PdII Complexes Research Articles

Experimental and Theoretical Evaluation of Four NLO‐Active Divalent Transition‐Metal Complexes Supported by an Enantiomerically Pure Tetradentate Schiff Base Ligand

AbstractThis paper reports on a series of five chiral Schiff base push‐pull compounds derived from enantiomerically pure (1R,2R)‐(−)‐1,2‐diaminocyclohexane. The NiII, CuII, ZnII and PdII complexes supported by a ferrocene‐containing unsymmetrically‐substituted N2O2 quadridentate Schiff base ligand were prepared via template reactions and isolated in 74–87 % yields. A combination of EA, IR, UV/vis and 1H/13C{1H} NMR spectroscopy, HRMS spectrometry, cyclic voltammetry and single‐crystal X‐ray analysis (for the proligand 2 and its NiII derivative 3), together with computational methods (DFT and TD‐DFT) was used to fully characterize and study the properties of all products. Both 2 and 3 crystallize in the orthorhombic non‐centrosymmetric space group P212121, with two (R,R)‐(−)‐chiral carbon atoms in their structure. Second‐order nonlinear polarizabilities β have been measured by using Harmonic Light Scattering at 1.91 μm, with the Pd(II) species showing the higher NLO response of 460×10−30 esu.

Sterically and Electronically Flexible Pyridylidene Amine Dinitrogen Ligands at Palladium: Hemilabile cis/trans Coordination and Application in Dehydrogenation Catalysis.

Ligand design is crucial for the development of new catalysts and materials with new properties. Herein, the synthesis and unique hemilabile coordination properties of new bis-pyridylidene amine (bis-PYE) ligands to palladium, and preliminary catalytic activity of these complexes in formic acid dehydrogenation are described. The synthetic pathway to form cationic complexes [Pd(bis-PYE)Cl(L)]X with a cis-coordinated N,N-bidentate bis-PYE ligand is flexible and provides access to a diversity of PdII complexes with different ancillary ligands (L=pyridine, DMAP, PPh3 , Cl, P(OMe)3 ). The 1 H NMR chemical shift of the trans-positioned PYE N-CH3 unit is identified as a convenient and diagnostic handle to probe the donor properties of these ancillary ligands and demonstrates the electronic flexibility of the PYE ligand sites. In the presence of a base, the originally cis-coordinated bis-PYE ligand adopts a N,N,N-tridentate coordination mode with the two PYE units in mutual trans position. This cis-trans isomerization is reverted in presence of an acid, demonstrating a unique structural and steric flexibility of the bis-PYE ligand at palladium in addition to its electronic adaptability. The palladium complexes are active in formic acid dehydrogenation to H2 and CO2 . The catalytic performance is directly dependent on the ligand bonding mode, the nature of the ancillary ligand, the counteranion, and additives. The most active system features a bidentate bis-PYE ligand, PPh3 as ancillary ligand and accomplishes turnover frequencies up to 525 h-1 in the first hour and turnover numbers of nearly 1000, which is the highest activity reported for palladium-based catalysts to date.

Spectral, crystallographic, theoretical, and catalytic activity studies of the PdII complexes in different coordination modes of benzoylthiourea ligand

Syntheses of neutral monodentate dichloro bis[N‐(diethylcarbamothioyl)‐4‐fluorobenzamido-κS] palladium(II), [PdIICl2(LH-κS)2] and anionic bidentate bis[N‐(diethylcarbamothioyl)‐4‐fluorobenzamido-κ2O,S] palladium(II), [PdII(L-κ2S,O)2] complexes of N‐(diethylcarbamothioyl)‐4‐fluorobenzamide (LH) ligand is reported. While [PdIICl2(LH-κS)2] was obtained by reaction between PdCl2 and LH in acetonitrile solution as a single crystal form, [PdII(L-κ2S,O)2] was formed recrystallization of [PdIICl2(LH-κS)2] in dichloromethane: ethanol solvent mixture as powder form. The PdII complexes were characterized by elemental analysis, FT-IR, 1H NMR, and 13C NMR spectral measurements. Furthermore, the molecular structure of [PdIICl2(LH-κS)2] was defined by single crystal X-ray diffraction, and the result obtained was also confirmed by spectral data. The optimized molecular geometry of the ligand and [PdIICl2(LH-κS)2] complex was obtained by density functional theory calculation at the B3LYP/6-311G(d,p) and LanL2DZ level of theory, respectively. We found that the optimized geometrical parameters agree very well with the experimental one. Therefore, we used the same theoretical level (B3LYP/LanL2DZ) for the [PdII(L-κ2S,O)2] which is a powder form, not a single crystal form. The energies of frontier molecular orbitals (EHOMO and ELUMO), energy band gap, and quantum molecular descriptors of the prepared compounds were calculated. Information about the site of chemical reactivity, charge density distribution, the size, and shape of the molecules was obtained by mapping with molecular electrostatic potential (MEP). NBO analysis was applied for the investigation of intra and inter-molecular bonding and conjugative interaction in molecular systems. The Mulliken and natural population analyses were used to predict positive and negative charges on every atom in the molecules. Hirshfeld surface analysis and 2D fingerprint plots were applied to visualize and quantify intermolecular interactions and packing modes in the supramolecular structure. The Coulomb interaction, dispersion, and total energy calculations were used to visualize and analyze the three-dimensional figures of the crystal lattice. Furthermore, the catalytic efficiencies of both palladium complexes have been confirmed in the Suzuki-Miyaura C-C reaction using a very low 0.01 mol% catalyst loading.

Synthesis of PdII Triazolylidene Complexes via an Unusual Csp2‐Csp2 Decoupling Reaction: Applications in α‐Arylation of Amide and Suzuki‐Miyaura Coupling Reactions

AbstractMononuclear PdII complexes bearing mixed MIC/Py/PPh3 donor set ligands are presented starting from a bis‐triazolium salt featuring 4,4’‐substitution pattern of central biphenyl ring. The mononuclear PEPPSI (pyridine enhanced precatalyst preparation, stabilization and initiation) type complexes bearing triazolylidene donor ligand have been synthesized via an unusual Csp2‐Csp2 decoupling reaction. The complexes have been characterized by 1H, 13C{1H} NMR spectroscopy and mass spectrometry. Two of the complexes have also been structurally characterized by single crystal XRD. All the complexes appeared as active precatalysts in α‐arylation of amide and Suzuki‐Miyaura coupling reactions. Catalytic outcomes clearly indicate the superior activities of the PdII complexes with mixed MIC/PPh3 donor set ligands compared to the corresponding PEPPSI type complexes in α‐arylation of oxindole.

Di-chlorido-(4-methyl-aniline-κN)[N-(4-methyl-phen-yl)-1-(thio-phen-2-yl)methanimine-κN]palladium(II).

The structure of a mono-amine PdII complex, [PdCl2(C7H9N)(C12H11NS)], which crystallizes in the triclinic space group, P , is reported. The primary geometry around the PdII atom closely resembles square planar (τ4' = 0.069). In the (E)-1-(thio-phen-2-yl)-N-(p-tol-yl)methanimine ligand, the phenyl and thio-phene rings are not coplanar, subtending a dihedral angle of 38.5 (1)° because of steric effects. The PdCl2N2 coordination plane is almost perpendicular to the planes of the coordinated o-toluidine and the NC2 fragment [dihedral angles of 84.7 (1) and 72.50 (4)°, respectively]. The Pd-NH2 length of 2.040 (2) Å is slightly shorter than the observed mean value for other complexes involving a Pd atom attached to the nitro-gen of an aniline derivative. The mol-ecules display an inter-esting supra-molecular synthon based on reciprocal inter-molecular N-H⋯Cl hydrogen-bonding inter-actions of the p-toluidine amine fragment, which results in centrosymmetric dimeric units. These units are further linked by C-H⋯Cl inter-actions, resulting in chains in the c-axis direction where the mean-planes of the repeating fragment are oriented in the (110) plane.

Selective Formation of Intramolecular Hydrogen-Bonding Palladium(II) Complexes with Nucleosides Using Unsymmetrical Tridentate Ligands.

Three palladium(II) complexes with amino-amidato-phenolato-type tridentate ligands were synthesized and characterized by 1H NMR spectroscopy and X-ray crystallography. The strategic arrangement of a hydrogen-bond donor and acceptor adjacent to the substitution site of the PdII complex allowed the selective coordination of nucleosides. Among two pyrimidine-nucleosides, cytidine and 5-methyluridine, cytidine was successfully coordinated to the PdII complex while 5-methyluridne was not. On the other hand, both purine-nucleosides, adenosine and guanosine, were coordinated to the PdII complex. As purines have several coordination sites, adenosine afforded three kinds of coordination isomers expected from the three different donors. However, guanosine afforded a sole product according to the ligand design such that the formation of double intramolecular hydrogen-bond strongly induced the specific coordination by N1-position of guanine moiety. Furthermore, the preference of the nucleosides was evaluated by scrambling reactions. It was found that the preference of guanosine is nearly twice as high as adenosine and cytidine, owing to the three-point interaction of a coordination bond and two hydrogen bonds. These results show that the combination of a coordination and hydrogen bonds, which is reminiscent of the Watson–Crick base pairing, is an effective tool for the precise recognition of nucleosides.

Effect of the Nuclearity on the Catalytic Performance of a Series of Pd(Ii) Complexes in the Suzuki-Miyaura Reaction

Effect of the Nuclearity on the Catalytic Performance of a Series of Pd(Ii) Complexes in the Suzuki-Miyaura Reaction

1,2,3-Triazole based ligands with phosphine and pyridine functionalities: synthesis, PdII and PtII chemistry and catalytic studies.

This manuscript describes the syntheses of pyridine appended triazole-based mono- and bisphosphines, [o-Ph2P(C6H4){1,2,3-N3C(Py)C(H)}] (2), [o-Br(C6H4){1,2,3-N3C(Py)C(PPh2)}] (3), [C6H5{1,2,3-N3C(Py)C(PPh2)}] (4), [Ph2P(C6H4){1,2,3-N3C(Py)C(PPh2)}] (5) and [3-Ph2P-2-{1,2,3-N3C(Ph)C(PPh2)}C5H3N] (6), their palladium and platinum chemistry and catalytic applications. These ligands upon treatment with [M(COD)Cl2] (M = Pd or Pt) yielded complexes with different coordination modes, depending on the reaction conditions. Both κ2-P,N and κ2-P,P coordination modes were observed in many of the complexes indicating the ambidentate nature of these ligands. Monophosphine 2 in the presence of a base afforded rare fused-5,6-membered PCN pincer complexes [MCl{o-Ph2P(C6H4){1,2,3-N3C(Py)C(H)}}-κ3-P,C,N] (7, M = Pd; 8, M = Pt), whereas the reactions of 4 with [M(COD)Cl2] (M = Pd, Pt) produced κ2-P,N chelate complexes [MCl2{C6H5{1,2,3-N3C(Py)C(PPh2)}-κ2-P,N}] (9, M = Pd; 10, M = Pt). Similar reactions of 5 and 6 resulted in κ2-P,P chelate complexes [MCl2{{3-Ph2P-2-{1,2,3-N3C(Ph)C(PPh2)}C5H3N}-κ2-P,P}] (11, M = Pd; 12, M = Pt) and [MCl2{3-Ph2P-2-{1,2,3-N3C(Ph)C(PPh2)}C5H3N}-κ2-P,P}] (13, M = Pd; 14, M = Pt), respectively. The palladium(II) complexes have shown excellent catalytic activity in the α-alkylation reaction of acetophenone derivatives.

Phosphorus guiding palladium: [4 + 4] metallomacrocyclic PdII complex and self-assembly of heterometallic PdII/ZnII grid-type complex.

The reaction of heteroditopic ligand 1 featuring a hard pyridine-hydrazone-pyrimidine (N,N,N) site and a softer pyrimidine-hydrazone-phosphane (N,N,P) pocket with [Pd(CH3CN)4](OTf)2 in different metal-to-ligand ratios (M : L) gave the homobimetallic PdII complex [Pd2(1)(CH3CN)2](OTf)4 (2, M : L ratio 2 : 1), the [4 + 4] metallomacrocyclic PdII complex [Pd(1)]4(OTf)8 (3, M : L ratio 1 : 1) and the monometallic complex [Pd(1)2](OTf)2 (4, M : L ratio 1 : 2). The soft N,N,P pocket preferably coordinates PdII, while the harder N,N,N coordination site selectively binds ZnII forming the homoleptic meridional "corner" complexes [Zn(1)2](OTf)2 (5) and [Pd2Zn(1)2](OTf)6 (6). The distinctive coordination behavior of ligand 1 is highlighted by the self-assembly of the heterometallic PdII/ZnII grid-type complex [Pd2Zn2(1)2](OTf)8 (7) in a one-pot reaction. Complexes 2-7 were characterized by mass spectrometry, UV/Vis and NMR spectroscopy including DOSY NMR, and single-crystal X-ray diffraction studies were performed for 2-4 and 7.

DFT characterisation of a PdII → IIII adduct, and a PdII complex formed after oxidative alkenylation of PdII by [Ph(alkenyl)IIII]+, in Pd-mediated synthesis of benzofurans involving PdIV, annulation and chain-walking.

The synthesis of benzofurans by the reaction of the palladium(II) complex Pd{1-C6H4-2-OCH(CO2Et)-C,C}(bipy) (bipy = 2,2'-bipyridine) with hypervalent iodine(III) reagents [Ph(CHCHR)I]+ has been examined by Density Functional Theory. Results highlight the role of oxidative alkenylation to form PdIV intermediates and the role of initial adduct formation in this process, an annulation process facilitated by PdII, and the role of 'chain-walking' at PdII centres to allow formation of the lowest energy product. Computation (R = Me) allows assignment of an initially formed adduct with a 'PdII → IIII' interaction at -50 °C, and, after oxidative alkenylation of PdII and reductive elimination from a PdIV centre via Ar⋯Alkenyl coupling, formation of a second intermediate with a structure consistent with NMR detection (R = n-hexyl) at -30 °C is obtained. This PdII complex, containing a coordinated alkene group in Pd{1-(RHCγCβ)C6H4-2-OCαH(CO2Et)-η2-CαCβ,C}(bipy), undergoes a 5-exo-trig annulation by forming a Cα-Cβ bond to give a complex with a bicyclic carbon skeleton suitable for subsequent formation of benzofurans. A series of facile rearrangements including chain-walking results in formation of a lowest energy complex of three feasible hydrido(alkene)palladium(II) species, leading to decomposition and release of the observed benzofuran isomer isolated under synthesis conditions. The computational study allows reinterpretation of the NMR data reported previously, in particular the determination of barriers in the reaction pathway allowing assignment of structure for key intermediates.

Bimetallic PdII complexes with NHC/Py/PCy3 donor set ligands: applications in α-arylation, Suzuki–Miyaura and Sonogashira coupling reactions

Bimetallic PdII complexes bearing mixed NHC/Py/PCy3 donor set ligands are presented. A complex with a mixed NHC/PCy3 donor set ligands shows superior activity compared to the PEPPSI type complexes in α-arylation and Sonogashira coupling reactions.

Cavity‐Controlled Coordination of Square Planar Metal Complexes and Substrate Selectivity by NHC‐Capped Cyclodextrins (ICyDs)

AbstractEncapsulation of a metal center inside the cavity of a cyclodextrin (CD) allows the control of the possible coordination modes for the metal depending on the nature and size of the cavity. We show here that the formation of encapsulated square planar AuIII and PdII complexes with CD‐N‐heterocyclic carbene (NHC) ligands, is only possible in the largest β‐ and γ‐CD cavities. In the case of α‐CD‐derived ligands and PdII, an unexpected reversal of the NHC ligand was observed. These extraverted or introverted conformations of metal complexes were carefully studied by NMR and their different behaviors depending on the cavity could be revealed. The size of the CD cavity was also found to have a significant effect on the ability of AuI to be oxidized into AuIII. Furthermore, in the PdII‐catalyzed nucleophilic allylation of aldehydes, the β‐CD‐derived ligand was able to discriminate different substrates from a mixture according to their size, leading to a significantly favored reaction with the smallest substrate.

Pd-Catalyzed Alkene Diamination Reactions with O-Benzoylhydroxylamine Electrophiles: Evidence Supporting a Pd(II/IV) Catalytic Cycle, the Role of 2,4-Pentanedione Derivatives as Ligands, and Expanded Substrate Scope.

This article describes continued studies on Pd-catalyzed alkene diamination reactions between N-allylguanidines or ureas and O-benzoylhydroxylamine derivatives, which serve as N-centered electrophiles. The transformations generate cyclic guanidines and ureas bearing dialkylaminomethyl groups in moderate to good yield. We describe new mechanistic experiments that have led to a revised mechanistic hypothesis that involves a key oxidative addition of the electrophile to a PdII complex, followed by reductive elimination from PdIV to form the alkyl carbon-nitrogen bond. In addition, we demonstrate that acac, not phosphine, serves as a key ligand for palladium. Moreover, simple acac derivatives bearing substituted aryl groups outperform acac in the catalytic reactions, and phosphines inhibit catalysis in many cases. These discoveries have led to a significant expansion in the scope of this chemistry, which now allows for the coupling of a variety of cyclic amines, acyclic secondary amines, and primary amines. In addition, we also demonstrate that these new conditions allow for the use of amide nucleophiles, in addition to guanidines and ureas.

Bis(CBT)palladium(II) Derivatives (CBT = m-carborane-1-thiolate): Synthesis, Molecular Structure, and Physicochemical Properties of cis-[(bipy)Pd(CBT)2] and trans-[(py)2Pd(CBT)2

The new synthesized PdII complex cis-[(bipy)Pd(CBT)2] (bipy = 2,2'-bipyridyl; CBT = m-carborane-1-thiolate anion), which is a potential BNCT (boron neutron capture therapy) agent and of structure elucidated by single-crystal X-ray work, has been studied by infrared (IR) and ultraviolet-visible light (UV-vis) spectra and its properties compared with those of the previously reported and also the structurally characterized analogue trans-[(py)2Pd(CBT)2]. This trans species, prepared via a direct method, was previously isolated from a pyridine solution, consequent to the occurring releasing of the external Pd(CBT)2 moieties of the porphyrazine macrocycle [{Pd(CBT)2}4LZn]·xH2O (L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato anion), which is an active photosensitizer in photodynamic therapy (PDT) and a potential bimodal PDT/BNCT agent. The UV-vis spectral behavior of both cis and trans species in CHCl3 solution and in the gas phase has been examined in detail by density functional theory (DFT) and time-dependent density functional theory (TDDFT) studies devoted to explain their distinct behavior observed in the region of 400-500 nm, as determined by the presence in the cis structure of a vicinal arrangement of the two CBT groups, an ensemble of results closely similar to those observed for the macrocycles [{Pd(CBT)2}4LM]·xH2O (M = MgII(H2O), ZnII, PdII). It has also been experimentally proved the tendency of the cis isomer in CHCl3/pyridine solution to be changed to the respective trans analogue, with conversion occurring in two steps, as interpreted by detailed DFT studies.

A mononuclear PdII complex with Naphcon; crystal structure, experimental and computational studies of the interaction with DNA/BSA and evaluation of anticancer activity

Throughout this study, a new palladium (II) complex, trans-[Pd(Naph)2Cl2], with naphazoline hydrochloride (Naphcon) as an imidazole derivative, 2-(naphthalen-1-ylmethyl)-4,5-dihydro-1H-imidazole;hydrochloride, was synthesized and characterized by elemental analysis, spectroscopic methods (UV–Vis, IR, and 1H NMR) and single crystal X-ray structure analysis. The cytotoxicity of Naphcon and the PdII complex were investigated in vitro against human breast (MCF-7) and cervical epithelial carcinoma (HeLa) cancer cells. The results revealed the higher anticancer activity of complex rather that of Naphcon against MCF-7 cell line. The findings of in vitro studies including fluorescence and UV–Vis spectroscopy, circular dichroism (CD), thermal denaturation and viscosity measurement indicated the interaction of the PdII complex with calf-thymus DNA (CT-DNA) via a combination of covalent and non-covalent interactions, whereas the free Naphcon interacted with CT-DNA mainly through the groove binding mode. Moreover, the ability of Naphcon and the PdII complex to cleave pUC57 plasmid DNA was investigated. In addition, the interaction of both Naphcon and its PdII complex was explored with bovine serum albumin (BSA) by means of absorption and fluorescence spectroscopy. The binding constant (Kb) could be calculated for compounds through these spectroscopic methods. Based on the competitive binding studies using Eosin, Ibuprofen and Digoxin as site markers, the binding site of the PdII complex and Naphcon was found to be located on site-III and I of BSA, respectively. Furthermore, protease activity of compounds was examined under physiological conditions. Finally, to validate all data obtained from biophysical studies, the molecular docking simulation was employed as a computational method.

DFT Investigation of the Molecular Properties of the Dimethylglyoximato Complexes [M(Hdmg)2] (M = Ni, Pd, Pt)

Important applications of the NiII, PdII and PtII complexes [M(Hdmg)2] (H2dmg = dimethylglyoxime) stem from their metal...metal stacked virtually insoluble aggregates. Given the virtual insolubility of the materials, we postulated that the rare reports on dissolved species in solution do not represent monomolecular species but oligomers. We thus studied the structural and spectral properties of the monomolecular entities of these compounds using density functional theory (DFT) and time-dependent DFT computations in dimethyl sulfoxide (DMSO) as a solvent. The molecular geometries, IR and UV-vis spectra, and frontier orbitals properties were computed using LANL2DZ ecp and def2TZVP as basis sets and M06-2X as the functional. The results are compared with the available experimental and other calculated data. The optimised molecular geometries proved the asymmetric character of the two formed O–H…O bonds which connect the two Hdmg‒ ligands in the completely planar molecules. Calculated UV-vis spectra revealed the presence of three absorptions in the range 180 to 350 nm that are red-shifted along the series Ni–Pd–Pt. They were assigned to essentially ligand-centred π−π* transitions in part with metal(d) to ligand(π*) charge transfer (MLCT) contributions. The notorious d‒p transitions dominating the colour and electronics of the compounds in the solid-state and oligomeric stacks are negligible in our monomolecular models strongly supporting the idea that the previously reported spectroscopic observations or biological effects in solutions are not due to monomolecular complexes but rather to oligomeric dissolved species.

Single-Stranded DNA as Supramolecular Template for One-Dimensional Palladium(II) Arrays.

Atomic-level control over the position and growth of a single and continuous metal chain is an ambitious goal that often requires complex and costly processes. Herein, we demonstrate that 1Pd-DNA molecules, comprising a continuous single chain of PdII ions, can be prepared by a simple self-assembly reaction between the complex [Pd(Cheld)(CH3 CN)] (1Pd_CH3 CN) (Cheld=chelidamic acid) and single-stranded DNA homopolymers (ss-DNA) containing adenine (A) or 7-deazaadenine (X) bases. The single PdII -base pairs [1Pd(N1-A)] and [1Pd(N1-X)] were synthesized and characterized in solution and solid-state (X-ray diffraction) revealing an arrangement similar to that of natural Watson-Crick base pairs. Subsequently, 1Pd-DNA hybrids were prepared, characterized, and their structures studied by small-angle X-ray scattering (SAXS) and ab-initio calculations. The results indicate that the 1Pd-DNA structures resemble that of double-stranded DNA, with one strand being replaced by a supramolecular stack of continuous PdII complexes.

Single‐Stranded DNA as Supramolecular Template for One‐Dimensional Palladium(II) Arrays

AbstractAtomic‐level control over the position and growth of a single and continuous metal chain is an ambitious goal that often requires complex and costly processes. Herein, we demonstrate that 1Pd‐DNA molecules, comprising a continuous single chain of PdII ions, can be prepared by a simple self‐assembly reaction between the complex [Pd(Cheld)(CH3CN)] (1Pd_CH3CN) (Cheld=chelidamic acid) and single‐stranded DNA homopolymers (ss‐DNA) containing adenine (A) or 7‐deazaadenine (X) bases. The single PdII‐base pairs [1Pd(N1‐A)] and [1Pd(N1‐X)] were synthesized and characterized in solution and solid‐state (X‐ray diffraction) revealing an arrangement similar to that of natural Watson–Crick base pairs. Subsequently, 1Pd‐DNA hybrids were prepared, characterized, and their structures studied by small‐angle X‐ray scattering (SAXS) and ab‐initio calculations. The results indicate that the 1Pd‐DNA structures resemble that of double‐stranded DNA, with one strand being replaced by a supramolecular stack of continuous PdII complexes.

Bis[2,3-bis-(pyridin-2-yl)pyrazine-κ2 N 2,N 3]palladium(II) dinitrate aceto-nitrile monosolvate.

The title compound, [Pd(C14H10N4)2](NO3)2·CH3CN, consists of a cationic PdII complex, two anions and one lattice solvent mol-ecule, all in general positions. In the complex, the PdII cation is four-coordinated in a slightly distorted square-planar geometry defined by the four N atoms of two bidentate 2,3-di-2-pyridyl-pyrazine ligands. The complex, anions and solvent mol-ecule are linked by weak C-H⋯O inter-molecular hydrogen bonds. In the crystal, the complex mol-ecules are stacked in columns along the a axis.

(Nitrato-κO)(2,2':6',2''-terpyridine-κ3 N,N',N'')palladium(II) nitrate.

The title complex, [Pd(NO3)(C15H11N3)]NO3, comprises a cationic PdII complex and a nitrate anion. In the complex, the PdII cation is four-coordinated in a distorted square-planar coordination geometry defined by the three N atoms of the tridentate 2,2':6',2''-terpyridine ligand and one O atom from the NO3 - anion. In the crystal, the complex mol-ecules are stacked in columns along the a axis being connected by π-π stacking [closest inter-centroid separation between pyridyl rings = 3.878 (3) Å]. The connections between columns and anions to sustain a three-dimensional architecture are C-H⋯O hydrogen bonds.