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Carbene radicals, in which the carbene is bonded to an open-shell metal with the carbene carbon possessing a radical character. Carbene radicals have features of both Fischer and Schrock carbenes, but are typically long-lived reaction intermediates. The "second generation" of the Grubbs catalysts for alkene metathesis features an NHC ligand.
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Carbyne molecules are generally found to be in electronic doublet states: the non-bonding electrons on carbon are arranged as one radical (unpaired electron) and one electron pair, leaving a vacant atomic orbital, rather than being a triradical (the quartet state).
Bonding scheme of carbene radical complexes as compared to Schrock and Fischer-type carbene complexes. Carbene radicals are a special class of organometallic carbenes.The carbene radical can be formed by one-electron reduction of Fischer-type carbenes using an external reducing agent, or directly upon carbene formation at an open-shell transition metal complex (in particular low-spin cobalt(II ...
A transition metal carbene complex is an organometallic compound featuring a divalent carbon ligand, itself also called a carbene. [1] Carbene complexes have been synthesized from most transition metals and f-block metals , [ 2 ] using many different synthetic routes such as nucleophilic addition and alpha-hydrogen abstraction. [ 1 ]
Bonding between carbene and the metal centre involves a strong σ donation from sp 2 orbital to an empty d orbital on metal centre and a weak π back donation from the metal centre to the empty p z orbital. Because the π donation is weak, the carbene carbon is electrophilic in nature. [1] Because of this bonding property, Fischer carbenes ...
Methylene (IUPAC name: Methylidene, also called carbene or methene) is an organic compound with the chemical formula CH 2 (also written [CH 2] and not to be confused with compressed hydrogen, which is also denoted CH 2). It is a colourless gas that fluoresces in the mid-infrared range, and only persists in dilution, or as an adduct.
Separating a carbene from a carbene-metal complex can be problematic due to the stability of the complex. Accordingly, it is preferable to make the carbene free from these metals in the first place. Indeed, some metal ions, rather than stabilising the carbene, have been implicated in the catalytic dimerisation of unhindered examples.