Electron Transfer and Hydride Transfer Reactions of Copper Hydrides

Copper hydrides such as [Ph₃PCuH]₆ (Stryker’s Reagent) are textbook reagents in organic chemistry for the selective hydrogenation of α,β-unsaturated carbonyl compounds. Despite their widespread use both stoichiometrically and catalytically, there are many important questions about polynuclear copper hydrides that have not been answered. I have investigated the electron transfer chemistry of [Ph₃PCuH]₆ and related copper hydrides. Copper hydrides (E₁/₂ = –1.0 to –1.2 V vs FcH/FcH⁺) are good one-electron reducing agents. Stopped-flow techniques have allowed the detection of electron transfer intermediates in copper hydride reactions. The fate of the copper containing products after electron transfer or hydride transfer reactions has been investigated. An unusual cationic copper hydride, [(Ph₃P)₇Cu₇H₆]⁺ was found to be the major product of these reactions. Methods of converting this species back to [Ph₃PCuH]₆ have been investigated. The chemistry of this cationic species plays an important role in catalytic use of copper hydrides.