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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.
NHCs as ligands are known for their strong σ donation and high structural tunability. [11] More in-depth computational analyses also highlight the role of M to NHC π back-donation, with respect to a description of an M-NHC bond. [12] Contour line diagrams of the Laplacian distribution of three (NHC)MCl complexes.
In organometallic chemistry, palladium-NHC complexes are a family of organopalladium compounds in which palladium forms a coordination complex with N-heterocyclic carbenes (NHCs). They have been investigated for applications in homogeneous catalysis , [ 4 ] particularly cross-coupling reactions .
Ever since the first crystalline carbene structure was isolated by Arduengo ins 1990, tuning different properties of NHCs has been a popular area of study in main group chemistry. [4] The first NHC boryl anion was synthesized by Segawa in 2006. [ 1 ]
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 ...
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.
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 ...
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.