title: Activation of the manganese(I) tricarbonyl core by selective variation of bidentate ligands (L,L'-Bid = N,N' and N,O donor atom sets) in fac-[Mn(CO)3(L,L'-Bid)(CH3OH)](n) complexes.
abstract: A range of fac-[Mn(CO)3(L,L'-Bid)(H2O)](n) (L,L'-Bid = neutral or monoanionic bidentate ligands with varied L,L' donor atoms, N,N' and N,O, 1,10-phenanthroline, 2,2'-bipyridine, 2-picolinate, 2,4-quinolinate; n = 0, +1) has been synthesized and the methanol substitution has been investigated for the first time. The complexes were characterized by UV/vis, IR and NMR spectroscopy and X-ray crystallographic studies of the compounds fac-[Mn(CO)3(Bipy)(H2O)][CF3SO3] () and fac-[Mn(CO)3(Phen)(H2O)][CF3SO3] () are reported. A two order-of-magnitude of activation for the methanol substitution is induced as manifested by the second order rate constants with (N,N'-Bid) < (N,O-Bid). Forward and reverse rate and stability constants from slow and stopped-flow UV/vis measurements (k1, M(-1) s(-1); k-1, s(-1); K1, M(-1)) for pyridine as entering nucleophile are as follows: fac-[Mn(CO)3(Phen)(CH3OH)](+) (2.39 ± 5) × 10(-3), (1.5 ± 0.3) × 10(-5), 159 ± 32; fac-[Mn(CO)3(2,4-QuinH)(CH3OH)] (4.5 ± 0.2), (4 ± 1) × 10(-2), 113 ± 29. Activation parameters (ΔH, kJ mol(-1); ΔS, J K(-1) mol(-1)) from Eyring plots for entering nucleophiles as indicated are as follows: fac-[Mn(CO)3(Phen)(CH3OH)](+) (bromide ions) 66.7 ± 0.6, -27 ± 2; (pyridine) 80 ± 3, -25 ± 11; fac-[Mn(CO)3(Pico)(CH3OH)] (bromide ions) 68 ± 2, -24 ± 5. A dissociative interchange mechanism is proposed.
authors.affiliation: Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa. visserhg@ufs.ac.za.
authors.forename: T N
authors.initials: TN
authors.lastname: Twala
authors.forename: M
authors.initials: M
authors.lastname: Schutte-Smith
authors.forename: A
authors.initials: A
authors.lastname: Roodt
authors.forename: H G
authors.initials: HG
authors.lastname: Visser
mesh_terms: D018360:Crystallography, X-Ray; D008024:Ligands; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000737:chemistry* / Q000378:metabolism; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008024:Ligands; D020030:Nitric Oxide Donors; D009942:Organometallic Compounds; D008345:Manganese