title: Electrochemical Properties and CO2-Reduction Ability of m-Terphenyl Isocyanide Supported Manganese Tricarbonyl Complexes.
abstract: To circumvent complications with redox-active ligands commonly encountered in the study of manganese electrocatalysts for CO2reduction, we have studied the electrochemistry of the manganese mixed carbonyl/isocyanide complexes XMn(CO)3(CNArDipp2)2(X = counteranion), to evaluate the pairing effects of the counteranion and their influence over the potential necessary for metal-based reduction. The complexes described herein have been shown to act as functional analogues to the known homoleptic carbonyl manganese complexes [Mn(CO)5]n(n = 1-, 0, 1+). The m-terphenyl isocyanide ligand CNArDipp2improves the kinetic stability of the resulting mixed carbonyl/isocyanide systems, such that conversion among all three oxidation states is easily effected by chemical reagents. Here, we have utilized an electrochemical study to fully understand the redox chemistry of this system and its ability to facilitate CO2reduction and to provide comparison to known manganese-based CO2electrocatalysts. Two complexes, BrMn(CO)3(CNArDipp2)2and [Mn(THF)(CO)3(CNArDipp2)2]OTf, have been studied using infrared spectroelectrochemistry (IR-SEC) to spectroscopically characterize the redox states of these complexes during the course of electrochemical reactions. A striking difference in the necessary potential leading to the first one-electron reduction has been found for the halide and triflate species, respectively. Complete selectivity for the formation of CO and CO32-is observed in the reactivity of [Mn(CO)3(CNArDipp2)2]-with CO2, which is deduced via the trapping and incorporation of liberated CO into the zerovalent species Mn(CO)3(CNArDipp2)2to form the dimers Mn2(CO)7(CNArDipp2)3and Mn2(CO)8(CNArDipp2)2.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093, United States.
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Agnew
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093, United States.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Sampson
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093, United States.
authors.forename: Curtis E
authors.initials: CE
authors.lastname: Moore
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093, United States.
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093, United States.
authors.forename: Clifford P
authors.initials: CP
authors.lastname: Kubiak
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093, United States.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Figueroa