Ferrocene, complexes with dienes

Ferrocene forms ground-state complexes with dienes such as piperylene and isoprene. Irradiation of these yields a 1.25 trans/cis piperylene ratio in the first case and 92% cyclobutanes in the second,284 both indications of a high-energy sensitizer. However, ferrocene itself quenches anthracene triplets, so that it probably has a fairly low triplet energy. Therefore it has been postulated that an excited ferrocene-diene complex dissociates into an excited diene triplet which then proceeds to decay just as though it had been formed by normal bi-molecular sensitization. 

Dannenberg and Richards21 have reported evidence for a piperylene-ferrocene complex on the basis of (I) new absorptions between 220 and 300 mjj. for piperylene/ferrocene mixtures in n-heptane and n-hexane, and (2) the appearance in the nmr spectrum of rrans-piperylene of a new methyl doublet when ferrocene is present. Guillory, Cook, and Scott16 have reported that, although they were unable to detect a complex using nmr, they did note small shifts in the uv spectrum of ferrocene when piperylene was added. This latter observation is consistent with a diene-ferrocene complex. 

In view of the current interest in iron complexes for organic synthesis, we have employed dimethyldioxirane for epoxidation purposes. For example, the quite reluctant iron tricarbonyl diene complex with the alkenyl side chain led to the desired epoxide in moderate yield [35]. Also the isoprenyl-substituted ferrocene could be oxyfunctionalized without any difficulties [36],... 

The complexes with ferrocene were found to be thermally stable in vacuo to at least 180 °C. The decomposed products were only ferrocene, cyclopenta-diene, and uranium. This results further supports the mode of decomposition by the proton abstraction by R from a Cp group as suggested by Marks [214],... 

Ferrocene was the first organometallic guest incorporated and numerous spectroscopic and electrochemical studies have been performed on ferrocene, substituted ferrocene, and related metallocene (e.g. cobaltocene) inclusion complexes (444-469]. Half-sandwich cyclopentadienyl- and benzene-metal carbonyl complexes have also been studied quite extensively [470-479] as have // -allyl metal (palladium) complexes [480], diene metal (rhodium) complexes [481-484], acetylene cobalt carbonyl cluster complexes [485], and complexes with metal carbonyls, e.g. Fe(CO)5, Mn2(CO)io, and CoNO(CO)3 [485a]. 

The first complex of a conjugated diene was reported in 1930 by Reihlen and coworkers. Reaction of butadiene with FefCOjs gave a yellow-brown oil with the molecnlar formnla (C4H6)Fe(CO)3. The elucidation of the stmctnre of ferrocene eventnally lead HaUam and Panson to propose a 7r-complex (1) for (C4H6)Fe(CO)3 and this was eventually confirmed by crystal structure analysis at low temperatnre. Since that time interest in... 

Ferrocene is a very robust organometallic complex that has been incorporated into an impressive number of molecules with various applications and properties. Therefore, ferrocene-containing polymers have been pursued for many possible applications by different routes. Three metathesis-based approaches toward metallocene-containing polymers (mainly ferrocenes) have been reported so far (i) homo-ROMP or co-ROMP of olefins bearing a metallocenyl substituent, (ii) ROMP of strained an.ya-metallocenes, and (iii) ADMET polymerization of bis(alkenyl)metallocenes, including ADMET copolymerization with a.ty-dienes. 

Carretero and coworkers have further extended the scope of N-sulfonyl imine heterodienophiles in enantioselective copper-catalyzed aza-Diels-Alder reactions (Scheme 17.65) [94]. In contrast to previous work that had been limited to the highly reactive N-tosyl imine of ethyl glyoxylate, chiral Cu(I) complexes of phosphino sulfenyl ferrocenes catalyze cycloaddition of Danishefsky s diene (286) to N-tosyl imines (292) of both aromatic and aliphatic aldehydes. Phosphorous substitution proved to play a critical role in both reactivity and enantioselectivity of the reaction with complex [151 CuBr]2 bearing 1-naphthyl substituents on the phosphorous... 

Chiral Lewis acids derived from complexes between copper(I) chloride with phosphino sulfenyl ferrocenes are efficient catalysts for enantioselective aza-Diels-Alder reaction of A-sulfonyl imines with Danishefsky-type dienes (eq 47), and asymmetric conjugate addition of Grignard reagents to cyclic enones (eq 48).136... 

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