Schwartz's reagent is the common name for the organozirconium compound with the formula (C5H5)2ZrHCl, sometimes called zirconocene hydrochloride or zirconocene chloride hydride, and is named after Jeffrey Schwartz, a chemistry professor at Princeton University.
[2] It can be purchased or readily prepared by reduction of zirconocene dichloride with lithium aluminium hydride: This reaction also affords (C5H5)2ZrH2, which is treated with methylene chloride to give Schwartz's reagent [3] An alternative procedure that generated Schwartz's reagent from dihydride has also been reported.
[19][20] When treated with one equivalent of Cp2ZrClH, diphenylacetylene gives the corresponding alkenylzirconium as a mixture of cis and trans isomers.
With two equivalents of hydride, the endproduct was a mixture of erythro and threo zircono alkanes: In 1974 Hart and Schwartz reported that the organozirconium intermediates react with electrophiles such as hydrochloric acid, bromine and acid chlorides to give the corresponding alkane, bromoalkanes, and ketones:[21] The corresponding organoboron and organoaluminum compounds were already known, but these are air-sensitive and/or pyrophoric whereas organozirconium compounds are not.
The rate of addition to unsaturated carbon-carbon bonds is terminal alkyne > terminal alkene ≈ internal alkyne > disubstituted alkene [29] Acyl complexes can be generated by insertion of CO into the C–Zr bond resulting from hydrozirconation.