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Proton Transfer to CpRuH(CO)(PCy 3 ) Studied by Low‐Temperature IR and NMR Spectroscopy
Author(s) -
Belkova Natalia V.,
Ionidis Alexei V.,
Epstein Lina M.,
Shubina Elena S.,
Gruendemann Stephan,
Golubev Nikolai S.,
Limbach HansHeinrich
Publication year - 2001
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 - 10.1002/1099-0682(200107)2001:7<1753::aid-ejic1753>3.0.co;2-h
Subject(s) - chemistry , protonation , cationic polymerization , agostic interaction , hydride , proton , ruthenium , hydrogen bond , proton nmr , nuclear magnetic resonance spectroscopy , photochemistry , hydrogen , crystallography , ion , stereochemistry , molecule , polymer chemistry , organic chemistry , catalysis , metal , physics , quantum mechanics
The interaction of the ruthenium hydride complex RuH ≡ CpRuH(CO)(PCy 3 ) ( 1 ) with various proton donors AH ≡ CF 3 CH 2 OH ( 2a ), (CF 3 ) 2 CHOH ( 2b ), (CF 3 ) 3 COH ( 2c ), CF 3 COOH ( 2d ), and HBF 4 ( 2e ) has been studied by variable‐temperature IR spectroscopy using hexane and CH 2 Cl 2 as solvents of different polarity. A low‐temperature NMR study of the interaction of 1 with 2c was performed using [D 8 ]methylcyclohexane, CD 2 Cl 2 , and a liquefied mixture of CDF 2 Cl/CDF 3 (2:1). The first stage of the proton transfer process was found to be the formation of hydrogen‐bonded complexes of the type RuH ··· HA. The hydrogen bonds in these complexes are of medium strength (−Δ H ° = 5.3−7.6 kcal mol −1 ). The second stage is the slow conversion of the H‐complex to a dihydrogen complex to which a hydrogen‐bonded ion‐pair structure [Ru(η 2 ‐H 2 )] + ··· A − was assigned. The kinetics of this unusually slow proton transfer reaction was monitored in the case of 2c at 200 K in CH 2 Cl 2 . Fast protonation of 1 by 2d leads additionally to a species assigned as the free cationic complex [Ru(η 2 ‐H 2 )] + , whose formation is driven by the formation of the homoconjugated anionic complex [AHA] − . At temperatures above 220 K both the hydrogen‐bonded ion pair and the free cationic complex easily release dihydrogen, producing RuA.