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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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Répertoire International de Littérature Musicale (International Repertory of Music Literature; Internationales Repertorium der Musikliteratur), commonly known by its acronym RILM, is a nonprofit organization that offers digital collections and advanced tools for locating research on all topics related to music. [1]
Since that time the Bibliography of Music Literature has been a regular publication of the Staatliches Institut für Musikforschung. The last volume in print format was published in 2001 and covered the year 1988 (Frankfurt am Main: Hofmeister , 1954-1968 [volumes 1.1950/51 to 6.1960], Mainz: Schott , 1969-2001 [volumes 1961 to 1988]).
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]
The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (NHC) [1] (sometimes called Arduengo carbenes), in which nitrogen atoms flank the formal carbene. Modern theoretical analysis suggests that the term "persistent carbene" is in fact a misnomer .
The net reaction gives a transition metal carbene complex: L n M≡CR + HX → L n (X)M=CHR. These complexes can also undergo photochemical reactions. In some carbyne complexes, coupling of the carbyne ligand to a carbonyl is observed. Protonation of the carbyne carbon and conversion of the carbyne ligand into a π-allyl. [13]
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 ...