title: Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel(II) complex containing proton relays in the second and outer coordination spheres.
abstract: A nickel bis(diphosphine) complex containing proton relays in the second and outer coordination spheres, Ni(P(Cy)2N((CH2)2OMe))2, (P(Cy)2N((CH2)2OMe) = 1,5-di(methoxyethyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni(II) complex results in rapid formation of three isomers of the doubly protonated Ni(0) complex, [Ni(P(Cy)2N((CH2)2OMe)2H)2](2+). The three isomers show fast interconversion at 40 °C, unique to this complex in this class of catalysts. Under conditions of 1.0 atm H2 using H2O as a base, catalytic oxidation proceeds at a turnover frequency of 5 s(-1) and an overpotential of 720 mV, as determined from the potential at half of the catalytic current. Compared to the previously reported Ni(P(Cy)2N(Bn))2 complex, the new complex operates at a faster rate and at a lower overpotential.
authors.affiliation: Center for Molecular Electrocatalysis, Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland 99352, Washington, USA. monte.helm@pnnl.gov.
authors.forename: Parthapratim
authors.initials: P
authors.lastname: Das
authors.forename: Ming-Hsun
authors.initials: MH
authors.lastname: Ho
authors.forename: Molly
authors.initials: M
authors.lastname: O'Hagan
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Shaw
authors.forename: R Morris
authors.initials: RM
authors.lastname: Bullock
authors.forename: Simone
authors.initials: S
authors.lastname: Raugei
authors.forename: Monte L
authors.initials: ML
authors.lastname: Helm