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1. Selective electrochemical capture and release of uranyl from aqueous alkali, lanthanide, and actinide mixtures using redox-switchable carboranes

   https://doi.org/10.1039/D1SC07070C  

   Keener, Megan; Mattejat, Maxwell; Zheng, Shao-Liang; Wu, Guang; Hayton, Trevor W.; Ménard, Gabriel (March 2022, Chemical Science)

   We report the selective electrochemical biphasic capture of the uranyl cation (UO 2 2+ ) from mixed-metal alkali (Cs + ), lanthanide (Nd 3+ , Sm 3+ ), and actinide (Th 4+ , UO 2 2+ ) aqueous solutions to an organic, 1,2-dichloroethane (DCE), phase using the ortho -substituted nido -carborane anion, [1,2-(Ph 2 PO) 2 -1,2-C 2 B 10 H 10 ] 2− (POCb2−). The reduced POCb2− is generated by electrochemical reduction of the closo -carborane, POCb, prior to mixing with the aqueous mixed-metal solution. Subsequent UO 2 2+ release from the captured product, [UO2(POCb)2]2−, was performed by galvanostatic bulk electrolysis of the DCE phase and back-extraction of UO 2 2+ to a fresh aqueous phase. The selective capture and release of UO 2 2+ was confirmed by combined ICP-OES and NMR spectral analyses of the aqueous and organic phases, respectively, against the newly synthesized nido -carborane complexes, [[CoCp*2][Cs(POCb)]]2, [CoCp*2]3[Nd(POCb)3], [CoCp*2]3[Sm(POCb)3], and [CoCp*2]2[Th(POCb)3]. 

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2. Reactivity of bi- and monometallic trifluoroacetates towards amorphous SiO ₂

   https://doi.org/10.1039/d2dt02822k  

   Munasinghe, Hashini N.; Imer, Marcos R.; Szlag, Regina G.; Suescun, Leopoldo; Rabuffetti, Federico A. (December 2022, Dalton Transactions)

   The reactivity of alkali–manganese( ii ) and alkali trifluoroacetates towards amorphous SiO 2 (a-SiO 2 ) was studied in the solid-state. K 4 Mn 2 (tfa) 8 , Cs 3 Mn 2 (tfa) 7 (tfaH), KH(tfa) 2 , and CsH(tfa) 2 (tfa = CF 3 COO – ) were thermally decomposed under vacuum in fused quartz tubes. Three new bimetallic fluorotrifluoroacetates of formulas K 4 Mn 3 (tfa) 9 F, Cs 4 Mn 3 (tfa) 9 F, and K 2 Mn(tfa) 3 F were discovered upon thermolysis at 175 °C. K 4 Mn 3 (tfa) 9 F and Cs 4 Mn 3 (tfa) 9 F feature a triangular-bridged metal cluster of formula [Mn 3 (μ 3 -F)(μ 2 -tfa) 6 (tfa) 3 ] 4− . In the case of K 2 Mn(tfa) 3 F, fluoride serves as an inverse coordination center for the tetrahedral metal cluster K 2 Mn 2 (μ 4 -F). Fluorotrifluoroacetates may be regarded as intermediates in the transformation of bimetallic trifluoroacetates to fluoroperovskites KMnF 3 , CsMnF 3 , and Cs 2 MnF 4 , which crystallized between 250 and 600 °C. Decomposition of these trifluoroacetates also yielded alkali hexafluorosilicates K 2 SiF 6 and Cs 2 SiF 6 as a result of the fluorination of fused quartz. The ability to fluorinate fused quartz was observed for monometallic alkali trifluoroacetates as well. Hexafluorosilicates and heptafluorosilicates K 3 SiF 7 and Cs 3 SiF 7 were obtained upon thermolysis of KH(tfa) 2 and CsH(tfa) 2 between 200 and 400 °C. This ability was exploited to synthesize fluorosilicates under air by simply reacting alkali trifluoroacetates with a-SiO 2 powder. 

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3. Mechanochemical synthesis and structural analysis of trivalent lanthanide and uranium diphenylphosphinodiboranates

   https://doi.org/10.1039/d1dt01932e  

   Fetrow, Taylor V.; Daly, Scott R. (August 2021, Dalton Transactions)

   null (Ed.)

   Phosphinodiboranates (H 3 BPR 2 BH 3 − ) are a class of borohydrides that have merited a reputation as weakly coordinating anions, which is attributed in part to the dearth of coordination complexes known with transition metals, lanthanides, and actinides. We recently reported how K(H 3 BP t Bu 2 BH 3 ) exhibits sluggish salt elimination reactivity with f-metal halides in organic solvents such as Et 2 O and THF. Here we report how this reactivity appears to be further attenuated in solution when the t Bu groups attached to phosphorus are exchanged for R = Ph or H, and we describe how mechanochemistry was used to overcome limited solution reactivity with K(H 3 BPPh 2 BH 3 ). Grinding three equivalents of K(H 3 BPPh 2 BH 3 ) with UI 3 (THF) 4 or LnI 3 (Ln = Ce, Pr, Nd) allowed homoleptic complexes with the empirical formulas U(H 3 BPPh 2 BH 3 ) 3 (1), Ce(H 3 BPPh 2 BH 3 ) 3 (2), Pr(H 3 BPPh 2 BH 3 ) 3 (3), and Nd(H 3 BPPh 2 BH 3 ) 3 (4) to be prepared and subsequently crystallized in good yields (50–80%). Single-crystal XRD studies revealed that all four complexes exist as dimers or coordination polymers in the solid-state, whereas 1 H and 11 B NMR spectra showed that they exist as a mixture of monomers and dimers in solution. Treating 4 with THF breaks up the dimer to yield the monomeric complex Nd(H 3 BPPh 2 BH 3 ) 3 (THF) 3 (4-THF). XRD studies revealed that 4-THF has one chelating and two dangling H 3 BPPh 2 BH 3 − ligands bound to the metal to accommodate binding of THF. In contrast to the results with K(H 3 BPPh 2 BH 3 ), attempting the same mechanochemical reactions with Na(H 3 BPH 2 BH 3 ) containing the simplest phosphinodiboranate were unsuccessful; only the partial metathesis product U(H 3 BPH 2 BH 3 )I 2 (THF) 3 (5) was isolated in poor yields. Despite these limitations, our results offer new examples showing how mechanochemistry can be used to rapidly synthesize molecular coordination complexes that are otherwise difficult to prepare using more traditional solution methods. 

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4. Threshold Ion Energies and Cleaning of Etch Residues During Inductively Coupled Etching of NiO/Ga ₂ O ₃ in BCl ₃

   https://doi.org/10.1149/2162-8777/ac9ff3  

   Chiang, Chao-Ching; Xia, Xinyi; Li, Jian-Sian; Ren, Fan; Pearton, S. J. (November 2022, ECS Journal of Solid State Science and Technology)

   BCl 3 is an attractive plasma etchant for oxides because it is a Lewis acid used to scavenge native oxides on many semiconductors due to the strong B–O bonding. We investigated BCl 3 -based dry etching of the NiO/Ga 2 O 3 heterojunction system. BCl 3 /Ar Inductively Coupled Plasmas produced maximum etch rates for NiO up to 300 Å.min −1 and 800 Å.min −1 for β -Ga 2 O 3 under moderate plasma power conditions suitable for low damage pattern transfer. The selectivity for NiO: Ga 2 O 3 was <1 under all conditions. The ion energy threshold for initiation of etching of NiO was between 35–60 eV, depending on the condition and the etch mechanism was ion-driven, as determined by the linear dependence of etch rate on the square root of ion energy incident on the surface. By sharp contrast, the etching of Ga 2 O 3 had a stronger chemical component, without a well-defined ion energy threshold. The as-etched NiO and Ga 2 O 3 surfaces show chlorine residues, which can be removed on both materials by the standard 1NH 4 OH: 10H 2 O or 1HCl: 10H 2 O rinses used for native oxide removal. According to the location of the Cl 2p 3/2 peak, the Cl is ionically bonded. 

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5. Reduction-induced CO dissociation by a [Mn(bpy)(CO) ₄ ][SbF ₆ ] complex and its relevance in electrocatalytic CO ₂ reduction

   https://doi.org/10.1039/c9dt04150h  

   Kuo, Hsin-Ya; Tignor, Steven E.; Lee, Tia S.; Ni, Danrui; Park, James Eujin; Scholes, Gregory D.; Bocarsly, Andrew B. (January 2020, Dalton Transactions)

   [Mn(bpy)(CO) 3 Br] is recognized as a benchmark electrocatalyst for CO 2 reduction to CO, with the doubly reduced [Mn(bpy)(CO) 3 ] − proposed to be the active species in the catalytic mechanism. The reaction of this intermediate with CO 2 and two protons is expected to produce the tetracarbonyl cation, [Mn(bpy)(CO) 4 ] + , thereby closing the catalytic cycle. However, this species has not been experimentally observed. In this study, [Mn(bpy)(CO) 4 ][SbF 6 ] ( 1 ) was directly synthesized and found to be an efficient electrocatalyst for the reduction of CO 2 to CO in the presence of H 2 O. Complex 1 was characterized using X-ray crystallography as well as IR and UV-Vis spectroscopy. The redox activity of 1 was determined using cyclic voltammetry and compared with that of benchmark manganese complexes, e.g. , [Mn(bpy)(CO) 3 Br] ( 2 ) and [Mn(bpy)(CO) 3 (MeCN)][PF 6 ] ( 3 ). Infrared spectroscopic analyses indicated that CO dissociation occurs after a single-electron reduction of complex 1 , producing a [Mn(bpy)(CO) 3 (MeCN)] + species. Complex 1 was experimentally verified as both a precatalyst and an on-cycle intermediate in homogeneous Mn-based electrocatalytic CO 2 reduction. 

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