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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.

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An explanation is given for the enhancement of Raman intensity of the (symmetrical) stretching mode of the carbonyl(s) cis with respect to L when complexes of the type (0 )4_ . [ ( )3] (M = Cr, Mo, W; x = 0, 1; L = 1,4-diazabutadiene, pyridine-2-carbaldehyde imine, 2,2'-bipyridine, 1,10-phenanthroline) are excited within the lowest MLCT band. The influence of the central metal atom, of the ligand L, and of the co-ligand is discussed in detail. Irradiation within the lowest MLCT band also causes photosubstitution of a cis carbonyl ligand with quantum yields varying from 10"1 2345 to 10"2. A relationship appears to exist between these photosubstitution quantum yields and the resonance enhancement of the carbonyl stretching mode.

Complexes of the type [Ru(X)(R)(CO)2(L)] (X = halide, CF3S03; R = alkyl; L = N,N '-diisopropyl-1,4-diaza-1,3-butadiene, pyridine-2-carbaldehyde TV-isopropylimine, 2,2,-bipyridine) experience significant influences of X and R on the energies and relative intensities of their lowest-energy electronic transitions. The halide complexes show two absorption bands in the visible region, which are assigned to two sets of charge transfer transitions from mixed metal-halide orbitals. Variation of the halide from Cl to I gives rise to a change in character of the lowestenergy band from MLCT to XLCT, as evidenced by resonance Raman spectra. These spectra show enhancement of Raman intensity for both ys(CN) and vs(CO) in the case of the Cl complex, but only for vs(CN) for the corresponding I complex. Variation of the alkyl ligand from Me to iPr leads to a shift of both absorption bands to lower energy with a concomitant change of their relative intensities. The latter effect is again ascribed to a change of charge transfer character of the electronic transitions.

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