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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.
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).
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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] The term carbene ligand is a formalism since many are not directly derived from carbenes and most are much less reactive than lone carbenes. [2]
A Fischer carbene is a type of transition metal carbene complex, which is an organometallic compound containing a divalent organic ligand. In a Fischer carbene, the carbene ligand is a σ-donor π-acceptor ligand. Because π-backdonation from the metal centre is generally weak, the carbene carbon is electrophilic.
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.
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 ...
Dichterliebe, A Poet's Love (composed 1840), is the best-known song cycle by Robert Schumann (Op. 48).The texts for its 16 songs come from the Lyrisches Intermezzo by Heinrich Heine, written in 1822–23 and published as part of Heine's Das Buch der Lieder.