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Cobalt in Organic Synthesis



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Cobalt in Organic Synthesis Respect Cobalt Zhongxing Huang February 20th 2013 1 About Cobalt Uses of cobalt Dyes glass pottery china Magnetic material along with iron and nickel Co 60 as gamma ray source Common organocobalt complexes Co2 CO 8 Sensitive to air and temperature Polymerize under high temperature Stabilized by CO atmosphere pressure Disproportionation under Lewis bases 2 About Cobalt Common organocobalt complexes HCo Co 4 sensitive to air and very sensitive to temperature Precatalyst in many carbonylation reaction Co I Co II and Co III CoX2 Co acac 2 Co acac 3 Thermodynamically stable compounds In situ reduced to active intermediate CpCo I 14e dienophile crucial for cyclization High temperature to dissociate for vac sites 3 Cobalt Catalyzed Hydroformylation Fisher Tropsch reaction Oxo Process 1st Generation Cobalt Catalyst Otto Roelen s contribution Hebrard F Kalck P Chem Rev 2009 109 4272 Self generating and activating catalyst Limitation decomposition n iso separation Replaced by Rh catalyst later World production 106 ton year w Rh 4 Cobalt Catalyzed Hydroformylation Catalytic cycle Hebrard F Kalck P Chem Rev 2009 109 4272 Oxo process n iso 3 1 Shell oxo process n iso 8 1 5 Outline Reactions based on acetylenehexacarbonyl dicobalt complex Nicholas reaction Pauson Khand reaction Cobalt mediated catalyzed cyclization Cobalt catalyzed coupling reaction Cobalt catalyzed C H activation 6 Outline Reactions based on acetylenehexacarbonyl dicobalt complex Nicholas reaction Pauson Khand reaction Cobalt mediated catalyzed cyclization Cobalt catalyzed coupling reaction Cobalt catalyzed C H activation 7 Reactions based on acetylenehexacarbonyl dicobalt complex Reaction of cobalt carbonyl and alkyne Typically high yields Proceed at ambient temperature Stable product some can be isolated with column Protecting groups for alkynes Generally stable in acidic conditions Sensitive to base unstable in catalytic hydrogenation Removed by mild oxidation Fe3 Ce4 Nicholas K M



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