Hydrogen bonding and proton transfer to ruthenium hydride complex CpRuH(dppe): metal and hydride dichotomy.
The combination of variable temperature (190-297 K) IR and NMR spectroscopy studies with quantum-chemical calculations at the DFT/B3PW91 and AIM level had the aim to determine the mechanism of proton transfer to CpRuH(dppe) (1, dppe = Ph(2)P(CH(2))(2)PPh(2)) and the structures of intermediates. Dihydrogen bond (DHB) formation was established in the case of interaction with weak proton donors like CF(3)CH(2)OH. Low-temperature protonation (at about 200 K) by stronger proton donors leads via DHB complex to the cationic nonclassical complex [CpRu(η(2)-H(2))(dppe)](+) (2). Thermodynamic parameters of DHB formation (for CF(3)CH(2)OH: ΔH°(HB) = -4.9 ± 0.2 kcal·mol(-1), ΔS°(HB) = -17.8 ± 0.7 cal·mol(-1)·K(-1)) and proton transfer (for (CF(3))(2)CHOH: ΔH°(PT) = -5.2 ± 0.3 kcal·mol(-1), ΔS°(PT) = -23 ± 1 cal·mol(-1)·K(-1)) were determined. Above 240 K 2 transforms into trans-[CpRu(H)(2)(dppe)](+) (3) yielding a mixture of 2 and 3 in 1:2 ratio. Kinetic analysis and activation parameters for the "[Ru(η(2)-H(2))](+) → trans-[Ru(H)(2)](+)" transformation indicate reversibility of this process in contrast to irreversible intramolecular isomerization of the Cp* analogue. Calculations show that the driving force of this process is greater stability (by 1.5 kcal·mol(-1) in ΔE scale) of the dihydride cation in comparison with the dihydrogen complex. The calculations of the potential energy profile indicate the low barrier for deprotonation of 2 suggesting that the formation of trans-[CpRu(H)(2)(dppe)](+) proceeds via deprotonation of [Ru(η(2)-H(2))](+) to DHB complex, formation of hydrogen bond with Ru atom and subsequent proton transfer to the metal site.
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov St. 28, 119991 Moscow, Russia.
Gleb A
GA
Silantyev
Oleg A
OA
Filippov
Peter M
PM
Tolstoy
Natalia V
NV
Belkova
Lina M
LM
Epstein
Klaus
K
Weisz
Elena S
ES
Shubina
D006860:Hydrogen Bonding; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D013816:Thermodynamics
D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; D011522:Protons; C049078:bis(diphenylphosphine)ethane; D012428:Ruthenium