The first structurally characterized example of a trioxaborinanone (2) is produced by the reaction of a 9-carbene-9-borafluorene monoanion and carbon dioxide. When compound 2 is heated or irradiated with UV light, carbon monoxide (CO) is released, and a luminescent dioxaborinanone (3) is formed. Notably, carbon monoxide releasing molecules (CORMs) are of interest for their ability to deliver a specific amount of CO. Due to the turn-on fluorescence observed as a result of the conversion to 3, CORM 2 serves as a means to optically observe CO loss “by eye” under thermal or photochemical conditions.

Ferroelectric HfO₂ holds promise for many applications, including non-volatile on-chip memory and ferroelectric field-effect transistors. One challenge preventing the integration of ferroelectric HfO₂ into devices is the difficulty to unambiguously prepare phase-pure material without the benefits of epitaxy. Here, a new method for preparing ferroelectric HfO₂ is presented using High-Power Impulse Magnetron Sputtering (HiPIMS). HiPIMS offers a unique combination of processing parameters such as incident ion energy and gas atmosphere that are inaccessible through conventional HfO₂ synthesis by atomic layer deposition (ALD). In this work, the impact of plasma oxygen content on the crystallization, phase constitution, microstructure, and ferroelectric properties of undoped HfO₂ films deposited by HiPIMS is investigated. HfO₂ thin films were reactively sputtered with plasma oxygen content varied from 7.1 to 8.0 %. The impact of grain size on performance and phases present was assessed, and the results show that the microstructure does not strongly vary between ferroelectric and non-ferroelectric samples. It will be shown that the oxygen content in the plasma directly relates to the oxygen content in the films, as assessed by electron energy-loss spectroscopy, X-ray photoelectron spectroscopy, and positron annihilation spectroscopy. This oxygen content strongly influences phase formation and ferroelectric performance. High concentrations of neutral oxygen vacancies are identified in crystalline ferroelectric samples and allow for low leakage currents. These results show that oxygen content can be used to dictate phase nucleation and provide a path toward phase-pure polycrystalline ferroelectric HfO₂.

Silica-supported Pd, Rh and Pt metal nanoparticles catalyze the hydrogenolysis of the Pt−OPh bond of (^tbpy)Pt(OPh)Cl to release PhOH. Based on kinetic studies monitored by ¹H NMR spectroscopy, the reactivity trend is Pd>Rh>Pt. Kinetic studies with Pd/SiO₂ are consistent with a first-order dependence on the catalyst and the molecular Pt(II) complex (^tbpy)Pt(OPh)Cl. Using TEM-EDS mapping and ICP-OES measurements of a recovered Pd catalyst, after 1 hour of hydrogenolysis of (^tbpy)Pt(OPh)Cl, approximately 10–16 % Pt deposition (relative to Pd mol %) on the Pd/SiO₂ surface was quantified.

A recent advance in the synthesis of alkenylated arenes was the demonstration that the Pd(OAc)₂ catalyst precursor gives >95% selectivity toward styrene from ethylene and benzene under optimized conditions using excess Cu(II) carboxylate as the in situ oxidant [ Organometallics 2019, 38(19), 3532−3541]. To understand the mechanism underlying this catalysis, we applied density functional theory (DFT) calculations in combination with experimental studies. From DFT calculations, we determined the lowest-energy multimetallic Pd and Pd–Cu mixed metal species as possible catalyst precursors. From the various structures, we determined the cyclic heterotrinuclear complex PdCu₂(μ-OAc)₆ to be the global minimum in Gibbs free energy under conditions of excess Cu(II). For cyclic PdCu₂(μ-OAc)₆ and the parent [Pd(μ-OAc)₂]₃, we evaluated the barriers for benzene C–H activation through concerted metalation deprotonation (CMD). The PdCu₂(μ-OAc)₆ cyclic trimer leads to a CMD barrier of 33.5 kcal/mol, while the [Pd(μ-OAc)₂]₃ species leads to a larger CMD barrier at >35 kcal/mol. This decrease in the CMD barrier arises from the insertion of Cu(II) into the trimetallic species. Because cyclic PdCu₂(μ-OAc)₆ is likely the predominant species under experimental conditions (the Cu to Pd ratio is 480:1 at the start of catalysis) with a predicted CMD barrier within the range of the experimentally determined activation barrier, we propose that cyclic PdCu₂(μ-OAc)₆ is the Pd species responsible for catalysis and report a full reaction mechanism based on DFT calculations. For catalytic conversion of benzene and ethylene to styrene at 120 °C using Pd(OAc)₂ as the catalyst precursor and Cu(OPiv)₂ (OPiv = pivalate) as the oxidant, an induction period of ∼1 h was observed, followed by catalysis with a turnover frequency of ∼2.3 × 10^–3 s^–1. In situ¹H NMR spectroscopy experiments indicate that during the induction period, Pd(OAc)₂ is likely converted to cyclic PdCu₂(η²-C₂H₄)₃(μ-OPiv)₆, which is consistent with the calculations and consistent with the proposal that the active catalyst is the ethylene-coordinated heterotrinuclear complex cyclic PdCu₂(η²-C₂H₄)₃(μ-OPiv)₆.

Ruthenium(II) complexes with the general formula TpRu(L)(NCMe)Ph (Tp = hydrido(trispyrazolyl)borate, L = CO, PMe₃, P(OCH₂)₃CEt, P(pyr)₃, P(OCH₂)₂(O)CCH₃) have previously been shown to catalyze arene alkylation via Ru-mediated arene C–H activation including the conversion of benzene and ethylene to ethylbenzene. Previous studies have suggested that the catalytic performance of these TpRu(II) catalysts increases with reduced electron-density at the Ru center. Herein, three new structurally related Ru(II) complexes are synthesized, characterized, and studied for possible catalytic benzene ethylation. TpRu(NO)Ph₂ exhibited low stability due to the facile elimination of biphenyl. The Ru(II) complex (Tp^Br3)Ru(NCMe)(P(OCH₂)₃CEt)Ph (Tp^Br3 = hydridotris(3,4,5-tribromopyrazol-1-yl)borate) showed no catalytic activity for the conversion of benzene and ethylene to ethylbenzene, likely due to the steric bulk introduced by the bromine substituents. (Ttz)Ru(NCMe)(P(OCH₂)₃CEt)Ph (Ttz = hydridotris(1,2,4-triazol-1-yl)borate) catalyzed approximately 150 turnover numbers (TONs) of ethylbenzene at 120 °C in the presence of Lewis acid additives. Here, we compare the activity and features of catalysis using (Ttz)Ru(NCMe)(P(OCH₂)₃CEt)Ph to previously reported catalysis based on TpRu(L)(NCMe)Ph catalyst precursors.

Two new pyrazine-bridged, linear chain complexes of Cu(II) of formula [Cu(pzdo)2(H2O)2(pz)](A)2·nH2O [pzdo = pyrazine-N,N′-dioxide; pz = pyrazine; A = BF4− (1), ClO4− (2)] have been prepared. Single-crystal X-ray diffraction shows the Cu ions to be six-coordinate, pyrazine-bridged chains with trans-pairs of ancillary ligands. The pzdo molecules are coordinated through their oxygen atoms. The ClO4− and BF4− anions are each two-site disordered in the lattice. Further, there are partial occupancy water molecules in the lattice which are very weakly bound. The structures are stabilized by hydrogen bonds between the coordinated water molecules and the non-coordinated pzdo oxygen atoms as well as the anions. Variable temperature magnetic susceptibility data show antiferromagnetic interactions and the data were fit to the uniform chain model yielding J/kB = −13.0(2) K and −11.8(2) K for 1 and 2, respectively []. In addition, the structure of the serendipitously prepared compound [Cu(pz)(pzdo)(H2O)2](ClO4)2 (3) is described. The compound crystallizes as rectangular layers of Cu(II) ions bridged by pzdo (parallel to the a-axis) and pyrazine (parallel to the b-axis) with water molecules coordinated in the axial sites.

We report a new terpyridine-based FeN₃O catalyst, Fe(tpy^tbupho)Cl₂, which reduces O₂ to H₂O. Variable concentration and variable temperature spectrochemical studies with decamethylferrocene as a chemical reductant in acetonitrile solution enabled the elucidation of key reaction parameters for the catalytic reduction of O₂ to H₂O by Fe(tpy^tbupho)Cl₂. These mechanistic studies suggest that a 2 + 2 mechanism is operative, where hydrogen peroxide is produced as a discrete intermediate, prior to further reduction to H₂O. Consistent with this proposal, the spectrochemically measured first-order rate constant k (s⁻¹) value for H₂O₂ reduction is larger than that for O₂ reduction. Further, significant H₂O₂ production is observed under hydrodynamic conditions in rotating ring-disk electrode measurements, where the product can be swept away from the cathode surface before further reduction occurs.

A novel process is described for the synthesis of di- and trisubstituted cyclohexenes from an arene. These compounds are prepared from three independent nucleophilic addition reactions to a phenyl sulfone (PhSO₂R; R = Me, Ph, and NC₄H₈) dihapto-coordinated to the tungsten complex {WTp(NO)(PMe₃)}(Tp = trispyrazolylborate). Such a coordination renders the dearomatized aryl ring susceptible to protonation at a carbon ortho to the sulfone group. The resulting arenium species readily reacts with the first nucleophile to form a dihapto-coordinated sulfonylated diene complex. This complex can again be protonated, and the subsequent nucleophilic addition forms a trisubstituted cyclohexene species bearing a sulfonyl group at an allylic position. Loss of the sulfinate anion forms a π-allyl species, to which a third nucleophile can be added. The trisubstituted cyclohexene can then be oxidatively decomplexed, either before or after substitution of the sulfonyl group. Nucleophiles employed include masked enolates, cyanide, amines, amides, and hydride, with all three additions occurring to the same face of the ring, anti to the metal. Of the 12 novel functionalized cyclohexenes prepared as examples of this methodology, nine compounds meet five independent criteria for evaluating drug likeliness. Structural assignments are supported with nine crystal structures, density functional theory studies, and full 2D NMR analysis.