Strong Exchange Couplings Drastically Slow Down Magnetization Relaxation in an Air‐Stable Cobalt(II)‐Radical Single‐Molecule Magnet (SMM)

The energy barrier leading to magnetic bistability in molecular clusters is determined by the magnetic anisotropy of the cluster constituents. By incorporating a highly anisotropic four‐coordinate cobalt(II) building block into a strongly coupled fully air‐ and moisture‐stable three‐spin system, it proved possible to suppress under‐barrier Raman processes leading to 350‐fold increase of magnetization relaxation time and pronounced hysteresis. Relaxation times of up to 9 hours at low temperatures were found

Synthesis, Structures and Their Application in the Suzuki-Miyaura Cross Coupling Reaction

A series of novel palladium(ii) acetylacetonato complexes bearing mesoionic carbenes (MICs) have been synthesized and characterized. The synthesis of the complexes of type (MIC)Pd(acac)I (MIC = 1-mesityl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (1), 1,4-(2,4,6-methyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (2), 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (3); acac = acetylacetonato) via direct metalation starting from the corresponding triazolium iodides and palladium(ii) acetylacetonate is described herein. All complexes were characterized by 1H- and 13C-NMR spectroscopy and high resolution mass spectrometry. Additionally, two of the complexes were characterized by single crystal X-ray crystallography confirming a square- planar coordination geometry of the palladium(ii) center. A delocalized bonding situation was observed within the triazolylidene rings as well as for the acac ligand respectively. Complex 2 was found to be an efficient pre- catalyst for the Suzuki-Miyaura cross coupling reaction between aryl-bromides or -chlorides with phenylboronic acid. View Full-Tex

Redox-active multinuclear Pd(II) complexes with bis- and tris-mesoionic carbenes

Synthesis of a ligand platform to generate di- and tri-mesoionic carbenes is reported together with their multinuclear Pd(II) complexes. Complete structural characterization and preliminary electrochemical data are presented

structural characterization of Pd(II) complexes and their catalytic properties

The exclusive formation of the 1,5-cycloaddition product between azides and alkynes is taken advantage of in generating the first examples of abnormal carbenes from these precursors. This new route provides unprecedented post- functionalization possibilities for such abnormal carbenes

Isomeric separation in donor–acceptor systems of Pd(II) and Pt(II) and a combined structural, electrochemical and spectroelectrochemical study

Compounds of the form [(pap)M(Q2−)] (pap = phenylazopyridine; Q = 3,5-di-tert- butyl-benzoquinone, M = Pd, 1a and 1b, M = Pt, 2a and 2b; Q = 4-tert-butyl- benzoquinone, M = Pd, 3a and 3b; M = Pt, 4a and 4b) were synthesized in a one- pot reaction. The geometrical isomers, which are possible because of the built in asymmetry of these ligands, have been separated by using different temperatures and variable solubility. Structural characterization of 1b shows that the metal centers are in a square planar environment, the pap ligand is in the unreduced neutral state and the quinones are in the doubly reduced, Q2−catecholate form. Cyclic voltammetric measurements on the complexes display two one-electron oxidations and two one-electron reductions. EPR and vis-NIR spectra of the one-electron oxidized forms of the complexes indicate that the first oxidation takes place on the Q2− ligands to produce a metal bound semiquinone (Q˙−) radical. Reduction takes place on the pap ligand, generating metal bound pap˙− as seen from the 14N (I = 1) coupling in their EPR spectrum. All the complexes in their [(pap)M(Q2−)] neutral forms show strong absorptions in the NIR region which are largely LLCT (ligand to ligand charge transfer) in origin. These NIR bands can be tuned over a wide energy range by varying the metal center as well as the Q ligand. In addition, the intensity of NIR bands can be switched on and off by a simple electron transfer at relatively low potentials. DFT studies were used to corroborate these findings

electrochemical properties, electronic structures and catalysis

A mesoionic carbene with a ferrocene backbone is used as a metalloligand to generate the first example of their Fe–Au heterobimetallic complexes. The details of geometric and electronic structures in different redox states and preliminary catalytic results are presented

a combined structural, electrochemical and spectroscopic study

Reactions of [(az-H)Pd(μ-Cl)2Pd(az-H)] (az = azobenzene) with the zwitterionic, p-benzoquinonemonoimine-type ligands 4-(n-butylamino)-6(n-butylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q1) or 4-(isopropylamino)-6(isopropylimino)-3-oxocyclohexa-1,4-dien-1-olate) (Q2) in the presence of a base leads to the formation of the mononuclear complexes [(az-H)Pd(Q1-H)] (1) and [(az-H)Pd(Q2-H)] (2) respectively. Structural characterization of 2 shows an almost square planar coordination geometry around the Pd(II) centre, a short Pd–C bond, a slight elongation of the N[double bond, length as m-dash]N double bond of the az-H ligand and localization of the double bonds within the Q2-H ligand. Additionally, intermolecular N–H–O interactions exist between the uncoordinated N–H and O groups of two different molecules. Cyclic voltammetry of the complexes reveals an irreversible oxidation and two reversible reduction processes. A combination of electrochemical and UV-vis-NIR and EPR spectroelectrochemical studies are used to show that both coordinated ligands participate successively in the redox processes, thus revealing their non-innocent character

examples of monometallic, homobimetallic and heterobimetallic complexes

Mononuclear PtII and the first dinuclear PtII complexes along with a cyclometalated heterobimetallic IrIII/PdII complex bearing mesoionic carbene donor ligands are presented starting from the same bis-triazolium salt. The mononuclear PtII complex possesses a free triazole moiety which is generated from the corresponding triazolium salt through an N-demethylation reaction, whereas the mononuclear IrIII complex features an unreacted triazolium unit

Structural Characterization and Catalytic Hydrosilylation Reactions

Two series of different Cu(I)-complexes of “click” derived mesoionic carbenes are reported. Halide complexes of the type (MIC)CuI (with MIC = 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (for 1b), 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 1c)) and cationic complexes of the general formula [Cu(MIC)2]X (with MIC =1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene, X = CuI2− (for 2á), 1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene, X = BF4− (for 2a), 1,4-(2,6-diisopropyl)phenyl-3-methyl-1,2,3-triazol-5-ylidene, X = BF4− (for 2b), 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene, X = BF4− (for 2c)) have been prepared from CuI or [Cu(CH3CN)4](BF4) and the corresponding ligands, respectively. All complexes were characterized by elemental analysis and standard spectroscopic methods. Complexes 2á and 1b were studied by single-crystal X-ray diffraction analysis. Structural analysis revealed 2á to adopt a cationic form as [Cu(MIC)2](CuI2) and comparison of the NMR spectra of 2á and 2a confirmed this conformation in solution. In contrast, after crystallization complex 1b was found to adopt the desired neutral form. All complexes were tested for the reduction of cyclohexanone under hydrosilylation condition at elevated temperatures. These complexes were found to be efficient catalysts for this reaction. 2c was also found to catalyze this reaction at room temperature. Mechanistic studies have been carried out as well