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Arene–Ruthenium Complexes with Phosphanylferrocenecarboxamides Bearing Polar Hydroxyalkyl Groups – Synthesis, Molecular Structure, and Catalytic Use in Redox Isomerizations of Allylic Alcohols to Carbonyl Compounds
Author(s) -
Schulz Jiří,
Císařová Ivana,
Štěpnička Petr
Publication year - 2012
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.201200733
Subject(s) - chemistry , ruthenium , isomerization , catalysis , medicinal chemistry , allylic rearrangement , hexamethylbenzene , double bond , redox , ferrocene , benzene , stereochemistry , organic chemistry , electrode , electrochemistry
Phosphanylferrocenecarboxamide Ph 2 P–fc–CONHCH 2 CH 2 OH ( 1 , fc = ferrocene‐1,1′‐diyl) and its newly synthesized congeners, Ph 2 P–fc–CONHCH(CH 2 OH) 2 ( 2 ) and Ph 2 P–fc–CONHC(CH 2 OH) 3 ( 3 ), were converted to a series of (η 6 ‐arene)ruthenium complexes [(η 6 ‐arene)RuCl 2 (L‐κ P )] 5 – 7 , where arene is benzene, p ‐cymene, and hexamethylbenzene and L = 1 – 3 . All compounds were characterized by multinuclear NMR and IR spectroscopy, by mass spectrometry, and by elemental analysis. The molecular structures of 2 , 3 , 3O (a phosphane oxide resulting from the oxidation of 3 ), 5c· CH 2 Cl 2 , and 6c· Et 2 O were determined by single‐crystal X‐ray diffraction analysis. The ruthenium complexes were further evaluated as catalysts in the redox isomerization of allyl alcohols to carbonyl compounds. Complex [(η 6 ‐ p ‐cymene)RuCl 2 ( 1 ‐κ P )] ( 5b ) proved to be a particularly attractive catalyst, being both readily available and catalytically active. Substrates with unsubstituted double bonds were cleanly isomerized with this catalyst in 1,2‐dichloroethane (0.5 mol‐% Ru, 80 °C), whereas for those bearing substituents at the double bond (particularly in the position closer to the OH group) lower conversions and selectivities were achieved. A similar trend was noted when pure water was used as the solvent, except that the best results (complete conversion with 2 mol‐% Ru) were seen for 1,3‐diphenylallyl alcohol, the most hydrophobic substrate.