Theoretical Studies of the Acidity of the Dihydrogen Complexes trans-[LM(H₂PCH₂CH₂PH₂)₂(η²-H₂)]ⁿ⁺

Abstract

The acidity of transition-metal dihydrogen complexes of the general type trans-[LM(H 2 -PCH 2 CH 2 PH 2 ) 2 (η 2 -H 2 )] n+ (M ) Ru, Os; L ) H -, CH 3 -, F -, CF 3 -, CN -, Cl -, Br -, CO, NCH, NH 3 , PH 3 ; n ) 1, 2) has been modeled by calculating deprotonation energies using the B3LYP density functional method and effective core potentials. Calculated DP energies correlate well with experimental pK a values. For anionic L with strong σ-donor properties the DP energies are higher and acidities lower, due to significant destabilization of the conjugate hydride. When L is neutral, the complexes are dicationic and have much lower DP energies. The acidities of these complexes are governed by the π-accepting ability of L, as the less positively charged conjugate hydride can be stabilized through metal(d) f π* back-donation. The effect of the metal center on acidity is also dependent upon the electronic properties of L. Dihydrogen complexes of Ru with L that is either a σ-donor or π-acceptor are less acidic when compared with those of Os. The effect of a strong σ-donor leads to greater destabilization of the Ru conjugate hydrides, while the π-accepting property of L preferentially stabilizes the Os conjugate hydrides.

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“…In agreement with a computational study[45], the HÀH distance in the homologous series [RuX(h 2 -H 2 )(dppp) 2 ] and [RuX(h 2 -H 2 )(dppe) 2 ] (X Cl, Br, or I) remains constant on going from chloride to iodide [41b], which suggests that the donor properties of the halides are very similar. In agreement with a computational study[45], the HÀH distance in the homologous series [RuX(h 2 -H 2 )(dppp) 2 ] and [RuX(h 2 -H 2 )(dppe) 2 ] (X Cl, Br, or I) remains constant on going from chloride to iodide [41b], which suggests that the donor properties of the halides are very similar.…”

Simplified process for the production of sesame protein concentrate. Differential scanning calorimetry and nutritional, physicochemical and functional properties

“…Density functional studies were used to investigate and predict the geometries, metal–ligand bonding,12 and J H,D values in molecular dihydrogen complexes 13. Furthermore, it supports the H 2 activation mechanism,14 exchange processes between M(H)(H 2 ),15 and the acidity of the dihydrogen complexes 16. In this paper, we have used hybrid density functional calculations at the B3LYP level of theory to study the Ru 2+ complexes.…”

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

“…This includes [MoH 2 (CO)Cp*(PMe 3 ) 2 ] + (entry 36). 116 34,35) has been characterized by X-ray crystallography. 117 The catalytic activity of the complexes MoH(CO) x (PMe 3 ) 3-x (Cp or Cp*) were tested for the decomposition of formic acid.…”

“…The enthalpy of protonation of a wide range of Ir(Cp*) and Ir(Cp) complexes were determined by Wang and Angelici (entries 10,12,13,17,30,32,33,35,37,38,[47][48][49]. 29,112 The hydrides generated in situ include [IrH(Cp*)(CO) 2 ]CF 3 SO 3 (entry 10, pK a LAC 3), [IrH 3 (Cp)(P(OPh) 3 )]CF 3 SO 3 (entry 12, pK a LAC 7) and [IrH 3 (Cp)(PPh 3 )]CF 3 SO 3 (entry 13, pK a LAC 7).…”