Hydrogenation and Dehydrogenation of Dinuclear Boron‐ and Gallium Hydrides: Quantum Chemical Calculations and Experiments

Himmel, Hans‐Jörg

doi:10.1002/9783527636402.ch26

Cited by 9 publications

(2 citation statements)

References 64 publications

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“…Guanidines are attractive ligands and guanidine-metal complexes served as catalysts in many reactions. − Especially copper-guanidine complexes were thoroughly studied. − Also, GFAs were shown to be versatile redox-active ligands . Recently, we showed that the radical monocationic complex [ 1 {Cu(OAc) 2 } 2 ] + • could be synthesized either by oxidation of the neutral complex [ 1 {Cu(OAc) 2 } 2 ] or by a comproportionation reaction from the neutral complex [ 1 {Cu(OAc) 2 } 2 ] and the dicationic complex [ 1 {Cu(OAc) 2 } 2 ] 2+ (see Scheme b) .…”

Section: Introductionmentioning

confidence: 99%

Radical Monocationic Guanidino-Functionalized Aromatic Compounds (GFAs) as Bridging Ligands in Dinuclear Metal Acetate Complexes: Synthesis, Electronic Structure, and Magnetic Coupling

et al. 2016

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In this work, the oxidation of several new dinuclear metal (M) acetate complexes of the redox-active guanidino-functionalized aromatic compound (GFA) 1,2,4,5-tetrakis(tetramethylguanidino)benzene (1) was studied. The complexes [1{M(OAc)2}2] (M = Ni or Pd) were oxidized to the radical monocationic complexes [1{M(OAc)2}2](+ •). From CV (cyclic voltammetry) measurements, the Gibbs free enthalpy for disproportionation of [1{M(OAc)2}2](+ •) into [1{M(OAc)2}2] and [1{M(OAc)2}2](2+) could be estimated to be roughly +20 kJ mol(-1) in CH2Cl2 solution. A characteristic feature of the [1{M(OAc)2}2](+ •) complexes is the presence of intense metal-ligand charge-transfer bands in the electronic absorption spectra. The complex [1{Ni(OAc)2}2](+ •) combines three paramagnetic centers with four metal-centered unpaired electrons and a ligand centered π-radical and exhibits a sextet electronic ground state. Spin distribution of the Ni complexes was evaluated by paramagnetic (1)H and (13)C NMR and was correlated with calculations. The strong ferromagnetic metal-ligand magnetic coupling was studied in the solid state by magnetometric (SQUID) measurements and by quantum chemical (DFT) calculations. The temperature dependence of the paramagnetic NMR shift was used for the evaluation of the magnetic coupling between the Ni centers and the π-radical in solution.

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Section: Introductionmentioning

confidence: 99%

Radical Monocationic Guanidino-Functionalized Aromatic Compounds (GFAs) as Bridging Ligands in Dinuclear Metal Acetate Complexes: Synthesis, Electronic Structure, and Magnetic Coupling

et al. 2016

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“…Guanidines are versatile ligands and substituents . Bicyclic guanidinates have been used extensively for the stabilization of dinuclear transition-metal complexes with multiple bonds between two highly oxidized metal atoms and for catalytic applications. , Acyclic guanidinates with sterically demanding organic groups have been used as substituents in dimeric Mg I compounds .…”

Section: Introductionmentioning

confidence: 99%

Trinuclear Complexes and Coordination Polymers of Redox-Active Guanidino-Functionalized Aromatic (GFA) Compounds with a Triphenylene Core

et al. 2014

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Herein, we report on the synthesis, redox activity, and coordination chemistry of 2,3,6,7,10,11-hexakis(tetramethylguanidino)triphenylene. CV measurements indicated that the new compound could be oxidized in three separate reversible two-electron oxidation events. The HOMO and LUMO energies were estimated from the oxidation wave and the onset of absorption in the UV/vis spectrum. Our discussion also includes the related new compound 2,3,6,7,10,11-hexakis(N,N'-dimethylethyleneguanidino)triphenylene. Then trinuclear Cu(I) and Cu(II) complexes of the new triphenylene ligands were characterized, and their electronic properties are discussed. In contrast to previously studied redox-active GFA ligands, oxidation of trinuclear copper(I) iodide complexes with I2 leads to copper instead of ligand oxidation. In the tetra-coordinated Cu(II) complexes, the coordination mode is intermediate between tetrahedral and square planar. The optical properties of the complexes were studied, and low-energy electronic transitions were assigned to ligand-to-metal charge-transfer (LMCT) excitations. We then extended our analysis to trinuclear Ni(II) and Co(II) complexes. The magnetic coupling mediated through the triphenylene ligand in the trinuclear Cu(II) and Co(II) complexes was studied by SQUID magnetometry, revealing ferromagnetic coupling of the spin centers and different degrees of spin delocalization into the guanidino groups. Finally, we show that the GFA ligands could be linked to one- or two-dimensional coordination polymers and porous materials with a layer structure by reaction with silver halides.

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Bisguanidines with Biphenyl, Binaphthyl, and Bipyridyl Cores: Proton‐Sponge Properties and Coordination Chemistry

Maronna

Hübner

Enders

et al. 2013

Chemistry A European J

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Herein, we report on the synthesis, protonation, and coordination chemistry of chelating guanidine ligands with biphenyl, binaphthyl, and bipyridyl backbones. The ligands are shown to be proton sponges, and this protonation was studied experimentally and by using quantum-chemical calculations. Group 10 metal (Ni, Pd, and Pt) complexes with different metal/ligand ratios were synthesized. In the case of the bipyridyl systems, coordination occurs exclusively at the pyridine N atoms, as opposed to protonation. The spin-density distribution and the magnetism were evaluated for a series of paramagnetic Ni(II) complexes with the aid of paramagnetic NMR spectroscopic studies in alliance with quantum-chemical calculations and magnetic (SQUID) measurements. Through direct delocalization from the singly occupied molecular orbitals (SOMOs), a significant amount of spin density is placed on the guanidinyl groups, and spin polarization also transports spin density onto the aromatic backbone.

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Hydrogenation and Dehydrogenation of Dinuclear Boron‐ and Gallium Hydrides: Quantum Chemical Calculations and Experiments

Cited by 9 publications

References 64 publications

Radical Monocationic Guanidino-Functionalized Aromatic Compounds (GFAs) as Bridging Ligands in Dinuclear Metal Acetate Complexes: Synthesis, Electronic Structure, and Magnetic Coupling

Radical Monocationic Guanidino-Functionalized Aromatic Compounds (GFAs) as Bridging Ligands in Dinuclear Metal Acetate Complexes: Synthesis, Electronic Structure, and Magnetic Coupling

Trinuclear Complexes and Coordination Polymers of Redox-Active Guanidino-Functionalized Aromatic (GFA) Compounds with a Triphenylene Core

Bisguanidines with Biphenyl, Binaphthyl, and Bipyridyl Cores: Proton‐Sponge Properties and Coordination Chemistry

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