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Electronic transitions and bonding properties in a series of five-coordinate "16-electron" complexes [Mn(CO)(3)(L-2)](-) (L-2 = chelating redox-active pi-donor ligand)
| hal.structure.identifier | van ‘t Hoff Institute for Molecular Sciences | |
| dc.contributor.author | HARTL, Frantisek | |
| hal.structure.identifier | Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB] | |
| dc.contributor.author | ROSA, Patrick | |
| hal.structure.identifier | Laboratoire Hétéroéléments et Coordination [DCPH] | |
| dc.contributor.author | RICARD, Louis | |
| hal.structure.identifier | Laboratoire Hétéroéléments et Coordination [DCPH] | |
| dc.contributor.author | LE FLOCH, Pascal | |
| hal.structure.identifier | J Heyrovsky Institut of Physical Chemistry [-] | |
| dc.contributor.author | ZALIS, Stanislav | |
| dc.date.issued | 2007 | |
| dc.identifier.issn | 0010-8545 | |
| dc.description.abstractEn | In this article we present for the first time accurate density functional theory (DFT) and time-dependent (TD) DFT data for a series of electronically unsaturated five-coordinate complexes [Mn(CO)(3)(L-2)](-), where L-2 stands for a chelating strong pi-donor ligand represented by catecholate, dithiolate, amidothiolate, reduced alpha-diimine (1,4-dialkyl-1,4-diazabutadiene (R-DAB), 2,2'-bipyridine) and reduced 2,2'-biphosphinine types. The single-crystal X-ray structure of the unusual compound [Na(BPY)][Mn(CO)(3)(BPY)]center dot Et2O and the electronic absorption spectrum of the anion [Mn(CO)(3)(BPY)](-) are new in the literature. The nature of the bidentate ligand determines the bonding in the complexes, which varies between two limiting forms: from completely pi-delocalized diamagnetic {(CO)(3)Mn-L-2}(-) for L-2 = alpha-diimine or biphosphinine, to largely valence-trapped {(CO)(3)Mn-1-L-2(2-)}(-) for L-2(2-) = catecholate, where the formal oxidation states of Mn and L-2 can be assigned. The variable degree of the pi-delocalization in the Mn(L-2) chelate ring is indicated by experimental resonance Raman spectra of [Mn(CO)(3)(L-2)](-) (L-2=3,5-di-tBu-catecholate and iPr-DAB), where accurate assignments of the diagnostically important Raman bands have been aided by vibrational analysis. The L-2 = catecholate type of complexes is known to react with Lewis bases (CO substitution, formation of six-coordinate adducts) while the strongly pi-delocalized complexes are inert. The five-coordinate complexes adopt usually a distorted square pyramidal geometry in the solid state, even though transitions to a trigonal bipyramid are also not rare. The experimental structural data and the corresponding DFT-computed values of bond lengths and angles are in a very good agreement. TD-DFT calculations of electronic absorption spectra of the studied Mn complexes and the strongly pi-delocalized reference compound [Fe(CO)(3)(Me-DAB)] have reproduced qualitatively well the experimental spectra. Analyses of the computed electronic transitions in the visible spectroscopic region show that the lowest-energy absorption band always contains a dominant (in some cases almost exclusive) contribution from a pi(HOMO) -> pi*(LUMO) transition within the MnL2 metallacycle. The character of this optical excitation depends strongly on the composition of the frontier orbitals, varying from a partial L-2 -> Mn charge transfer (LMCT) through a fully delocalized pi(MnL2) -> pi*(MnL2) situation to a mixed (CO)Mn -> L-2 charge transfer (LLCT/MLCT). The latter character is most apparent in the case of the reference complex [Fe(CO)(3)(Me-DAB)]. The higher-lying, usually strongly mixed electronic transitions in the visible absorption region originate in the three lower-lying occupied orbitals, HOMO - 1 to HOMO - 3, with significant metal-d contributions. Assignment of these optical excitations to electronic transitions of a specific type is difficult. A partial LLCT/MLCT character is encountered most frequently. The electronic absorption spectra become more complex when the chelating ligand L-2, such as 2,2'-bipyridine, features two or more closely spaced low-lying empty pi* orbitals. | |
| dc.language.iso | en | |
| dc.publisher | Elsevier | |
| dc.subject.en | Manganese carbonyl | |
| dc.subject.en | pi-donor ligand | |
| dc.subject.en | Electronic delocalization | |
| dc.subject.en | Five-coordinate complex | |
| dc.subject.en | Crystal structure | |
| dc.subject.en | Density functional theory | |
| dc.subject.en | Electronic absorption spectrum | |
| dc.subject.en | Resonance Raman | |
| dc.title.en | Electronic transitions and bonding properties in a series of five-coordinate "16-electron" complexes [Mn(CO)(3)(L-2)](-) (L-2 = chelating redox-active pi-donor ligand) | |
| dc.type | Article de revue | |
| dc.identifier.doi | 10.1016/j.ccr.2006.09.003 | |
| dc.subject.hal | Chimie/Chimie de coordination | |
| bordeaux.journal | Coordination Chemistry Reviews | |
| bordeaux.page | 557-576 | |
| bordeaux.volume | 251 | |
| bordeaux.issue | 3-4 | |
| bordeaux.peerReviewed | oui | |
| hal.identifier | hal-00168514 | |
| hal.version | 1 | |
| hal.popular | non | |
| hal.audience | Internationale | |
| hal.origin.link | https://hal.archives-ouvertes.fr//hal-00168514v1 | |
| bordeaux.COinS | ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Coordination%20Chemistry%20Reviews&rft.date=2007&rft.volume=251&rft.issue=3-4&rft.spage=557-576&rft.epage=557-576&rft.eissn=0010-8545&rft.issn=0010-8545&rft.au=HARTL,%20Frantisek&ROSA,%20Patrick&RICARD,%20Louis&LE%20FLOCH,%20Pascal&ZALIS,%20Stanislav&rft.genre=article |
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