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A new series of bifunctional Ru complexes with pendent Lewis acidic boranes were prepared by late-stage modification of an active hydrogen-transfer catalyst. The appended boranes modulate the reactivity of a metal hydride as well as catalytic hydrogenations. After installing acidic auxiliary groups, the complexes become multifunctional and catalyze the cis-selective hydrogenation of alkynes with higher rates, conversions, and selectivities compared with the unmodified catalyst.

A detailed mechanistic analysis of the acceptorless double dehydrogenation of primary amines to form nitriles by HRu(bMepi)(PPh3)2 (1, bMepi = 1,3-bis(6′-methyl-2′-pyridylimino)isoindolate) is presented. The presence of the ortho-CH3 substituents on bMepi is critical for amine dehydrogenation, and no catalysis was observed with HRu(bpi)(PPh3)2 (1-bpi, bpi = 1,3-bis(2′-pyridylimino)isoindolate). Outer-sphere, inner-sphere, and hemilabile pathways were evaluated through ligand substitution and kinetic studies, catalyst modifications, and computational analysis. We propose an inner-sphere mechanism in which a Ru–hydride is protonated by coordinated amine followed by H2 release, which forms a Ru–amido intermediate. The stability of Ru–amido species was evaluated through NBO, AIM, and NCI analyses, revealing steric pressure as well as weak noncovalent interactions between the coordinated amido nitrogen atom and the ortho-alkyl substituents, and these interactions impact the overall thermodynamic profile for am...

The reversible transformations between ketones and alcohols via sequential hydrogenation–dehydrogenation reactions are efficiently achieved using a single precatalyst HRu(bMepi)(PPh3)2 (bMepi = 1,3-bis(6′-methyl-2′-pyridylimino)isoindolate). The catalytic mechanism of HRu(bMepi)(PPh3)2 mediated acceptorless alcohol dehydrogenation (AAD) has been investigated by a series of kinetic and isotopic labeling studies, isolation of intermediates, and evaluation of Ru(b4Rpi)(PPh3)2Cl (R = H, Me, Cl, OMe, OH) complexes. Two limiting dehydrogenation scenarios are interrogated: inner-sphere β-H elimination and outer-sphere bifunctional double hydrogen transfer. Isotopic labeling experiments demonstrated that the proton and hydride transfer in a stepwise manner. Catalyst modifications suggest that the imine group on the bMepi pincer scaffold is not necessary for catalytic alcohol dehydrogenation. Evaluation of the kinetic experiments and catalyst modifications suggests a pathway whereby HRu(bMepi)(PPh3)2 operates via ...

An amide-derived N,N,N-Fe(II) complex catalyzes the hydroboration of alkenes at room temperature. Alkylation of a remote site on the ligand backbone was used as a late-stage modification to provide a more electrophilic complex as determined by electrochemical studies. The alkylated variant, compared to the parent complex, catalyzes olefin hydroboration with an increased reaction rate and exhibits distinct regioselectivity for internal alkene hydroboration.

Homogeneous catalysts can promote the oxidation of primary amines to nitriles without added chemical oxidants. An amide-derived N,N,N-ruthenium(II)–hydride complex was discovered that promotes the dehydrogenation of primary and secondary amines to the corresponding nitriles and imines with concomitant liberation of H2, notably without added hydrogen acceptor or base. The dehydrogenative protocol is tolerant of substrates that contain oxidizable functionality and is selective for the dehydrogenation of primary amines (-CH2NH2) in the presence of amines without α-CH hydrogens.

The bmpi (1,3-bis(6′-methyl-2′-pyridylimino)isoindoline) pincer Ru(II) hydride complex catalyzes base-free, acceptorless, and chemoselective dehydrogenation of alcohols with liberation of dihydrogen under moderate (

An amide-derived N,N,N-Ru(II) complex catalyzes the conversion of EtOH to 1-BuOH with high activity. Conversion to alcohol upgraded products exceeds 250 turnovers per hour (>50% conversion) with 0.1 mol% catalyst loading. In addition to high activity for ethanol upgrading, catalytic reactions can be set up under ambient conditions with no loss in activity.

The protocol does not require any oxidant or hydrogen acceptor additives, tolerates oxidizable functionalities and liberates hydrogen as a product.

An amide-derived NNN-Ru(II) hydride complex catalyzes oxidant-free, acceptorless, and chemoselective dehydrogenation of primary and secondary amines to the corresponding nitriles and imines with liberation of dihydrogen. The catalyst system tolerates oxidizable functionality and is selective for the dehydrogenation of primary amines (-CH2NH2) in the presence of amines without α-CH hydrogens.