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In coordination chemistry, a transition metal NHC complex is a metal complex containing one or more N-heterocyclic carbene ligands. Such compounds are the subject of much research, in part because of prospective applications in homogeneous catalysis.
Anionic boryl ligands can covalently bond to transition metals, which is different than how it bonds to main group elements (ionically). [19] These boryl ligands σ-bond but also are able to receive π-back donation into the vacant p z orbital that the boron has. It is said that boryl ligands, like NHC boryl anions, are the most effective ...
This suggests an origin for the efficacy of NHC transfer chemistry from Ag NHC complexes, with weaker M-NHC bonds in addition to the straightforward synthetic route described previously. [5] Further charge-decomposition analysis of the three model complexes suggests that the- major contribution to covalent bonding arises from the NHC to M σ ...
The transmetallated NHCs can either be isolated for subsequent reaction with palladium in a two-step method, or generated in the presence of palladium in a one-pot reaction. However, generation of Pd-NHC complexes by Ag transmetallation is cost-prohibitive and hampered by Ag complexes’ light sensitivity.
Most homoleptic organo-main group compounds adopt a characteristic oxidation state: RLi, R 2 Be, R 3 B/R 3 Al, R 4 Si, R 3 P, R 2 S. Members where the simplest stoichiometry violates the octet rule often aggregate by formation of bridging alkyl groups. When the alkyl group bridges two main group elements, the bonding is called three-center two ...
When a dimethyl group was added to C exo, the reaction no longer proceeds this way, and was able to polymerize lactide, δ-valerolactone, and ω-pentadecalactone. While this broadened the scope and speed of the polymerization, the reaction was difficult to control due to the formation of an enolate intermediate.
This effect can be used to stabilize highly reactive main group and transition metal compounds. [6] [22] Because excessive steric hindrance can be an issue for some reactivity, NHCs and CAACs bearing substituents with multiple spatial conformations (e.g. cyclohexyl) offer "flexible steric bulk" for catalysis.
In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. [1] The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are specifically designed to ...