Heterolysis of Dihydrogen by Nucleophilic Calcium Alkyls

Andrew Wilson, Chiara Dinoi, Michael Hill, Mary Mahon, Laurent Maron

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Abstract

β‐Diketiminato (BDI) calcium alkyl derivatives undergo hydrogenolysis with H2 to regenerate [(BDI)CaH]2, allowing the catalytic hydrogenation of a wide range of 1‐alkenes and norbornene under very mild conditions (2 bar H2, 298 K). The reactions are deduced to take place with the retention of the dimeric structures of the calcium hydrido‐alkyl and alkyl intermediates via a well‐defined sequence of Ca−H/C=C insertion and Ca−C hydrogenation events. This latter deduction is strongly supported by DFT calculations (B3PW91) performed on the 1‐hexene/H2 system, which also indicates that the hydrogenation transition states display features which discriminate them from a classical σ‐bond metathesis mechanism. In particular, NBO analysis identifies a strong second order interaction between the filled α‐methylene sp3 orbital of the n‐hexyl chain and the σ* orbital of the H2 molecule, signifying that the H−H bond is broken by what is effectively the nucleophilic displacement of hydride by the organic substituent.
Original languageEnglish
Pages (from-to)15500-15504
Number of pages5
JournalAngewandte Chemie-International Edition
Volume57
Issue number47
Early online date26 Oct 2018
DOIs
Publication statusPublished - 9 Nov 2018

Keywords

  • calcium
  • catalysis
  • density functional theory
  • hydrogenation
  • main group chemistry

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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