Search results
Results from the WOW.Com Content Network
Main page; Contents; Current events; Random article; About Wikipedia; Contact us; Help; Learn to edit; Community portal; Recent changes; Upload file
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.
Examples include (CO) 5 W=COMePh and (OC) 5 Cr=C(NR 2)Ph. Orbital interaction in a Fisher carbene. The carbene electrons are donated to a sigma bond, and weak pi-backbonding occurs. Fisher carbene complexes are related to the singlet form of carbenes, where both electrons occupy the same sp 2 orbital at the carbon. This lone pair donates to a ...
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.
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.
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]
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.
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).