Stryker's reagent ( PPh₃)CuHsub>6), also known as the Osborn complex, is a hexameric copper hydride ligated with

triphenylphosphine Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists a ...

. It is a brick red,

air-sensitive Air sensitivity is a term used, particularly in chemistry, to denote the reactivity of chemical compounds with some constituent of air. Most often, reactions occur with atmospheric oxygen (O2) or water vapor (H2O), although reactions with the other ...

solid. Stryker's reagent is a mildly hydridic reagent, used in

homogeneous catalysis In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysis ...

of conjugate reduction reactions of enones, enoates, and related substrates.

Preparation and structure

The compound is prepared by

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a Catalysis, catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or S ...

of copper(I) ''tert''-butoxide, generated in situ from

copper(I) chloride Copper(I) chloride, commonly called cuprous chloride, is the lower chloride of copper, with the formula CuCl. The substance is a white solid sparingly soluble in water, but very soluble in concentrated hydrochloric acid. Impure samples appear gre ...

and sodium ''tert''-butoxide. Other more convenient methods have been developed since its discovery. In terms of its structure, the compound is an octahedral cluster of Cu(PPh₃) centres that are bonded by Cu---Cu and Cu---H interactions. Originally six of the eight faces were thought to be capped by hydride ligands. This structural assignment was revised in 2014; the hydrides are now best described as edge bridging rather than face bridging.

Applications in organic synthesis

The compound can effect regioselective conjugate reductions of various carbonyl derivatives including unsaturated aldehydes, ketones, and esters. This reagent was assigned as the "Reagent of the year" in 1991 for its functional group tolerance, high overall efficiency, and mild reaction conditions in the reduction reactions. Stryker's reagent is used in a catalytic amount where it is regenerated in the reaction ''in situ'' using a stoichiometric hydride source, often being molecular hydrogen or

silane Silane is an inorganic compound with chemical formula, . It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Sila ...

s. If stored under an inert atmosphere (e.g. argon, nitrogen) it has indefinite shelf life. Brief exposure to the oxygen does not destroy its activity significantly, although solvents used with Stryker's reagent should be rigorously degassed.

Modifications to Stryker's reagent

Ligand-modified versions of Stryker's reagent have been reported. By changing the ligand to e.g. P(O-iPr)₃ the selectivity can be improved significantly. In addition, Lipshutz et al., have shown that the addition of a bidentate, achiral bis-phosphine ligand on the Cu center can lead to substrate-to-ligand ratios typically on the order of 1000−10000:1 can be used to afford products in high yields.

References

{{Commons category Copper complexes Triphenylphosphine complexes Metal hydrides Reducing agents