832076-22-9

Upstream product

• 832076-21-8 [(1,2,4-tri-tert-butylcyclopentadienyl)(1,2,4-tri-tert-butylcyclopentadienyl(-H))Ce] 
• 71-43-2 benzene 
• 832076-18-3 bis(1,2,4-tri-tert-butylcyclopentadienyl)cerium benzyl 

Relevant academic research and scientific papers

The reaction of bis(1,2,4-tri-t-butylcyclopentadienyl)ceriumbenzyl, Cp′2CeCH2Ph, with methylhalides: A metathesis reaction that does not proceed by a metathesis transition state

The experimental reaction between [1,2,4-(Me3C) 3C5H2]2CeCH2Ph and CH3X, X = F, Cl, Br, and I, yields the metathetical exchange products, [1,2,4-(Me3C)3C5H2] 2CeX and CH3CH2Ph. The reaction is complicated by the equilibrium between the benzyl derivative and the metallacycle [1,2,4-(Me3C)3C5H2][(Me 3C)2C5H2C(CH3) 2CH2]Ce, plus toluene since the metallacycle reacts with CH3X. Labelling studies show that the methyl group of the methylhalide is transferred intact to the benzyl group. The mechanism, as revealed by DFT calculations on (C5H5) 2CeCH2Ph and CH3F, does not proceed by way of a four-center mechanism, a σ-bond metathesis, but by a lower barrier process involving a haptotropic shift of the Cp2Ce fragment so that at the transition state the para-carbon of the benzene ring is attached to the Cp2Ce fragment while the CH2 fragment of the benzyl group attacks CH3F that is activated by coordination to the metal ion. As a result the mechanism is classified as an associative interchange process. The Royal Society of Chemistry 2010.

Hydrogen for fluorine exchange in C6F6 and C 6F5H by monomeric [1,3,4-(Me3C) 3C5H2]2CeH: Experimental and computational studies

The net reaction of monomeric Cp′2CeH [Cp′ = 1,3,4-(Me3C)3(C5H2)] in C 6D6 with C6F6 is Cp′2-CeF, H2, and tetrafluorobenzyne. The pentafluorophenylmetallocene, Cp′2Ce(C6F 5), is formed as an intermediate that decomposes slowly to Cp′2CeF and C6F4 (tetrafluorobenzyne), and the latter is trapped by the solvent C6D6 as a [2+4] cycloadduct. In C6F5H, the final products are also Cp′2CeF and H2, which are formed from the intermediates Cp′2Ce(C6F5) and Cp′2Ce(2,3,5,6-C6F4H) and from an unidentified metallocene of cerium and the [2+4] cycloadducts of tetra- and trifluorobenzyne with C6D6. The hydride, fluoride, and pentafluorophenylmetallocenes are isolated and characterized by X-ray crystallography. DFT-(B3PW91) calculations have been used to explore the pathways leading to the observed products of the exergonic reactions. A key step is a H/F exchange reaction which transforms C6F6 and the cerium hydride into C6F5H and Cp′2CeF. This reaction starts by an η1-F-C6F5 interaction, which serves as a hook. The reaction proceeds via a σ bond metathesis where the fluorine ortho to the hook migrates toward H with a relatively low activation energy. All products observed experimentally are accommodated by pathways that involve C-F and C-H bond cleavages.