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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 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.
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 deprotonated, NHOs can be ligands for main group hydrides. E = Ge, Sn. [1] NHOs can stabilize low oxidation state main group hydrides, like GeH 2 and SnH 2 that are coordinated to W(CO) 5. [1] When deprotonated, these NHOs become anionic, four-electron bridging ligands that can bind to two Ge centers, hence displaying carbanion-like ...
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]
One quintessential dinitrogen complex of a main group element is Gernot Frenking’s triphenylphosphinazine, first reported in 2013 in Angewandte Communications. [6] This compound was notable for demonstrating the double Lewis acid behavior of dinitrogen, as the publication describes the N 2 moiety in the doubly excited 1 Γ g state with four lone pairs on N—N fragment.
Methylene is the simplest carbene.. In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons.The general formula is R−:C−R' or R=C: where the R represents substituents or hydrogen atoms.