Solvent-mediated generation of cobalt-cluster-stabilised propargyl cations and radicals: allyl migration versus peroxide formation.
The protonation of [Co(2)(CO)(6){9-[(allyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (4), with HBF(4) in CH(2)Cl(2) led to migration of the allyl group from silicon to the cobalt-stabilised cationic site to furnish [Co(2)(CO)(6){9-allyl-9-[(dimethylfluorosilyl)ethynyl]-9H-fluorene}] (17). However, under the same conditions, [Co(2)(CO)(6){9-[(benzyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (5) underwent desilylation and rearrangement of the resulting terminal alkyne-dicobalt complex to give [Co(3)(CO)(9)(9H-fluorenylmethylcarbynyl)] (24); moreover, dimerisation of the (benzyldimethylsilyl)ethynyl-9H-fluorenyl moiety led to the propargyl-allene 26. In contrast, protonation of 5 in THF yielded [{Co(2)(CO)(6){[(benzyldimethylsilyl)ethynyl-9H-fluorenyl])}(2)peroxide] (27) through a radical coupling process. Analogously, protonation of [Co(2)(CO)(6){9-[(vinyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (6) yields the corresponding peroxide 28. X-ray crystallographic data are reported for, among others, complexes 17, 24, 26, 27 and 28.
Kaldis
John H
JH
Department of Chemistry, McMaster University, Hamilton, ON, Canada.
Brook
Michael A
MA
McGlinchey
Michael J
MJ
D002412:Cations; D003035:Cobalt / Q000737:chemistry*; D003500:Cyclization; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D009019:Morphinans / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010545:Peroxides / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry
D002412:Cations; D009019:Morphinans; C440369:N-propargyl; D009942:Organometallic Compounds; D010545:Peroxides; D012997:Solvents; D003035:Cobalt