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Half‐Sandwich Guanidinate–Osmium(II) Complexes: Synthesis and Application in the Selective Dehydration of Aldoximes
Author(s) -
Francos Javier,
GonzálezListe Pedro J.,
MenéndezRodríguez Lucía,
Crochet Pascale,
Cadierno Victorio,
Borge Javier,
Antiñolo Antonio,
FernándezGalán Rafael,
CarrilloHermosilla Fernando
Publication year - 2016
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.201501221
Subject(s) - chemistry , osmium , dehydration , medicinal chemistry , acetonitrile , chloride , stereochemistry , guanidine , catalysis , ruthenium , organic chemistry , biochemistry
The novel guanidinate–osmium(II) complexes [OsCl{κ 2 ‐( N , N′ )‐C(NR)(N i Pr)NH i Pr}(η 6 ‐ p ‐cymene)] [R = Ph ( 3a ), 4‐C 6 H 4 F ( 3b ), 4‐C 6 H 4 Cl ( 3c ), 4‐C 6 H 4 CF 3 ( 3d ), 3‐C 6 H 4 CF 3 ( 3e ), 3,5‐C 6 H 3 (CF 3 ) 2 ( 3f ), 4‐C 6 H 4 CN ( 3g ), 4‐C 6 H 4 Me ( 3h ), 3‐C 6 H 4 Me ( 3i ), 2‐C 6 H 4 Me ( 3j ), 4‐C 6 H 4 t Bu ( 3k ), 2,6‐C 6 H 3 i Pr 2 ( 3l ), 2,4,6‐C 6 H 2 Me 3 ( 3m )] have been synthesized in high yields (70–88 %) by treatment of THF solutions of the dimeric precursor [{OsCl(µ‐Cl)(η 6 ‐ p ‐cymene)} 2 ] ( 1 ) with 4 equivalents of the corresponding guanidine ( i PrHN) 2 C=NR ( 2a–m ) at room temperature. The easily separable guanidinium chloride salts [( i PrHN) 2 C(NHR)]Cl ( 4a–m ) were also formed in these reactions. The structures of 3a , 3d , and 3h were unequivocally confirmed by X‐ray diffraction methods. Complexes 3a – m proved to be active in the catalytic dehydration of aldoximes. The best results were obtained with [OsCl{κ 2 ‐( N , N′ )‐C(N‐4‐C 6 H 4 CF 3 )(N i Pr)NH i Pr}(η 6 ‐ p ‐cymene)] ( 3d ; 5 mol‐%), which, in acetonitrile at 80 °C, was able to convert selectively a large variety of aromatic, heteroaromatic, α,β‐unsaturated, and aliphatic aldoximes into the corresponding nitriles in high yields and short reaction times.