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Alkylation of zirconium tetrachloride with benzyl Grignard; Zirconium tetrabenzyl

SyntheticPage 1
DOI: 10.1039/SP1
Submitted May 30, 2001, published Jun 01, 2001
Peter Scott (peter.scott@warwick.ac.uk)
A contribution from Scott group, Warwick University


			Reaction Scheme: <span id="csm1276121193272" class="csm-reaction-type" title="Alkylation">Alkylation</span> of <span id="ent634117205363955692_414201469" class="csm-chemical-name csm-ambiguous" title="zirconium tetrachloride">zirconium tetrachloride</span> with benzyl Grignard

Chemicals Used

C6H5CH2MgCl (1M in diethyl ether, Aldrich)
ZrCl4 (not sublimed)
diethyl ether (dried over Na/K but Na would do)
toluene (dried over Na)

Procedure

Using Schlenk techniques, C6H5CH2MgCl (100 ml, 1M in diethyl ether, 4 equiv.) was added to ZrCl4 (6.0 g, 0.025 mol) in a diethyl ether (50 ml) slurry over 1 hr at -78°C, ensuring that the suspension was cool before addition of the Grignard reagent. Once the addition was complete, the mixture was allowed to warm slowly with stirring and any gas expansion was vented at the Schlenk line bubbler. The solution was stirred overnight at ambient temperature (in the absence of light) and the bright orange solution was then cooled to 0°C and filtered to remove MgCl2 [this residue should be "destroyed" by cautious hydrolysis before disposal]. The diethyl ether was removed in vacuo and the orange product was redissolved in toluene (30 ml) and filtered. Cooling to -30°C afforded orange crystals which were washed with cold toluene (2 x 10 ml). Yield variable, but about 70%.

Author's Comments

Keeping the reaction in the dark is important. Use aluminium foil. Sometimes the yield from the first crop is low and a second crop can be obtained by concentration and cooling. We store the product in the freezer in a Schlenk wrapped in foil and transfer the Schlenk to the glovebox to handle it. If you have a freezer in the box that is ideal. Don't forget that this type of method will only work for alkyls without beta-H atoms (beta elimination).

Data

1H NMR (293 K, d6-benzene) 7.15 (m, 12H, Ph), 6.42 (d, 8H, Ph), 1.57 (s, 8H, CH2).

Lead Reference

U. Zucchini, E. Albizatti and U. Gianni, J. Organomet. Chem., 1971, 26, 357.

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