RESUMEN
We report a new design of polymer phenylacetylene (PA) ligands and the ligand exchange methodology for colloidal noble metal nanoparticles (NPs). PA-terminated poly(ethylene glycol) (PEG) can bind to metal NPs through acetylide (M-C≡C-R) that affords a high grafting density. The ligand-metal interaction can be switched between σ bonding and extended π backbonding by changing grafting conditions. The σ bonding of PEG-PA with NPs is strong and it can compete with other capping ligands including thiols, while the π backbonding is much weaker. The σ bonding is also demonstrated to improve the catalytic performance of Pd for ethanol oxidation and prevent surface absorption of the reaction intermediates. Those unique binding characteristics will enrich the toolbox in the control of colloidal surface chemistry and their applications using polymer ligands.
RESUMEN
Mesoionic imidazolylidenes are recognized as excellent electron-donating ligands in organometallic and main group chemistry. However, these carbene ligands typically show poor π-accepting properties. A computational analysis of 71 mesoionic imidazolylidenes that bear different aryl or heteroaryl substituents in C2 position was performed. The study has revealed that a diphenyltriazinyl (Dpt) substituent renders the corresponding carbene particularly π-acidic. The computational results could be corroborated experimentally. A mesoionic imidazolylidene with a Dpt substituent was found to be a better σ-donor and a better π-acceptor compared to an Arduengo-type N-heterocyclic carbene. To demonstrate the utility of the new carbene, the ligand was used to stabilize a low-valent paramagnetic tin compound.
RESUMEN
In the cation of the title mol-ecular salt, C18H24N3O+·Cl-, an intra-molecular C-Hâ¯O hydrogen bond stabilizes the almost coplanar orientation of the aromatic ring of the indane unit and the amide plane. In the crystal, the packing is dominated by inter-molecular C-Hâ¯Cl hydrogen-bonding inter-actions that result in the formation of slab-like structures propagating along [010]. The slabs are linked by weak C-Hâ¯O inter-actions, forming layers lying parallel to (100). The methyl-ene carbon atom of the indanyl substituent is disordered over two positions with a refined occupancy ratio of 0.84â (2):0.16â (2). The crystal studied was refined as a twin with matrix [1 0 0.9, 0 0, 0 0 ]; the resulting BASF value is 0.30.