Borate Ligand Research Articles

Driving Barocaloric Effects in a Molecular Spin-Crossover Complex at Low Pressures.

Barocaloric effects─thermal changes in a material induced by applied hydrostatic pressure─offer promise for creating solid-state refrigerants as alternatives to conventional volatile refrigerants. To enable efficient and scalable barocaloric cooling, materials that undergo high-entropy, reversible phase transitions in the solid state in response to a small change in pressure are needed. Here, we report that pressure-induced spin-crossover (SCO) transitions in the molecular iron(II) complex Fe[HB(tz)3]2 (HB(tz)3- = bis[hydrotris(1,2,4-triazol-1-yl)borate]) drive giant and reversible barocaloric effects at easily accessible pressures. Specifically, high-pressure calorimetry and powder X-ray diffraction studies reveal that pressure shifts as low as 10 bar reversibly induce nonzero isothermal entropy changes, and a pressure shift of 150 bar reversibly induces a large isothermal entropy change (>90 J kg-1 K-1) and adiabatic temperature change (>2 K). Moreover, we demonstrate that the thermodynamics of the SCO transition can be fine-tuned through systematic deuteration of the tris(triazolyl)borate ligand. These results provide new insights into pressure-induced SCO transitions and further establish SCO materials as promising barocaloric materials.

Boosting oxygen evolution reaction of hierarchical spongy NiFe-PBA/Ni3C(B) electrocatalyst: Interfacial engineering with matchable structure

Rational interfacial structure with excellent charge transfer and exposure of numerous active sites plays vital roles in heterogeneous catalysis. Herein, a hierarchical spongy electrocatalyst with active NiFe Prussian blue analogues and nickel carbides interface (NiFe-PBA/Ni3C(B)) is proposed and fabricated by a borate-assisted strategy. The unique structure and matchable interface benefit from the desorption of borate ligands in-situ during the pyrolysis and carbonization process. The optimal electrocatalyst composing of metal–organic framework (NiFe prussian blue analogues) in conjunction with a metallic transition carbide phase (nickel carbide) exhibits an ultra-low overpotential of only 196 mV at 10 mA cm−2 and a small Tafel slope of 30.1 mV dec-1 for OER in KOH. The robust water oxidation performance can be ascribed to the abundant adsorption sites and effective interfacial interaction. In addition, computational simulations further confirm that NiFe-PBA/Ni3C(B) is favorable for OER since the optimized electronic distribution and metal-3d orbitals interact around Fermi level at the interface. This research provides a new insight into rationally designing efficient electrocatalysts via morphology engineering and integrating different functional phase with complementary advantages for catalysis application.

Coordination and Hydroboration of Ru(II)-Borate Complexes: Dihydridoborate vs. Bis(dihydridoborate).

Treatment of [Cp*RuCl2 ]2 , 1, [(COD)IrCl]2 , 2 or [(p-cymene)RuCl2 ]2, 3 (Cp*=η5 -C5 Me5, COD= 1,5-cyclooctadiene and p-cymene=η6 -i PrC6 H4 Me) with heterocyclic borate ligands [Na[(H3 B)L], L1 and L2 (L1 : L=amt, L2 : L=mp; amt=2-amino-5-mercapto-1,3,4-thiadiazole, mp=2-mercaptopyridine) led to the formation of borate complexes having uncommon coordination. For example, complexes 1 and 2 on reaction with L1 and L2 afforded dihydridoborate species [LA M(μ-H)2 BHL] 4-6 (4: LA =Cp*, M=Ru, L=amt; 5: LA =Cp*, M=Ru, L=mp; 6: LA =COD, M=Ir, L=mp). On the other hand, treatment of 3 with L2 yielded cis- and trans-bis(dihydridoborate) species, [Ru{(μ-H)2 BH(mp)}2 ], cis-7 and trans-7. The isolation and structural characterization of fac- and mer-[Ru{(μ-H)2 BH(mp)}{(μ-H)BH(mp)2 }], 8 from the same reaction offered an insight into the behaviour of these dihydridoborate species in solution. Fascinatingly, despite having reduced natural charges on Ru centres both at cis-and trans-7, they underwent hydroboration reaction with alkynes that yielded both Markovnikov and anti-Markovnikov addition products, 10 a-d.

Conversion of Uranium(III) Anilido Complexes to Uranium(IV) Imido Complexes via Hydrogen Atom Transfer

A family of low-valent uranium(III) anilido complexes supported by the bulky hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) ligand was synthesized by combining Tp*2UBn (Bn = benzyl) (1-Bn) with anilines of varying steric bulk and electronic profiles, including 4-fluoroaniline, 3,5-difluoroaniline, 3,5-bis(trifluoromethyl)aniline, 3,5-dimethylaniline, 2,4,6-trimethylaniline, and 2,4,6-tri-tBu-aniline. The corresponding uranium(III) anilido species, Tp*2UNH(4-fluorophenyl) (2-pF), Tp*2UNH(3,5-difluorophenyl) (2-bisF), Tp*2UNH(3,5-bis(trifluoromethyl)phenyl) (2-bisCF3), Tp*2UNH(3,5-dimethylphenyl) (2-bisCH3), Tp*2UNH(2,4,6-trimethylphenyl) (2-Mes), and Tp*2UNH(2,4,6-tri-tBu-phenyl) (2-Mes*), were isolated, and reactivity was explored. Conversion to their respective uranium(IV) imido species (3-pF, 3-bisF, 3-bisCF3, 3-bisCH3, 3-Mes, and 3-Mes*) was achieved by hydrogen atom transfer using either Gomberg’s dimer or the 2,4,6-tri-tBu-phenoxy radical (·OMes*) which eliminates the need to use potentially explosive organic azides, a reagent that has been commonly used for the synthesis of uranium(IV) imido complexes. For comparison of yields and purity of all methods, the uranium imido complexes were also prepared using the corresponding organic azides. Where applicable, compounds were characterized by multinuclear NMR spectroscopy (1H, 11B, 19F), infrared spectroscopy, electronic absorption spectroscopy, and single crystal X-ray crystallography.

Fluorinated tris(pyridyl)borate ligand support on coinage metals.

A useful ligand involving three pyridyl donor arms and fluorocarbon substituents surrounding the coordination pocket has been assembled and utilized in coinage metal chemistry. This tris(pyridyl)borate serves as an excellent ligand support for the stabilization of ethylene complexes of copper, silver and gold.

Terminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate.

Copper plays an important role in alkyne coordination chemistry and transformations. This report describes the isolation and full characterization of a thermally stable, copper(I) acetylene complex using a highly fluorinated bis(pyrazolyl)borate ligand support. Details of the related copper(I) complex of HC≡CSiMe3 are also reported. They are three-coordinate copper complexes featuring η2-bound alkynes. Raman data show significant red-shifts in C≡C stretch of [H2B(3,5-(CF3)2Pz)2]Cu(HC≡CH) and [H2B(3,5-(CF3)2Pz)2]Cu(HC≡CSiMe3) relative to those of the corresponding alkynes. Computational analysis using DFT indicates that the Cu(I) alkyne interaction in these molecules is primarily of the electrostatic character. The π-backbonding is the larger component of the orbital contribution to the interaction. The dinuclear complexes such as Cu2(μ-[3,5-(CF3)2Pz])2(HC≡CH)2 display similar Cu-alkyne bonding features. The mononuclear [H2B(3,5-(CF3)2Pz)2]Cu(NCMe) complex catalyzes [3 + 2] cycloadditions between tolyl azide and a variety of alkynes including acetylene. It is comparatively less effective than the related trinuclear copper catalyst {μ-[3,5-(CF3)2Pz]Cu}3 involving bridging pyrazolates.

Tris-(2-pyridyl)-pyrazolyl Borate Zinc(II) Complexes: Synthesis, DNA/Protein Binding and In Vitro Cytotoxicity Studies.

Zn(II) complexes bearing tris[3-(2-pyridyl)-pyrazolyl] borate (Tppy) ligand (1–3) was synthesized and examined by spectroscopic and analytical tools. Mononuclear [TppyZnCl] (1) has a Zn(II) centre with one arm (pyrazolyl-pyridyl) dangling outside the coordination sphere which is a novel finding in TppyZn(II) chemistry. In complex [TppyZn(H2O)][BF4] (2) hydrogen bonding interaction of aqua moiety stabilizes the dangling arm. In addition, solution state behaviour of complex 1 confirms the tridentate binding mode and reactivity studies show the exogenous axial substituents used to form the [TppyZnN3] (3). The complexes (1–3) were tested for their ability to bind with Calf thymus (CT) DNA and Bovine serum albumin (BSA) wherein they revealed to exhibit good binding constant values with both the biomolecules in the order of 104–105 M−1. The intercalative binding mode with CT DNA was confirmed from the UV-Visible absorption, viscosity, and ethidium bromide (EB) DNA displacement studies. Further, the complexes were tested for in vitro cytotoxic ability on four triple-negative breast cancer (TNBC) cell lines (MDA-MB-231, MDA-MB-468, HCC1937, and Hs 578T). All three complexes (1–3) exhibited good IC50 values (6.81 to 16.87 μM for 24 h as seen from the MTS assay) results which indicated that these complexes were found to be potential anticancer agents against the TNBC cells.

A Molecular Compound for Highly Selective Purification of Ethylene.

Purification of C2 H4 from an C2 H4 /C2 H6 mixture is one of the most challenging separation processes, which is achieved mainly through energy-intensive, cryogenic distillation in industry. Sustainable, non-distillation methods are highly desired as alternatives. We discovered that the fluorinated bis(pyrazolyl)borate ligand supported copper(I) complex {[(CF3 )2 Bp]Cu}3 has features very desirable in an olefin-paraffin separation material. It binds ethylene exclusively over ethane generating [(CF3 )2 Bp]Cu(C2 H4 ). This molecular compound exhibits extremely high and record ideal adsorbed solution theory (IAST) C2 H4 /C2 H6 gas separation selectivity, affording high purity (>99.5 %) ethylene that can be readily desorbed from separation columns. In-situ PXRD provides a "live" picture of the reversible conversion between [(CF3 )2 Bp]Cu(C2 H4 ) and the ethylene-free sorbent in the solid-state, driven by the presence or removal of C2 H4 . Molecular structures of trinuclear {[(CF3 )2 Bp]Cu}3 and mononuclear [(CF3 )2 Bp]Cu(C2 H4 ) are also presented.

A Molecular Compound for Highly Selective Purification of Ethylene

AbstractPurification of C2H4 from an C2H4 /C2H6 mixture is one of the most challenging separation processes, which is achieved mainly through energy‐intensive, cryogenic distillation in industry. Sustainable, non‐distillation methods are highly desired as alternatives. We discovered that the fluorinated bis(pyrazolyl)borate ligand supported copper(I) complex {[(CF3)2Bp]Cu}3 has features very desirable in an olefin–paraffin separation material. It binds ethylene exclusively over ethane generating [(CF3)2Bp]Cu(C2H4). This molecular compound exhibits extremely high and record ideal adsorbed solution theory (IAST) C2H4 /C2H6 gas separation selectivity, affording high purity (>99.5 %) ethylene that can be readily desorbed from separation columns. In‐situ PXRD provides a “live” picture of the reversible conversion between [(CF3)2Bp]Cu(C2H4) and the ethylene‐free sorbent in the solid‐state, driven by the presence or removal of C2H4. Molecular structures of trinuclear {[(CF3)2Bp]Cu}3 and mononuclear [(CF3)2Bp]Cu(C2H4) are also presented.

Chalcogen stabilized borate complexes of tantalum

In an attempt to isolate some electron precise early transition metal borate complexes, we have explored the reactions of [Cp*TaCl4] (Cp* = η5-C5Me5) with chalcogen-based borate ligand Li[BH3(SPh)]. The room-temperature reaction yielded bimetallic borate complex [(Cp*Ta)2(μ-SPh){S(BH3)}{SPh(BH3)}] (1) that present two types of borate ligands, i.e., {BH3(SPh)} and {BH3(S)} ligands having unique coordination with the tantalum atoms. Interestingly, the {BH3(S)} ligand is coordinated to both the Ta centers in µ-η1:η2 fashion. On the other hand, thermolysis of [Cp*TaCl4] in the presence of Li[BH3(SPh)] yielded a bimetallic borate species [(Cp*Ta)2(µ-η3:η3-B2H4S){µ-η2:η2-S(C6H4)BH3}] (2). Compound 2 contains a triborane analog and a borate ligand, which are coordinated to two Ta atoms. This can also be considered as a notable example of CH activated molecule, in which a B-C bond formation took place. Both the borate species have been characterized by mass spectrometry, IR spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction studies. The density functional theory (DFT) calculations further provided insights into the bonding and electronic structures of these bimetallic borate species.

Facile Synthesis of Carbon- and Nitrogen-Doped Iron Borate as a Highly Efficient Single-Component Heterogeneous Photo-Fenton Catalyst under Simulated Solar Irradiation.

The development of a heterogeneous catalyst for use in environmental remediation remains a challenging and attractive research endeavor. Specifically, for Fenton reactions, most research approaches have focused on the preparation of iron-containing heterostructures as photo-Fenton catalysts that utilize visible light for enhancing the degradation efficiency. Herein, the synthesis and novel application of C,N-doped iron borates are demonstrated as single-component heterogeneous photo-Fenton catalysts with high Fenton activity under visible light. Under the optimal conditions, 10 mg of the catalyst is shown to achieve effective degradation of 10 ppm methylene blue (MB) dye, Rhodamine B (RhB) dye, and tetracycline (TC) under simulated solar irradiation with a first-order rate constant of k = 0.218 min−1, 0.177 min−1, and 0.116 min−1, respectively. Using MB as a model system, the C,N-doped iron borate exhibits 10- and 26-fold increases in catalytic activity relative to that of the 50 nm hematite nanoparticles and that of the non-doped iron borate, respectively, in the presence of H2O2 under the simulated solar irradiation. Furthermore, the optimum reaction conditions used only 320 equivalents of H2O2 with respect to the concentration of dye, rather than the several thousand equivalents of H2O2 used in conventional heterogeneous Fenton catalysts. In addition, the as-prepared C,N-doped iron borate achieves 75% MB degradation after 20 min in the dark, thus enabling the continuous degradation of pollutants at night and in areas with poor light exposure. The stability and recyclability of C,N-doped iron borate for the oxidation of MB was demonstrated over three cycles with insignificant loss in photo-Fenton activity. The high Fenton activity of the C,N-doped iron borate is considered to be due to the synergistic action between the negatively-charged borate ligands and the metal center in promoting the Fenton reaction. Moreover, carbon and nitrogen doping are shown to be critical in modifying the electronic structure and increasing the conductivity of the catalyst. In view of its synthetic simplicity, high efficiency, low cost of reagents, and minimal cost of operation (driven by natural sunlight), the as-prepared heterogeneous single-component metal borate catalyst has potential application in the industrial treatment of wastewater.

Lanthanide Cerium(III) Tris(pyrazolyl)borate Complexes: Efficient Blue Emitters for Doublet Organic Light-Emitting Diodes.

Organic light-emitting diodes (OLEDs) have had commercial success in displays and lighting. Compared to red and green OLEDs, blue OLEDs are still the bottleneck because the high-energy and long-lived triplet exciton in traditional blue OLEDs causes the short operational lifetime of the device. As a new type emitter, lanthanide complexes with a 5d-4f transition could have short excited-state lifetimes on the order of nanoseconds. To achieve a high-efficiency 5d-4f transition, we systematically tuned the steric and electronic effects of tripodal tris(pyrazolyl)borate ligands and drew a full picture of their Ce(III) complexes. Intriguingly, all of these complexes show bright blue emission with high photoluminescence quantum yields exceeding 95% and short decay lifetimes of 35-73 ns both in the solid powder and in dichloromethane solutions. Using the Ce(III) complex emitter, we show a blue OLED with a maximum external quantum efficiency of 14.1% and a maximum luminance of 33,160 cd m-2, and the specific electroluminescence mechanism of direct exciton formation on the Ce(III) ion with a near-unity exciton utilization efficiency is also confirmed. The discovered photoluminescence and electroluminescence property-structure relationships may shed new light on the rational design of highly efficient lanthanide-based blue emitters and their optoelectronic devices such as OLEDs.

Iron(II)-alkoxide and -aryloxide complexes of a tris(thioether)borate ligand: synthesis, molecular structures, and implications on the origin of instability of their iron(II)-catecholate counterpart.

The phenyltris[(tert-butylthio)methyl]borate ligand, [PhTttBu], has been studied extensively as a platform for coordination, organometallic, and bioinorganic chemistry, especially with 3d metals. While [PhTttBu]Co(3,5-DBCatH) (3,5-DBCatH is 3,5-di-tert-butylcatecholate), a CoII-monoanionic catecholate complex, was successfully isolated to model the active site of cobalt(II)-substituted homoprotocatechuate 2,3-dioxygenase (Co-HPCD) [Wang et al. (2019). Inorg. Chim. Acta, 488, 49-55], its iron(II) counterpart, [PhTttBu]Fe(3,5-DBCatH), was not accessible via similar synthetic routes. Switching the nucleophile from catecholate to alkoxide or aryloxide, however, led to the successful isolation of three highly air-sensitive FeII-alkoxide and -aryloxide complexes, namely, (triphenylmethoxo){tris[(tert-butylsulfanyl)methyl]phenylborato-κ3S,S',S''}iron(II), [Fe(C21H38BS3)(C19H15O)], (2), (2,6-dimethylphenolato){tris[(tert-butylsulfanyl)methyl]phenylborato-κ3S,S',S''}iron(II), [Fe(C21H38BS3)(C8H9O)], (3), and bis{μ-tris[(tert-butylsulfanyl)methyl]phenylborato-κ3S,S':S''}bis[(phenolato-κO)iron(II)] toluene disolvate, [Fe2(C21H38BS3)2(C6H5O)2]·2C7H8, (4). In the solid state, compounds (2) and (3) are monomeric, with [PhTttBu] acting as a tridentate ligand. In contrast, compound (4) crystallizes as a dimeric complex, wherein each [PhTttBu] ligand binds to an iron centre with two thioethers and binds to the other iron centre with the third thioether. The molecular structures of (2)-(4) demonstrate a diversity in the binding modes of [PhTttBu] and highlight its potential use for assembling multinuclear complexes. In addition, the successful isolation of (2)-(4), as well as the structural information of a [PhTttBu] modification product, namely, bis{μ-tris[(tert-butylsulfanyl)methyl](2-oxidophenolato)borato-κO,O',S,S':O'}dicobalt(II), [Co2(C21H37BO2S3)2], (5), obtained from the reaction of [PhTttBu]CoCl with potassium monoanionic catecholate, shed light on the origin of the instability of [PhTttBu]Fe(3,5-DBCatH).

Thionitrite and Perthionitrite in NO Signaling at Zinc.

NO and H2 S serve as signaling molecules in biology with intertwined reactivity. HSNO and HSSNO with their conjugate bases - SNO and - SSNO form in the reaction of H2 S with NO as well as S-nitrosothiols (RSNO) and nitrite (NO2- ) that serve as NO reservoirs. While HSNO and HSSNO are elusive, their conjugate bases form isolable zinc complexes Ph,Me TpZn(SNO) and Ph,Me TpZn(SSNO) supported by tris(pyrazolyl)borate ligands. Reaction of Na(15-C-5)SSNO with Ph,Me TpZn(ClO4 ) provides Ph,Me TpZn(SSNO) that undergoes S-atom removal by PEt3 to give Ph,Me TpZn(SNO) and S=PEt3 . Unexpectedly stable at room temperature, these Zn-SNO and Zn-SSNO complexes release NO upon heating. Ph,Me TpZn(SNO) and Ph,Me TpZn(SSNO) quickly react with acidic thiols such as C6 F5 SH to form N2 O and NO, respectively. Increasing the thiol basicity in p-substituted aromatic thiols 4-X ArSH in the reaction with Ph,Me TpZn(SNO) turns on competing S-nitrosation to form Ph,Me TpZn-SH and RSNO, the latter a known precursor for NO.

Thionitrite and Perthionitrite in NO Signaling at Zinc

AbstractNO and H2S serve as signaling molecules in biology with intertwined reactivity. HSNO and HSSNO with their conjugate bases −SNO and −SSNO form in the reaction of H2S with NO as well as S‐nitrosothiols (RSNO) and nitrite (NO2−) that serve as NO reservoirs. While HSNO and HSSNO are elusive, their conjugate bases form isolable zinc complexes Ph,MeTpZn(SNO) and Ph,MeTpZn(SSNO) supported by tris(pyrazolyl)borate ligands. Reaction of Na(15‐C‐5)SSNO with Ph,MeTpZn(ClO4) provides Ph,MeTpZn(SSNO) that undergoes S‐atom removal by PEt3 to give Ph,MeTpZn(SNO) and S=PEt3. Unexpectedly stable at room temperature, these Zn‐SNO and Zn‐SSNO complexes release NO upon heating. Ph,MeTpZn(SNO) and Ph,MeTpZn(SSNO) quickly react with acidic thiols such as C6F5SH to form N2O and NO, respectively. Increasing the thiol basicity in p‐substituted aromatic thiols 4−XArSH in the reaction with Ph,MeTpZn(SNO) turns on competing S‐nitrosation to form Ph,MeTpZn‐SH and RSNO, the latter a known precursor for NO.

Directed Syntheses of CS2- and CS3-Bridged Decaborane-14 Analogues.

To establish a procedure for single-cage cluster expansion of open cage dimetallaoctaboranes(12), we have investigated the chemistry of nido-[(Cp*M)2B6H10] (η5-C5Me5 = Cp*, 1: M = Co; 2: M = Rh), with diverse chalcogen-based borate ligands. As a result, treatment of nido-1 and nido-2 with Li[BH2E3] (E = S, Se, or Te) yielded 10-vertex nido-[(Cp*Co)2B7EH9] (3: E = S; 4: E = Se; 5: E = Te) along with known 10-vertex nido-[(Cp*M)2B6H6E2] (6: E = S, M = Co; 7: E = Se, M = Co; 8: E = Te, M = Co; 9: E = Se, M = Rh). The geometries of dimetallachalcogenaboranes, 3-9, are isostructural with decaborane(14). Thermolysis of nido-1 and nido-2 with an intermediate, generated from CS2 and [LiBH4]·THF reaction in THF, produced nido-[(Cp*M)2B6S2H4(CH2S2)] (10: M = Co; 11: M = Rh) and nido-[(Cp*M)2B6S2H4(CS3)] (12: M = Co; 13: M= Rh). Clusters 10-13 are rare species in which one of the B-B bonds is coordinated with a {CS2}2- or {CS3}2- ligand, generating di(thioborolane) {B2S2CH2} or di(thioboralane)-thione {B2CS3} moieties. To examine further the coordination chemistry of CS2-bridged decaborane(14) analogue nido-10, photolysis was carried out with {M(CO)5·THF} (M = Mo or W) that led to the isolation of [(Cp*Co)2B6S2H4(CH2S2){M(CO)5}] (14: M = Mo; 15: M = W), where the {CH2S2} moiety is coordinated with one {M(CO)5} moiety in η1-fashion. All the synthesized clusters have been characterized by ESI-mass, multinuclear NMR spectroscopy, and IR spectroscopy and structurally solved by single-crystal XRD. Furthermore, DFT calculations probe the bonding of these CS2- and CS3-bridged decaborane analogues.

Synthesis, structural characterization, and reactivity of a dinuclear cobalt(II) (μ-hydroxo)(μ-pyrazolato) complex based on a hydrotris(pyrazolyl)borate ligand

A dinuclear (μ-hydroxo)(μ-pyrazolato)dicobalt(II) complex with hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (TpiPr), [CoII(TpiPr)]2(μ-OH)(μ-Pz) (8), was synthesized and structurally characterized, showing that the metal-hydroxide moiety acts as a nucleophile toward 4-nitrophenyl acetate and CO2, similarly to metalloenzymes. The X-ray analysis revealed that the complex 8 has a symmetry plane and that its two cobalt ions present distorted five-coordinated structures, that is, each of them is coordinated to one oxygen atom from the bridging μ-OH ligand and four nitrogen atoms from the TpiPr ligand and the bridging μ-Pz ligand. The Co1–O1 (1.966(2) Å) and Co1–N3 (2.085(4) Å, where N3 is from μ-Pz) bond lengths are shorter than the Mn–O (2.075(5) and 2.047(5) Å) and Mn–N (2.160(5) and 2.215(6) Å) ones of the previously reported dimanganese(II) analog complex due to the stronger Lewis acidity of cobalt(II). Upon reaction of the complex 8 with CO2, a dinuclear cobalt(II) μ-carbonato complex 7 was obtained. In case of reaction with 4-nitrophenyl acetate, a mononuclear cobalt(II) 4-nitrophenoxo complex with 3,5-diisopropylpyrazole (PzH) on the cobalt(II) center, [CoII(PzH)(TpiPr)(OC6H4-4NO2)] (9), was generated, thus serving as an important model for hydrolase enzyme.

Ethanol(nitrato)[tris-(4-cyano-3-phenyl-1H-pyrazol-1-yl)hydroborato]nickel(II).

The synthesis and structure is reported of TpPh,4CNNi(NO3)(EtOH) or [Ni(C30H19BN9)(NO3)(C2H6O)], the first half-sandwich complex of a cyano-scorpionate ligand. The pseudo-octa-hedral coordination sphere of the NiII ion is comprised of a tridentate tris-(4-cyano-3-phenyl-pyrazol-yl)borate ligand, a bidentate nitrate ligand and a neutral ethanol ligand. The phenyl substituents on the TpPh,4CN ligand are relatively parallel to the planes of the ethanol and nitrate ligands. An inter-molecular hydrogen-bonding inter-action is evident between the ethanol OH group and the pyrazole CN substituent. The ethanol ligand was modeled with a 0.572 (13)/0.428 (13) disorder of the methyl C atom.

Phosphine–Borane Ligands Induce Chemoselective Activation and Catalytic Coupling of Acyl Chlorides at Palladium

Acyl chlorides are highly reactive and widely used substrates in catalytic cross-coupling reactions, but so far, site selectivity over other functional groups has remained an issue. In this work, Pd complexes deriving from the phosphine-boranes [i-Pr2P(o-C6H4)](2)BFXyl and i-Pr2P(o-C6H4)-BFXyl(2) (Fxyl = 3,5-(F3C)(2)C6H3) were found to preferentially activate acyl chlorides over C-I, C-Br, C-Cl, C-OTf, and C-OTs bonds. The system is amenable to catalysis (Stille and Negishi couplings), providing a simple and efficient means to forge C(=O)-C bonds in a site-selective manner and to readily access functionalized ketones. To gain insight into the role and influence of the ambiphilic ligands, key Pd complexes have been authenticated and the reaction profiles have been analyzed by density functional theory (DFT) calculations.

Gold(I) ethylene complexes supported by electron-rich scorpionates.

Ethylene complexes of gold(i) have been stabilized by electron-rich, κ2-bound tris(pyrazolyl)borate ligands. Large up-field shifts of olefinic carbon NMR resonances and relatively long C[double bond, length as m-dash]C distances of gold bound ethylene are indicative of significant Au(i) → ethylene π-backbonding relative to the analog supported by a weakly donating ligand, consistent with the computational data.