Remarkable Reactions of Cyclooctatetraene Diiron‐Bridging Carbyne Complexes with Amino and Amido Compounds: Nucleophilic Addition to and Breaking of the Cyclooctatetraene Ring
Abstract:The reactions of the cationic, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(8)-C(8)H(8))]BF(4) (1, Ar=C(6)H(5); 2, Ar=p-CH(3)C(6)H(4); 3, Ar=p-CF(3)C(6)H(4)) with LiN(C(6)H(5))(2) in THF at low temperature gave novel N-nucleophilic-addition products, namely, the neutral, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(7)-C(8)H(8)N(C(6)H(5))(2))] (4, Ar=C(6)H(5); 5, Ar=p-CH(3)C(6)H(4); 6, Ar=p-CF(3)C(6)H(4))). Cationic bridging carbyne complexes 1-3 react with (C(2)H(5))(2)NH, (iC(3)H… Show more
“…The µ‐η 1 :η 3 ‐coordination mode of the vinyliminium ligand in 29 is rather rare in the literature, being previously reported only for triruthenium and triosmium clusters . Otherwise, vinyliminium fragments can be found coordinated in a few polynuclear complexes through the alkene carbons or via µ‐η 1 :η 2 ‐fashion . The reactivity of all of these cited species has been barely explored.…”
Section: Reactivity Of Aminoalkylidyne Complexesmentioning
The chemistry of diiron complexes has seen a recent renaissance, due to the prominent role played by the element iron in the development of sustainable synthetic processes and the cooperative effects provided by two metal centers working in concert, that is a concept amazingly exploited by Nature. Aminoalkylidyne derivatives of [Fe 2 Cp 2 (CO) 4 ] are a convenient scaffold to grow organic fragments; in particular, the facile re-[a] received his PhD degree in Chemistry from the University of Bologna in 2003, then he moved to the University of Pisa in 2006, where he is currently Professor of Inorganic Chemistry. He has co-authored over 150 papers in international journals, dealing with several aspects of the coordination chemistry of transition metal compounds. He was awarded the Nasini Prize by the Italian Chemical Society in 2014, for his contribution to the chemistry of group 5 and 6 metal compounds and to the exploration of unconventional modes of metal mediated C-C bond formation. 3990 Scheme 7. Coupling of isocyanide ligands promoted by acetylide addition to aminoalkylidyne complexes. (a) R = Xyl, R′ = Ph; R = Xyl, R′ = 4-C 6 H 4 Me; R = Me, R′ = Ph. (b) γ-Al 2 O 3 , R′ = SiMe 3 . [51]Eur.
3991Scheme 8. Base-assisted coupling of aminoalkylidyne ligand (R = Me, Xyl or 4-C 6 H 4 OMe) with (a) alkenes (R′ = H, R′′ = CN, CO 2 Me, Ph; R′ = R′′ = CO 2 Et) [53] and (b) allenes (R′ = R′′ = Me; R′ = Me, CO 2 Et, R′′ = H). [54] Scheme 9. Synthesis of vinyliminium complexes via alkyne insertion into Fe-μ-carbyne bond. Inset: possible forms of isomerism. [61][62][63] Eur.
“…The µ‐η 1 :η 3 ‐coordination mode of the vinyliminium ligand in 29 is rather rare in the literature, being previously reported only for triruthenium and triosmium clusters . Otherwise, vinyliminium fragments can be found coordinated in a few polynuclear complexes through the alkene carbons or via µ‐η 1 :η 2 ‐fashion . The reactivity of all of these cited species has been barely explored.…”
Section: Reactivity Of Aminoalkylidyne Complexesmentioning
The chemistry of diiron complexes has seen a recent renaissance, due to the prominent role played by the element iron in the development of sustainable synthetic processes and the cooperative effects provided by two metal centers working in concert, that is a concept amazingly exploited by Nature. Aminoalkylidyne derivatives of [Fe 2 Cp 2 (CO) 4 ] are a convenient scaffold to grow organic fragments; in particular, the facile re-[a] received his PhD degree in Chemistry from the University of Bologna in 2003, then he moved to the University of Pisa in 2006, where he is currently Professor of Inorganic Chemistry. He has co-authored over 150 papers in international journals, dealing with several aspects of the coordination chemistry of transition metal compounds. He was awarded the Nasini Prize by the Italian Chemical Society in 2014, for his contribution to the chemistry of group 5 and 6 metal compounds and to the exploration of unconventional modes of metal mediated C-C bond formation. 3990 Scheme 7. Coupling of isocyanide ligands promoted by acetylide addition to aminoalkylidyne complexes. (a) R = Xyl, R′ = Ph; R = Xyl, R′ = 4-C 6 H 4 Me; R = Me, R′ = Ph. (b) γ-Al 2 O 3 , R′ = SiMe 3 . [51]Eur.
3991Scheme 8. Base-assisted coupling of aminoalkylidyne ligand (R = Me, Xyl or 4-C 6 H 4 OMe) with (a) alkenes (R′ = H, R′′ = CN, CO 2 Me, Ph; R′ = R′′ = CO 2 Et) [53] and (b) allenes (R′ = R′′ = Me; R′ = Me, CO 2 Et, R′′ = H). [54] Scheme 9. Synthesis of vinyliminium complexes via alkyne insertion into Fe-μ-carbyne bond. Inset: possible forms of isomerism. [61][62][63] Eur.
“…Carbon–carbon couplings on small transition metal units have attracted considerable attention since they may serve as models for related catalytic processes . In this context, the reactivity of hydrocarbyl units, bridging coordinated in dinuclear iron or ruthenium complexes bearing ancillary cyclopentadienyl and/or carbonyl ligands, has been widely investigated .…”
“…The carbene species (e) might be thermally unstable and isomerizes to the corresponding bridging carbene complexes 2 − 4 via an exchange between the terminal and bridging ligands under the reaction conditions (at −30 to 0 °C). It has been observed in our recent studies 6b, that the terminal carbene complexes [Fe 2 (CArNHAr‘)(μ-CO)(CO) 3 (η 8 -C 8 H 8 )] (Ar = C 6 H 5 , p -CH 3 C 6 H 4 , p -CF 3 C 6 H 4 ; Ar‘ = C 6 H 5 , 2-naphthyl), the analogues of the intermediates (e), are highly thermally unstable in solution and very easily isomerize to the corresponding chelated iron-carbene complexes (over −40 °C). 2 …”
The reactions of pentacarbonyl(cyclooctatetraene)diiron, [Fe 2 (CO) 5 (η 8 -C 8 H 8 )] (1), with aryllithium reagents, ArLi (Ar ) C 6 H 5 , p-CH 3 C 6 H 4 , p-CF 3 C 6 H 4 ), in ether at low temperature followed by alkylation with Et 3 OBF 4 in aqueous or CH 2 Cl 2 solution at low temperature gave the COT-coordinated diiron bridging alkoxycarbene complexes [Fe 2 {µ-C(OC 2 H 5 )Ar}(CO) 4 (η 8 -C 8 H 8 )] (2, Ar ) C 6 H 5 ; 3, Ar ) p-CH 3 C 6 H 4 ; 4, Ar ) p-CF 3 C 6 H 4 ) and the novel COT-coordinated bridging alkoxycarbyne complexes [Fe 2 {µ-C(OC 2 H 5 )}-(COAr)(CO) 3 (η 8 -C 8 H 8 )] ( 5, Ar ) C 6 H 5 ; 6, Ar ) p-CH 3 C 6 H 4 ; 7, Ar ) p-CF 3 C 6 H 4 ) in 60-74% and 2-8% isolated yields, respectively. In solution complexes 5-7 were transformed into thermodynamically more stable complexes 2-4. The structure of 6 has been established by the X-ray diffraction studies.
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