Sulfuric acid as a hydride ion acceptor in cobalt(I) cyclopentadiene complexes

Леонова, Е. В.; Malkov, A. V.; Kochetkova, N. O.; Sokolova, A. N.; Rukhlyada, N. N.

doi:10.1007/bf00995730

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“…14 Still later, Leonova described the conversion of 4-Me, and related alkyl analogues (4-R; R = Et, i Pr, and so forth), to cobaltocenium cations (5-R) upon treatment with H 2 SO 4 (eq 5). 15,16 The authors noted that outside an optimal H 2 SO 4 concentration range, 4-Me underwent partial decomposition, leading to a decreased yield of 5-Me. Based on the earlier work of El Murr (eq 3), we speculate that this decomposition may involve formation of C 5 H 5 R. More recently, Leonova found that reaction of H 2 SO 4 with 4-R (R = CH 2 CN, SiPh 3 , NEt 2 , etc.)…”

Section: ■ Introductionmentioning

confidence: 99%

Acid-Induced Liberation of Polysubstituted Cyclopentadiene Ligands from Cyclopentadienyl Cobalt: A [2 + 2 + 1] Cycloaddition Route toward 1,2,4-Trisubstituted Cyclopentadienes

et al. 2019

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Here, we report that trifluoroacetic acid (TFAH) induces demetallation and protodesilylation of the cyclopentadiene ligand in cobalt−η4-cyclopentadiene complexes of general formula [(η5-C5H5)Co(η4-exo-C(TMS)C(SO2Ph)CHCRCH(CO2Et))] (1-Ph, R = Ph; 1-Ar t Bu, R = p-C6H4 t Bu; 1-ArNMe2, R = p-C6H4NMe2; and 1-Me, R = Me). The trisubstituted cyclopentadiene products are isolated as a mixture of two tautomers, [(CH2C(SO2Ph)CHC(CO2Et)CR)] (8-R-A) and [(CHC(SO2Ph)CH2C(CO2Et)CR)] (8-R-B). The endo isomer, [(η5-C5H5)Co(η4-endo-C(TMS)C(SO2Ph)CHCPhCH(CO2Et))] (1-Ph-endo), also undergoes demetallation and protodesilylation to give 8-Ph-A and 8-Ph-B in excellent yield. The cobalt–cyclopentadiene complex, [(η5-C5H5)Co(η4-exo-C(TMS)C(SO2Ph)CHC(CO2Me)CH(CO2Et))] (1-CO2Me), undergoes demetallation and protodesilylation upon treatment with TFAH to give a hydrogen-bonded fulvenol (8-CO2Me). Liberation of the ethoxy-substituted cyclopentadiene ligand of [(η5-C5H5)Co(η4-exo-C(TMS)C(SO2Ph)CHC(OEt)CH(CO2Et))] (1-OEt) leads to formation of a cyclopentenone derivative (11). Thermolysis of 8-Ph-A/8-Ph-B in the presence of maleimide leads to a highly functionalized Diels–Alder adduct, whereas 8-Ph-A/8-Ph-B serves as precursors to trisubstituted ruthenocenes by in situ deprotonation and reaction with [(η5-C5R5)Ru(NCMe)3]PF6 (16-H, R = H; 16-Me, R = Me).

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Section: ■ Introductionmentioning

confidence: 99%