A Bidentate Ligand Featuring Ditopic Lewis Acids in the Second Sphere for Selective Substrate Capture and Activation

We present a ligand platform featuring appended ditopic Lewis acids to facilitate capture/activation of diatomic substrates. We show that incorporation of two 9-borabicyclo[3.3.1]nonane (9-BBN) units on a single carbon tethered to a pyridine pyrazole scaffold maintains a set of unquenched nitrogen donors available to coordinate FeII, ZnII, and NiII. Using hydride ion affinity and competition experiments, we establish an additive effect for ditopic secondary sphere boranes, compared to the monotopic analogue. These effects are exploited to achieve high selectivity for binding NO2− in the presence of competitive anions such as F− and NO3−. Finally, we demonstrate hydrazine capture within the second-sphere of metal complexes, followed by unique activation pathways to generate hydrazido and diazene ligands on Zn and Fe, respectively.We report the synthesis of a bidentate ligand featuring secondary sphere ditopic Lewis acids. We verify a Lewis acid additivity effect for the ditopic boranes compared to a monotopic analogue using hydride ion affinity and competition studies. We show chemoselective nitrite capture in the presence of other anions. Pre-organized hydrazine adducts in the second sphere of Zn and Fe are functionalized to hydrazido and diazene ligands, respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/176032/1/ange202218907.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/176032/2/ange202218907_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/176032/3/ange202218907-sup-0001-misc_information.pd

Hydrazine Capture and N–N Bond Cleavage at Iron Enabled by Flexible Appended Lewis Acids

Incorporation of two 9-borabicyclo[3.3.1]­nonyl substituents within the secondary coordination sphere of a pincer-based Fe­(II) complex provides Lewis acidic sites capable of binding 1 or 2 equiv of N₂H₄. Reduction of the 1:1 Fe:N₂H₄ species affords a rare Fe­(NH₂)₂ complex in which the amido ligands are stabilized through interactions with the appended boranes. The NH₂ units can be released as NH₃ upon protonation and exchanged with exogenous N₂H₄

Hydrogen Bonds Dictate O₂ Capture and Release within a Zinc Tripod

Six directed hydrogen bonding (H-bonding) interactions allow for the reversible capture and reduction of dioxygen to a <i>trans</i>-1,2-peroxo within a tripodal zinc­(II) framework. Spectroscopic studies of the dizinc peroxides, as well as on model zinc diazides, suggest H-bonding contributions serve a dominant role for the binding/activation of these small molecules

Hydrazone and Oxime Olefination via Ruthenium Alkylidenes

We describe the development of an efficient method for the olefination of hydrazones and oximes. The key design approach that enables this transformation is tuning of the energy/polarity of C=N π-bonds by employing heteroatom functionalities (NR2, OR). The resulting hydrazones or oximes facilitate olefination with ruthenium alkylidenes. Through this approach, we show that air-stable, commercially available ruthenium alkylidenes provide access to functionalized alkenes (20 examples) in ring-closing reactions with yields up to 88 %.Olefination of carbon–heteroatom double bonds is a powerful approach to access highly functionalized olefins. An approach is reported here that uses air-stable and commercially available ruthenium alkylidenes to promote C=N/olefin ring closure. The enabling strategy for this reaction is the use of hydrazones and oximes as readily accessible substrates that preferentially react with ruthenium alkylidenes, even in the presence of carbonyl groups.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/172859/1/anie202112101-sup-0001-misc_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172859/2/anie202112101_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172859/3/anie202112101.pd

Hydrazone and Oxime Olefination via Ruthenium Alkylidenes

We describe the development of an efficient method for the olefination of hydrazones and oximes. The key design approach that enables this transformation is tuning of the energy/polarity of C=N π-bonds by employing heteroatom functionalities (NR2, OR). The resulting hydrazones or oximes facilitate olefination with ruthenium alkylidenes. Through this approach, we show that air-stable, commercially available ruthenium alkylidenes provide access to functionalized alkenes (20 examples) in ring-closing reactions with yields up to 88 %.Olefination of carbon–heteroatom double bonds is a powerful approach to access highly functionalized olefins. An approach is reported here that uses air-stable and commercially available ruthenium alkylidenes to promote C=N/olefin ring closure. The enabling strategy for this reaction is the use of hydrazones and oximes as readily accessible substrates that preferentially react with ruthenium alkylidenes, even in the presence of carbonyl groups.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/172797/1/ange202112101-sup-0001-misc_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172797/2/ange202112101_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172797/3/ange202112101.pd