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Isolable sulfonium-ylide stabilized palladium carbene complexes were synthesized through palladium(II)-induced cyclization of 1,2-alkynylarylsulfanes. X-ray crystallographic analysis characterized the maintenance of a palladium +2 oxidation state, with carbene-carbon–palladium bond lengths of 1.95 Å, indicating partial double bond character. These endocyclic sulfonium ylide carbenes represent the first characterized and/or isolable examples of this ligand class; such groups were previously proposed as reaction intermediates during cyclization–carbonylation reactions. A variety of palladium(II) complexes bearing sulfonium ylide carbene ligands, with differing substituents, were synthesized and the structure and stability of these complexes in solution were analyzed by 1H and 13C NMR spectroscopy, revealing reversibility and a stability dependence on substituents. The chirality of the sulfur heteroatom and the overall properties these ligands provide a potential electronic and steric alternative to existing carbene ligands, which could facilitate the future development of complementary metal-based reactivity.
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Dynamics of rotation in two‐coordinate thiazolyl copper(I) carbazolyl complexes
Two‐coordinate carbene Cu(Ι) amide complexes with sterically bulky groups such as the diisopropyl phenyl (dipp) on the carbenes have been shown to have comparable performance to the phosphorescent emitters bearing heavy atoms such as iridium and platinum. These bulky groups enforce a coplanar molecular structure and suppress the nonradiative decay rates. Here, three different two‐coordinate Cu(Ι) complexes were investigated that bear a common thiazole carbene, 3‐(2,6‐diisopropylphenyl)‐4,5‐dimethylthiazol‐2‐ylidene, with only a single dipp group, and carbazolyl ligands with substituents of varying steric bulkorthoto N. These substituents have a negligible impact on luminescence energies of the complexes but serve to modulate the rotation barriers along the metal–ligand coordinate bond. The geometric arrangement of ligands (syn‐ oranti‐conformer) in complexes with alkyl substituents were found to differ, beingsynin the solid state versusantiin solution as revealed by crystallographic analysis and nuclear magnetic resonance spectroscopy. In addition, calculations were performed to determine potential energy surfaces for different conformations of the three complexes to provide a theoretical evaluation of rotation barriers around the metal–ligand bond axis. The relationship between rotation barriers and photophysical properties demonstrate that rates for nonradiative decay decrease with increasing bulk of the substituents on the carbazolyl ligand.
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- Award ID(s):
- 2018740
- PAR ID:
- 10367620
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Applied Organometallic Chemistry
- Volume:
- 38
- Issue:
- 10
- ISSN:
- 0268-2605
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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