Dicationic Complexes Research Articles

Pd(II) Complexes Ligated by 1,3-Bis(diphenylphosphino)calix[4]arene: Preparation, X-ray Structures, and Catalyses

syn-1,3-Bis(diphenylphosphino)-2,4-dimethoxycalix[4]arene (7) was synthesized via an Ullmann-type phosphinoylation of the syn-1,3-bis(triflate ester) (2) of p-tert-butylcalix[4]arene, followed by reduction of the phosphinoyl moieties and subsequent methylation of the remaining hydroxy groups. The treatment of diphosphine 7 with 2 molar equiv of PdCl2(MeCN)2 in benzonitrile afforded di-μ-chloro-bridged dinuclear palladium complex 8, formulated as Pd2(7)Cl4, whereas the same reaction conducted in acetonitrile with 1 molar equiv of PdCl2(MeCN)2 yielded mononuclear palladium complex 9, formulated as [Pd(7)Cl(MeCN)]Cl. Complex 9 was transformed into dicationic complex 11, formulated as [Pd(7) MeCN)2](BF4)2, by treatment with AgBF4 in dichloromethane, followed by the addition of acetonitrile. On the other hand, refluxing complex 9 in 1,2-dichloroethane yielded neutral complex 12, formulated as Pd(7)Cl2. In each of the mononuclear complexes, the palladium ion adopts a tetracoordinated square-planar geometry perp...

Crystal structure of μ-oxalodi-hydroxamato-bis-[(2,2'-bipyrid-yl)(di-methyl sulfoxide-κO)copper(II)] bis-(perchlorate).

The centrosymmetric binuclear complex, [Cu2(C2H2N2O4)(C10H8N2)2(C2H6OS)2](ClO4)2, contains two copper(II) ions, connected through an N-deprotonated oxalodi-hydroxamic acid dianion, two terminal 2,2'-bi-pyridine ligands, and two apically coordinating dimethylsulfoxide mol-ecules. Two non-coordinating perchlorate anions assure electrical neutrality. The copper(II) ions in the complex dication [Cu2(C10H8N2)2(μ-C2H2N2O4)(C2H6SO)2](2+) are in an O2N3 square-pyramidal donor environment, the Cu-Cu separation being 5.2949 (4) Å. Two hydroxamate groups in the deprotonated oxalodi-hydroxamic acid are located trans to one each other. In the crystal, O-H⋯O and C-H⋯O hydrogen bonds link the complex cations to the perchlorate anions. Further C-H⋯O hydrogen bonds combine with π-π contacts with a centroid-to-centroid separation of 3.6371 (12) Å to stack the mol-ecules along the a-axis direction.

Different structural preference of Ag(I) and Au(I) in neutral and cationic luminescent heteropolynuclear platinum(II) complexes: Z (U)-shaped Pt2M2 type vs. trinuclear PtM2 type.

The reactions of monocationic Pt(II) complexes bearing N^C chelate ligands and Me2pzH, [Pt(N^C)(Me2pzH)2]PF6 (N^C = 2-phenylpyridinate (ppy(-)), 2-(2,4-difluorophenyl)pyridinate (dfppy(-)), benzo[h]quinolinate (bzq(-)); Me2pzH = 3,5-dimethylpyrazole), with Ag(I) ions gave Z (or U)-shaped neutral tetranuclear Pt2Ag2 complexes [Pt2Ag2(N^C)2(Me2pz)4], while those with Au(I) ions gave neutral trinuclear PtAu2 complexes [PtAu2(N^C)(Me2pz)3]. On the contrary, the reactions of the dicationic Pt(II) complex bearing a N^N chelate ligand and Me2pzH, [Pt(bpy)(Me2pzH)2](PF6)2 (bpy = 2,2'-bipyridine), with Ag(I) and Au(I) ions both gave Z (or U)-shaped dicationic tetranuclear Pt2M2 complexes, [Pt2M2(bpy)2(Me2pz)4](PF6)2 (M = Ag, Au). The structures of heteropolynuclear Pt(II) complexes were dominated by the nature of incorporated group 11 metal ions and the charge of complexes.

ジカチオン性パラジウム錯体を用いたフルオロアルキル化合物の触媒的不斉合成

ジカチオン性パラジウム錯体を用いたフルオロアルキル化合物の触媒的不斉合成

Synthesis and structure of the first discrete dinuclear cationic aluminum complexes.

The reactions of the charge neutral dinuclear aluminum tetraalkyl complexes of di-Schiff base ligands, i.e. [AlMe2{ON}-R-{ON}AlMe2] (1a, R = 1,3-propylene; 1b, R = 1,3-cyclohexylene) with B(C6F5)3 and [H(Et2O)2](+)[H2N{B(C6F5)3}2](-) were investigated. When B(C6F5)3 was used as the cationizing agent (1 or 2 equiv. vs. Al), only monocationic dinuclear complexes [2a,b]+[MeB(C6F5)3]- were obtained. In contrast, with [H(Et2O)2](+)[H2N{B(C6F5)3}2](-), both mixed-dicationic [3a,b·(OEt2)2]2+[MeB(C6F5)3]-[H2N{B(C6F5)3}2]- and homo-dicationic [3a,b·(OEt2)2]2+[H2N{B(C6F5)3}2]-2 ion-pairs were prepared. All cationic complexes were characterized by (1)H, (13)C, (19)F and (11)B NMR spectroscopy, and an X-ray diffraction study was performed for [3b·(OEt2)2]2+[H2N{B(C6F5)3}2]-2.

Synthesis and Structure of Homoleptic Iron Complex Bearing Pincer-Type 1,2,3-Triazol-5-ylidene

Novel iron(II) complex bearing pyridine-bridged bis(1,2,3-triazol-5-ylidene) ligand was synthesized. During many attempts to obtain the compounds, we found generation of dicationic homoleptic iron(II) complex with two tridentate ligands. Analogous monocationic complex with only one tridentate ligand, which is an unstable intermediary complex during formation of the dicationic complex was detected. Structural identification of the homoleptic dicationic product revealed that octahedral geometry stabilized the iron complex and also π-stacking interaction exists between these two tridentate ligands.

Ni-Fe and Pd-Fe Interactions in Nickel(II) and Palladium(II) Complexes of a Ferrocene-Bridged Bis(imidazolin-2-imine) Ligand.

The bis(imidazolin-2-imine) ligand N,N'-bis(1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene)-1,1'-ferrocenediamine, fc(NIm)2 (1) was prepared. Its reaction with [NiCl2(dme)] (dme = 1,2-dimethoxyethane) or [PdCl2(MeCN)2] afforded the tetrahedral, paramagnetic complex [(1-κ(2)N,N')NiCl2] (6a) or the diamagnetic, square-planar complex [(1-κ(2)N,N')PdCl2] (6b), respectively. For the latter, slow rearrangement to the ionic complex [(1-κFe,κ(2)N,N')PdCl]Cl, [7]Cl, was observed, which was followed by (1)H NMR and UV/vis spectroscopy. Treatment of [7]Cl with NaBF4 afforded [7]BF4; the palladium atoms in both cations adopt square-planar environments with short Fe-Pd bonds (ca. 2.65 Å). In addition, a series of dicationic complexes of the type [(1-κFe,κ(2)N,N')ML](BF4)2 (8a: M = Ni, L = MeCN; 8b: M = Pd, L = MeCN; 9a: M = Ni, L = PMe3; 9b: M = Pd, L = PMe3) was prepared from 6a (M = Ni) or [7]BF4 by chloride abstraction with NaBF4 or AgBF4 in the presence of acetonitrile or trimethylphosphine, respectively. In the presence of triphenylphosphine, the palladium(II) complex [(1-κFe,κ(2)N,N')Pd(PPh3)](BF4)2 (10) was isolated. Iron-nickel and iron-palladium bonding in these complexes was studied experimentally by NMR, UV/vis, and Mössbauer spectroscopy and by cyclic voltammetry. Detailed DFT calculations were carried out for the cations [(1-κFe,κ(2)N,N')M(MeCN)](2+) in the 8a/8b couple, with Bader's atoms in molecules theory revealing the presence of noncovalent, closed-shell metal-metal interactions. Potential energy surface scans with successive elongation of the Fe-M bonds allow an estimation of the iron-metal bond dissociation energies (BDE) as BDE(Fe-Ni) = 11.3 kcal mol(-1) and BDE(Fe-Pd) = 24.3 kcal mol(-1).

Copper(I) Complexes of Zwitterionic Imidazolium-2-Amidinates, a Promising Class of Electroneutral, Amidinate-Type Ligands.

The first complexes containing imidazolium-2-amidinates as ligands (betaine-type adducts of imidazolium-based carbenes and carbodiimides, NHC-CDI) are reported. Interaction of the sterically hindered betaines ICyCDI(DiPP) and IMeCDI(DiPP) [both bearing 2,6-diisopropylphenyl (DiPP) substituents on the terminal N atoms] with Cu(I) acetate affords mononuclear, electroneutral complexes 1a and 1b, which contain NHC-CDI and acetate ligands terminally bound to linear Cu(I) centers. In contrast, the less encumbered ligand ICyCDI(p-Tol), with p-tolyl substituents on the nitrogen donor atoms, affords a dicationic trigonal paddlewheel complex, [Cu2(μ-ICyCDI(p-Tol))3](2+)[OAc(-)]2 (2-OAc). The nuclear magnetic resonance (NMR) resonances of this compound are broad and indicate that in solution the acetate anion and the betaine ligands compete for binding the Cu atom. Replacing the external acetate with the less coordinating tetraphenylborate anion provides the corresponding derivative 2-BPh4 that, in contrast with 2-OAc, gives rise to sharp and well-defined NMR spectra. The short Cu-Cu distance in the binuclear dication [Cu2(μ-ICyCDI(p-Tol))3](2+) observed in the X-ray structures of 2-BPh4 and 2-OAc, ca. 2.42 Å, points to a relatively strong "cuprophilic" interaction. Attempts to force the bridging coordination mode of IMeCDI(DiPP) displacing the acetate anion with BPh4(-) led to the isolation of the cationic mononuclear derivative [Cu(IMeCDI(DiPP))2](+)[BPh4](-) (3b) that contains two terminally bound betaine ligands. Compound 3b readily decomposes upon being heated, cleanly affording the bis-carbene complex [Cu(IMe)2](+)[BPh4(-)] (4) and releasing the corresponding carbodiimide (C(═N-DiPP)2).

Antibacterial, in vitro antitumor activity and structural studies of rhodium and iridium complexes featuring the two positional isomers of pyridine carbaldehyde picolinic hydrazone ligand

Half-sandwich organometallic rhodium and iridium complexes [1–6] have been synthesized with ligands L1 (L1=Pyridin-2-ylmethylene picolinichydrazine) and L2 (L2=Pyridin-3-ylmethylene picolinichydrazine). Treatment of [{Cp∗MCl2}2] (M=Rh/Ir) with L1 in methanol has yielded mononuclear cationic complexes such as [{Cp∗M(L1N∩N)Cl}]PF6 where {M=Rh (1) and Ir (2)} and dinuclear complexes such as [{(Cp∗MCl)2(L1N∩N, N∩N)}]PF6 where {M=Rh (3) and Ir (4)} in 1:2 and 1:1 metal dimer to ligand ratios respectively. Reactions of [{Cp∗MCl2}2] with L2 in both 1:2 and 1:1 metal dimer to ligand ratios have yielded two metalla-macrocyclic dinuclear and dicationic complexes such as [{Cp∗M(L2N∩NμN)}2](PF6)2 where {M=Rh (5) and Ir (6)}. Spectroscopic and crystallographic data were used to elucidate the structures of the synthesized complexes. The in vitro antitumor evaluation of the complexes 1 and 2 by fluorescence based apoptosis study revealed their antitumor activity against Dalton’s ascites lymphoma (DL) cells. The antibacterial evaluation of complexes 1, 2, 5 and 6 by agar well-diffusion method revealed their significant activity against the two species considered viz., Proteus vulgaris (MTCC 426) and Vibrio parahaemolyticus (MTCC 451) with zone of inhibition up to 43mm. The docking study with few key enzymes associated with cancer viz., ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase and topoisomerase II revealed their strong interactions with complexes under study. Complexes 1–6 exhibited a HOMO (highest occupied molecular orbital) – LUMO (lowest unoccupied molecular orbital) energy gap from 2.95eV to 3.59eV. TDDFT calculations explain the nature of electronic transitions and found well agreement with the experiments.

Lewis Acid Catalyzed Asymmetric Three-Component Coupling Reaction: Facile Synthesis of α-Fluoromethylated Tertiary Alcohols.

A chiral dicationic palladium complex is found to be an efficient Lewis acid catalyst for the synthesis of α-fluoromethyl-substituted tertiary alcohols using a three-component coupling reaction. The reaction transforms three simple and readily available components (terminal alkyne, arene, and fluoromethylpyruvate) to valuable chiral organofluorine compounds. This strategy is completely atom-economical and results in perfect regioselectivities and high enantioselectivities of the corresponding tertiary allylic alcohols in good to excellent yields.

Catalytic Asymmetric Synthesis of Tertiary Alcohols and Oxetenes Bearing a Difluoromethyl Group.

The catalytic asymmetric ene reaction with difluoropyruvate as an electrophile in the presence of a dicationic palladium complex is shown. This is the reliable and practical catalytic asymmetric synthesis for various α-CF2H tertiary alcohols in high yields and enantioselectivities. The reaction with isobutene can be catalyzed efficiently under solvent-free conditions with low catalyst loading (up to S/C 2000). Furthermore, difluoropyruvate is applicable to the [2 + 2] cycloaddition reaction in high yields and enantioselectivities.

Chiral Iron(II) NPPN Complexes: Synthesis and Application in the Asymmetric Strecker Reaction of Azomethine Imines

The open-chain NPPN ligand (1S,1′S)-1,1′-((ethane-1,2-diylbis(phenylphosphanediyl))bis(2,1-phenylene))bis(N-cyclohexylmethanimine) (1) was prepared by condensation of cyclohexylamine with enantiomerically pure (1S,1′S)-2,2′-(ethane-1,2-diylbis(phenylphosphanediyl))dibenzaldehyde ((S,S)-6). Ligand 1 coordinates to [Fe(OH2)6](BF4)2 or [Fe(MeCN)6](SbF6)2 in acetonitrile to give the dicationic complex [Fe(MeCN)2(1)](X)2 (2) (X = BF4– or SbF6–). The corresponding carbonyl (3), bromocarbonyl (4), and bis(tert-butylisonitrile) (5) derivatives were prepared and fully characterized. Complex 2 reacts with Me3SiCN to give the corresponding trimethylsilyl isocyanide derivative 18 featuring a Fe–CNSiMe3 linkage. The X-ray structures of 2, 3, 5, and 18 show that ligand 1 assumes the Λ-cis-α geometry, which allows comparing the trans influence of these ligands. Complexes 2, 3, 5, and 18 were applied in the asymmetric addition of trimethylsilyl cyanide to azomethine imines (Strecker reaction), whose enantioselectivity re...

Chiral Pd-catalyzed trifluoropyruvate-ene reactions with steroidal side chains for late-stage fluoromethyl-functionalization: remarkably high agonist activities of ene products even in low VDR binding affinity

The highly enantioselective trifluoropyruvate-ene reactions of chiral steroid side chain olefins were achieved by dicationic palladium complexes as chiral Lewis acid catalysts to give steroidal ene-products in high diastereoselectivity. The ene products exhibited remarkably high agonist activities for human osteocalcin even in low vitamin D receptor binding affinity for human vitamin D hormone receptor.

Tuning the excited state of water-soluble Ir(III)-based DNA intercalators that are isostructural with [Ru(II)(NN)2(dppz)] light-switch complexes.

The synthesis of two new Ir(III) complexes which are effectively isostructural with well-established [Ru(NN)2(dppz)](2+) systems is reported (dppz=dipyridophenazine; NN=2,2'-bipyridyl, or 1,10-phenanthroline). One of these Ir(III) complexes is tricationic and has a conventional N6 coordination sphere. The second dicationic complex has a N5C coordination sphere, incorporating a cyclometalated analogue of the dppz ligand. Both complexes show good water solubility. Experimental and computational studies show that the photoexcited states of the two complexes are very different from each other and also differ from their Ru(II) analogues. Both of the complexes bind to duplex DNA with affinities that are two orders of magnitude higher than previously reported Ir(dppz)-based systems and are comparable with Ru(II)(dppz) analogues.

Tuning the Excited State of Water‐Soluble IrIII‐Based DNA Intercalators that are Isostructural with [RuII(NN)2(dppz)] Light‐Switch Complexes

AbstractThe synthesis of two new IrIII complexes which are effectively isostructural with well‐established [Ru(NN)2(dppz)]2+ systems is reported (dppz=dipyridophenazine; NN=2,2′‐bipyridyl, or 1,10‐phenanthroline). One of these IrIII complexes is tricationic and has a conventional N6 coordination sphere. The second dicationic complex has a N5C coordination sphere, incorporating a cyclometalated analogue of the dppz ligand. Both complexes show good water solubility. Experimental and computational studies show that the photoexcited states of the two complexes are very different from each other and also differ from their RuII analogues. Both of the complexes bind to duplex DNA with affinities that are two orders of magnitude higher than previously reported Ir(dppz)‐based systems and are comparable with RuII(dppz) analogues.

1,2-Bis(di-tert-butylphosphino)imidazole (dtbpi): A Versatile Imidazole-Based, Rigid, Bulky Bisphosphine Ligand for Transition Metals

A bulky bisphosphine, 1,2-bis(di-tert-butylphosphino)imidazole (dtbpi), featuring a rigid imidazole backbone, was synthesized in a simple two-step procedure. The ligand’s coordination chemistry and electron-donating abilities were investigated in the complexes (dtbpi)Ni(FDN) (3) and [(dtbpi)Rh(CO)2]BF4 (4). Protonation of 4 at the ligand backbone’s nitrogen with strong Bronsted acids such as HBF4 and HBArF gave the dicationic dicarbonyl complexes [(H-dtbpi+)Rh(CO)2](BF4)(BArF) (5a) and [(H-dtbpi+)Rh(CO)2](BF4)2 (5b), which served as model complexes of the ligand’s imidazolium-phosphine form and permitted characterization of its donating character. In order to evaluate solely the different electronic characters of the two isosteric P donors, the complexes (dtbpi)PdCl(Me) (6) and [(dtbpi)RhCl]2 (7) were synthesized. An unexpected rearrangement of one of the formed stereoisomers of 6, with cleavage of an N–P bond, was found. A novel phosphine-phosphonium ylide ligand (8) has been made accessible via chemosel...

Crystal structure of bis-(2,2'-bi-pyridine)[N'-(quino-lin-2-ylmethylidene)pyridine-2-carbohydrazide]ruthenium(II) bis(tetra-fluorido-borate) di-chloro-methane tris-olvate.

The title compound, [Ru(C10H8N2)2(C16H12N4O)](BF4)2·3CH2Cl2, crystallizes with one complex dication, two BF4 (-) counter-anions and three di-chloro-methane solvent mol-ecules in the asymmetric unit. The central Ru(II) atom adopts a distorted octa-hedral coordination sphere with two 2,2'-bi-pyridine (bpy) and one quinoline-2-carbaldehyde (pyridine-2-carbon-yl)hydrazone (HL) ligand. The hydrazone ligand has a Z form and coordinates to the Ru(II) atom via the amide-O and imine-N atoms, affording a planar five-membered chelate ring, while its pyridine-N and quinoline-N donor atoms in the substituents are non-coordinating. The hydrazone N-H group forms an intra-molecular hydrogen bond with the quinoline-N atom. In the crystal, the quinoline moiety of HL shows the shortest π-π stacking inter-action with the pyridine substituent of HL in a neighbouring complex, the centroid-to-centroid distance being 3.793 (3) Å.

Energy decomposition analysis of cation–π, metal ion–lone pair, hydrogen bonded, charge‐assisted hydrogen bonded, and π–π interactions

This study probes the nature of noncovalent interactions, such as cation-π, metal ion-lone pair (M-LP), hydrogen bonding (HB), charge-assisted hydrogen bonding (CAHB), and π-π interactions, using energy decomposition schemes-density functional theory (DFT)-symmetry-adapted perturbation theory and reduced variational space. Among cation-π complexes, the polarization and electrostatic components are the major contributors to the interaction energy (IE) for metal ion-π complexes, while for onium ion-π complexes (NH4+, PH4+, OH3+, and SH3+) the dispersion component is prominent. For M-LP complexes, the electrostatic component contributes more to the IE except the dicationic metal ion complexes with H2 S and PH3 where the polarization component dominates. Although electrostatic component dominates for the HB and CAHB complexes, dispersion is predominant in π-π complexes.

Stepwise isolation of low-valent, low-coordinate Sn and Pb mono- and dications in the coordination sphere of platinum.

Synthetic access to low-coordinate Pb mono- and dications is in general impeded due to their poor solubility and highly electrophilic nature. However, the electrophilicity of these cations can be tamed by attaching them to electron-rich transition metals. Following this principle we have isolated low-valent Pb mono- ([(Cy3P)2Pt-PbCl]2[AlCl4]2, 8a) and dications ([(Cy3P)2Pt(Pb)][AlCl4]2, 11) in the coordination sphere of platinum. The same approach then has been implemented for the isolation of analogous low-valent Sn mono- (7a) and dications (10). An energy decomposition analysis (EDA-NOCV) was performed to investigate the nature of Pt-Pb and Pb-Cl bonding in [(Cy3P)2Pt(PbCl2)] (2), 8a and 11. The results show that the Pt-Pb bonds in 8a and 11 are electron-sharing in nature, whereas that of the precursor 2 is a dative bond. The breakdown of attractive interactions in 2, 8a and 11 reveals that the ionic interactions in the analyzed Pt-Pb and Pb-Cl bonds are always stronger than the covalent interactions, except for the Pb-Cl bond in 8a. The calculated D3 dispersion energies show that dispersion interactions play a key role in the thermodynamic stability of 2, 8a and 11.

Supramolecular Assemblies of Polyphosphorus Ligands Based on Weak Tl–P and In–P Interactions

Abstract A systematic investigation of the coordination behavior of Pn complexes towards the main group Lewis acids Tl+ and In+ is presented. While the reaction of the tetrahedral P2 complex [{CpMo(CO)2}2(μ,η2:η2-P2)] (A1) with Tl[TEF] ([TEF] = [Al{OC(CF3)3}4]-) leads to the formation of the dicationic complex [Tl2(A1)6]2+ (1) with a central six-membered Tl2P4 ring, the analogous reaction with In[TEF] leads instead to a tetranuclear [In4(A1)8]4+ complex (3) exhibiting a weak InI-InI interaction in the solid state. When the Cp*-analogous P2 complex [{Cp*Mo(CO)2}2(μ,η2:η2-P2)] (A2) is reacted with Tl[TEF] the dinuclear complex [Tl2(A2)4]2+ (2) is formed, containing only four P2 ligands but also featuring a six-membered Tl2P4 ring motif. From the reactions of the cyclo-P3 complexes [CpM'(CO)2(η3-P3)] (M' = Cr (B1), Mo (B2)) with In[TEF] and Tl[TEF], a series of four isostructural one-dimensional coordination polymers (4a-d) are obtained which exhibit a novel bridging coordination mode of the cyclo-P3 ligands in the solid state. Additionally, the mixed PmSn ligand complex [(Cp*Mo)2(μ,η3:η3-P3)(μ,η2:η2-PS)] (C) was reacted with Tl[TEF] to afford a novel one-dimensional coordination polymer (5), which shows an unprecedented bridging s-1,3-coordination mode of ligand C towards Tl+. The compounds were analyzed by single-crystal X-ray structure determination, elemental analysis, and mass spectrometry, as well as by multinuclear NMR and IR spectroscopy. All products are readily soluble in CH2Cl2, despite in many cases being polymeric in the solid state. Multinuclear NMR spectroscopy suggests a highly dynamic coordination behavior in solution, including fast equilibria between different monomeric species, which is also supported by DFT calculations. The one-dimensional polymers 4c and 4d reveal a triplet in the 31P{1H} MAS NMR spectrum at room temperature, which could be explained by fast rotation of the P3 rings in the solid state.