Oxygen Atom Transfer and Intramolecular Nitrene Transfer in a Rhenium β‑Diketiminate Complex

We present two routes to the oxo rhenium complex OReCl₂(BDI) (<b>1</b>) (BDI = <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)-β-diketiminate) and discuss the properties and reactivity of this material. Several adducts of <b>1</b> with DMAP (<b>1-DMAP</b>; DMAP = 4-dimethylaminopyridine), isonitriles (<b>1-XylNC</b>; XylNC = 2,6-dimethylphenyl isocyanide), and phosphines (<b>1-PEt</b>_<b>3</b>; PEt₃ = triethylphosphine) were isolated and characterized. Additionally, to probe the ancillary limitations of the BDI framework in high-valent rhenium complexes, oxygen atom transfer (OAT) reactivity with <b>1</b> was pursued. It was found that under thermolysis conditions OAT between <b>1</b> and PEt₃ was observed by NMR spectroscopy, which indicated the formation of a new species, (ArN)­ReCl₂­(MAD)­(PEt₃) (<b>2</b>; Ar = 2,6-diisopropylphenyl, MAD = 4-((2,6-diisopropylphenyl)­imino)­pent-2-enide). A mechanism for the generation of <b>2</b> involving nitrene transfer to rhenium from the BDI ligand is proposed. X-ray crystal structures of complexes <b>1</b>, <b>1-PEt</b>_<b>3</b>, <b>1-DMAP</b>, and <b>2</b> were determined and are discussed in detail

Oxygen Atom Transfer and Intramolecular Nitrene Transfer in a Rhenium β‑Diketiminate Complex

We present two routes to the oxo rhenium complex OReCl₂(BDI) (<b>1</b>) (BDI = <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)-β-diketiminate) and discuss the properties and reactivity of this material. Several adducts of <b>1</b> with DMAP (<b>1-DMAP</b>; DMAP = 4-dimethylaminopyridine), isonitriles (<b>1-XylNC</b>; XylNC = 2,6-dimethylphenyl isocyanide), and phosphines (<b>1-PEt</b>_<b>3</b>; PEt₃ = triethylphosphine) were isolated and characterized. Additionally, to probe the ancillary limitations of the BDI framework in high-valent rhenium complexes, oxygen atom transfer (OAT) reactivity with <b>1</b> was pursued. It was found that under thermolysis conditions OAT between <b>1</b> and PEt₃ was observed by NMR spectroscopy, which indicated the formation of a new species, (ArN)­ReCl₂­(MAD)­(PEt₃) (<b>2</b>; Ar = 2,6-diisopropylphenyl, MAD = 4-((2,6-diisopropylphenyl)­imino)­pent-2-enide). A mechanism for the generation of <b>2</b> involving nitrene transfer to rhenium from the BDI ligand is proposed. X-ray crystal structures of complexes <b>1</b>, <b>1-PEt</b>_<b>3</b>, <b>1-DMAP</b>, and <b>2</b> were determined and are discussed in detail

Oxygen Atom Transfer and Intramolecular Nitrene Transfer in a Rhenium β‑Diketiminate Complex

We present two routes to the oxo rhenium complex OReCl₂(BDI) (<b>1</b>) (BDI = <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)-β-diketiminate) and discuss the properties and reactivity of this material. Several adducts of <b>1</b> with DMAP (<b>1-DMAP</b>; DMAP = 4-dimethylaminopyridine), isonitriles (<b>1-XylNC</b>; XylNC = 2,6-dimethylphenyl isocyanide), and phosphines (<b>1-PEt</b>_<b>3</b>; PEt₃ = triethylphosphine) were isolated and characterized. Additionally, to probe the ancillary limitations of the BDI framework in high-valent rhenium complexes, oxygen atom transfer (OAT) reactivity with <b>1</b> was pursued. It was found that under thermolysis conditions OAT between <b>1</b> and PEt₃ was observed by NMR spectroscopy, which indicated the formation of a new species, (ArN)­ReCl₂­(MAD)­(PEt₃) (<b>2</b>; Ar = 2,6-diisopropylphenyl, MAD = 4-((2,6-diisopropylphenyl)­imino)­pent-2-enide). A mechanism for the generation of <b>2</b> involving nitrene transfer to rhenium from the BDI ligand is proposed. X-ray crystal structures of complexes <b>1</b>, <b>1-PEt</b>_<b>3</b>, <b>1-DMAP</b>, and <b>2</b> were determined and are discussed in detail

A Homoleptic Uranium(III) Tris(aryl) Complex

The reaction of 3 equiv of Li–C₆H₃-2,6-(C₆H₄-4-^<i>t</i>Bu)₂ (Terph–Li) with UI₃(1,4-dioxane)_1.5 led to the formation of the homoleptic uranium­(III) tris­(aryl) complex (Terph)₃U (<b>1</b>). The U–C bonds are reactive: treatment with excess ^<i>i</i>PrNCN^<i>i</i>Pr yielded the double-insertion product [TerphC­(N^<i>i</i>Pr)₂]₂U­(Terph) (<b>2</b>). Complexes <b>1</b> and <b>2</b> were characterized by X-ray crystallography, which showed that the U–C bond length in <b>2</b> (2.624(4) Å) is ∼0.1 Å longer than the average U–C bond length in <b>1</b> (2.522(2) Å). Thermal decomposition of <b>1</b> yielded Terph–H as the only identifiable product; the process is unimolecular with activation parameters Δ<i>H</i>^⧧ = 21.5 ± 0.3 kcal/mol and Δ<i>S</i>^⧧ = −7.5 ± 0.8 cal·mol^–1 K^–1, consistent with intramolecular proton abstraction. The protonolysis chemistry of <b>1</b> was also explored, which led to the uranium­(IV) alkoxide complex U­(OCPh₃)₄(DME) (<b>3·DME</b>)

Hydroboration Reactivity of Niobium Bis(N-heterocyclic carbene)borate Complexes

The syntheses of high-valent niobium imido complexes [H₂B­(^MesIm)₂]­Nb­(N^<i>t</i>Bu)­Cl₂ (<b>2</b>) and [H₂B­(^MesIm)₂]­Nb­(N^<i>t</i>Bu)­Me₂ (<b>3</b>) bearing a bis­(NHC)­borate (NHC = N-heterocyclic carbene) supporting ligand are described. The reaction of the dimethyl complex (<b>3</b>) with excess CO generates an equivalent of acetone, which inserts into a B–H bond of the bis­(NHC)­borate ligand to form a boryl isopropoxide/niobium­(III) dicarbonyl complex (<b>4</b>). This mode of hydroboration reactivity also occurs readily upon the treatment of either <b>2</b> or <b>3</b> with ketones, aldehydes, and isocyanates. Modification of the bis­(carbene) ligand of <b>3</b> via the hydroboration of benzophenone produces the dimethylniobium complex [(OCHPh₂)₂B­(^MesIm)₂]­Nb­(N^<i>t</i>Bu)­Me₂ (<b>12</b>), which undergoes intramolecular η⁶-arene coordination upon hydrogenation

Low Part-Per-Trillion, Humidity Resistant Detection of Nitric Oxide Using Microtoroid Optical Resonators

The nitric oxide radical plays pivotal roles in physiological as well as atmospheric contexts. Although the detection of dissolved nitric oxide in vivo has been widely explored, highly sensitive (i.e., low part-per-trillion level), selective, and humidity-resistant detection of gaseous nitric oxide in air remains challenging. In the field, humidity can have dramatic effects on the accuracy and selectivity of gas sensors, confounding data, and leading to overestimation of gas concentration. Highly selective and humidity-resistant gaseous NO sensors based on laser-induced graphene were recently reported, displaying a limit of detection (LOD) of 8.3 ppb. Although highly sensitive (LOD = 590 ppq) single-wall carbon nanotube NO sensors have been reported, these sensors lack selectivity and humidity resistance. In this report, we disclose a highly sensitive (LOD = 2.34 ppt), selective, and humidity-resistant nitric oxide sensor based on a whispering-gallery mode microtoroid optical resonator. Excellent analyte selectivity was enabled via novel ferrocene-containing polymeric coatings synthesized via reversible addition–fragmentation chain-transfer polymerization. Utilizing a frequency locked optical whispering evanescent resonator system, the microtoroid’s real-time resonance frequency shift response to nitric oxide was tracked with subfemtometer resolution. The lowest concentration experimentally detected was 6.4 ppt, which is the lowest reported to date. Additionally, the performance of the sensor remained consistent across different humidity environments. Lastly, the impact of the chemical composition and molecular weight of the novel ferrocene-containing polymeric coatings on sensing performance was evaluated. We anticipate that our results will have impact on a wide variety of fields where NO sensing is important such as medical diagnostics through exhaled breath, determination of planetary habitability, climate change, air quality monitoring, and treating cardiovascular and neurological disorders