A perspective on nanocluster catalysis: polyoxoanion and ( n-C 4H 9) 4N + stabilized Ir(0) ∼300 nanocluster ‘soluble heterogeneous catalysts’

Abstract

Following a review of the background terms, definitions and key literature necessary to understand the rapidly developing and promising area of nanocluster catalysis, the recent report of polyoxoanion-stabilized Ir(0) ∼190–450 (hereafter Ir(0) ∼300) nanocluster catalysts is reviewed. Specifically, the experimental observations relating to three principle questions concerning these soluble-oxide-supported, Ir(0) ∼300 nanocluster catalysts are reviewed: (i) their catalytic activity (in a prototypical structure-insensitive reaction, cyclohexene hydrogenation); (ii) their lifetime; and (iii) their thermal stability, each in direct comparison to three established heterogeneous Ir(0) catalysts [7.9% dispersed 1% Ir(0) γ- Al 2O 3 , Exxon's 80% dispersed 1% Ir η- Al 2O 3 , and a low surface area Ir(0) precipitate]. In addition, observations of W VI to W V· reduction of the polyoxoanion by Ir(0) ∼300 and H 2 are summarized, results which provide the first soluble-oxide version of the well known spillover of hydrogen in heterogeneous catalysis.