Mechanism of Electroless Copper Deposition from [CuIIEDTA]²– Complexes Using Aldehyde-Based Reductants

In this article, we present a mechanism for electroless copper deposition from alkaline solutions containing [Cu II EDTA] 2– (aq) and hydrolyzed aldehydes. The mechanism is based on quantum chemical calculations of the activation energies and reversible electron-transfer potentials. Low-coordinated, electroless-deposited surface Cu atoms are found to activate H abstraction from the C–H bond of the aldehyde group, putting H on the surface and releasing a highly reducing electron in the process; this electron reduces [Cu II EDTA] 2– (aq) to [Cu I EDTA] 3– (aq) . [Cu I EDTA] 3– (aq) is subsequently reduced to Cu 0 (ads) by a second electron generated by the same process, releasing EDTA 4– (aq) . Calculated reversible potentials for the reduction steps aid in interpretation of the catalytic behavior observed in experimental polarization curves.