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Synthesis of the cobalt-alkyne complex (η5-C 5H5)(PPh3)Co{η2-(Me 3Si)CC(CO2Et)} and structural characterization of trimethylsilyl substituted cobaltacyclopentadiene complexes derived therefrom

  • Author(s): Bunker, KD
  • Rheingold, AL
  • Moore, CE
  • Aubrey, M
  • O'Connor, JM
  • et al.
Abstract

The reaction of (η -C H )Co(PPh ) with TMSCC(CO Et) leads to the formation of the cobalt-alkyne complex (η -C H ) (PPh )Co{η -(Me Si)CC(CO Et)} (6). In benzene-d solution containing PPh , 6 undergoes slow conversion to the cobaltacyclopentadiene complex (η -C H )(PPh )Co{κ -(TMS) CC(CO Et)C(TMS)C(CO Et)} (7, TMS = SiMe ). Alternatively, reaction of 6 and PhCCPh forms the metallacyclopentadiene regioisomers (η -C H )(PPh )Co{κ -(R )CC(R )C(Ph) C(Ph)} [9-major, R = SiMe , R = CO Et; 9-minor, R = CO Et, R = SiMe ). The metallacycle substitution pattern in 9-major and 9-minor is readily deduced from the H NMR spectral resonances of the diastereotopic ethoxycarbonyl hydrogens. When the diastereotopic hydrogens of the ethoxycarbonyl have similar chemical shifts the ester is situated on the β-carbon of the metallacycle. When the methylene hydrogens give rise to well-separated resonances the ethoxycarbonyl is situated on the α-carbon of the metallacycle. The solid state structures of 7 and 9-major were determined by X-ray crystallography. © 2013 Elsevier B.V. All rights reserved. 5 5 2 5 2 5 2 1 2 = 1 2 1 2 1 5 5 3 2 2 5 5 3 3 2 6 3 5 5 3 2 2 3 5 5 3 3 2 2 3

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