104350-80-3Relevant academic research and scientific papers
Electron transfer versus nucleophilic pathways in the ion-pair annihilation of organoborate anions by carbonylmanganese(I) cations
Zhu, Dunming,Kochi, Jay K.
, p. 295 - 303 (2007/10/03)
Substituted carbonylmanganese cations [Mn(CO)5L]+, where L = py, PPh3 and PPh2Me, readily react with various organoborate anions (tetramethylborate, methyltriphenylborate and tetraphenylborate) in THF solution to afford a mixture of dimanganese carbonyls, hydridomanganese carbonyls and alkylmanganese carbonyls. The formation of the dimanganese carbonyl dimers as well as the hydridomanganese carbonyls suggests the involvement of 19-electron carbonylmanganese radicals that stem from an initial electron transfer. On the other hand, the acetonitrile-substituted analogue [Mn(CO)5(CH3CN)]+ reacts with the same borate anions to afford the alkylated RMn(CO)5, where R = CH3 and C6H5, as the sole carbonylmanganese product. As such, this alkylative annihilation is best formulated as a direct attack on the carbonyl carbon by the borate nucleophile. The two different pathways can be understood in terms of the balance between the electrophilicity of the carbonyl ligand and the electron affinity of the carbonylmanganese cation.
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.
