15444-75-4Relevant academic research and scientific papers
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.
Manganese(0) radicals and the reduction of cationic carbonyl complexes: Selectivity in the ligand dissociation from 19-electron species
Kuchynka,Amatore,Kochi
, p. 4087 - 4097 (2008/10/08)
Products and stoichiometry for the cathodic reduction of the series of carbonylmanganese(I) cations Mn(CO)5L+, where L - CO, MeCN, pyridine, and various phosphines, derive from 1-electron transfer to generate the 19-electron radicals Mn(CO)5L? as reactive intermediates. The CO derivative Mn(CO)6+ affords mainly the anionic Mn(CO)5- by the facile ligand dissociation of Mn(CO)6? to the 17-electron radical Mn(CO)5? followed by reduction. The acetonitrile and pyridine derivatives Mn(CO)5NCMe+ and Mn(CO)5py+ produce high yields of the dimer Mn2(CO)10 by an unusual and highly selective heterolytic coupling of Mn(CO)5- and the reactant cation. Structural factors involved in the conversion of 19-electron radicals to their 17-electron counterparts are examined in the reduction of the graded series of phosphine derivatives Mn(CO)5P+, where P = triaryl- and trialkylphosphines. The formation of the hydridomanganese complexes HMn(CO)4P is ascribed to hydrogen atom transfer to the 19-electron radicals Mn(CO)5P? followed by extrusion of CO. The lability of carbonylmanganese radicals is underscored by rapid ligand substitution to afford the bis(phosphine) byproduct HMn(CO)3P2.
