Catalysis by polyoxometalate-supported atomically-dispersed iridium(I). The synthesis, characterization and kinetic and mechanistic studies of ((n-butyl)(4)nitrogen)(5)sodium(3)((1,5-carbonyl deuterium)iridium.phosphorous(2)tungsten(15)niobium(3)oxygen(6

The reaction of (Ir(1,5-COD)(CH{dollar}sb3{dollar}CN){dollar}sb2{dollar}) BF{dollar}sb4{dollar} with {dollar}lbrack (n{dollar}-{dollar}rm Csb4Hsb9)sb4Nrbrack sb9Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}{dollar} leads to the novel compound {dollar}lbrack (n{dollar}-{dollar}rm Csb4Hsb9)sb4Nrbracksb5Nasb3lbrack (1,5{dollar}-{dollar}rm COD)Ircdot Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}rbrack{dollar}, 1, in which the organometallic group is regiospecifically supported on the polyoxometalate. The supported complex 1 has been characterized by {dollar}sp{lcub}31{rcub}{dollar}P NMR, {dollar}sp{lcub}183{rcub}{dollar}W NMR, {dollar}sp1{dollar}H NMR, {dollar}sp{lcub}13{rcub}{dollar}C NMR, IR, elemental analysis and solution molecular-weight measurements. These data show that 1 is also unusual in that it offers the first example of non-aqueous ion-pairing in polyoxometalate chemistry; this complex is also only the fourth example in the literature of a stereochemically rigid pentacoordinate d{dollar}sp8{dollar} organometallic complex.; The supported-organometallic complex 1 undergoes a stoichiometric reaction with CO to yield {dollar}lbrack (n{dollar}-{dollar} rm Csb4Hsb9)sb4Nrbracksb5Nasb3lbrack (OC)sb2Ircdot Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}rbrack{dollar}, 2. Compared to 1, 2 is composed of multiple isomers that interconvert with changing temperature. At increased temperature 2 undergoes a thermal decomposition to give Ir(0) and an undetermined polyoxometalate product by a pathway that has been rationalized as a polyoxometalate-assisted reaction. The catalyst precursor 1 also undergoes stoichiometric reactions with 3.0 equiv H{dollar}sb2{dollar} to yield 1.0 equiv cyclooctane and {dollar}{lcub}lbrack (n{dollar}-{dollar} rm Csb4Hsb9)sb4Nrbracksb5Nasb3lbrack (H)sb2Ircdot Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}rbrack{rcub}sb2{dollar}, 3, at 22{dollar}spcirc{dollar}C and with 2.0 equiv H{dollar}sb2{dollar} to yield {dollar}{lcub}lbrack (n{dollar}-{dollar} rm Csb4Hsb9)sb4Hrbracksb5Nasb3lbrack (Csb8Hsb{lcub}15{rcub})HIrcdot Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}rbrack{rcub}sb5{dollar}, 4, at 0{dollar}spcirc{dollar}C.; {dollar}lbrack (n{dollar}-{dollar} rm Csb4Hsb9)sb4Nrbracksb5Nasb3lbrack (1,5{dollar}-{dollar}rm COD)Ircdot Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}rbrack{dollar}, 1, under 40 psig H{dollar}sb2{dollar}, and in acetone yields an active, soluble and long-lived hydrogenation catalyst without the production of insoluble Ir(0)--the first bona fide example of a polyoxoanion-supported catalyst. Several control experiments are described documenting the ability of the {dollar}rm Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}sp{lcub}9-{rcub}{dollar} polyoxometalate in 1 to completely inhibit over-reduction to Ir(0) in acetone, thereby establishing the novelty of 1 in comparison to all previously examined transition-metal polyoxometalate combinations. Detailed kinetic and mechanistic studies, as well as traditional "heterogeneous vs. homogeneous" tests, are also reported with an emphasis on experiments designed to probe whether the polyoxometalate-to-iridium bonding is retained in the active catalyst derived from 1. Those studies provide strong against the participation of polyoxometalate-free Ir(0) colloids.; Numerical integration of hydrogen loss data by a seven-step mechanistic model demonstrates that the activation of 1 to the form the active catalyst is auto-catalytic and that the catalysis derived from 1 proceeds by the so-called hydrogen pathway. Ex post facto calculations confirm that the resting state of the catalyst is the alkyl-hydrido-iridium species, {dollar}lbrack (n{dollar}-{dollar} rm Csb4Hsb9)sb4Nrbracksb5Nasb3 lbrack (Csb6Hsb{lcub}11{rcub})HIrcdot Psb2Wsb{lcub}15{rcub}Nbsb3Osb{lcub}62{rcub}rbrack{dollar}. Indeed, if the reaction is run under deuterium, a {dollar}sp2...