The effect of coordination of alkanes, Xe and CO2 (η1-OCO) on changes in spin state and reactivity in organometallic chemistry: a combined experimental and theoretical study of the photochemistry of CpMn(CO)3. (14th October 2019)

• Record Type: Journal Article
• Authors: Wu, Xue; Liu, Zhen; Murphy, Thomas S.; Sun, Xue Z.; Hanson-Heine, Magnus W. D.; Towrie, Michael; Harvey, Jeremy N.; George, Michael W.
• Is Part Of: Faraday discussions. Volume 220(2020)
• Page Start: 86
• Page End: 104
• Publication Date: 2019-10-14
• Subjects: Chemistry -- Periodicals; Metallurgy -- Periodicals; Electrochemistry -- Periodicals; 540
• DOI: 10.1039/c9fd00067d
• Languages: English
• ISSNs: 1359-6640

Abstract

Abstract : A study is presented of ligand addition reactions of the fragment 3 CpMn(CO)2 formed upon photolysis of CpMn(CO)3 . Abstract : A combined experimental and theoretical study is presented of several ligand addition reactions of the triplet fragment 3 CpMn(CO)2 formed upon photolysis of CpMn(CO)3 . Experimental data are provided for reactions in n -heptane and perfluoromethylcyclohexane (PFMCH), as well as in PFMCH doped with C2 H6, Xe and CO2 . In PFMCH we find that the conversion of 3 CpMn(CO)2 to 1 CpMn(CO)2 (PFMCH) is much slower ( τ = 18 (±3) ns) than the corresponding reactions in conventional alkanes ( τ = 111 (±10) ps). We measure the effect of the coordination ability by doping PFMCH with alkane, Xe and CO2 ; these doped ligands form the corresponding singlet adducts with significantly variable formation rates. The reactivity as measured by the addition timescale follows the order 1 CpMn(CO)2 (C5 H10 ) ( τ = 270 (±10) ps) > 1 CpMn(CO)2 Xe ( τ = 3.9 (±0.4) ns) ∼ 1 CpMn(CO)2 (CO2 ) ( τ = 4.7 (±0.5) ns) > 1 CpMn(CO)2 (C7 F14 ) ( τ = 18 (±3) ns). Electronic structure theory calculations of the singlet and triplet potential energy surfaces and of their intersections, together with non-adiabatic statistical rate theory, reproduce the observed rates semi-quantitatively. It is shown that triplet adducts of the ligand and 3 CpMn(CO)2 play a role in the kinetics, and account for the variable timescales observed experimentally.