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Resonance structure of the allyl anion. The cation is identical, but carries an opposite-sign charge. [7] In terms of MO theory, the MO diagram has three molecular orbitals: the first one bonding, the second one non-bonding, and the higher energy orbital is antibonding. [2] MO diagram for allyl π orbitals.
Structure of allylpalladium chloride dimer. Transition-metal allyl complexes are coordination complexes with allyl and its derivatives as ligands.Allyl is the radical with the connectivity CH 2 CHCH 2, although as a ligand it is usually viewed as an allyl anion CH 2 =CH−CH 2 −, which is usually described as two equivalent resonance structures.
First, the palladium coordinates to the alkene, forming a η 2 π-allyl-Pd 0 Π complex. The next step is oxidative addition in which the leaving group is expelled with inversion of configuration and a η 3 π-allyl-Pd II is created (also called ionization). The nucleophile then adds to the allyl group regenerating the η 2 π-allyl-Pd 0 complex.
Contributing structures of the carbonate ion. In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, [1] also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory.
Thermal additions of stannanes are limited (because of the high temperatures and pressures required) to only simple aldehyde substrates. Lewis acid promoted and transmetalation reactions are much milder and have achieved synthetic utility. Intramolecular addition gives five- or six-membered rings under Lewis acidic or thermal conditions. (6)
The compound has a dimeric structure that is centrosymmetric. Each allyl group lies in a plane at an angle of about 111.5° to the square formed by the palladium and carbon atoms, and the Pd–C distances are all equal. Its unit cell is monoclinic. [1]
Enolate anions are electronically related to allyl anions. The anionic charge is delocalized over the oxygen and the two carbon sites. Thus they have the character of both an alkoxide and a carbanion. [5] Although they are often drawn as being simple salts, in fact they adopt complicated structures often featuring aggregates. [6]
In allyl lithium compounds, the lithium cation coordinates to the face of the carbon π bond in an η 3 fashion instead of a localized, carbanionic center, thus, allyllithiums are often less aggregated than alkyllithiums. [6] [12] In aryllithium complexes, the lithium cation coordinates to a single carbanion center through a Li−C σ type bond ...