Characterization of complexes with hemilable ligands in different oxidation states

Es gelang die Synthese von neuen hemilabilen DAB-Liganden des Typs ENNE (DABEMe, E = O (1), N (2), S (3)), wie auch die Synthese entsprechender Cu+-, Cu2+-, Zn2+-, Ag+-, Co2+- und Co3+-Komplexe. Der erste Teil (Kapitel 2) befasst sich mit der Synthese von Komplexen dieser Liganden mit d10-Metallionen (Zn2+, Ag+) und insbesondere mit dem Cu+/Cu2+-Redoxsystem. Bei der Synthese der Cu+-Komplexe mit den Liganden DABSMe und DABSeMe wurden 1:1-Verbindungen erhalten, wohingegen auf Grund der schwachen Koordination der Etherfunktion 2:1-Komplexe (Ligand:Metall) mit dem Liganden DABOMe gebildet wurden. Die synthetisierten Komplexe wurden sowohl strukturell und elektrochemisch als auch spektroskopisch untersucht. Alle Cyclovoltammogramme zeigen eine quasireversible Oxidation, in der Reduktion unterscheiden sich der Komplex [Cu(DABOMe)2]+ von [CuDABSMe]+ und [CuDABSeMe]+. Somit konnte gezeigt werden, dass in den Komplexen [CuDABSMe]+ und [CuDABSeMe]+ die Reorganisationsenergie (Kristallstrukturen, Diederwinkel in Cu+-Komplexen) relativ gering ist. Außerdem konnte der hemilabile Charakter der Etherfunktion im Cu+/Cu2+-Redoxsystem ([Cu(DABOMe)2]n) durch die Einkristallstrukturanalyse belegt werden. Zum strukturellen Vergleich wurden die Liganden mit den Metallen Zn2+ und Ag+ in entsprechenden Verhältnissen umgesetzt. Im zweiten Teil der Arbeit wurden Cobaltchloridkomplexe mit den neuen Liganden des Typs DABEMe synthetisiert. Die drei Co2+-Komplexe [CoCl2DABOMe] (12), [CoCl2DABSMe] (13) und [CoCl2DABSeMe] (14) wurden dargestellt. SQUID-Messungen ergaben effektive magnetische Momente von 4.2-5.2 was auf das Vorliegen von Co2+ im „high-spin“ Zustand hinweist. Durch Einkristallstrukturanalyse konnte gezeigt werden, dass in allen Co2+-Komplexen die Koordinationsgeometrie ein zweifach überkappter, verzerrter Tetraeder ist. Die oxidierten Komplexe [CoCl2DABSMe]+ und [CoCl2DABSeMe]+ konnten ebenfalls mittels Einkristallstrukturanalyse untersucht werden. Diese zeigen eine oktaedrische Koordinationssphäre wie sie für Co3+ (d6, l.s.) erwartet wird. Es konnte belegt werden, dass durch die zusätzliche Koordination der Thioether- und Selenoetherfunktionen einerseits die Koordinationssphäre verändert wird und andererseits mehr Elektronendichte zum Co2+-Zentrum geschoben wird, so dass eine chemisch reversible Oxidation des Co2+-Zentrums unter starker Veränderung der Koordinationssphäre ermöglicht wird. Die Synthese und Charakterisierung von Ruthenium- und Osmium-Aren-Amidophenolat-Komplexen war Bestandteil des dritten Teils dieser Arbeit. Zum Einen wurden hemilabile Amidophenolat-Liganden mit Ether-, Thioether- und Selenoetherfunktion verwendet, zum Anderen nicht hemilabile Liganden die sich in sterischen und elektronischen Eigenschaften unterscheiden. Die kristallographisch charakterisierten Komplexe [RuCymQSMe] / [RuCymQSMe]+ und [RuCymQSeMe] / [RuCymQSeMe]+ zeigen ein ähnliches elektrochemisches Verhalten wie der zuvor beschriebene Iridium-Komplex [IrCp*QSMe] es läuft eine reversible oxidative Addition mit einer intramolekularen Anlagerung der Thioether- bzw. Selenoetherfunktion ab. Mittels Cyclovoltammetrie, der Simulation der Cyclovoltammogramme und der UV-Vis-Spektroelektrochemie konnte gezeigt werden dass die „geschlossene“ Form B die bevorzugte Konformation für die monokationischen Komplexe ist und die „offene“ Form für die neutralen Komplexe bevorzugt wird. Die TD-DFT-Berechnungen zeigen, dass die Spindichte nicht ausschließlich ligandenbasiert ist, sondern auch Metallanteile besitzt. Dies bedeutet, dass schon ein geringer Spintransfer vom Liganden zum Metall ausreicht um eine Koordinationsänderung am Metall hervorzurufen. Im Gegensatz zu den von Ringenberg et al. synthetisierten [IrIIICp*Qt-Bu] ist die katalytische Aktivität gegenüber der Wasserstoffspaltung nur sehr schwach vorhanden.The syntheses of new hemilabile DAB ligands of the type ENNE (DABEMe, E = O (1), N (2), S (3)) as well as the preparation of the corresponding Cu+, Cu2+, Zn2+, Ag+, Co2+ and Co3+ complexes is reported here in. Chapter 2 covers the synthesis of complexes containing ligands mentioned above with d10 metal ions (Zn2+, Ag+) and with the Cu+/Cu2+ redox system. The synthesis of the Cu+ complexes with the ligands DABSMe and DABSeMe result in the formation of 1:1 compounds, while due to the proposed weaker coordination of the ether function 2:1 complexes (ligand:metal) were formed with the ligand DABOMe. The resulting complexes were characterized structurally, electrochemically as well as spectroscopically. Crystal structure were obtained for the Cu+ complexes [Cu(DABOMe)2]+, [CuDABSMe]+ and [CuDABSeMe]+ the coordination sphere as tetrahedrally distorted. The coordination spheres of the Cu2+ complexes [CuDABSMe]2+ and [CuDABSeMe]2+ can be described as pyramidal. The complex [Cu(DABOMe)2]2+ had coordination numbers of seven or eight in the crystal structure, in addition to the imine nitrogen atoms, the ether functions coordinated weakly. All cyclic voltammograms (CVs) show a quasireversible oxidation, only in the reduction process complex [Cu(DABOMe)2]+ differs from [CuDABSMe]+ and [CuDABSeMe]+. In order to compare the structures of the complexes, the ligands were reacted with Zn2+ and Ag+ in corresponding ratios. The second part of this thesis, cobalt chloride complexes with the new DABEMe type ligands were synthesized. The three Co2+ complexes [CoCl2DABOMe], [CoCl2DABSMe] and [CoCl2DABSeMe] were obtained in pure form, and single crystals were used for X-ray diffraction. SQUID measurements gave effective magnetic moments of 4.2-5.2 all three complexes (12-14), indicating the presence of „high-spin“ (h.s.) Co2+. Single crystal analysis showed the coordination geometry of a doubly capped distorted tetrahedron in all Co2+ complexes, with imine nitrogen atoms and chloride ions at the peaks of the tetrahedron, and ether, thioether or selenoether functions capped two sides each. The oxidized complexes [CoCl2DABSMe]+ and [CoCl2DABSeMe]+ could be characterized by x-ray diffraction. These structures contain an octahedral coordination sphere for Co3+ (d6, l.s.) as one might expect. The synthesis and characterization of ruthenium and osmium areneamidophenolate complexes make up the third part of this thesis. Hemilabile amidophenolate ligands with ether, thioether- and selenoether functions were used and compared to non-hemilabile ligands with different steric as well as electronic properties.The by crystal structure characterized complexes [RuCymQSMe]/ [RuCymQSMe]+ and [RuCymQSeMe]/ [RuCymQSeMe]+ show a similar electrochemical behavior as the iridium complex [IrCp*QSMe]described before, a reversible oxidative addition was combined with an intramolecular coordination of the thioether or selenoether function. Using cyclic voltammetry, a simulation of the CVs obtained and UV-Vis spectroelectrochemistry it was shown that the oxidation of [RuCymQOMe] and the analogous osmium complexes [OsCymQSMe] and [OsCymQSeMe] proceeds by the mechanism depicted. The equilibrium constants from the CV simulations as well as DFT calculations resulted in the "closed" Form B with increased coordination number at the metal as the preferred configuration for the monocationic compounds. TD-DFT calculations show that the spin density was not exclusively ligand based but also has contributions from the metal. Thus a small transfer of spin from the ligand to the metal is sufficient to effect a change of coordination at the metal. In contrast to the compounds [IrIIICp*Qt-Bu] synthesized by Ringenberg et al., a catalytic activity regarding cleavage of dihydrogen was present only to a weak extend

Tetra-μ3-iodido-tetrakis[(tri-n-butylphosphane-κP)copper(I)]

The title complex, [Cu4I4(C12H27P)4], crystallizes with six molecules in the unit cell and with three independent one-third molecule fragments, completed by application of the relevant symmetry operators, in the asymmetric unit. The tetranuclear copper core shows a tetrahedral geometry (site symmetry 3..). The I atoms also form a tetrahedron, with I...I distances of 4.471 (1) Å. Both tetrahedra show an orientation similar to that of a pair of self-dual platonic bodies. The edges of the I-tetrahedral structure are capped to the face centers of the Cu-tetrahedron and vice versa. The Cuface...I distances are 2.18 Å (averaged) and the Iface...Cu distances are 0.78 Å (averaged). As a geometric consequence of these properties there are eight distorted trigonal–bipyramidal polyhedra evident, wherein each trigonal face builds up the equatorial site and the opposite Cu...I positions form the axial site. As expected, the n-butyl moieties are highly flexible, resulting in large elongations of their anisotropic displacement parameters. Some C atoms of the n-butyl groups were needed to fix alternative discrete disordered positions

New saccharinate complexes with 3,3′-azobispyridine ligand: synthesis, characterization, and spectroscopic properties

<p>The new metal complexes with saccharinate (sac) and 3,3′-azobispyridine (3,3′-abpy), [Ni(H₂O)₄(3,3′-abpy)₂](sac)₂ (<b>1</b>), [Cu(sac)₂(H₂O)(μ-3,3′-abpy)]_n (<b>2</b>), [Zn(H₂O)₄(3,3′-abpy)₂](sac)₂ (<b>3</b>), [Cd(sac)₂(H₂O)₂(μ-3,3′-abpy)]_n (<b>4</b>), and [Hg₂(μ-sac)₂(sac)₂(μ-3,3′-abpy)(3,3′-abpy)₂]_n (<b>5</b>), were synthesized and characterized by IR spectra, elemental analysis, and single-crystal X-ray diffraction. Spectroscopic (UV–vis and photoluminescence) and thermal properties were also investigated. Single-crystal X-ray analysis reveals that Ni(II) and Zn(II) are coordinated by four aqua ligands and two nitrogens of 3,3′-abpy, while sac is a counter-ion in <b>1</b> and <b>3</b>. In <b>2</b>, Cu(II) and all ligands are linked by coordination bonds and 3,3′-abpy ligands connect the Cu(II) centers forming a 1-D coordination polymer. In <b>4</b>, sac N-coordinated to Cd(II) and distorted octahedral geometry of Cd(II) ion is completed by two aqua and bridging 3,3′-abpy ligands. In <b>5</b>, sac bridges two Hg(II) ions to generate dinuclear [Hg₂(μ-sac)₂] units. These dinuclear units are connected by 3,3′-abpy to form a 1-D coordination polymer. The photoluminescence spectra of <b>3</b> and <b>5</b> show blue fluorescent emission bands, and these emissions can probably be assigned to intraligand fluorescent emissions. Thermal decompositions of the compounds are also discussed. For all complexes, magnetic susceptibility measurements show expected magnetic behavior.</p

Heterotetranuclear Complexes of Reduced and Non-reduced Bridging 1,2,4,5-Tetrazine Ligands with 1,1′-Bis(diphenylphosphanyl)-ferrocene-copper(I)

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Structure and spectroelectrochemical response of arene− ruthenium and arene−osmium complexes with potentially hemilabile noninnocent ligands

Nine of the compounds [M(L2−)(p-cymene)] (M = Ru, Os, L2− = 4,6-di-tert-butyl-N-aryl-o-amidophenolate) were prepared and structurally characterized (Ru complexes) as coordinatively unsaturated, formally 16 valence electron species. On L2−-ligand based oxidation to EPR-active iminosemiquinone radical complexes, the compounds seek to bind a donor atom (if available) from the N-aryl substituent, as structurally certified for thioether and selenoether functions, or from the donor solvent. Simulated cyclic voltammograms and spectroelectrochemistry at ambient and low temperatures in combination with DFT results confirm a square scheme behavior (ECEC mechanism) involving the Ln ligand as the main electron transfer site and the metal with fractional (δ) oxidation as the center for redox-activated coordination. Attempts to crystallize [Ru(Cym)(QSMe)](PF6) produced single crystals of [RuIII(QSMe •−)2](PF6) after apparent dissociation of the arene ligand

Structural Reassessment of [W(CO)₅(TCNE)]: N (σ) Coordination Instead of an Olefin (π) Complex

The blue title compound, long assumed to be an olefin complex on the basis of an apparently single unresolved CN stretching band in the IR spectrum, has been identified by experiment and through DFT analysis as a σ complex with the tungsten atom coordinated to one of the nitrile N centers. The previously reported data are reinterpreted in light of the new structural assignment, and spectroelectrochemical results (UV–vis, IR, EPR) are presented

A Diruthenium Complex of a “Nindigo” Ligand

The compound {(μ-Nindigo)­[Ru­(acac)₂]₂} = <b>1</b>, H₂(Nindigo) = indigo-<i>N</i>,<i>N</i>′-diphenylimine and acac^– = 2,4-pentanedionate, has been structurally characterized in the <i>rac</i> form, which exhibits two edge-sharing six-membered chelate rings involving ruthenium, and the former β-diketiminato functions with a twist angle of 33.9° around the central C–C bond. The metric parameters suggest a neutral π acceptor bridge containing coupled <i>s</i>-<i>trans</i> configurated α-diimines, which are coordinated by two ruthenium­(II) centers. DFT calculations confirm the experimental structure and oxidation state assignment of the <i>rac</i> form; both diastereoisomers are present in solution according to ¹H NMR spectroscopy. A very intense long-wavelength MLCT absorption at 630 nm (ε = 66 800 M^–1 cm^–1) and a weaker near-IR band at 1120 nm (ε = 3000 M^–1 cm^–1) are observed for the CH₃CN solution. Reversible one-electron reduction and oxidation steps were studied by cyclic voltammetry, differential pulse voltammetry, EPR, and UV–vis–NIR spectroelectrochemistry to exhibit metal-centered oxidation and mixed metal/ligand-centered reduction. These results are supported by TD-DFT calculations of the species <i>rac</i>- or <i>meso</i>-<b>1</b>^<i>n</i>, <i>n</i> = 3+, 2+, +, 0, −, 2–

Ruthenium Azocarboxamide Half-Sandwich Complexes: Influence of the Coordination Mode on the Electronic Structure and Activity in Base-Free Transfer Hydrogenation Catalysis

Azocarboxamides were used as chelating ligands in ruthenium half-sandwich complexes. The synthesis and characterization of two new complexes with an unprecedented coordination motif are presented together with an in-depth investigation of two recently published complexes. Three different coordination modes of the ligands were realized, as evident by NMR spectroscopy and single-crystal X-ray diffraction. The use of base during the synthesis leads to a coordination of a deprotonated ligand, while the introduction of additional donor atoms results in a noncoordinated amide group. The first systematic experimental (cyclic voltammetry and UV–vis–NIR and EPR spectroelectrochemistry) and theoretical (DFT) investigation of the electronic structure of metal complexes bearing this redox-active ligand class is presented, revealing redox processes with ligand contribution. The absorption spectra and electrochemistry are mainly determined by the protonation state of the ligand. While complexes <b>2­[PF</b>_<b>6</b><b>]</b>, <b>3­[PF</b>_<b>6</b><b>]</b>, and <b>4­[PF</b>_<b>6</b><b>]</b> with neutral azocarboxamides show similar electronic spectra and cyclovoltammograms, the incorporation of a deprotonated monoanionic ligand in complex <b>1</b> leads to significant changes of these properties. In contrast, the catalytic activity in the base-free transfer hydrogenation reaction is mainly dependent on the coordination of the amide group, with only minor effects of the protonation state. While complexes <b>3­[PF</b>_<b>6</b><b>]</b> and <b>4­[PF</b>_<b>6</b><b>]</b>, with an uncoordinated amide group, are inactive without the addition of base, complexes <b>1</b> and <b>2­[PF</b>_<b>6</b><b>]</b>, with a metal-bound amide group, show activity under base-free conditions. The impact of the position of the amide group together with the detection of metal hydride species in ¹H NMR spectroscopy suggests the operation of metal–ligand bifunctional catalysis to take place when no base is added

Ruthenium Azocarboxamide Half-Sandwich Complexes: Influence of the Coordination Mode on the Electronic Structure and Activity in Base-Free Transfer Hydrogenation Catalysis

Azocarboxamides were used as chelating ligands in ruthenium half-sandwich complexes. The synthesis and characterization of two new complexes with an unprecedented coordination motif are presented together with an in-depth investigation of two recently published complexes. Three different coordination modes of the ligands were realized, as evident by NMR spectroscopy and single-crystal X-ray diffraction. The use of base during the synthesis leads to a coordination of a deprotonated ligand, while the introduction of additional donor atoms results in a noncoordinated amide group. The first systematic experimental (cyclic voltammetry and UV–vis–NIR and EPR spectroelectrochemistry) and theoretical (DFT) investigation of the electronic structure of metal complexes bearing this redox-active ligand class is presented, revealing redox processes with ligand contribution. The absorption spectra and electrochemistry are mainly determined by the protonation state of the ligand. While complexes <b>2­[PF</b>_<b>6</b><b>]</b>, <b>3­[PF</b>_<b>6</b><b>]</b>, and <b>4­[PF</b>_<b>6</b><b>]</b> with neutral azocarboxamides show similar electronic spectra and cyclovoltammograms, the incorporation of a deprotonated monoanionic ligand in complex <b>1</b> leads to significant changes of these properties. In contrast, the catalytic activity in the base-free transfer hydrogenation reaction is mainly dependent on the coordination of the amide group, with only minor effects of the protonation state. While complexes <b>3­[PF</b>_<b>6</b><b>]</b> and <b>4­[PF</b>_<b>6</b><b>]</b>, with an uncoordinated amide group, are inactive without the addition of base, complexes <b>1</b> and <b>2­[PF</b>_<b>6</b><b>]</b>, with a metal-bound amide group, show activity under base-free conditions. The impact of the position of the amide group together with the detection of metal hydride species in ¹H NMR spectroscopy suggests the operation of metal–ligand bifunctional catalysis to take place when no base is added