Toggling the Z-type interaction off-on in nickel-boron dihydrogen and anionic hydride complexes

Prat, Jacob R.; Cammarota, Ryan C.; Graziano, Brendan J.; Moore, James T.; Lu, Connie C.

doi:10.1039/d2cc03219h

Cited by 12 publications

(23 citation statements)

References 42 publications

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“…The hydricity of an anionic Re hydride was recently reported to be 3 kcal mol −1 more hydridic in THF than MeCN, 14 and very recently, Lu and co-workers reported that [B–Ni–H] − has a hydricity of 21.4 kcal mol −1 in THF. 67 With this caveat in mind, the anionic hydrides described here may be amongst the most hydridic ground-state metal hydrides that are sufficiently stable for characterization. In MeCN, the most hydridic 1st row metal hydride has a hydricity of 31.8 kcal mol −1 (the most hydridic ground-state metal hydride has a hydricity of 26.6 kcal mol −1 ).…”

Section: Resultsmentioning

confidence: 99%

Large changes in hydricity as a function of charge and not metal in (PNP)M–H (de)hydrogenation catalysts that undergo metal–ligand cooperativity

Schlenker

Casselman

VanderLinden

et al. 2023

Catal. Sci. Technol.

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Section: Resultsmentioning

confidence: 99%

Large changes in hydricity as a function of charge and not metal in (PNP)M–H (de)hydrogenation catalysts that undergo metal–ligand cooperativity

Schlenker

Casselman

VanderLinden

et al. 2023

Catal. Sci. Technol.

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“…Such ligands can assist coordination by lowering the energy of the s-antibonding d-orbital 2,4,6,20,23,49,53,[55][56][57] and, in some cases, allow H2 deprotonation to form strongly hydridic d 10 hydrides. 58,59 The observation of complex 2 demonstrates that a single p-acidic olefin ligand is sufficient to stabilize a H2 complex of a d 10 metal and can cooperatively generate an active hydride without the need for full oxidative addition to a dihydride intermediate, warranting consideration of such pathways in catalytic hydrogenation reactions.…”

Section: Resultsmentioning

confidence: 99%

Cooperative H2 Activation at a Nickel(0)-Olefin Center

Sansores-Paredes

Lutz

Moret

2023

Preprint

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Catalytic olefin hydrogenation reactions are ubiquitous in organic synthesis. Most proposed catalytic cycles for the homogeneous hydrogenation of olefins using molecular H2 start with the oxidative addition of H2 by metal complexes to form two reactive M–H bonds, often via a non-classical metal dihydrogen (M–H2) intermediate. Previous reports had provided indirect evidence for an alternative mechanism involving direct hydrogen transfer from a metal-bound H2 molecule to a metal-bound olefin without the oxidative addition step. However, the key metal(olefin)(H2) and the corresponding ligand-to-ligand hydrogen transfer (LLHT) step had not been directly observed. Herein, we show that incorporating a precoordinated olefin in a P(C=C)P pincer ligand framework allows for the observation of both a non-classical Ni-(H2) complex and the Ni(alkyl)(hydrido) product of LLHT in rapid equilibrium with dissolved H2. The utility of this cooperative H2-activation mechanism for catalysis is demonstrated in the semihydrogenation of diphenylacetylene under mild conditions. Mechanistic investigations supported by DFT calculations back the central role of LLHT for both cooperative H2 activation and catalytic semihydrogenation. These results provide an experimental basis for the role of LLHT steps in olefin hydrogenation mechanisms and demonstrate the utility of olefin-based pincer ligands for cooperative catalysis with non-noble metals.

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“…Figure 5 indicates that the neutral metal hydrides are near the hydricity of formate in THF and that the anionic congeners are significantly more hydridic. The hydricities of Co-M and Ni-M bimetallic hydrides (with exception of the Ni-B system), 17,66 and that of an anionic Re species (37.6 kcal•mol -1 ) 14 lie between the two regions of the MLC catalysts. This re-enforces the effect that charge has on hydricity.…”

Section: Ramifications For Catalysismentioning

confidence: 97%

“…The hydricity of an anionic Re hydride was recently reported to be 3 kcal•mol -1 more hydridic in THF than MeCN, 14 and very recently, Lu and co-workers reported that [B-Ni-H]has a hydricity of 21.4 kcal•mol -1 in THF. 66 With this caveat in mind, the anionic hydrides described here may be amongst the most hydridic ground-state metal hydrides that are sufficiently stable for characterization. In MeCN, the most hydridic 1 st row metal hydride has a hydricity of 31.8 kcal•mol -1 (the most hydridic ground-state metal hydride has a hydricity of 26.6 kcal•mol -1 ).…”

Section: Ramifications For Catalysismentioning

confidence: 99%

“…The plot of Figure 5 also includes two M-Co and four M-Ni complexes for which pertinent thermodynamic data is available. 17,66 These do not undergo MLC, and their fit to the line may be coincidental, or suggest that in THF, hydricity is generally correlated with acidity. We emphasize that more data is required before conclusions can be made regarding broad trends across types of complexes or temperature.…”

Section: Interplay Of Hydricity and Aciditymentioning

confidence: 99%

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Large Changes in Hydricity as a Function of Charge and Not Metal in (PNP)M-H (De)hydrogenation Catalysts That Undergo Metal-Ligand Cooperativity

Schlenker

Casselman

VanderLinden

et al. 2022

Preprint

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Pincer-ligated catalysts that can undergo metal-ligand cooperativity (MLC), whereby H2 is heterolytically cleaved (with proton transfer to the ligand and hydride transfer to the metal), have emerged as potent catalysts for the hydrogenation of CO2 and organic carbonyls. Despite the plethora of systems developed that differ in metal/ligand identity, no studies establish how variation of the metal impacts the pertinent thermochemical properties of the catalyst, namely the equilibrium with H2, the hydricity of the resulting hydride, and the acidity of the ligand. These parameters can impact the kinetics, scope, and mechanism of catalysis and hence should be established. Herein, we describe how changing the metal (Co, Fe, Mn, Ru) and charge (neutral vs. anionic) impacts these parameters in a series of PNP-ligated catalysts (PNP = 2,6-bis[(di-tert-butylphosphino)methyl]pyridine). A linear correlation between hydricity and ligand pKa (when bound to the metal) is found, indicating that the two parameters are not independent of one another. This trend holds across four metals, two charges, and two different types of ligand (amine/amide and aromatization/dearomatization). Moreover, the effect of ligand deprotonation on the hydricity of (PNP)(CO)(H)Fe-H and (PNP)(CO)(H)Ru-H is assessed. It is determined that deprotonation to give anionic hydride species enhances the hydricity by ~ 16.5 kcal·mol-1 across three metals. Taken together, this work suggests that the metal identity has little effect on the thermodynamic parameters for PNP-ligated systems that undergo MLC via (de)aromatization, whilst the effect of charge is significant; moreover, ion-pairing allows for further tuning of the hydricity values. The ramifications of these findings for catalysis are discussed.

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Toggling the Z-type interaction off-on in nickel-boron dihydrogen and anionic hydride complexes

Abstract: Completing a series of nickel-group 13 complexes, a coordinatively unsaturated nickel-boron complex and its derivatives with a H2, N2, or hydride ligand were synthesized and characterized. The toggling “on” of...

Cited by 12 publications

References 42 publications

Large changes in hydricity as a function of charge and not metal in (PNP)M–H (de)hydrogenation catalysts that undergo metal–ligand cooperativity

Large changes in hydricity as a function of charge and not metal in (PNP)M–H (de)hydrogenation catalysts that undergo metal–ligand cooperativity

Cooperative H2 Activation at a Nickel(0)-Olefin Center

Large Changes in Hydricity as a Function of Charge and Not Metal in (PNP)M-H (De)hydrogenation Catalysts That Undergo Metal-Ligand Cooperativity

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