Palladium Coordination Research Articles

Synthesis of Bis(diimino)palladium Nanosheets as Highly Active Electrocatalysts for Hydrogen Evolution.

Development of efficient electrocatalysts for hydrogen evolution reactions (HERs) is necessary to achieve environmentally friendly and sustainable hydrogen production. To reduce cost and to circumvent the scarcity of platinum, the most efficient catalyst for HER, it is essential to develop catalysts using ubiquitous base metals or minimal amounts of precious noble metals. Bis(diimino)metal (MDI) coordination nanosheets are potential HER catalysts because their electric conductivities, two-dimensionality, and porous structures provide large surface areas and efficient mass and electron transfer. In addition, with sparse metal arrangements in their chemical structures, nanosheets can reduce the amount of metal needed. We synthesized bis(diimino)palladium coordination nanosheets (PdDI) as a coordination polymer composed of bis(diimino)palladium, with semiconducting characteristics, using gas-liquid interfacial synthesis and electrochemical oxidation. These electrochemically synthesized PdDIs exhibit remarkable catalytic performance with overpotential reaching 10 mA cm-2 of 34 mV, a Tafel slope of 47 mV dec-1, and an exchange current density of 2.1 mA cm-2 after appropriate activation. This performance is closely comparable to that of metallic platinum. An ex-situ investigation of the activation process revealed that reduction of the divalent Pd center in bis(diimino)palladium produced a composite of Pd(0) species and PdDI, combining high catalytic activity with smooth electron transfer.

New Catalyst Systems for the Polymerization of Norbornene and Its Derivatives Based on Cationic Palladium Cyclopentadienyl Complexes

The catalytic properties of systems based on [Pd(Cp)(L)n]m[BF₄]m (where Cp = η5-C5H5; n = 2, m = 1: L = tris(orthomethoxyphenyl)phosphine, triphenylphosphine, tris(2-furyl)phosphine (TFP), n = 1, m = 1: L = 1,1'-bis(diphenylphosphino)ferrocene, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: L = 1,6-bis(diphenylphosphino)hexane) in the addition homoand copolymerization of norbornene (NB) and its derivatives have been studied. These complexes can be activated with the Lewis-acids (BF₃ ∙ OEt2 or AlCl3). The productivity of the [Pd(Cp)(PPh3)2][BF₄]/BF₃ ∙ OEt2 catalyst system in the polymerization of norbornene is up to 188800 molNB molPd⁻¹. The homopolymerization of 5-methoxycarbonylnorbornene and copolymerization of NB with 5-methoxycarbonylnorbornene or 5-phenylnorbornene were studied in the presence of BF₃ ∙ OEt2 and [Pd(Cp)(L)2][BF₄] (L = PPh3 or TFP). A hypothesis for the catalyst’s formation via the intramolecular rearrangement of the η5-Cp ligand into the η1-Cp form upon interaction with a Lewis acid is suggested. The structure of the [Pd(Cp)(TFP)2]BF₄ (I) was determined by X-ray diffraction. In the crystal structure of I, the palladium coordination sphere is characterized by a slight distortion of the square planar geometry of the central atom, and the cyclopentadiyl fragment is in an eclipsed conformation. Based on the XRD data, the steric hindrance of the TFP ligand was estimated (the cone angle is 149°).

Harnessing Coordination‐Assisted Surface Functionalization for Ligand‐Induced Growth of Ultrafine Metal Nanoparticles on MXene

AbstractThe synthesis of ultrafine metal nanoparticles and their integration onto 2D nanomaterials have attracted significant interest due to their outstanding chemical and electrochemical activity. Among 2D materials, MXenes have emerged as promising candidates for hybridization owing to their abundant surface nucleation sites and high electrical conductivity. However, achieving uniform growth of ultrafine metal nanoparticles on MXene surfaces remains a challenge due to non‐uniform metal nucleation and growth behaviors. In this study, a novel coordination‐assisted surface functionalization method is presented to graft organic ligands onto MXene, promoting the uniform growth of ultrafine metal nanoparticles. By leveraging the mutual attraction between metal ions, organic ligands, and MXene surface functional groups, MXene surfaces are efficiently functionalized through palladium coordination complexes. Subsequent ligand‐induced growth facilitated the uniform nucleation of ultrafine metal nanoparticles, resulting in densely anchored nanoparticles of 1–3 nm in size on MXene. Comprehensive characterizations reveal the effectiveness of the method, demonstrating exceptional properties of the MXene‐metal nanoparticle hybrid, particularly in hydrogen sensing applications. This study highlights the potential of coordination‐assisted surface functionalization for the controlled synthesis of MXene‐based nanomaterials with tailored properties for diverse applications.

Relevance of Oxocyclam from Palladium(II) Coordination to Radiopharmaceutical Development.

We provide a comprehensive study of the coordination of oxocyclam with palladium(II), including presentation of a novel bifunctional analogue, p-H2N-Bn-oxocyclam, bearing an aniline pendant. The complexation of palladium(II) with oxocyclam was examined by various techniques, including NMR analysis and potentiometric titrations which revealed that the Pd(II) complex can adopt different configurations such as trans-I and trans-III. In addition, oxocyclam forms a thermodynamically stable palladium(II) complex, the stabilization being attributed to the deprotonation of the amide function. The crystal structures of [Pd(H-1oxocyclam)]+ and [Pd(oxocyclam)]2+ were obtained, revealing the structural details previously anticipated, including, in the second case, the presence of the proton on the carbonyl oxygen atom. Additionally, the study explored the redox behavior of the Pd(II)-oxocyclam complex through reduction and oxidation voltammograms at different pH values. Successful 109Pd-labeling of oxocyclam and p-H2N-Bn-oxocyclam at pH 3.5 demonstrated high labeling efficiencies, whatever the species formed. The stability of the radiocomplexes was assessed and moderate transchelation toward EDTA was observed. Overall, oxocyclam displayed favorable properties for Pd(II) coordination and radiolabeling, suggesting its potential as a chelating agent for this metal in palladium-based applications.

Metalla‐Carbaporphyrinoids Consisting of an Acyclic N‐Confused Tetrapyrrole Analogue Served as Stable Near‐Infrared‐II Dyes

AbstractWe present herein the synthesis of novel pseudo‐metalla‐carbaporphyrinoid species (1M: M=Pd and Pt) achieved through the inner coordination of palladium(II) and platinum(II) with an acyclic N‐confused tetrapyrrin analogue. Despite their tetrapyrrole frameworks being small, akin to well‐known porphyrins, these species exhibit an unusually narrow HOMO–LUMO gap, resulting in an unprecedentedly low‐energy absorption in the second near‐infrared (NIR‐II) region. Density functional theory (DFT) calculations revealed unique dπ‐pπ‐conjugated electronic structures involving the metal dπ‐ligand pπ hybridized molecular orbitals of 1M. Magnetic circular dichroism (MCD) spectroscopy confirmed distinct electronic structures. Remarkably, the complexes feature an open‐metal coordination site in the peripheral NN dipyrrin site, forming hetero‐metal complexes (1Pd‐BF2 and 1Pt‐BF2) through boron difluoride complexation. The resulting hetero metalla‐carbaporphyrinoid species displayed further redshifted NIR‐II absorption, highly efficient photothermal conversion efficiencies (η; 62–65 %), and exceptional photostability. Despite the challenges associated with the theoretical and experimental assessment of dπ‐pπ‐conjugated metalla‐aromaticity in relatively larger (more than 18π electrons) polycyclic ring systems, these organometallic planar tetrapyrrole systems could serve as potential molecular platforms for aromaticity‐relevant NIR‐II dyes.

Metalla-Carbaporphyrinoids Consisting of an Acyclic N-Confused Tetrapyrrole Analogue Served as Stable Near-Infrared-II Dyes.

We present herein the synthesis of novel pseudo-metalla-carbaporphyrinoid species (1M: M=Pd and Pt) achieved through the inner coordination of palladium(II) and platinum(II) with an acyclic N-confused tetrapyrrin analogue. Despite their tetrapyrrole frameworks being small, akin to well-known porphyrins, these species exhibit an unusually narrow HOMO-LUMO gap, resulting in an unprecedentedly low-energy absorption in the second near-infrared (NIR-II) region. Density functional theory (DFT) calculations revealed unique dπ-pπ-conjugated electronic structures involving the metal dπ-ligand pπ hybridized molecular orbitals of 1M. Magnetic circular dichroism (MCD) spectroscopy confirmed distinct electronic structures. Remarkably, the complexes feature an open-metal coordination site in the peripheral NN dipyrrin site, forming hetero-metal complexes (1Pd-BF2 and 1Pt-BF2) through boron difluoride complexation. The resulting hetero metalla-carbaporphyrinoid species displayed further redshifted NIR-II absorption, highly efficient photothermal conversion efficiencies (η; 62-65 %), and exceptional photostability. Despite the challenges associated with the theoretical and experimental assessment of dπ-pπ-conjugated metalla-aromaticity in relatively larger (more than 18π electrons) polycyclic ring systems, these organometallic planar tetrapyrrole systems could serve as potential molecular platforms for aromaticity-relevant NIR-II dyes.

Palladium Phthalocyanine Nanowire-Based Highly Sensitive Sensors for NO2(g) Detection.

Palladium phthalocyanine (PdPc) nanowires (NWs) were developed to achieve the gas sensing of NO2 in the sub-parts-per-million (ppm) range. Non-substituted metal phthalocyanine are well known for their p-type semiconducting behavior, which is responsible for its gas-sensing capabilities. Nanofabrication of the PdPc NWs was performed by physical vapor deposition (PVD) on an interdigitated gold electrode (IDE). The coordination of palladium in the structure was confirmed with UV-Vis spectroscopy. Gas-sensing experiments for NO2 detection were undertaken at different sensed gas concentrations from 4 ppm to 0.5 ppm at room temperature. In this work, the responses at different gas concentrations are reported. In addition, structural studies of the PdPc NWs with scanning electron microscopy (SEM) and electron-dispersive X-ray diffraction (EDS) are shown.

Coordination of Palladium with Polydentate Non‐planar Ligands with Competitive Donors (Oxygen and Double Bonds). Role of Stereochemistry

AbstractPalladium (II) complexes of three polydentate non‐planar bicyclo[4.4.0]decane ligands with at least one double bond and bridgehead cis‐substituents CH2OH or CH2OCH2 were prepared in order to investigate the role of stereochemistry and donor nucleophilicity in the Pd coordination. All ligands and their corresponding complexes were characterized using NMR, solid‐state NMR (ssNMR), HR‐MS, ATR‐IR, DSC‐TGA. For ligand cis‐1,4,5,8‐tetrahydro‐naphthalene‐4a,8a‐diyl‐dimethanol (L2) the X‐ray structure corresponded to the DFT optimised structure. The HR‐MS and thermal analysis data confirmed a complexation ratio: ligand/PdCl2 of 1/1. The experimental data as well as the computations are consistent with the structures proposed based on 13C‐ssNMR, namely palladium coordinates with one double bond and an oxygen atom for ligands with CH2OH groups and with both double bonds for the ligand with an etheric bridge, showing the prevalence of stereochemistry over donor nucleophilicity for such non‐planar ligands.

From Simple Palladium(II) Monomers to 2D Heterometallic Sodium-Palladium(II) Coordination Networks with 2-Halonicotinates.

The 2D heterometallic sodium-palladium(II) coordination polymers with 2-halonicotinates [2-chloropyridine-3-carboxylate (2-chloronicotinate), 2-Clnic- and 2-bromopyridine-3-carboxylate (2-bromonicotinate), 2-Brnic-], {[Na2(H2O)2(μ-H2O)4PdCl2(μ-2-Clnic-N:O')2]}n (1), and {[Na2(H2O)2(μ-H2O)4PdBr2(μ-2-Brnic-N:O')2]·2H2O}n (2) were prepared in aqueous solutions under the presence of NaHCO3, while palladium(II) monomers with the neutral 2-chloronicotinic and 2-bromonicotinic acid ligands, [PdCl2(2-ClnicH-N)2]·2DMF (3) and [PdCl2(2-BrnicH-N)2]·2DMF (4), were prepared in DMF/water mixtures (DMF = N,N'-dimethylformamide). The zigzag chains of water-bridged sodium ions are in turn bridged by [PdCl2(2-Clnic)2]2- moieties in 1 or by [PdBr2(2-Brnic)2]2- moieties in 2, leading to the formation of the infinite 2D coordination networks of 1 or 2. The DFT calculations showed the halosubstituents type (Cl vs Br) does not have an influence on the formation of either trans or cis isomers. The trans isomers were found in all reported compounds; being more stable for about 10 to 15 kJ mol-1. The 2D coordination networks 1 and 2 are more stabilized by the formation of Na-Ocarboxylate bonds, comparing to the stabilization of palladium(II) monomers 3 and 4 by hydrogen-bonding with DMF molecules. The difference in DFT calculated energy stabilization for 1 and 2 is ascribed to the type of halosubstituents and to the presence/absence of lattice water molecules in 1 and 2. The compounds show no antibacterial activity toward reference strains of Escherichia coli and Staphylococcus aureus bacteria and no antiproliferative activity toward bladder (T24) and lung (A549) cancer cell lines.

Reactivity of Schiff base-[C,N,S] pincer palladacycles: hydrolysis renders singular trinuclear, tetranuclear, and heteropentanuclear Pd3W2 coordinated complexes.

Treatment of the Schiff base ligands a-f with Li2[PdCl4]/NaAcO in methanol under reflux gave the single nuclear palladacycles 1a-1f, with the metal atom bonded to a terdentate monoanionic [C,N,S] iminic ligand and to a chloride ligand that completes the palladium coordination sphere. Reaction of 1a-1c with silver perchlorate/triphenylphosphine in acetone at room temperature yielded the single nuclear complexes 2a-2c as the perchlorate salts, after substitution of the chloride ligand by a triphenylphosphine. However, reaction of a-c with Na2[PdCl4]/NaAcO in methanol at room temperature also gave compounds 1a-1c albeit contaminated with small amounts of the corresponding free aldehyde (mixture A). Reaction of mixture A with silver perchlorate/triphenylphosphine in acetone at room temperature gave analogously 2a-2c with some of the corresponding free aldehyde (mixture B). Attempts to purify mixtures A and B via recrystallization produced single crystals of 5 and 6 respectively: two serendipitously formed complexes, bearing thiomethyl aniline and/or acetate ligands, and void of aldehyde or iminic residue; the structures contain eight- and six-membered rings of alternating palladium and nitrogen atoms, respectively. To clarify this situation the aniline itself was reacted with palladium(II) acetate or with Na2[PdCl4]; in the latter case after recrystallization a unique behavior is revealed, giving rise to a tetranuclear complex containing a Pd4N4 ring with three differing coordination environments on the palladium atoms. Treatment of 1d with Ph2PCH2PPh2 (dppm)/AgClO4 or with Ph2PCH2(PPh2)W(CO)5/AgClO4 gave 3d, with a mono-coordinated dppm ligand, and 4d, respectively; complex 3d could not be converted into 4d by reaction with W(CO)5(THF). Recrystallization of 4d gave a still further noticeable species, complex 8: a pentanuclear trans-configured heterometallic mixed valent Pd(II)/W(0) linear complex with the palladium atoms supported by two acetate and two thiomethyl aniline bridging ligands. The complexes were fully characterized by microanalysis, IR, 1H, and 31P NMR spectroscopies, as appropriate. The X-ray single-crystal analyses for compounds 1b, 5, 6, 7 and 8 are described.

Ytterbium valence ordering in the low-temperature superstructure of Yb2Pd2Cd

Abstract The intermetallic ytterbium compound Yb2Pd2Cd shows a structural phase transition at ∼150 K. The structures of the room-temperature (Mo2B2Fe type, P4/mbm, a = 757.07(7), c = 371.99(4) pm, wR2 = 0.0620, 272 F 2 values, 12 variables) and low-temperature (new type, P4/mbm, a = 747.26(4), c = 741.46(4) pm, wR2 = 0.0384, 511 F 2 values, 19 variables) modifications were refined from single crystal X-ray diffractometer data. The superstructure formation corresponds to an isomorphic transition of index 2. The driving force for the structural phase transition is an ytterbium charge ordering (the superstructure exhibits two crystallographically independent ytterbium sites) with a much higher degree of divalent ytterbium in the low-temperature modification. The striking structural feature concerns the ytterbium–palladium coordination with different Yb–Pd distances: longer ones for predominantly divalent Yb1 (2 × 284.7 and 4 × 296.1 pm, ∅ = 292.3 pm) and shorter ones for trivalent Yb2 (2 × 277.5 and 4 × 288.4 pm, ∅ = 284.8 pm).

Antiproliferative and antimycobacterial effects of mononuclear palladium(II) complexes with N-heterocyclic ligands

A series of mononuclear palladium(II) coordination compounds with N-heterocyclic ligands – 1,10-phenanthroline (phen), pyrazole (Hpz), 3,5-dimethylpyrazole (Hdmpz), and anions of 2-/3-furoic (2-Hfur and 3-Hfur) and trifluoromethanesulfonic (Hotf) acids were obtained. According to the single-crystal X-ray diffraction analysis data in complexes [Pd(Hdmpz)4]·2L (L = 2-fur (1); 3-fur (2)), [Pd(3-fur)2(phen)]·H2O (3) and [Pd(Hpz)2(phen)]·2otf (4), the cation has a square planar environment of N-, O-donor atoms {PdN4} for 1, 2, 4 and {PdN2O2} for 3. The cytotoxic effect of various concentrations of complexes 2, 3 and 4 on human ovarian adenocarcinoma cells (SKOV3) and human dermal fibroblasts (HDF) was measured in vitro. Complex 4 displayed antiproliferative activity against ovarian adenocarcinoma cells, with a six-fold weaker effect on healthy fibroblasts. The antimycobacterial activity of compounds 2–4 was determined in vitro against a non-pathogenic Mycolicibacterium smegmatis strain.

A combined approach toward enhancing 2-electron oxygen reduction through the incorporation of Pd-based complex into a carbonaceous matrix: Experimental and mechanistic-theoretical studies

The present work reports the development of a catalyst based on palladium (Pd) coordination compound covered and surrounded by Printex L6 (PL6C) carbon material and its application toward improving the selectivity and electrocatalysis involving the production of hydrogen peroxide via oxygen reduction reaction (2e–ORR). The morphology and structure of the Pd-based complex/PL6C catalyst were characterized by clusters of an average size of 2.4 µm composed of 1.3% (w/w) Pd2+ metal. Compared to the unmodified PL6C, the application of the Pd-based complex/PL6C led to a shift in the ORR onset potential by 250 mV vs Ag/AgCl 3 M to more positive potentials and 97% selectivity toward H2O2 production. This electrocatalytic effect was attributed to the π-π interactions between the dz2 orbital of the Pd2+ metal and the carbon close to the oxygenated functional groups present in the carbonaceous matrix. The mechanistic-theoretical analyses conducted showed that the oxygenated carboxyl functional group COOH is the group that favors most significantly the interaction between O2 and hydronium ions toward the formation of the OOH* species; the presence of the Pd2+ metal further contributes toward favoring this interaction. In addition, the Pd-based complex was found to influence the Laplacian of the electron density (V2ρ) for the bond between the carbon close to the COOH group and the oxygen atom of the ORR intermediates, and this facilitates the conversion of adsorbed O2 species into OOH* intermediates and increases the desorption capacity of the species from the active site, leading to H2O2 formation.

The palladium-rich silicides RE 3Pd20Si6 (RE = Sc, Y and Lu)

Abstract The silicides RE 3Pd20Si6 (RE = Sc, Y and Lu) were synthesized from the elements by arc-melting. The structures of Y3Pd20Si6 and Lu3Pd20Si6 were refined from single crystal X-ray diffractometer data: Mg3Ni20B6 type, F m 3 ‾ m $Fm\overline{3}m$ , a = 1216.04(8) pm, wR = 0.0328, 219 F 2 values, 14 variables for Y3Pd20Si6 and a = 1211.69(10) pm, wR = 0.0374, 217 F 2 values, 14 variables for Lu3Pd20Si6. The isotypy of Sc3Pd20Si6 was confirmed on the basis of a Guinier powder pattern (a = 1202.8(3) pm). The RE 3Pd20Si6 structures contain two crystallographically independent RE sites with relatively large coordination numbers, i.e. RE1@Pd16 and RE2@Pd12Si6. These polyhedra are arranged in a CaF2 related pattern with RE2@Pd12Si6 forming the fcc substructure and the RE1@Pd16 polyhedra filling the tetrahedral voids. The silicon atoms have slightly distorted square antiprismatic palladium coordination (4 × 239 pm Si–Pd1 and 4 × 245 pm Si–Pd2). Temperature dependent magnetic susceptibility measurements of the Lu3Pd20Si6 sample indicate Pauli paramagnetism.

The effects of palladium coordination complex speciation and concentration upon the ubiquitous bacterial species Pseudomonas aeruginosa

The toxicity of three different palladium (Pd) species to Pseudomonas aeruginosa, an environmentally ubiquitous bacterial species, is reported. Palladium was added to chemically-defined minimal media as three complex ion salts, namely sodium tetrachloropalladate (Na2[PdCl4]), tetraamminepalladium(II) chloride ([Pd(NH3)4]Cl2), and potassium hexachloropalladate(IV) (K2[PdCl6]), inoculated with log-phase cultures and incubated for 24 h at 25 °C. Toxicity was tested for Pd concentrations ranging from 6.55 μg/L (0.06 μM Pd) to 250 μg/L (2.33 μM Pd). Minimum inhibitory concentrations (MICs) were determined and growth tracked via optical absorption at 600 nm. Viability and minimum bactericidal concentrations (MBCs) were measured in parallel with dilution, plating and colony forming unit (CFU) counting. MICs for all forms of Pd were 62.5 μg Pd/L, approximately 1000 times lower than previously reported values. The MBCs for PdCl42- and Pd(NH3)42+ were 62.5 μg Pd/L and 125 μg Pd/L for PdCl62-. Pd(NH3)42+ and PdCl62- culture viability at 7.8–31.3 μg Pd/L was not different from controls. However, PdCl42- culture viability was different from the other additives, with decreasing viability at sub-MBC concentrations down to 6.55 μg Pd/L. To understand the possible effect of speciation upon toxicity, the equilibrium speciation of Pd was modeled for all solutions using PHREEQC and found to be dominated by Pd(NH3)3Cl+ (65.6 % of total Pd) and Pd(NH3)42+ (34.2 % total Pd). The juxtaposition of the equilibrium calculations and the toxicity results indicates that the kinetics of ligand exchange between the palladium complexes and the growth medium could influence bacterial response.

Synthesis and characterization of enantiopure chiral NH2/SO palladium complexes.

A series of enantiopure chiral NH2/SO palladium complexes have been synthesised with high yields by treating the corresponding tert-butylsulfinamide/sulfoxide derivatives with Pd(CH3CN)2Cl2. The enantiopure chiral ligands were prepared by stereoselective addition of tert-butyl or phenyl methylsulfinyl carbanions to different tert-butylsulfinylimines. In all cases, coordination occurs with concomitant desulfinylation. X-ray studies of the Pd complexes showed a higher trans influence of the phenylsulfinyl group in comparison to that of the tert-butylsulfinyl group. Furthermore, we have obtained and characterised two possible palladium amine/sulfonyl complexes, epimers at sulfur, resulting from N-desulfinylation and coordination of palladium with both oxygens of the prochiral sulfonyl group. The catalytic activity and enantioselectivity of the new Pd(II) complexes of acetylated amine/tert-butyl- and phenylsulfoxides in the carboxylated cyclopropanes arylation reaction has been studied, obtaining the best results with the phenylsulfoxide ligand 25(SC,SS) that produced the final arylated product in a 93 :7 enantiomeric ratio.

Differential Cytotoxic Activity of a New Cationic Pd(II) Coordination Compound with N4-Tetradentate Hybrid Ligand in Cancer Cell Lines

Objective: Successful cancer treatment still requires the discovery of novel compounds that hold promise for chemotherapeutics. The objective of this study was to examine the effectiveness of a newly synthesized cationic palladium(II) coordination compound that functions via several pathways to provide an efficient therapeutic option for various cancer cells. Materials and Methods: A new cationic palladium(II) coordination compound, [Pd(L)]Cl2·H2O, denoted as Complex 1, where the ligand L is the compound 6,6'-bis(NH-benzimidazol-2-yl)-2,2'-bipyridine), was synthesized and characterized by the attenuated total reflectance (ATR) - fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1 H NMR), electrospray ionization mass spectrometry (ESI-MS), and carbon-hydrogen-nitrogen (CHN) analyses. The density functional theory (DFT) calculations show the coordination sphere around the metal center in Complex 1 to be made up of tertiary N atoms of the pyridine (py) and benzimidazole (bim) rings completing the square-planar geometry with significant distortion. The anti-growth/cytotoxic activity of the complex was determined using the sulforhodamine B (SRB) and adenosine triphosphate (ATP) viability assays for 24 and 48 h in vitro. The study evaluates the determinations for annexin V-propidium iodide (PI) positivity, mitochondrial membrane potential loss, Bcl-2 protein inactivation, and deoxyribonucleic acid (DNA) damage to investigate the cell death mode and its partial mechanism. Results: Complex 1 caused cytotoxicity in a dose-dependent manner in all the cell lines used, with IC50 values ranging from 2.6-8.8 μM for 48 h. Among the cancer models, colon and breast cancer cell lines underwent cell death by well-described apoptosis through the intrinsic pathway involving the mitochondria. However, the other cell lines did not show such a cell death modality. This implies that differential cell death modes operate based on the cancer type. Conclusion: For the treatment of breast and colon cancers, the complex 1 appears to be a unique, promising complex. Therefore, complex 1 deserves further attention for proof of concept in animal models.

Genetically Encoded Phosphine Ligand for Metalloprotein Design.

Phosphine ligands are the most important class of ligands for cross-coupling reactions due to their unique electronic and steric properties. However, metalloproteins generally rely on nitrogen, sulfur, or oxygen ligands. Here, we report the genetic incorporation of P3BF, which contains a biocompatible borane-protected phosphine, into proteins. This step is followed by a straightforward one-pot strategy to perform deboronation and palladium coordination in aqueous and aerobic conditions. The genetically encoded phosphine ligand P3BF should significantly expand our ability to design functional metalloproteins.

Palladium‐Catalyzed Enantioselective Cyclization of 1,6‐Enynes through Intramolecular Chlorine Transfer as a Novel Strategy for Asymmetric Halopalladation

Palladium-catalyzed enantioselective cyclization of enynes has contributed significantly to the construction of chiral cyclic molecules. In contrast, the catalytic asymmetric cyclization involving halopalladation remains an unresolved challenge with the inevitable disturbance of the halide ions. Herein, an intramolecular chlorine transfer strategy is used to accomplish the enantioselective chloropalladation cyclization of 1,6-enynes. This reaction provides a redox-neutral approach to a variety of chiral α-chloromethylene-γ-butyrolactones with excellent E selectivity and enantioselectivity. The precisely controlled coordination of palladium with both the in situ generated nucleophilic species and the monodentate phosphoramidite ligand is crucial for enantioselectivity.

Novel trans iodo(2-(N-alkylsulfamoyl)phenyl)bis(-triphenylphosphine palladium) complexes: Synthesis, mass spectrometry, X-ray structural description, steric map, near infrared analyses and catalytic activities evaluation

2-iodo-N-ethylbenzenesulfonamide and 2-iodo-N-isopropylbenzenesulfonamide are used to prepare two novel palladium(II) complexes (4 and 5) by oxidative addition starting from Pd(PPh3)4. The desired complexes are fully characterized by 1H, 13C, 31P NMR and near infrared spectroscopy. Electron spray ionization mass spectrometry analyses showed identical fragmentation process of the complexes starting by the iodine cleavage. The molecular structures of the complexes 4 and 5 are confirmed by X-ray diffraction analysis. The crystal packing of these complexes are stabilized by the presence of hydrogen bonds established between oxygen and hydrogen atoms of the sulfonamide groups. In addition, Hirshfeld surface mapped over dnorm, Shape index and molecular electrostatic potential were used to describe the short interactions and electron reach domains. The analyses of molecular fingerprints reveal similar percentage of H···H (∼67%), H···C/C···H (∼23%), H···I/I···H (∼5%) and H···O/O···H (∼4.5%) contacts in 4 and 5. The valuation of the percentage of buried volume (%VBur) of these ligands shows that the N-ethyl- and N-isopropylbenzenesulfonamide substituents took around 30% share of the palladium coordination sphere. Finally, the catalytic activities of these new palladium complexes are evaluated in cyclopropanation of styrene and in atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). The results showed that trans cyclopropane was obtained as major product independently to the tested catalyst. In polymerization reaction, the catalysts show moderate activity and did not induce a controlled polymerization of MMA.