Crystal Structure Of Pd Research Articles

Palladium(II) complexes bearing thioether-NHC ligand: Synthesis, characterization, and their application in Suzuki-Miyaura coupling

A series of palladium(II) complexes bearing thioether-functionalized N-heterocyclic carbene ligands, namely [Pd(N-(R1,2,3)-N'-(2-(phenylthio)ethyl)-5,6-dimethylbenzimidazol-2-ylidene)Cl2(py)] (R1: 1-bromohexane, R2: 1-bromododecane, R3: 1-bromooctadecane, R’: 2-chloroethyl phenyl sulfide, py: pyridine), have been synthesized and characterized. The synthesized ligands (2a-c) and complexes (3a-c) were characterized by NMR, FT-IR, and elemental analysis. The crystal structure of Pd(II) complex 3a was determined by single-crystal X-ray diffraction. X-ray diffraction analysis revealed that the palladium ion has a slightly distorted square-planar geometry. The catalytic activity of all complexes (3a-c) for the Suzuki-Miyaura cross-coupling reaction was examined. Under the optimized conditions, aryl bromides were successfully converted into corresponding coupled products. Yields ranged high for electron-rich aryl bromides, moderate for electron-neutral bromides, and low for electron-poor bromides.

Photophysical Properties of Simple Palladium(0) Complexes Bearing Triphenylphosphine Derivatives.

Pd(0) complexes with monodentate phosphine ligands, [Pd(P)n] (n = 3, 4), are well-known catalysts. However, the nature of the Pd(0) complex, especially the basic photophysical properties of the Pd(0) complexes, has not been extensively explored. In this work, we measured the general photophysical properties and crystal structures of Pd(0)-bearing PPh3 derivatives in the solid state and in solution. In the solid state, four-coordinated Pd(0) complexes exhibited blue-yellow emission. On the other hand, three-coordinated Pd(0) complexes displayed yellow-orange emission. In solution, orange emission of three-coordinated complexes was observed, and prompt fluorescence was detected using time-resolved emission spectroscopy, which suggests a thermally activated delayed fluorescence mechanism. Density functional theory (DFT) and time-dependent DFT calculations show that the difference in the transition mechanism between the [Pd(PPh3)4] and [Pd(PPh3)3] complexes explains the different emission colors. The emitting states of both complexes have metal-to-ligand charge-transfer character, but the metal-centered d → p transition is considerably incorporated for emission of the tris complex.

Asymmetric palladacycle complexes with N,O-bidentate barbiturate ligands: Preparation, characterization and catalytic application in Suzuki-Miyaura reaction

Three N,O-chelate ligands (1a-1c) were synthesized by the reaction of aniline derivatives with 1,3-dimethyl-2,4,6-trioxohexahydropyrimidine-5-carbaldehyde. The corresponding palladacycles complexes (2a-2c) were prepared from treatment of N,O-chelate ligands (1a-1c) with [Pd(μ-OAc)(ppy)]2. The structures of all synthesized compounds were characterized by elemental analyses, ATR-FTIR, 1H- and 13C NMR spectroscopy. Crystal structures of Pd(II) complexes 2a and 2c were determined by single crystal X-ray diffraction. X-ray diffraction studies revealed that the palladium atom in 2a and 2c has distortion of square-planar geometry. Synthesized complexes were tested as catalyst in Suzuki-Miyaura cross-coupling reaction of various aryl bromide with phenyl boronic acid. All complexes behaved as efficient catalyst to produce the biaryls with both high yields and short time under mild reaction conditions.

Zinc (II), palladium (II) and cadmium (II) complexes containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline derivatives: Synthesis, characterization and methyl methacrylate polymerization

A series of Zn (II), Pd (II) and Cd (II) complexes, [(L)nMX2]m (L = L‐a–L‐c; M = Zn, Pd; X = Cl; M = Cd; X = Br; n, m = 1 or 2), containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline (L‐a), 4‐methoxy‐N‐(pyridin‐2‐ylmethyl) aniline (L‐b) and 4‐methoxy‐N‐methyl‐N‐(pyridin‐2‐ylmethyl) aniline (L‐c) have been synthesized and characterized. The X‐ray crystal structures of Pd (II) complexes [L1PdCl2] (L = L‐b and L‐c) revealed distorted square planar geometries obtained via coordinative interaction of the nitrogen atoms of pyridine and amine moieties and two chloro ligands. The geometry around Zn (II) center in [(L‐a)ZnCl2] and [(L‐c)ZnCl2] can be best described as distorted tetrahedral, whereas [(L‐b)2ZnCl2] and [(L‐b)2CdBr2] achieved 6‐coordinated octahedral geometries around Zn and Cd centers through 2‐equivalent ligands, respectively. In addition, a dimeric [(L‐c)Cd(μ‐Br)Br]2 complex exhibited typical 5‐coordinated trigonal bipyramidal geometry around Cd center. The polymerization of methyl methacrylate in the presence of modified methylaluminoxane was evaluated by all the synthesized complexes at 60°C. Among these complexes, [(L‐b)PdCl2] showed the highest catalytic activity [3.80 × 104 g poly (methyl methacrylate) (PMMA)/mol Pd hr−1], yielding high molecular weight (9.12 × 105 g mol−1) PMMA. Syndio‐enriched PMMA (characterized using 1H‐NMR spectroscopy) of about 0.68 was obtained with Tg in the range 120–128°C. Unlike imine and amine moieties, the introduction of N‐methyl moiety has an adverse effect on the catalytic activity, but the syndiotacticity remained unaffected.

Microbial synthesis of Pd–Pt alloy nanoparticles using Shewanella oneidensis MR-1 with enhanced catalytic activity for nitrophenol and azo dyes reduction

Bimetallic nanoparticles (NPs) often exhibit improved catalytic performance due to the electronic and spatial structure changes. Herein, a novel green biosynthesis method for Pd–Pt alloy NPs using Shewanella oneidensis MR-1 was proposed. The morphology, size and crystal structure of Pd–Pt alloy NPs were studied by a suite of characterization techniques. Results showed Pd–Pt alloy NPs were successfully synthesized inside and outside the cell. The biosynthesized Pd–Pt alloy NPs were polycrystalline and face-centered-cubic structure with the particle size ranged from 3–40 nm. Furthermore, the catalytic experiment demonstrated that the Pd–Pt alloy NPs exhibited the highest performance for the catalytic reduction of nitrophenol and azo dyes compared with the as-synthesized Pd and Pt monometallic NPs. This enlarged catalytic activity resulted from the synergistic effect of Pd and Pt element. Thereby, this paper provided a simple biosynthesis method for producing bimetallic alloy nanocatalyst with superior activity for contaminant degradation.

Electro-oxidation of alcohols using carbon supported gold, palladium catalysts in alkaline media

Mono and binary Pd-Au based catalysts were synthesized using the NaBH4 assisted ethylene glycol reduction method. The catalysts were supported on Vulcan XC 72 carbon black and denoted as Pd/C, Au/C, Pd(Au/C) and Pd-Au/C co-reduction. Pd:Au composition was maintained at 1:2 ratio. XRD profiles confirmed the face centered cubic crystal structure of Pd and Au. The average particle size for Pd/C, Au/C, Pd(Au/C) and Pd-Au/C co-reduction is 5 ±0.6 nm, 22 ±0.7 nm, 17 ±0.4 nm and 6 ±0.2 nm, respectively. The catalysts showed activity towards the oxidation of alcohols (methanol, ethanol, ethylene glycol and glycerol) in alkaline media. Cyclic voltammograms indicated that methanol and ethanol oxidation were more favoured on Pd/C than on Au/C catalysts. It was also noticed that the incorporation of Pd on Au, that is on Pd(Au/C) and Pd-Au/C co-reduction, enhances the onset potential for the oxidation of ethylene glycol and glycerol. When comparing all alcohols studied, it was observed that the maximum current density for the oxidation of ethylene glycol was highest for all catalysts at 54.4, 41.4, 39.8 and 12.1 mA/cm2 on Pd-Au/C co-reduction, Au/C, Pd(Au/C) and Pd/C, respectively. Pd-Au/C co-reduction showed better ADAFC performance under passive conditions as compared to Pd(Au/C) with glycerol and ethylene glycol at 8.34 and 8.46 mW/cm2 respectively, and 0.5 mgPd/cm2. Pd-Au/C cored is a more stable and poisoning tolerant catalyst for ethylene glycol and glycerol oxidation.

The crystal structure of Pd3 HgTe3, the synthetic analogue of temagamite

The crystal structure of the synthetic analogue of the mineral temagamite, Pd 3 HgTe 3 , was solved and refined to an R -factor of 0.0522 from single-crystal X-ray diffraction data. The structure is trigonal, space group P 3 m 1, with a = 7.8211(6) A, c = 17.281(1) A, V = 917.8(1) A 3 (hexagonal setting) and Z = 6. Layer modules (A–F) stacked along the c -axis form the crystal structure of Pd 3 HgTe 3 . Module A is composed of isolated octahedra [PdTe 6 ], which share faces with adjacent octahedra from neighbouring modules. The edge-sharing [PdTe 6 ] octahedra and [PdTe 4 ] squares form the modules B and F, whereas the corner-sharing [PdTe 4 ] squares constitute modules C, D and E. The Hg atoms occupy the anti-cubooctahedral voids formed by Te atoms. The Pd–Pd and Pd–Hg bonds are also present in the structure. The symmetry of temagamite was revised based on the structural results of this study.

Perfluoroalkylation of Square-Planar Transition Metal Complexes: A Strategy To Assemble Them into Solid State Materials with a π–π Stacked Lamellar Structure

Formation of π–π stacked lamellar structure is important for high performance organic semiconductor materials. We previously demonstrated that perfluoroalkylation of aromatics and heteroaromatics was one of the strategies to design organic crystalline materials with π–π stacked lamellar structures while improving air stability as a result of the strong electron withdrawing ability of perfluoroalkyl substituents. Square-planar transition metal complexes with large π-conjugated ligands are also an important category of semiconductor materials. We have perfluoroalkylated square-planar transition metal complexes, leading to the formation of a π–π stacked lamellar crystal packing motif in the solid state. Here we report six crystal structures of Pd and Pt complexes with bis-perfluorobutylated catechol ligand as one of the two ligands that bonds to the metal centers. This structural design possesses similar molecular topology when compared to perfluoroalkylated aromatics and heteroaromatics we have reported pre...

N,N′,X-bidentate versus N,N′,X-tridentate N-substituted 2-iminomethylpyridine- and 2-iminomethylquinoline-coordinated palladium(II) complexes

The reaction of [Pd(CH3CN)2Cl2] with N-functional group-substituted 2-iminomethylpyridine and 2-iminomethylquinoline can produce N,N′,X-bidentate Pd(II) complexes and N,N′,X-tridentate Pd(II) complexes depending on the functional group substitution on the nitrogen of the imine moiety. For example, N,N-dimethyl-3-((pyridin-2-ylmethylene)amino)propan-1-amine (L1), N,N-dimethyl-3-((quinolin-2-ylmethylene)amino)propan-1-amine (L2), and N-(3-(methylthio)propyl)-1-(pyridin-2-yl)methanimine (L3) were coordinated to palladium as N,N′,X-tridentate mode in the presence of NaClO4 to yield two fused ring metallacyclic [(NN′X)PdCl]ClO4 complexes with high yield, i.e. [LnPdCl]ClO4 (Ln = L1, L2, L3), respectively. However, N-methyl-N-(3-((pyridin-2-ylmethylene)amino)propyl)aniline (L4) and N-(3-methoxypropyl)-1-(pyridin-2-yl)methanimine (L5) yield (in the absence of NaClO4) N,N′,X-bidentate metallacyclic [(NN′)PdCl2] complexes with high yield, i.e. [L4PdCl2] and [L5PdCl2], respectively. The X-ray crystal structure of Pd(II) complexes revealed that the palladium in [LnPdCl]ClO4 (Ln = L1, L2, L3) and [LnPdCl2] (Ln = L4, L5) formed a slightly distorted square planar geometry involving two nitrogens of iminomethylpyridine ligand, one X, and one or two chlorides. The N,N′,X-tridentate complex [L2PdCl]ClO4 and the N,N′,X-bidentate complex [L5PdCl2] showed high catalytic activity for polymerization of methyl methacrylate in the presence of co-catalyst, modified methylaluminoxane at 60 °C compared to the reference complex anhydrous [PdCl2]. Specifically, the activities of [L2PdCl]ClO4 and [L4PdCl2] were 1.43 × 105 and 1.08 × 105 g PMMA M−1 Pd h, respectively. The syndiotacticity of poly(methylmethacrylate) (PMMA), which was characterized using 1H NMR spectroscopy, was about 0.70 for the [L2PdCl]ClO4 and [L4PdCl2] complexes.

Synthesis, spectral characterization, and X-ray crystal structure of Pd(II) complexes containing the orthometallated C,C-chelating ligand C6H4-PPh2C(H)C(O)CH2Cl

The ylide-phosphonium salt [PPh3CH2C(O)CH2Cl]+Cl− (1) reacted with Pd(OAc)2 to give the chloro-bridged dinuclear complex [Pd{C(H)PPh3C(O)CH2Cl}(μ-Cl)(OAc)]2 (2), which underwent bridge cleavage reactions with a neutral bidentate N-donor to afford the cationic orthometallated complexes [Pd{(C,C)-C6H4PPh2C(H)C(O)CH2Cl}(N−N)]CF3SO3 [N−N=bipy (2,2’-bipyridine) (3), phen (1,10-phenanthroline) (4), 4-Me-phen (4-methyl-1,10-phenanthroline) (5), and 5-NO2 phen (5-nitro-1,10-phenanthroline) (6)]. The complexes were identified and characterized by spectroscopic studies (IR and NMR). X-ray single-crystal analysis of 4 and 5 revealed the presence of an orthometallated C6H4-PPh2 unit and a C-linked ylide Pd−C(H). Thermal behavior of 3–6 is investigated by thermogravimetry.

Characterization of DMSO coordination to palladium(II) in solution and insights into the aerobic oxidation catalyst, Pd(DMSO)2(TFA)2.

Recent studies have shown that Pd(DMSO)(2)(TFA)(2) (TFA = trifluoroacetate) is an effective catalyst for a number of different aerobic oxidation reactions. Here, we provide insights into the coordination of DMSO to palladium(II) in both the solid state and in solution. A crystal structure of Pd(DMSO)(2)(TFA)(2) confirms that the solid-state structure of this species has one O-bound and one S-bound DMSO ligand, and a crystallographically characterized mono-DMSO complex, trans-Pd(DMSO)(OH(2))(TFA)(2), exhibits an S-bound DMSO ligand. (1)H and (19)F NMR spectroscopic studies show that, in EtOAc and THF-d(8), Pd(DMSO)(2)(TFA)(2) consists of an equilibrium mixture of Pd(S-DMSO)(O-DMSO)(TFA)(2) and Pd(S-DMSO)(2)(TFA)(2). The O-bound DMSO is determined to be more labile than the S-bound DMSO ligand, and both DMSO ligands are more labile in THF relative to EtOAc as the solvent. DMSO coordination to Pd(II) is substantially less favorable when the TFA ligands are replaced with acetate. An analogous carboxylate ligand effect is observed in the coordination of the bidentate sulfoxide ligand, 1,2-bis(phenylsulfinyl)ethane to Pd(II). DMSO coordination to Pd(TFA)(2) is shown to be incomplete in AcOH-d(4) and toluene-d(8), resulting in Pd(II)/DMSO adducts with <2:1 DMSO/Pd(II) stoichiometry. Collectively, these results provide useful insights into the coordination properties of DMSO to Pd(II) under catalytically relevant conditions.

Part 1: Experimental and theoretical studies of 2-cyano-2-isonitroso-N-piperidynylacetamide (HPiPCO), 2-cyano-2-isonitroso-N-morpholylacetamide (HMCO) and their Pt- and Pd-complexes

The reaction between substituted cyan-acetamides NC–CH2–C(O)X (X=N-piperidyne or N-morpholyl residues) and gaseous methylnitrite CH3ONO in isopropanol at room temperature in the presence of a base within minutes leads to colorless cyanoximes 2-cyano-2-isonitroso-N-piperidynylacetamide (further as HPiPCO), and 2-cyano-2-isonitroso-N-morpholylacetamide (HMCO) in 70–90% yield. The deprotonation of HPiPCO and HMCO with a base such as NaOEt affords anionic Na-salts, bright-yellow in color originated from n→π∗ transitions in the nitroso-chromophore. Anionic cyanoximates react with aqueous solutions of K2MCl4 (M=Pd, Pt) to form yellow-orange PdL2 and dark blue-green polymeric [PtL2]n (L=PiPCO−, MCO−), which upon treatment with DMSO or DMF breaks down to pale-yellow monomeric PtL2. Synthesized metal complexes were characterized by spectroscopic methods (IR, UV–Vis), measurement of the electric conductivity and the X-ray analysis. Both PdL2 and PtL2 exhibit non-electrolyte behavior in DMSO and DMF. Crystal structures of Pd(PiPCO)2 and Pt(PiPCO)2 were determined and revealed the formation of the cis-complexes with nearly planar geometry around the metal core and an adoption of the cis-anti configuration by anions, in contrast to the trans–anti geometry in structures of uncomplexed HPiPCO and HMCO. Ab initio calculations were performed for all six compounds: two cyanoxime ligands and four Pd and Pt metal complexes. A very satisfactory agreement between the calculated and experimental values of geometrical parameters of all evaluated compounds was attained. The electron densities, energies of HOMO and LUMO orbitals and molecular electrostatic potentials were calculated as well.

Bulky and Modular 3,3′‐Bipyrazoles as Ligands: Synthesis, Characterization, and Catalytic Activity of Pd Complexes

AbstractIn the present study, the properties of a new bidentate N,N′‐chelating ligand class that bears an electron‐excessive 3,3′‐bipyrazole core have been investigated. The ligands are easily accessible in a three‐step procedure by condensation with diethyl oxalate followed by tandem condensation with hydrazine hydrate and finally by aryl‐ or alkylation exclusively at the N‐1,1′‐pyrazole positions to furnish overall eleven new ligands with different electronic properties. After structural analysis of the ligands, their coordination to palladium, copper, and cobalt has been studied. These ligands coordinate the 2,2′‐pyrazolyl nitrogen atoms in a bidentate fashion to the metals to realize complexes with an (L)MX2 motif. We present two crystal structures of Pd and Cu complexes, which to the best of our knowledge represent the first d8 and d9 2,2′‐bipyrazole compounds coordinated through bidentate complexation. Initial catalytic experiments have been performed with palladium complexes with three bipyrazole ligands of this new class; the palladium‐catalyzed copper‐free Wacker oxidation of different alkenes showed superior activity compared to 2,2′‐bipyridines. We attribute this to a higher redox potential of the 3,3′‐bipyrazoles, which are ― besides electronic effects ― also strongly influenced by steric effects. These might be enforced by the extended ligand backbone, the choice of the wingtip substitution, and the smaller coordination cavity within the N2,N2′ atoms compared to 2,2′‐bipyridine ligands.

Synthesis and Characterization of New Palladium(II) Complexes with Ligands Derived from Furan-2-carbaldehyde and Benzaldehyde Thiosemicarbazone and their in vitro Cytotoxic Activities against Various Human Tumor Cell Lines

With the ligands 4-phenyl-1-(furan-2-carbaldehyde)thiosemicarbazone, HTSC1, (1), 4-phenyl-1- (5´-phenyl-furan-2-carbaldehyde)thiosemicarbazone, HTSC2 (2), o-methoxy-benzaldehydethiosemicarbazone, HTSC3 (3), and o-cyano-benzaldehydethiosemicarbazone, HTSC4 (4), the corresponding palladium(II) complexes, Pd(TSC1)2 (5), Pd(TSC2)2 (6), Pd(TSC3)2 (7), and Pd(TSC4)2 (8) were synthesized and characterized by elemental analysis and spectroscopic techniques. The crystal structure of Pd(TSC3)2 (7) was determined by single-crystal X-ray diffraction. Complex 7 shows a squareplanar geometry, where two deprotonated ligands are coordinated to the PdII center through the nitrogen and sulfur atoms in a trans arrangement. In vitro antitumor studies against different human tumor cell lines have revealed that the palladium(II) complexes 5- 8 are more cytotoxic (IC50 values in the range of 0.21 - 3.79 μM) than their corresponding ligands (1 - 4) (&gt; 60 μM). These results indicate that the antiproliferative activity is enhanced when thiosemicarbazone ligands are coordinated to the metal. Among the studied palladium(II) complexes, 8 exhibits high antitumor activity on K562 chronic myelogenous leukemia cells with a low value of the inhibitory concentration (IC50 = 0.21 μM).

Synthesis, X-ray crystal structure, and reactivity of Pd2(μ-dotpm)2 (dotpm=bis(di-ortho-tolylphosphino)methane)

Abstract Alkylation of PdCl 2 (dotpm) (dotpm = bis(di- ortho -tolylphosphino)methane) with n -butyllithium produces the binuclear Pd(0) complex Pd 2 ( μ -dotpm) 2 and the elimination byproducts 1-butene, cis -2-butene, trans -2-butene, butane, and octane. The dibutyl complex, Pd(dotpm)( n -Bu) 2 , is presumed to be the reaction intermediate. The crystal structure of Pd 2 ( μ -dotpm) 2 reveals that the methylene groups of the bridging dotpm ligands are located on opposite sides of the Pd 2 P 4 unit, forming an 8-membered ring that is in an elongated chair conformation. The four phosphorus atoms are not coplanar, and the P1–P2–P3–P4 ring has a torsion angle of 13.8°, which minimizes the spatial interactions among the o -tolyl rings. The Pd–Pd bond distance is 2.8560(6) A, which indicates that there is a weak “closed-shell” bonding interaction between the d 10 –d 10 metal centers. Each palladium atom has a nearly linear geometry, and the eight methyl groups of the dotpm ligands shield the open coordination sites on the metal centers. Four methyl groups shield the metal atoms above and below the Pd 2 P 4 ring cavity, and four methyl groups block the open metal sites outside of the Pd 2 P 4 ring. The Pd 2 ( μ -dotpm) 2 complex readily undergoes oxidative addition of dichloromethane to form the rigid A-frame complex Pd 2 Cl 2 (μ-CH 2 )( μ -dotpm) 2 .

Pd(SeO3), Pd(SeO4), and Pd(Se2O5): The First Palladium Oxoselenates.

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Cyclic tetranuclear and hexanuclear palladium(II) complexes and their host-guest chemistry.

Cyclic tetrameric complexes have been prepared by the reaction of Pd(en)Cl2 or Pd(dapol)Cl2, or their nitrato analogues, with Na2(5'GMP) in aqueous solution, where en=1,2-diaminoethane, dapol=1,3-diamino-2-propanol, and 5'GMP=guanosine 5'-monophosphate. Addition of certain small molecules containing hydrophobic groups resulted in the expansion of the tetramer to a cyclic hexamer with strong bonding of one guest per hexameric host. At pH 5-6, the guest molecule can be a cation, anion, or neutral, and those species containing trimetylsilyl and t-butyl groups bonded the most strongly. The size of the central cavity of the [Pd(en)(5'GMP)]6 host has been estimated to be 5.2 A. Formation of the host-guest complex caused a large upfield shift (Deltadelta) of 2.5-2.9 ppm in the 1H NMR spectrum of the most highly affected guest protons, which were those in closest proximity to the guanine nucleobases. NOESY spectra were used to determine the interaction sites between the host and the guest. Apparent association constants determined at 26 degrees C and pD 5.4 for the [Pd(en)(5'GMP)]6-DSS and [Pd(en)(5'GMP)]6-t-butanol systems, where DSS is 3-(trimethylsilyl)-1-propanesulfonate anion, were 1.36+/-0.11x10(4) and 2.74+/-0.95x10(4) M(-3/2), respectively. The Pd(dapol)-5'GMP system forms hexameric host-guest complexes, similar in nature to those of the Pd(en)-5'GMP system. The molecular and crystal structures of Pd(dapol)Cl2 are also reported.

Pd(SeO3), Pd(SeO4), and Pd(Se2O5): The First Palladium Oxoselenates

AbstractDepending on the reaction conditions, the reaction of elemental palladium with H2SeO4 in sealed glass tubes at 350 °C leads to red single crystals of Pd(SeO3) [C2/m, Z = 4, a = 6.788(2), b = 7.030(2), c = 7.008(2) Å, β = 118.09(3)°] or to yellow‐orange single crystals of Pd(SeO4) [C2/c, Z = 4, a = 8.171(1), b = 5.286(1), c = 8.115(1) Å, β = 94.54(1)°]. Yellow‐orange single crystals of Pd(Se2O5) [I2/a, Z = 4, a = 7.212(1), b = 5.569(1), c = 12.177(3) Å, β = 106.84(2)°] are obtained when SeO3 is added to the reaction mixture. X‐ray single‐crystal diffraction shows that Pd(SeO3) consists of layers that are formed by square‐planar coordinated Pd2+ ions and pyramidal SeO32– groups. These layers are held together by weak interactions involving the lone electron pairs of the selenium atoms. The Se–O distances within the selenite ion are different (1.69 and 1.76 Å), in accordance with the different attachment of the oxygen atoms to the Pd2+ ions. The square‐planar [PdO4] units in the crystal structure of Pd(SeO4) are linked by tetrahedral SeO42– ions into a three‐dimensional network. These anions act as monodentate ligands towards the Pd2+ ions, with Se–O distances of around 1.65 Å. The Pd2+ ions in the crystal structure of Pd(Se2O5) are coordinated by two chelating diselenite ions. The Se2O52– ions link the palladium ions into corrugated chains, which are held together by weak interactions only. The IR spectra of these compounds display the typical bands for oxoselenate anions.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

Electrochemical reduction properties of A-frame compounds and crystal structure of Pd 2(dppm) 2(Me) 2(Br) + dimer

Two series of A-frame complexes, [Pd 2(dppm) 2(R) 2(μ-X)] + (R = Me and X = Cl, Br, I, H; R = Mes and X = Br, I), were investigated by cyclic voltammetry (CV). The 2-electron reduction potentials for the first series increase from I (−1.10), Br (−1.17), Cl (−1.25) to H (−1.65 V versus SCE, in CHCl 3), as well as in the second series; Br (−1.35) and I (−1.38 V versus SCE, in THF). The nature of the LUMO where the electron reduction takes place is qualitatively addressed by DFT on the corresponding model complexes [Pd 2(H 2PCH 2PH 2) 2(R) 2(μ-X)] +. The LUMO and (LUMO + 1) of the halide derivatives exhibit the presence of Pd d x 2 - y 2 atomic orbitals interacting in an anti-bonding fashion with the n-donor orbitals of X −, P, and Me −, explaining in part the observed reactivity upon reduction. The X-ray structure of [Pd 2(dppm) 2(Me) 2(μ-Br)] + compound exhibits the typical A-frame structure with a Pd⋯Pd non-bonding distance of 3.036(1) Å, and long Pd–Br bonds of 2.5623(5) and 2.5793(5) Å.

Bimetallic complexes with porphyrins containing a cyclometalated phenylpyridine group

Treatment of Ni(HP 1) (H 3P 1 = meso-5-[4′-(2″-pyridyl)phenyl]-10,15,20-triphenyporphyrin) with K 2[PdCl 4] in EtOH afforded [Pd{Ni(P 1)}] 2(μ-Cl) 2 that reacted with NaS 2CNEt 2 to give Pd(S 2CNEt 2)[Ni(P 1)]. Reaction of Ni(HP 1) with [Ir(H) 2(PPh 3) 2(Me 2CO) 2][BF 4] afforded Ir(H)Cl(PPh 3) 2[Ni(P 1)]. The crystal structures of Pd(S 2CNEt 2)[Ni(P 1)] and Ir(H)(Cl)(PPh 3) 2[Ni(P 1)] have been determined.