Thermal elimination of methane

The aluminiumalkyi-catalysed dimerization of propene, followed by thermal elimination of methane, provides an industrial route to isoprene, which itself is subsequently, polymerized by a transition metal aluminium alkyl catalyst ... 

A tetrakis(trimethylphosphine)ruthenium complex of benzyne has been prepared6 26 by a reaction similar to that used for the Group 4 and 5 metals thermally induced /3-hydride elimination of methane or benzene from 1 or 2, respectively [Eq. (3)]. A careful study of the kinetics of the elimination of methane from 1 revealed that dissociation of trimethylphosphine pre-... 

The reactions of the chloro-derivatives are summarized in Scheme I. Both methyl derivatives are readily soluble in pentane from which they can be crystallized. They are thermally stable to ca. 130°C. Heating the methyls to ca. 20°C above their respective melting point results, in each case, in elimination of methane and formation of the unique metallocycle VI (21). 

The most useful procedure for the preparation of early transition metal complexes of type 13 is the thermal elimination of benzene or methane from diphenyl or arylmethyl compounds,respectively (12 and 14 in Scheme 1) [5-9]. At the end of the 1960s, the first studies of the reactivity of such a complex, specifically the aryne-titanocene complex 15, showed that it reacts with species such as alkynes, CO2, N2 or selenium to form titanacycles [7]. Particularly interesting for the aim of this chapter is the insertion of alkynes to form titana-cyclopentadienes 16. This reaction takes place in moderately good yields with both electron-rich and electron-poor alkynes (Scheme 2) [13-15]. 

---