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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. One such success is the second generation Grubbs catalyst. [1] IMes is a popular NHC ligand.
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.
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 ...
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.
When the alkyl group bridges two main group elements, the bonding is called three-center two-electron bonds. This pattern is seen for dimethyl beryllium and trimethylaluminium. In the case of methyl lithium, the methyl group can be shared (bonded to) three Li centers. These bonding aspects influence the structures: Trimethylaluminium, dimethyl ...
Adding "steric hindrance" to a molecule's reactive site through bulky groups is a common strategy in molecular chemistry to stabilize reactive moieties within a molecule. [3] In this case bulky ligands like terphenyls , bulky alkoxides , aryl-substituted NHCs , etc. serve as a protective wrapper on the molecule. [ 1 ]
Nvidia stock led gains among the “Magnificent Seven” tech stocks to start the new year after a group-wide sell-off in the last days of 2024.Shares of the AI chipmaker rose 4.5% Friday after ...
Owing their large radii, transition metals generally form clusters that are larger than main group elements. One consequence of their increased size, these clusters often contain atoms at their centers. A prominent example is [Fe 6 C(CO) 16] 2-. In such cases, the rules of electron counting assume that the interstitial atom contributes all ...