51371-61-0Relevant articles and documents
Kinetics and Mechanism of CO Substitution of M2(CO)10 (M = Mn, Re) with an Entering Ligand (PPh3 or Py) in the Presence of an O-Atom Transfer Reagent (Me3NO or (CH3OC6H4)2TeO)
Gao, Yi-Ci,Shen, Jian-Kun,Peng, Li,Shi, Qi-Zhen,Basolo, Fred
, p. 464 - 469 (2007/10/02)
Detailed kinetic data are reported for the CO substitution of M2(CO)10 ( M = Mn, Re) with PPh3 or Py in the presence of Me3NO or (CH3OC6H4)TeO as an O atom transfer reagent in CHCl3 solvent.The rates of reactions are first order in concentrations of M2(CO
Formation of metal-metal bonds by ion-pair annihilation. Dimanganese carbonyls from manganate(-I) anions and manganese(I) cations
Lee,Kuchynka,Kochi
, p. 1886 - 1897 (2008/10/08)
The coupling of the anionic Mn(CO)5- and the cationic Mn(CO)6+ occurs upon mixing to afford the dimeric Mn2(CO)10 in essentially quantitative yields. Dimanganese decacarbonyl is formed with equal facility from the coupling of Mn(CO)5- with Mn(CO)5(py)+ and Mn(CO)5(NCMe)+. By way of contrast, the annihilation of Mn(CO)4PPh3- with Mn(CO)6+ yields a pair of homo dimers Mn2(CO)10 and Mn2(CO)8(PPh3)2 together with the cross dimer Mn2(CO)9PPh3. Extensive scrambling of the carbonylmanganese moieties also obtains with Mn(CO)4P(OPh)3- and Mn(CO)5PPh3+, as indicated by the production of Mn2(CO)8[P(OPh)3]2, Mn2(CO)8[P(OPh)3](PPh3), and Mn2(CO)8(PPh3)2 in more or less statistical amounts. These diverse Mn-Mn couplings can be accounted for by a generalized formulation (Scheme VI), in which the carbonylmanganese anions Mn(CO)4P- and the cations Mn(CO)5L+ undergo an initial electron transfer to produce Mn(CO)4P? and Mn(CO)5L?, respectively. The behaviors of these 17- and 19-electron radicals coincide with those independently generated in a previous study of the anodic oxidation of Mn(CO)4P- and the cathodic reduction of Mn(CO)5L+, respectively. The facile associative ligand substitution of 17-electron carbonylmanganese radicals by added phosphines provides compelling evidence for the interception of Mn(CO)4P? and its interconversion with 19-electron species in the course of ion-pair annihilation. The reactivity trend for the various ion pairs qualitatively parallels the driving force for electron transfer based on the oxidation and reduction potentials of Mn(CO)4P- and Mn(CO)5L+, respectively, in accord with the radical-pair mechanism in Scheme VI.
Substitution of Mn(CO)5 Is Associative
Herrinton, Thomas R.,Brown, Theodore L.
, p. 5700 - 5703 (2007/10/02)
The substitution of Mn(CO)5 radicals by triphenylphosphine (PPh3) or triphenylarsine (AsPh3) in hexane has been studied by observing the manner in which the competition between CCl4 and PPh3 or between CH2Br2 and AsPh3 is affected by changes in concentrations of the reactants.In both cases the substitution process shows kinetics behavior indicative of an associative process.The second-order rate constants are 1.7 (+/- 0.2) E7 and 6.5 (+/-0.8) E4 M-1 s-1 for PPh3 and AsPh3, respectively, in hexane at 24 deg C.Less extensive measurements provide analogous bimolecular rate constants for substitution by P(n-Bu)3, P(i-Pr)3, and P(O-i-Pr)3 of 1.0 (+/-0.1) E9, 6.7 (+/-0.7) E7, and 3.1 (+/-0.3) E7 M-1 s-1, respectively.There is no evidence in the results for a concurrent dissociative loss of CO from Mn(CO)5.On the basis of the data for AsPh3, which exhibits the smallest associative rate constant, the first-order dissociative rate constant must be less than about 90 s-1.
