the same side of the triple bond. The zirconium atom transfers the least stable anion among its ligands. This is obviously II as Cl is much more stable. The metal prefers to take the terminal position because the resulting o-complex is more stable as it is a o-complex of the less-substituted carbanion.27... 

Synthesis of a,p-Unsaturated Selenol Esters and Vinylic Selenol Esters by the Use of Zirconocene Hydrochloride... 

Solvent choice can sometimes affect the efficiency and outcome of a reaction performed using microwave heating. Polar solvents are normally chosen because they are directly heated efficiently via interaction with microwave energy. Some micro-wave syntheses have been carried out with excellent results under solvent-free conditions. Other synthetic procedures require a nonpolar reaction medium. In such cases, graphite is often used as a microwave absorber that in turn heats the reaction mixture. The metal complex itself, however, is often capable of absorbing microwave irradiation. An example from the literature is the observation of rapid heating of a toluene solution containing zirconocene hydrochloride under microwave irradiation. ... 

Organozirconium compounds also undergo the Pd-catalyzed cross-coupling reaction with acyl halides.h i in the presence of ZnCF, the reaction can be carried out more efficiently. Acykirconium species, which are produced via hydrozirconation of alkynes or alkenes by zirconocene hydrochloride followed by insertion of CO, couple with acyl chlorides to give a-diketones (Scheme 12). 

A solution of 1-hexyne (52 mg, 0.64mmol) in 2 ml of CH2CI2 was kept under a nitrogen atmosphere and treated at rt with zirconocene hydrochloride (160 mg. 0.64 mmol) (Scheme 4.9) [62aj. The mixture was stirred at rt until a homogeneous solution had formed, then cooled to —65 °C. Dimethylzinc (0.33 ml, 2.0 M solution in toluene) was added over 5 min. 

Nonanoylzirconocene chloride (1), readily prepared by the reaction of 1-octene and zirconocene hydrochloride (Schwartz reagent) followed by exposure to 1 atm of CO, serves as an umnasked acyl anion and provides ketones or a-diketones in moderate to good yields by the reaction with electrophiles (aryl iodide, benzyl bromide, acyl chloride, allyl chloride, aUyl acetate) in the presence of 5% of PdCl2(PPh3)2 (Scheme 47). ... 

In a dry and nitrogen-flushed flask, a solution of l-hexyne (324, 0.053 g, 0.64 mmol) in CH2CI2 (2mL) is treated with zirconocene hydrochloride (0.160 g, 0.64 mmol). The reaction mixture is stirred at 25 °C until a homogeneous solution is formed. After cooling to -65 °C, dimethylzinc (0.33 mL, 2.0 m in toluene, 0.66 mmol) is added over 5 min and the mixture is warmed to 0 °C. A solution of /rons-cinnamaldehyde (0.070 g, 0.53 mmol) in CH2CI2 (2mL) is added over 10 min. The reaction mixture is extracted twice with diethyl ether and the solvents are evaporated. Purification by column chromatography affords the allyl alcohol 325 (0.108 g, 94%). ... 

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