Cyclopentadienyl transfer reagent

In a first approximation supra-Cp metal complexes can be prepared the same way as normal or other Cp-metal and organo-metal bonds in general. The methods used most often (see Appendix) are the metathesis reaction [Eq. (1)] followed in number by oxidative additions (Eq. (2)] and metallation/deprotonation reactions [Eq. (3)]. The latter is especially important for the cyclpentadienyl alkali metal compounds. A useful variation of reaction (3) is the formation of CpTl in an acid/base reaction from cyclopentadiene and thallium ethoxide [Eq. (3b)]. This represents a convenient route to cyclopentadienylthallium compounds, which are also valued (in place of Cp alkalis) as mild Cp-transfer reagents for the synthesis of difficultly isolable cyclopentadienyl derivatives (77). 

The X-ray structure analysis of the monohydrate, HgFc2 H2O, has confirmed that the cyclopentadienyl rings in the ferrocenyl substituents possess an eclipsed conformation [158]. The mercurial HgFcj can be used as ferrocenyl transfer reagent thus, rare-earth dihalides react with HgFc2 to give new diferrocenyl metal compounds such as YbFcj [159, 160], SmFcj and EuFc2 [160]. 

Gansaeuer and Narayan have reviewed the use of epoxides as substrates for radical reactions via electron transfer <2002ASC465>. The discussion focuses on recent developments in the use of titanocene(lll) reagents as stoichiometric reagents, and the catalytic use of cyclopentadienyl ligands in reagent-controlled radical reactions. 

Reactions of thioketones with nucleophilic reagents have been studied to some extent. Thiobenzophenone (20) and its 4,4 -substituted derivatives react with cyclopentadienyliron dicarbonyl anion and cyclopentadienyl-molybdenum or -tungsten tricarbonyl anion at room temperature to give fulvenes. Phase-transfer catalysis conditions improve the yields. An electron-transfer mechanism has been proposed for this desulphurization and coupling reaction. An electron-transfer mechanism has also been proposed for the reduction of thiopivalophenone (54) by 1-benzyl-1,4-dihydronicotinamide in acetonitrile. 2,3-Diphenylcyclopropene-thione (55) reacts with 7V-methylarylamines to give the bicyclic thioamides (56). The formation of a thioketen as an intermediate has been suggested. A similar reaction scheme has also been proposed for the reaction of (55) with 3,4-dihydroisoquinoline. ... 

---