RESUMO
Herein, we report a simple one-pot route to enantiopure copper(I) complexes featuring a unique [2.2]paracyclophane-based P,N-ligand system. Phosphine and pyridine moieties can be varied allowing the modular synthesis of these rigid and stable [2.2]paracyclophane-based P,N-ligands. These P,N-ligands are a new ligand class for different transition-metal complexes, which is shown exemplarily for palladium(II).
RESUMO
[2.2]Paracyclophane, with its unique structure, allows the design of unusual 3D structures by functionalization of this rigid and stable hydrocarbon scaffold. Therefore different mono- and homodisubstituted [2.2]paracyclophanes with pyridyl, pyrimidyl and oxazolinyl substituents were developed in order to evaluate their ability as bridging ligands for two ruthenium centres. With the successfully synthesized [2.2]paracyclophane-based N-donor functions, the cycloruthenation reaction using [RuCl2 (p-cymene)]2 as precursor was explored. Compared to 2-phenylpyridine, the [2.2]paracyclophane derivative is clearly inferior in the cycloruthenation reaction, resulting in poor yields for the neutral complexes. By addition of KPF6 , the cationic complexes can be obtained in good yields and are formed diastereoselectively in case of a pyridyl substituent, resulting in only one diastereomer for dinuclear ruthenium complexes of bispyridyl-substituted [2.2]paracyclophanes as bridging ligands.
RESUMO
For a long time d(10)-ML2 fragments have been known for their potential to activate unreactive bonds by oxidative addition. In the development of more active species, two approaches have proven successful: the use of strong σ-donating ligands leading to electron-rich metal centers and the employment of chelating ligands resulting in a bent coordination geometry. Combining these two strategies, we synthesized bis-NHC chelate complexes of nickel(0) and platinum(0). Bis(1,5-cyclooctadiene)nickel(0) and -platinum(0) react with bisimidazolium salts, deprotonated in situ at room temperature, to yield tetrahedral or trigonal-planar bis-NHC chelate olefin complexes. The synthesis and characterization of these complexes as well as a first example of C-C bond activation with these systems are reported. Due to the enforced cis arrangement of two NHCs, these compounds should open interesting perspectives for bond-activation chemistry and catalysis.
RESUMO
The prediction of coordination modes is of high importance when structure-property relationships are discussed. Herein, the coordination chemistry of copper(i) with pyridine-amines with a varying number of coordinating N-atoms, namely pyridine-benzimidazole, -triazole and -tetrazole, or their deprotonated analogues, and different phosphines was systematically studied and the photoluminescence properties of all synthesized complexes examined and related to DFT data. Each complex was characterized by single-crystal X-ray analysis and elemental analysis, and a set of prediction rules derived for the coordination chemistry of copper(i) with these ligands. A mononuclear cationic coordination motif was found for PPh3 or DPEPhos with all N^N ligands, which exhibits blue to green luminescence of MLCT character d(Cu) â π*(pyridine-amine ligand) with quantum yields up to 46%. With the deprotonated N^N ligands, mononuclear neutral complexes were only expected with DPEPhos. The emission's nature of this complex type is strongly dependent on the electronic effects of the N^N ligand and was characterized as (ML + IL)CT transition. In contrast to the high quantum yields up to 78% for the tetrazolate complexes (as reported before), the triazolate and imidazolate based complexes show much lower emission efficiencies below 10%. Besides the mononuclear copper(i) complexes, cluster-type complexes were obtained, which show moderate luminescence in the blue to green region of the visible spectrum (469-505 nm).