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Electronic Control of the Rotational Barrier in η 2 ‐Alkyne‐1‐thio Complexes
Author(s) -
Seidel Wolfram W.,
Sánchez Beatriz López,
Meel Matthias J.,
Hepp Alexander,
Pape Tania
Publication year - 2007
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.200600619
Subject(s) - alkyne , chemistry , steric effects , isocyanide , ligand (biochemistry) , thio , pyridine , molybdenum , medicinal chemistry , cyclic voltammetry , acetylene , crystallography , nuclear magnetic resonance spectroscopy , electrochemistry , stereochemistry , inorganic chemistry , organic chemistry , biochemistry , receptor , electrode , catalysis
A family of thio‐alkyne complexes [Tp′Mo(CO)(L)(BnSC 2 S)] {Bn = benzyl, Tp′ = hydrotris(3,5‐dimethylpyrazolyl)borate, L = carbonyl ( 2 ), 2,6‐dimethylphenyl isocyanide ( 7 ), tert ‐butyl isocyanide ( 8 ), 4‐(dimethylamino)pyridine ( 9 )} was prepared by reductive removal of a benzyl group in the corresponding bis(benzylthio)acetylene complexes [Tp′Mo(CO)(L)(BnSC 2 SBn)](PF 6 ) ( 1 ‐PF 6 , 4 ‐PF 6 , 5 ‐PF 6 and 6 ‐PF 6 ). All complexes were characterized by IR, 1 H, 13 C spectroscopy and cyclic voltammetry. X‐ray diffraction studies of 5 ‐PF 6 , 8 and 9 were carried out. The alkyne ligand is bound symmetrically to molybdenum in 5 ‐PF 6 and unsymmetrically in 8 and 9 . The trend in the π‐acidity of ligand L is reflected in the spectroscopic and electrochemical data as well as in the molecular structures. Variable temperature 1 H NMR investigations with 7 , 8 and 9 disclosed that the barrier of the alkyne rotation at molybdenum decreases in the order of rising electron density at the metal center while the steric demand increases. Therefore, electronic control of the barrier by the specific character of the ligand L is evident.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)