568587-17-7Relevant academic research and scientific papers
Electronic properties of 4,4′,5,5′-tetramethyl-2,2′-biphosphinine (tmbp) in the redox series fac-[Mn(Br)(Co)3(tmbp)], [Mn(Co)3(tmbp)]2, and [Mn(Co)3(tmbp)]-: Crystallographic, spectroelectrochemical, and DFT computational study
Hartl, Frantisek,Mahabiersing, Taasje,Le Floch, Pascal,Mathey, Francois,Ricard, Louis,Rosa, Patrick,Zalis, Stanislav
, p. 4442 - 4455 (2003)
Stepwise electrochemical reduction of the complex fac-[Mn(Br)(CO)3(tmbp)] (tmbp = 4,4′,5,5′-tetramethyl-2,2′-biphosphinine) produces the dimer [Mn(CO)3(tmbp)]2 and the five-coordinate anion [Mn(CO)3(tmbp)]-. All three members of the redox series have been characterized by single-crystal X-ray diffraction. The crystallographic data provide valuable insight into the localization of the added electrons on the (carbonyl)manganese and tmbp centers. In particular, the formulation of the two-electron-reduced anion as [Mn0(CO)3(tmbp-)]- also agrees with the analysis of its IR v(CO) wavenumbers and with the results of density functional theoretical (DFT) MO calculations on this compound. The strongly delocalized π-bonding in the anion stabilizes its five-coordinate geometry and results in the appearance of several mixed Mn-to-tmbp charge-transfer/IL(tmbp) transitions in the near-UV-vis spectral region. A thorough voltammetric and UV-vis/IR spectroelectrochemical study of the reduction path provided evidence for a direct formation of [Mn(CO)3(tmbp)]- via a two-electron ECE mechanism involving the [Mn(CO)3(tmbp)]., radical transient. At ambient temperature [Mn(CO)3(tmbp)]- reacts rapidly with nonreduced fac-[Mn(Br)(CO)3(tmbp)] to produce [Mn(CO)3(tmbp)]2. Comparison with the analogous 2,2′-bipyridine complexes has revealed striking similarity in the bonding properties and reactivity, despite the stronger π-acceptor character of the tmbp ligand.
