The Remarkable Photochemistry of fac-XMn(CO)3(.alpha.-diimine) (X =Halide): Formation of Mn2(CO)6(.alpha.-diimine)2 via the mer Isomer and Photocatalytic Substitution of X- in the Presence of PR3

Abstract

The remarkable photochemistry of fac-XMn(CO)sub3(alpha-diimine) (X=halide). Formation of Mnsub2(CO)sub6(alpha-diimine)sub2 via the mer-isomer and photocatalytic disproportionation in the presence of PRsub3 Stor, G.J.; Morrison, S.L.; Stufkens, D.J.; Oskam, A. Published in: Organometallics DOI:10.1021/om00019a021Link to publication Citation for published version (APA):Stor, G. J., Morrison, S. L., Stufkens, D. J., & Oskam, A. (1994). The remarkable photochemistry of facXMn(CO)sub3(alpha-diimine) (X=halide). Formation of Mnsub2(CO)sub6(alpha-diimine)sub2 via the mer-isomer and photocatalytic disproportionation in the presence of PRsub3. Organometallics, 13, 2641-2650. DOI: 10.1021/om00019a021 General rightsIt 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. This article describes the remarkable photochemistry of complexes fac-XMn(CO)&~-diimine) (X = C1, Br, I) upon irradiation into their lowest-energy CT band. The primary photoprocess is loss of CO, as was established by flash photolysis and low-temperature IR spectroscopy. The CO-loss product reacted thermally and photochemically to give mer-XMn(CO)s(a-diimine), which in turn transformed thermally into thefac isomer at temperatures above 213 K. Irradiation of mer-XMn(CO)&~-diimine) resulted in the formation of the 16-electron radical complexes Mn+(CO)s(a-diimine*-), which were identified at room temperature by ESR spectroscopy and which dimerized to give Mn&O)&-diimine)2 for a-diimine = bpy. At low temperatures these radical complexes formed rather stable adducts Mn+(C0)3(a-diimine0-)(PR3) with PRs (R = nBu, OMe). At room temperature these adducts initiated the catalytic substitution of X-by PR3 in the starting complex fac-XMn(CO)s(a-diimine). The primary photoprocess of facXMn(CO)s(a-diimine) (loss of CO) most likely occurs from the lowest LF state. Contrary to this, irradiation of mer-XMn(CO)s(a-diimine) gives rise to homolysis of the Mn-X bond. This remarkable difference in photochemical behavior of the fuc and mer isomers is discussed.

Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO2 Reduction

“…This behavior is similar to that reported for the symmetric non-aromatic Mn R-DAB (R = alkyl) compounds. 8,30 The formation of a stable bicarbonate complex, either through the coordination to the metal center or via the imino C=N bond 23,37 leads to the need of increased overpotential. From that point of view, the steric hindering (protection) of the metal center/the imino C=N bond in the Mn(IP) complexes is advantageous as it disfavors the Mn Mn dimerization (when comparing MnIMP with MnDIPIMP).…”

“…23 Indeed, it has recently been shown that the use of bipyridines incorporating bulky groups in the 6,6 -positions 24,25 (or, another bulkier heterocyclic ligand 26 ) largely inhibits dimerization in the catalytic cycle. The result is the formation of the stable 5-coordinate anion via the two-electron transfer (ECE) at the first cathodic wave.…”

“…In particular, this change should affect the energy of the LUMO, the reduction potential, and catalytic activity. [23][24][25][26][27][28][29][30][31][32][33] Introducing steric bulk 23,25 to prevent unwanted reactions of the catalytic species, including dimerization as either Mn Mn, 9 or C(imino) C(imino) bound species, 21 whilst at the same time reducing the risk of increased overpotential is a challenging task. Molecular designs that allow for steric and electronic effects to be decoupled are required.…”

Photochemistry of the metal-metal-bonded complexes [(CO)5MnRu(Me)(CO)2(α-diimine)]. Crystal structure of the photoproduct [(CO)4Mn-μ-(σ(N),σ(N′),ν2(CN)-iPr-PyCa)Ru(Me)(CO)2]

“…Irradiation into these transitions gives rise to homolysis of the metal-metal or metal-alkyl bond and/or release of CO [1,8]. Release of CO has been observed only for the complexes [L,M-Mn(CO)3(a-diimine)] [12,13]; this reaction probably occurs from a low-lying LF state, since it was also observed for the corresponding halide complexes [Mn(X)(CO)3(a-diimine) ] [14]. The homolysis reactions, previously studied in detail for the above-mentioned metal-metal-bonded complexes [L,M-M'(CO)3(a-diimine)] [1][2][3][4][5][6], proceeded with very high quantum yields (0.3-0.9).…”

Study of Mechanisms of Light-Induced Dissociation of Ru(dcbpy)(CO)2I2 in Solution down to 20 fs Time Resolution

“…9 Such a mechanism would explain, for instance, formation of the CO back reaction product of mer-MnCl(CO) 3 (R-diimine) after irradiation of the corresponding fac isomer. 14 Upon UV excitation of transition metal carbonyl complexes, a greater amount of energy is deposited into the reacting molecule than is needed to dissociate the metal-CO bond. In the process, part of the excess energy is transformed into translational energy of the dissociating carbonyl group, and the rest is converted into heat via intramolecular vibrational redistribution, which finally is dissipated into the solvent.…”