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Preliminary Theoretical Insights into SmI 2 ‐Mediated Reactions: Activation of Ketones in THF
Author(s) -
Kefalidis Christos E,
Perrin Lionel,
Maron Laurent
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201300288
Subject(s) - chemistry , ketone , adduct , iodide , dissociation (chemistry) , medicinal chemistry , pinacol , reactivity (psychology) , dimer , electrophile , endothermic process , computational chemistry , catalysis , organic chemistry , medicine , alternative medicine , pathology , adsorption
The structure of samarium iodide in THF solution and its reactivity towards aromatic ketones has been studied by means of DFT calculations. A comparison between the X‐ray and DFT optimised structure of [SmI 2 (THF) 3 (η 2 ‐MeOCH 2 H 4 OMe)] and [SmI 2 (THF) 5 ] + shows that the use of DFT‐B3PW91 in conjunction with the appropriate relativistic electron core potential is able to reproduce the structures of these complexes. In THF solution, the simulation of SmI 2 (THF) n complexes reveals that an equilibrium should exist between SmI 2 (THF) 5 , SmI 2 (THF) 4 , SmI 2 (THF) 3 and dimetallic [SmI(μ‐I)(THF) 2 ] 2 . The formation of SmI 2 (THF) 2 and the dissociation of an iodide to yield [SmI (THF) n ] + is less likely to occur. A first estimation of the thermodynamics of ketone reduction by SmI 2 (THF) n is given and qualitative values compared with experiment are presented. Concerning the pinacolic coupling of ketones, a “key intermediate” based on experimental interpretation has been considered. Formation of this so‐called “Streitwiser dimer” is strongly endothermic with respect to the monomeric Sm III –OCPh 2 radical anion adduct. A doubly reduced ketone sandwiched between two Sm centres is more likely to occur and is consistent with the overall pinacol coupling reaction.