Theoretical Investigation on the Nature of Intramolecular Interactions in Aminocyclopentadienyl Ruthenium Hydride Complexes

Abstract

Aminocyclopentadienyl ruthenium hydride complexes were optimized at the second-order Møller−Plesset (MP2) level of theory with 6-31G(d) and 6-311++G(d,p) basis sets to investigate the nature of intramolecular interactions. The computations show that both Ru−H···H−N dihydrogen bond interactions and Ru···H−N interactions are responsible for the stability of these complexes. The BSSE-corrected interaction energies, computed at the B3LYP and MP2 levels of theory with 6-31G(d), 6-311++G(d,p), and 6-311++G(2d,2p) basis sets, indicate that the dihydrogen bond interaction energy accounts for only 20% of the total interaction energy. Therefore, the Ru···H−N interactions play a key role in stabilizing the aminocyclopentadienyl ruthenium hydride complexes. Topological analysis of electron density at bond critical points confirms the formation of the dihydrogen bonds between oppositely charged hydrogen atoms. Analysis of charge distributions (Mulliken charges) shows there is a strong electronic attraction between Ru and the hydrogen atom.

Thermodynamic Properties of the Ni−H Bond in Complexes of the Type [HNi(P2RN2R‘)2](BF4) and Evaluation of Factors That Control Catalytic Activity for Hydrogen Oxidation/Production

“…This increase in the p K a values for 2 suggests that the positioning of the nitrogen atom in close proximity to the Ni(0) center or to a second amine results in stabilization of the NH proton by about 3.8 p K a units (13.4 − expected value of 9.6), or 5 kcal/mol. Recent theoretical studies have suggested similar interactions of ammonium NH protons with the metal in ruthenium complexes . These interactions could also be partly responsible for the large positive shift of the Ni(I/0) potential observed for 2 compared to 1a …”

Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides

“…In the ruthenium complex [(η 5 -C 5 H 4 (CH 2 ) 2 NHMe 2 )­RuH­(PPh 3 ) 2 ] + , the ammonium proton is close to both the hydride and the metal (Figure , left), and the linearity of the NH···Ru moiety suggests that this is a primary interaction. Its importance is further supported by AIM analysis, which reveals the NH···H Ru bond path to be highly bent toward the metal. The proposed mechanism for proton/hydride exchange in this complex does not involve a proton transfer within the dihydrogen bond, but rather involves rotation of the aminocyclopentadienyl ligand and protonation of the metal through another hydrogen-bonded intermediate with a very similar NH···Ru interaction (Figure , right).…”

Directionality of Dihydrogen Bonds: The Role of Transition Metal Atoms

“…The study of proton-transfer reactions via dihydrogen-bonded intermediates to isostructural hydrides of the group 8 metals [Cp*MH(dppe)] and [(PP 3 )MH 2 ] (PP 3 = k 4 -P(CH 2 CH 2 PPh 2 ) 3 ) showed that the experimentally determined hydride basicity in hydrogen bonding E j [23] increases evenly down the group, and that the ability of [(PP 3 )MH 2 ] complexes to undergo proton transfer to form hydrido/dihydrogen complex changes aperiodically: Fe < Os < Ru. Only the intramolecular interaction between a pendant NH group of an aminocyclopentadienyl ligand and the RuÀH bond of an aminocyclopentadienyl ruthenium hydride complex has been analyzed, [28] although the use of electronic parameters to estimate the metal-atom participation in the dihydrogen bond suffered from incorrect application of the atoms in molecules (AIM) approach to a transition metal with its core electrons described by an effective core potential (ECP). [22,25] In such non-d 0 transition metal hydrides the incoming proton in a DHB is faced with two contiguous basic centers: the metal and the hydride.…”

“…[21,26] Interestingly short metal-proton distance and significant Mo···HF overlap population were found in one of the first computational works on DHB [27] but were barely discussed. Only the intramolecular interaction between a pendant NH group of an aminocyclopentadienyl ligand and the RuÀH bond of an aminocyclopentadienyl ruthenium hydride complex has been analyzed, [28] although the use of electronic parameters to estimate the metal-atom participation in the dihydrogen bond suffered from incorrect application of the atoms in molecules (AIM) approach to a transition metal with its core electrons described by an effective core potential (ECP). [29] Herein, we report a systematic study aimed at analyzing transition-metal involvement in dihydrogen bonds.…”