Electrochemical and IR/UV−Vis Spectroelectrochemical Studies of fac-[Mn(X)(CO)₃(iPr-DAB)]ⁿ (n = 0, X = Br, Me, Bz; n = +1, X = THF, MeCN, nPrCN, P(OMe)₃; iPr-DAB = 1,4-Diisopropyl-1,4-diaza-1,3-butadiene) at Variable Temperatures:  Relation between Electrochemical and Photochemical Generation of [Mn(CO)₃(α-diimine)]^-

Abstract

Electrochemical and IR/UV-Vis Spectroelectrochemical Studies of fax-[MnX)(CO)3(iPr-DABGeneral rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The title complexes [Mn(X)(CO) 3 (iPr-DAB)] n (n ) 0, X ) Br; n ) +1, X ) donor solvent) undergo a two-electron reduction according to an ECE sequence. The chemical step (C) involves prompt dissociation of the X ligand from the primary one-electron reduction product, followed by instantaneous one-electron reduction of the five-coordinate transient [Mn(CO) 3 -(iPr-DAB)] • producing the anion [Mn(CO) 3 (iPr-DAB)] -. The latter complex remains rather stable at T < 190 K, whereas at higher temperatures it undergoes an electron-transfer reaction with the parent complexes producing the dimer [Mn(CO) 3 (iPr-DAB)] 2 (the second C step in the overall ECEC sequence). The rate of this reaction decreases in the order THF • , is probably only a minor alternative route. In the presence of excess P(OMe) 3 , the principal oxidation product is the cation [Mn{P(OMe) 3 }(CO) 3 (iPr-DAB)] + . The fivecoordinate anions [Mn(CO) 3 (R-diimine)] -can be regarded as strongly π-delocalized complexes with the negative charge equally distributed over the R-diimine and CO ligands. The intriguing mechanism of their photochemical formation from fac-[Mn(Br)(CO) 3 (R-diimine)] at low temperatures has been rectified on the basis of this (spectro)electrochemical study. Download date: 13 May 2018 Electrochemical and IR/UV-Vis Spectroelectrochemical Studies of fac-[Mn(X)(CO)

Electrocatalytic Reduction of CO2 Using the Complexes [Re(bpy)(CO)3L]n (n = +1, L = P(OEt)3, CH3CN; n = 0, L = Cl-, Otf-; bpy = 2,2‘-Bipyridine; Otf- = CF3SO3) as Catalyst Precursors: Infrared Spectroelectrochemical Investigation

“…This intriguing reduction pathway appears to be a characteristic property of the complexes [Mn(R-diimine)(CO) 3 -(halide)] with basic R-diimine ligands, as it was also observed for the related compound [Mn(iPr-DAB)-(CO) 3 Br] (iPr-DAB ) N,N′-diisopropyl-1,4-diaza-1,3-butadiene). 32 On the other hand, the reason for the absence of the 2e catalytic route in the case of [Mn(bpy)(CO) 3 Cl] seems to be different. Recent studies of bonding properties of the anions [M(iPr-DAB)(CO) 3 ] -(M ) Mn, Re), 32,33 which can also be extended for [M(bpy)(CO) 3 ] -(M ) Mn, Re), have revealed that the electron density on the fivecoordinate metal center significantly increases in the order Re < Mn, i.e.…”

“…32 On the other hand, the reason for the absence of the 2e catalytic route in the case of [Mn(bpy)(CO) 3 Cl] seems to be different. Recent studies of bonding properties of the anions [M(iPr-DAB)(CO) 3 ] -(M ) Mn, Re), 32,33 which can also be extended for [M(bpy)(CO) 3 ] -(M ) Mn, Re), have revealed that the electron density on the fivecoordinate metal center significantly increases in the order Re < Mn, i.e. upon proceeding from 5d to 3d transition metals, respectively.…”

“…This remarkable difference between the Re and Mn centers can be explained by considering a decreasing diffusion character of their frontier d π orbitals in the same order, which are involved in the π-bonding with the formally doubly-reduced R-diimine ligand. 32,33 The better matching of the d π orbitals with the lowest π * orbital of the reduced R-diimine in the same order then results in a stronger π-back-bonding from the reduced R-diimine toward the metal center. The stronger the delocalized π-bonding over the M(R-diimine) chelate ring, the higher is the electron density on the metal center and the more stable is its five-coordinate geometry.…”

“…In this respect [Re(bpy)(CO) 3 ] -differs significantly from [Mn(CO) 3 (bpy)] -and related Mn complexes, which remain always five-coordinate due to an extremely strongly delocalized π-bonding in the {Mn(bpy)} -metallacycle. 32,33 …”

Heterosite Effects in Novel Heteronuclear Clusters [Os2Ru(CO)11(PPh3)] and [Os2Ru(CO)10(2‐acetylpyridine‐N‐isopropylimine)]

“…Thus, while the unsaturated radicals [Re(CO) 3 (α-diimine)]· form at room temperature fairly stable 18e paramagnetic species [Re(CO) 3 -(α-diimine)(Sv)]· (Sv = MeCN, PrCN), [56][57][58] analogous radicals were not observed for [Mn(CO) 3 (α-diimine)]·. [59] Redox Behaviour of [Os 2 Ru(CO) 10 …”