Norbornadiene

About: Norbornadiene is a research topic. Over the lifetime, 2389 publications have been published within this topic receiving 38603 citations.

Scanning tunneling microscopy of organic molecules and monolayers on silicon and germanium (001) surfaces

Abstract: High-resolution scanning tunneling microscopy has been used to investigate the adsorption of a variety of unsaturated organic molecules on the (001) surface of silicon and germanium. Results are presented for a number of prototypical alkenes, conjugated and non-conjugated dienes, and aromatic compounds. These include cyclopentene, 1,5-cyclooctadiene, norbornadiene, 2,3-dimethyl-1,3-butadiene, and benzene on the Si(001) surface, and for cyclopentene on the Ge(001) surface. Factors controlling the selectivity of various reaction pathways and the consequences for preparation of ordered organic overlayers are discussed.

A Versatile and Highly Z-Selective Olefin Metathesis Ruthenium Catalyst Based on a Readily Accessible N-Heterocyclic Carbene

Abstract: A ruthenium catalyst for Z-selective olefin metathesis has been synthesized from a readily accessible N-heterocyclic carbene (NHC) ligand that is prepared using an efficient, practical, and scalable multicomponent synthesis. The desired ruthenium complex with cyclometalated NHC ligand is obtained by means of selective C(sp3)-H activation at the adamantyl fragment and X-ray diffraction analysis unambiguously confirmed the structure of the precatalyst. The catalyst demonstrated attractive catalytic performance in self- and cross-metathesis at low catalyst loading to afford the desired internal olefins with high conversion and very high Z-selectivity (up to >99%). The versatility of the chelated catalyst is illustrated by the high cis-selectivity (up to >98%) and high tacticity control (up to >98% syndiotactic) achieved in ring-opening polymerization, allowing for the production of highly microstructurally controlled norbornene-, norbornadiene-, and cyclopropene-derived polymers.

Photocatalytic isomerization of norbornadiene to quadricyclane over metal (V, Fe and Cr)-incorporated Ti–MCM-41

Abstract: The photoisomerization of norbornadiene using M–Ti–MCM-41 (M = V, Fe and Cr) has been studied to develop an alternative for solar energy accumulation and high energy aerospace fuel synthesis. The photocatalysts were prepared via hydrothermal method and characterized by EDX, XRD, N 2 adsorption–desorption, TEM, UV–vis, XPS and IR. With the same Si/M ratio in starting materials, the final concentration of V in the photocatalyst is significantly lower than that of Fe and Cr. V 5+ and Fe 3+ ions are highly dispersed in Si–O framework with tetrahedral coordination when the metal content is low, and the ordered structure is well retained. However, some species in higher coordination and polymerized environments present with increasing metal content, and the ordered structure becomes to collapse. Cr ions are difficult to get into the framework with various species like extraframework Cr 6+ and bulk Cr 2 O 3 formed, also the ordered structure is greatly destroyed. Under UV irradiation, the transition metal ions can improve the photoisomerization activity, with the order of V > Fe > Cr. The activities of V– and Fe–Ti–MCM-41 rise with the increase of Si/M ratio, whereas the performance of Cr–Ti–MCM-41 is irregular. The photocatalysts do not exhibit any activity under visible light, regardless of their absorption in visible-light region. The activity is closely related to the extent of dispersion and local structure of metal ions, about which an indirect excitation process of Ti–O species is suggested.