Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides

Abstract

The dihydrogen bond-an interaction between a transition-metal or main-group hydride (M-H) and a protic hydrogen moiety (H-X)-is arguably the most intriguing type of hydrogen bond. It was discovered in the mid-1990s and has been intensively explored since then. Herein, we collate up-to-date experimental and computational studies of the structural, energetic, and spectroscopic parameters and natures of dihydrogen-bonded complexes of the form M-H···H-X, as such species are now known for a wide variety of hydrido compounds. Being a weak interaction, dihydrogen bonding entails the lengthening of the participating bonds as well as their polarization (repolarization) as a result of electron density redistribution. Thus, the formation of a dihydrogen bond allows for the activation of both the MH and XH bonds in one step, facilitating proton transfer and preparing these bonds for further transformations. The implications of dihydrogen bonding in different stoichiometric and catalytic reactions, such as hydrogen exchange, alcoholysis and aminolysis, hydrogen evolution, hydrogenation, and dehydrogenation, are discussed.

Fe(II) Hydride Complexes for the Homogeneous Dehydrocoupling of Hydrazine Borane: Catalytic Mechanism via DFT Calculations and Detailed Spectroscopic Characterization

“…Supporting Information page S16). This is rather unusual as reactions of transition metal hydrides with protonating agents such as amine boranes typically have an activation barrier and as those reactions can be stopped at low temperature in many cases. , …”

Fe(II) Hydride Complexes for the Homogeneous Dehydrocoupling of Hydrazine Borane: Catalytic Mechanism via DFT Calculations and Detailed Spectroscopic Characterization

“…Supporting Information page S16). This is rather unusual as reactions of transition metal hydrides with protonating agents such as amine boranes typically have an activation barrier and as those reactions can be stopped at low temperature in many cases. , …”

Comprehensive Insight into the Hydrogen Bonding of Silanes

“…In neat HFIP the SiH resonances appear strongly up‐field (Δ δ SiH =−0.1 to −1.1 ppm) relative to their position in noncoordinating solvents ([D 6 ]benzene, [D 8 ]toluene, methylcyclohexane‐ d 14 ) or in neat silane even at room temperature (Table S3). That conforms the criteria of DHB formation and is in line with the up‐field chemical shift of ν SiH resonance by 0.2 ppm observed for ( n ‐Hex) 3 SiH:PFTB at a very high molar ratio (1:56) . We used 1 H NOE difference spectroscopy to get further NMR proofs of SiH⋅⋅⋅HO interaction.…”

N‐Thiophosphorylthioureas RNHC(S)NHP(S)(OiPr)2 as an Excellent Platform for Studying the Synergy between Hydrogen‐Hydrogen Bonding and Other Families of Non‐Covalent Interactions

“…[114] An intriguing cooperative action of the two types of dihydrogen interactions C-H/H-C and C-H/H-N in the dimer of AQOYAH, leads to ΔE int = -11.33 kcal/mol (Figure S2 in the Supporting Information). The latter seems at first glance similar to well established B-H/H-N, [21][22][23][24][25] However, it is not the case since they are characterized by alike partial charges C-H δ+ / +δ H-N, as opposed to abundant in BN -hydrogen storage materials hydride-proton contacts of the type B-H δ-/ +δ H-N. [21][22][23][24][25] Interestingly, C-H/H-C, supported by C-H/S and π/π in the trimeric model of MOWPEU, gives rise to an extremely high stabilization, ΔE int = -28.58 kcal/ mol (Figure S7 in the Supporting Information). Furthermore, we have identified herein an interesting C-H/H-C interaction formed in MOWPEU not as usual between typically saturated C-H units, but between the aliphatic and aromatic C-H bonds (Figure 19).…”

Fe(II) Hydride Complexes for the Homogeneous Dehydrocoupling of Hydrazine Borane: Catalytic Mechanism via DFT Calculations and Detailed Spectroscopic Characterization

“…Supporting Information page S16). This is rather unusual as reactions of transition metal hydrides with protonating agents such as amine boranes typically have an activation barrier and as those reactions can be stopped at low temperature in many cases. , …”

Comprehensive Insight into the Hydrogen Bonding of Silanes

“…In neat HFIP the SiH resonances appear strongly up‐field (Δ δ SiH =−0.1 to −1.1 ppm) relative to their position in noncoordinating solvents ([D 6 ]benzene, [D 8 ]toluene, methylcyclohexane‐ d 14 ) or in neat silane even at room temperature (Table S3). That conforms the criteria of DHB formation and is in line with the up‐field chemical shift of ν SiH resonance by 0.2 ppm observed for ( n ‐Hex) 3 SiH:PFTB at a very high molar ratio (1:56) . We used 1 H NOE difference spectroscopy to get further NMR proofs of SiH⋅⋅⋅HO interaction.…”

N‐Thiophosphorylthioureas RNHC(S)NHP(S)(OiPr)2 as an Excellent Platform for Studying the Synergy between Hydrogen‐Hydrogen Bonding and Other Families of Non‐Covalent Interactions

“…[114] An intriguing cooperative action of the two types of dihydrogen interactions C-H/H-C and C-H/H-N in the dimer of AQOYAH, leads to ΔE int = -11.33 kcal/mol (Figure S2 in the Supporting Information). The latter seems at first glance similar to well established B-H/H-N, [21][22][23][24][25] However, it is not the case since they are characterized by alike partial charges C-H δ+ / +δ H-N, as opposed to abundant in BN -hydrogen storage materials hydride-proton contacts of the type B-H δ-/ +δ H-N. [21][22][23][24][25] Interestingly, C-H/H-C, supported by C-H/S and π/π in the trimeric model of MOWPEU, gives rise to an extremely high stabilization, ΔE int = -28.58 kcal/ mol (Figure S7 in the Supporting Information). Furthermore, we have identified herein an interesting C-H/H-C interaction formed in MOWPEU not as usual between typically saturated C-H units, but between the aliphatic and aromatic C-H bonds (Figure 19).…”

Fe(II) Hydride Complexes for the Homogeneous Dehydrocoupling of Hydrazine Borane: Catalytic Mechanism via DFT Calculations and Detailed Spectroscopic Characterization

“…Supporting Information page S16). This is rather unusual as reactions of transition metal hydrides with protonating agents such as amine boranes typically have an activation barrier and as those reactions can be stopped at low temperature in many cases. , …”

Comprehensive Insight into the Hydrogen Bonding of Silanes

“…In neat HFIP the SiH resonances appear strongly up‐field (Δ δ SiH =−0.1 to −1.1 ppm) relative to their position in noncoordinating solvents ([D 6 ]benzene, [D 8 ]toluene, methylcyclohexane‐ d 14 ) or in neat silane even at room temperature (Table S3). That conforms the criteria of DHB formation and is in line with the up‐field chemical shift of ν SiH resonance by 0.2 ppm observed for ( n ‐Hex) 3 SiH:PFTB at a very high molar ratio (1:56) . We used 1 H NOE difference spectroscopy to get further NMR proofs of SiH⋅⋅⋅HO interaction.…”

N‐Thiophosphorylthioureas RNHC(S)NHP(S)(OiPr)2 as an Excellent Platform for Studying the Synergy between Hydrogen‐Hydrogen Bonding and Other Families of Non‐Covalent Interactions

“…[114] An intriguing cooperative action of the two types of dihydrogen interactions C-H/H-C and C-H/H-N in the dimer of AQOYAH, leads to ΔE int = -11.33 kcal/mol (Figure S2 in the Supporting Information). The latter seems at first glance similar to well established B-H/H-N, [21][22][23][24][25] However, it is not the case since they are characterized by alike partial charges C-H δ+ / +δ H-N, as opposed to abundant in BN -hydrogen storage materials hydride-proton contacts of the type B-H δ-/ +δ H-N. [21][22][23][24][25] Interestingly, C-H/H-C, supported by C-H/S and π/π in the trimeric model of MOWPEU, gives rise to an extremely high stabilization, ΔE int = -28.58 kcal/ mol (Figure S7 in the Supporting Information). Furthermore, we have identified herein an interesting C-H/H-C interaction formed in MOWPEU not as usual between typically saturated C-H units, but between the aliphatic and aromatic C-H bonds (Figure 19).…”