Role of coordination geometry in dictating the barrier to hydride migration in d6 square-pyramidal iridium and rhodium pincer complexes.
作者： Michael Findlater , Alison Cartwright-Sykes , Peter S. White , Cynthia K. Schauer , Maurice Brookhart
DOI: 10.1021/JA204851X
关键词:
摘要: Syntheses of the olefin hydride complexes [(POCOP)M(H)(olefin)][BArf4] (6a-M, M = Ir or Rh, C2H4; 6b-M, C3H6; POCOP 2,6-bis(di-tert-butylphosphinito)benzene; BArf tetrakis(3,5-trifluoromethylphenyl)borate) are reported. A single-crystal X-ray structure determination 6b-Ir shows a square-pyramidal coordination geometry for Ir, with ligand occupying apical position. Dynamic NMR techniques were used to characterize these complexes. The rates site exchange between and olefinic hydrogens yielded ΔG⧧ 15.6 (6a-Ir), 16.8 (6b-Ir), 12.0 (6a-Rh), 13.7 (6b-Rh) kcal/mol. data also established that migration in propylene yields exclusively primary alkyl intermediate arising from 1,2-insertion. Unexpectedly, no averaging top bottom faces is observed spectra at high temperatures, indicating barrier facial equilibration >20 kcal/m...
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