Search Results (3)

Niobocene hydride–silyl complexes exhibit intriguing structural characteristics with the potential for direct hydride/silyl exchange, where hydride migration plays a crucial role during conformational interconversion. In this study, quantum chemical calculations were utilized to investigate the transformation pathways involved in hydride/silyl exchange in niobocene trihydride complexes with various dichlorosilanes, including SiCl₂Me₂, SiCl₂ⁱPr₂, and SiCl₂MePh ligands. The conformational changes and hydride shifts within these niobocene hydride–silyl complexes were examined, and key intermediates were identified. Electronic wavefunction analysis provided insights into the coordination configurations and the nature of inter-ligand interactions. Interaction region indicator (IRI) analysis revealed Van der Waals interactions between chloride atoms and cyclopentadienyl rings, as well as between chloride atoms and Me, ⁱPr, and Ph groups. Notably, distinct interactions between hydride ligands, including those from Si-H moieties and coordinated hydrogen atoms, were observed. Both lateral and central conformations, with respect to silicon coordination to the niobium center, were considered. This study enhances the understanding of intermediate conformations in the hydride/silyl exchange process and provides a detailed characterization of inter-ligand interactions, offering valuable insights for analyzing metallocene complexes with organic ligand coordination. Full article

The reactive acrylate-terminated CdZnSeS/ZnS quantum dots (QDs) were designed and prepared by the effective synthetic route to bond with a siloxane matrix via hydrosilylation. The conventional QD with oleic acid ligands does not have any reactivity, so the QDs were functionalized to assign reactivity for the QDs by the ligand modification of two step reactions. The oleic acid of the QDs was exchanged for hydroxyl-terminated ligands as an intermediate product by one-pot reaction. The hydroxyl-terminated QDs and acrylate-containing isocyanates were combined by nucleophilic addition reaction with forming urethane bonds and terminal acrylate groups. No degradation in quantum yield was observed after ligand exchange, nor following the nucleophilic addition reaction. The modification reactions of ligands were quantitatively controlled and their molecular structures were precisely confirmed by FT-IR and ¹H-NMR. The QDs with acrylate ligands were then reacted with hydride-terminated polydimethylsiloxane (H-PDMS) to form a QD-siloxane matrix by thermal curing via hydro-silylation for the first time. The covalent bonding between the QDs and the siloxane matrix led to improvements in the stability against oxygen and moisture. Stability at 85 °C and 85% relative humidity (RH) were both improved by 22% for the QD-connected siloxane QD films compared with the corresponding values for conventional QD-embedded poly(methylmethacrylate) (PMMA) films. The photo-stability of the QD film after 26 h under a blue light-emitting diode (LED) was also improved by 45% in comparison with those of conventional QD-embedded PMMA films. Full article

: This paper reports the synthesis of two new organotin hydrides containing a (phenyldimethylsilyl)methyl ligand. It was found that the reaction of (phenyldime thylsilyl) methylmagnesium bromide in ether afforded ((phenyldimethylsilyl)methyl) trimethyltin (3) (72%), and with (−)-menthyldimethyltin bromide (4) gave (((phenyl dimethylsilyl)methyl)(1R,2R,5R) -2-isopropyl-5-methylcyclohexyl)dimethyltin (5) (84%). Bromo dealkylation of 3 with bromine in MeOH led to ((phenyldimethylsilyl)methyl)dimethyltin bromide (6) (82%), which upon reduction with LiAlH₄ yielded ((phenyldimethyl silyl)methyl)dimethyltin hydride (7) (95%). The best method for obtaining the corresponding bromostannylated derivative of compound 5, i.e., (((phenyldimethylsilyl) methyl)(1R,2R,5R)-2-isopropyl-5-methylcyclohexyl) methyltin bromide (8) was the exchange reaction between 4 and HgBr₂ that led to 8 with 90% yield. The reduction of bromide 8 with LiAlH₄ gave a diastereomeric mixture of (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl-5- methylcyclohexyl)methyltin hydride (9). Some physical properties and ¹H, ¹³C, and ¹¹⁹Sn NMR of the new organotin hydrides, as well as that of their intermediate precursors are included. Full article