Thermodynamic and kinetic studies of the complexes W(CO)3(PCy3)2L (L = H2, N2, NCCH3, pyridine, P(OMe)3, CO)

Agostic interaction and intramolecular proton transfer from the protonation of dihydrogen ortho metalated ruthenium complexes

“…This allows the estimation of the strength of the agostic interaction in 1-H and 3-H, namely 16 kJ mol Ϫ1 and 24.9 kJ mol Ϫ1 , respectively. As expected, these agostic interactions are weak in nature, and the calculated values compare well with the experimental data of 41.8 Ϯ 25 kJ mol Ϫ1 obtained for intramolecular W⅐⅐⅐HOC agostic interactions in W(CO) 3 (PCy 3 ) 2 by Hoff and coworkers (43). The above results point to a slightly stronger interaction in 3-H than in 1-H, contrary to what has been inferred from the proton chemical shift and J CH coupling constant values; this illustrates the difficulty to obtain quantitative information on such weak interactions.…”

Evaluation of the Thermodynamic Properties of H2 Binding in Solid State Dihydrogen Complexes [M(η2-H2)(CO)dppe2][BArF24] (M = Mn, Tc, Re): An Experimental and First Principles Study

“…19, 28 The standard Gibbs free energy for the transformation from the open configuration to the agnostic configuration was also calculated from the vibrational analysis, and was found to be Δ G ∘ = −39.6 kJ/mol, similar to values found for other agostic interactions. 12 …”

“…Calorimetric studies have reported solution-state binding enthalpies of Δ H ∘ = −41.8 and −46.9 kJ/mol for the complexes W(CO) 3 (PCy 3 ) 2 and W(CO) 3 (P-i-Pr 3 ) 2 in toluene, respectively. 12, 13 A similiar study in THF, attempting to develop relationships between the group 6 metals in the complexes M(CO)(PCy 3 ) 2 (M=Cr, Mo, W), found Δ H ∘ between −27.2 kJ/mol and −41.8 kJ/mol, and entropy values Δ S ∘ between −100 and −110 J/mol-K.. 14 Solid-state measurements are limited and show deviations from solution behavior, with one study giving Δ H ∘ = −13.22 kJ/mol and Δ S ∘ = −9.62 J/mol-K for hydrogen absorption over the complex 15 [Ir(cod)(PPh 3 ) 2 ]SbF 6 , representing a significant reduction in binding strength and an unexpected increase in the entropy of the bound state. While most of the data are consistent with values obtained from hydrogen storage materials, the current measurements represent a wide range of metals and ligands providing different chemical properties that, apart from the systematic study performed by Gonzalez, et al for the group 6 complexes, do not provide chemical trends to aid in the design of new materials.…”

Agostic bonds in cyclometalation

“…Other g-CeH agostic compounds were reported on phenylphosphines [80a,80b], cyclohexyphosphines [113,114], tert-butylphosphines [115e117], iso-propylphosphines [118e120], and phosphites [83].…”