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Heterolysis of Dihydrogen by Nucleophilic Calcium Alkyls
Author(s) -
Wilson Andrew S. S.,
Dinoi Chiara,
Hill Michael S.,
Mahon Mary F.,
Maron Laurent
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201809833
Subject(s) - chemistry , hydrogenolysis , nucleophile , heterolysis , alkyl , substituent , norbornene , hydride , natural bond orbital , medicinal chemistry , metathesis , photochemistry , methylene , stereochemistry , molecule , catalysis , organic chemistry , polymerization , hydrogen , polymer
β‐Diketiminato (BDI) calcium alkyl derivatives undergo hydrogenolysis with H 2 to regenerate [(BDI)CaH] 2 , allowing the catalytic hydrogenation of a wide range of 1‐alkenes and norbornene under very mild conditions (2 bar H 2 , 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/H 2 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 sp 3 orbital of the n‐hexyl chain and the σ* orbital of the H 2 molecule, signifying that the H−H bond is broken by what is effectively the nucleophilic displacement of hydride by the organic substituent.