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Formation of Different Isomers of Phosphine–Imidazolyl and –Pyridyl Ruthenium(II) Complexes Affecting the Catalyst Activity in the Acceptorless Dehydrogenation of Alcohols
Author(s) -
Langer Robert,
Gese Alexander,
Gesevičius Donatas,
Jost Maximilian,
Langer Bastian R.,
Schneck Felix,
Venker Alexander,
Xu Weiqin
Publication year - 2015
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.201402970
Subject(s) - chemistry , moiety , phosphine , ligand (biochemistry) , medicinal chemistry , ruthenium , catalysis , pyridine , isomerization , hydride , steric effects , dehydrogenation , reactivity (psychology) , imidazole , stereochemistry , organic chemistry , hydrogen , medicine , biochemistry , receptor , alternative medicine , pathology
The synthesis, reactivity, and catalytic activity of Ru II complexes with different pyridine‐ and imidazole‐based P,N ligands are reported. The investigations reveal a strong influence of the N‐heterocycle and the steric demand of the phosphine groups on the stability of different isomers of [L 2 RuX 2 ] (L = P,N ligand; X = Cl, H). The imidazole‐based complex 5 with dicyclohexylphosphine groups was found to be the most active precatalyst for the acceptorless dehydrogenation of primary alcohols, whereas different phosphine groups at the imidazole ligand as well as pyridine‐based ligands caused a drop in catalytic activity. In the presence of a primary amine, imines are preferentially formed under these conditions. In summary, the investigations show that comparably small changes in the ligand moiety have a strong effect on the relative stability of stereoisomers for both hydride and chloride complexes, whereas isomerization of the kinetic reaction products was observed in some cases. The described changes in the ligand moiety most probably have a strong impact on the relative stabilities of isomeric intermediates as well and thus affect the catalytic activity of these complexes.