Electrooxidation of metal cabonyl anions. Formation and reactivity of 17-electron manganese(0) radicals

Reduction of [Re(X)(CO)3(R‘-DAB)] (X = Otf-, Br-; DAB = Diazabutadiene; R‘ = iPr, pTol, pAn) and [Re(R)(CO)3(iPr-DAB)] (R = Me, Et, Bz) Complexes: A Comparative (Spectro)electrochemical Study at Variable Temperatures

“…The π ML HOMO of the [Re(CO) 3 (pTol-DAB)] -and [Re(CO) 3 (pAn-DAB)] -anions should therefore possess more R′-DAB character, the bonding situation resembling more that of the [Mn(CO) 3 (DBCat)] -anion (Scheme 3). Indeed, the average CO force constant of the latter anions increases with regard to that of [Re(CO) 3 (iPr-DAB)] -by 38 N m -1 (Table 2) 62 In fact, definition of nonintegral oxidation states of M would be necessary to reflect the higher electron density on the Mn center with respect to 14. Such an attempt is however meaningless in this case where the strong delocalization of the π-electron density over the M(iPr-DAB) chelate ring demands us to abandon the localized-valence concept.…”

Kinetic Destabilization of Metal–Metal Single Bonds: Isolation of a Pentacoordinate Manganese(0) Monoradical

“…Accordingly,this instability has necessitated that [Mn(CO) 5 ]becharacterized and studied under cryogenic conditions, [7][8][9][10] or at higher temperatures by using either ultrafast spectroscopic [11] or nitrosoarene spin-trapping techniques. [15][16][17][18] However,such derivatized [Mn(CO) 5Àn L n ]c omplexes have remained susceptible to facile dimerization/redistributionp rocesses when concentrated and isolable examples remain unknown. [15][16][17][18] However,such derivatized [Mn(CO) 5Àn L n ]c omplexes have remained susceptible to facile dimerization/redistributionp rocesses when concentrated and isolable examples remain unknown.…”

“…[12][13][14] Importantly,efforts to prepare stabilized variants of [Mn(CO) 5 ]bysubstitution of one or more CO ligands with more encumbering ligands such as phosphines (PR 3 )h ave been shown to extend the lifetime of [MnL 5 ]-type radicals to the order of hours in solution. [16,17] Given the challenges faced in exploring the properties of [Mn(CO) 5 ]a nd related zerovalent [MnL 5 ]c omplexes,i ti s notable that they continue to be of significant interest as transient species.F or example,[ MnL 5 ]m onoradicals of the type [Mn(CO) 3 (bipy)] (bipy = 2,2'-bipyridine) are now recognized as the key intermediates on the pathway to catalyst deactivation (by MnÀMn bond formation) in electrocatalytic CO 2 reduction. Additionally, investigations into the one-electron activation chemistry of [Mn(CO) 5Àn L n ]s pecies with small molecule substrates are limited.…”

“…[12][13][14] Importantly,efforts to prepare stabilized variants of [Mn(CO) 5 ]bysubstitution of one or more CO ligands with more encumbering ligands such as phosphines (PR 3 )h ave been shown to extend the lifetime of [MnL 5 ]-type radicals to the order of hours in solution. [15][16][17][18] However,such derivatized [Mn(CO) 5Àn L n ]c omplexes have remained susceptible to facile dimerization/redistributionp rocesses when concentrated and isolable examples remain unknown. Additionally, investigations into the one-electron activation chemistry of [Mn(CO) 5Àn L n ]s pecies with small molecule substrates are limited.…”

Kinetic Destabilization of Metal–Metal Single Bonds: Isolation of a Pentacoordinate Manganese(0) Monoradical

“…Additionally, investigations into the one-electron activation chemistry of [Mn(CO) 5Àn L n ]s pecies with small molecule substrates are limited. [16,17] Given the challenges faced in exploring the properties of [Mn (CO) ) 2 ]( Ar Dipp2 = 2,6-(2,6-(iPr) 2 C 6 H 3 ) 2 C 6 H 3 )f eaturing two m-terphenyl isocyanide ligands. [22,23] Thesterically encumbering nature of these isocyanidel igands effectively prevents the formation of MnÀMn single bonds,thus rendering this 17e…”