title: Regioselective intramolecular Pauson-Khand reactions of C60: an electrochemical study and theoretical underpinning.
abstract: Suitably functionalized fulleropyrrolidines endowed with one or two propargyl groups at the C-2 position of the pyrrolidine ring (1,6-enynes) react efficiently and regioselectively with [Co2(CO)8] to afford the respective Pauson-Khand products with an unprecedented three (5 a-d, 7, and 24) or five (25) pentagonal rings, respectively, fused onto the fullerene sphere. Fulleropyrrolidines with 1,7-, 1,9-, 1,10-, or 1,11-enyne moieties do not undergo the PK reaction and, instead, the intermediate dicobalt complexes formed with the alkynyl group are isolated in quantitative yields. These differences in reactivity have been studied by DFT calculations with a generalized gradient approximation (GGA) functional and several important energy and structural differences were found for the intermediates formed by the interaction between the coordinatively unsaturated Co atom and the pi system of C60 in 1,6- and 1,7-enynes. The different lengths of the alkyne chains are responsible for the observed reactivities. Cyclic voltammetry reveals that the presence of the cyclopentenone's carbonyl group connected directly to the C60 core results in PK compounds with remarkable electron-accepting ability.
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, Spain. nazmar@quim.ucm.es
authors.forename: Nazario
authors.initials: N
authors.lastname: Martín
authors.forename: Margarita
authors.initials: M
authors.lastname: Altable
authors.forename: Salvatore
authors.initials: S
authors.lastname: Filippone
authors.forename: Angel
authors.initials: A
authors.lastname: Martín-Domenech
authors.forename: Albert
authors.initials: A
authors.lastname: Poater
authors.forename: Miquel
authors.initials: M
authors.lastname: Solà
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004563:Electrochemistry; D037741:Fullerenes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011759:Pyrrolidines / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D037741:Fullerenes; D011759:Pyrrolidines; D003035:Cobalt