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1,2,3,4,5-Pentakis(4-butylphenyl)-1,3-cyclopentadiene is an organochemical compound from the diene group and a cyclopentadiene derivative. The anion of this compound is used as a sterically demanding ligand, often abbreviated as Cp [BIG] , in the organometallic chemistry of sandwich compounds .
Cyclopentadiene is a highly reactive diene in the Diels–Alder reaction because minimal distortion of the diene is required to achieve the envelope geometry of the transition state compared to other dienes. [11]
The parent cyclopentadienone is rarely encountered, because it rapidly dimerizes. [1] Many substituted derivatives are known, notably tetraphenylcyclopentadienone. Such compounds are used as ligands in organometallic chemistry. [2] The Knölker complex, derived from a substituted cyclopentadienone, is a catalyst for transfer hydrogenation. [3]
Typical examples of this type of complex are group 14 metal complexes such as CpSiMe 3. An example of both is (Cp 2 Fe(CO) 2). It is probable that η 1-Cp complexes are intermediates in the formation of η 5-Cp complexes. Still rarer, the Cp unit can bond to the metal via three carbons. In these η 3-Cp complexes, the bonding resembles that in ...
1,4-Pentadiene can be prepared from 1,5-pentadiol via the diacetate. [6] 1,3-Pentadiene, like 1,3-butadiene, undergoes a variety of cycloaddition reactions. For example, it forms a sulfolene upon treatment with sulfur dioxide. [7]
[2] [1] Illustrative of the unusual complexes made possible with these bulky ligands is molecular iron nitrido complex (t Bu 3 C 5 H 2) 2 Fe 2 N 2. [3] In contrast to (C 5 Me 5) 2 Ir 2 Cl 4, (t Bu 3 C 5 H 2)IrCl 2 is monomeric. [4]
The central ring can serve as a diene in Diels–Alder reactions with various dienophiles. For example, reaction with benzyne leads to 1,2,3,4-tetraphenylnaphthalene and reaction with diphenylacetylene leads to hexaphenylbenzene. [5] In this way, it is a precursor to graphene-like molecules, [6] such as coronene.
[3] These correlation diagrams indicate that only a conrotatory ring opening of 3,4-dimethylcyclobutene is symmetry allowed whereas only a disrotatory ring opening of 5,6-dimethylcyclohexa-1,3-diene is symmetry allowed. This is because only in these cases would maximum orbital overlap occur in the transition state. Also, the formed product ...