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Further calculations revealed the two highest-occupied molecular orbitals to be primarily localised on the central carbon atom as two lone pairs, like with the hexaphenylcarbodiphosphorane, albeit with slightly more delocalisation of the π-symmetric orbital onto the N-heterocyclic carbene carbon atoms due to their improved π-accepting ...
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.
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 metal-based empty d orbital, forming a σ bond. π-backbonding from a filled metal d orbital to the empty p orbital of the carbon atom is possible.
Delocalization of the lone pair from the substituent on carbene carbon raises the energy of p z orbital, thus forcing the two of electrons of carbene stay as an electron pair. 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 ...
The σ-symmetry lone pair (σ(out)) is formed from a hybrid orbital that mixes 2s and 2p character, while the π-symmetry lone pair (p) is of exclusive 2p orbital parentage. The s character rich O σ(out) lone pair orbital (also notated n O (σ) ) is an ~sp 0.7 hybrid (~40% p character, 60% s character), while the p lone pair orbital (also ...
The distannene (Me 3 Si) 2 CHSn=SnCH(SiMe 3) 2 has a tin-tin bond length just a little shorter than a single bond, a trans bent structure with pyramidal coordination at each tin atom, and readily dissociates in solution to form (Me 3 Si) 2 CHSn: (stannanediyl, a carbene analog). The bonding comprises two weak donor acceptor bonds, the lone pair ...
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 ...
Density functional theory (DFT) calculations showed that this is a result of partial double bond character between the carbene carbon and the bismuth(I) center, wherein the p-type lone pair of electrons on the bismuth atom interact with the partially-filled p orbitals on the carbene carbon. [2]