Dppf Ligand Research Articles

Two Novel Heterothiometallic Clusters Modified by 1,1′-Bis(diphenylphosphino) ferrocene (dppf) in Quasi-Closed Bridging Mode: Syntheses, Structures and Properties

Two heterothiometallic clusters modified by 1,1′-bis(diphenylphosphino) ferrocene (dppf) ligand [(Ag4Mo2S8)(dppf)2] (1) and [(Ag4Mo2S6O2)(dppf)2] (2) have been synthesized and characterized. X-ray single-crystal studies reveal that the structures of the two clusters are both hexagonal prism-shaped cages, which are modified by dppf ligands in rarely quasi-closed mode. While, the terminal atoms of the hexagonal prism cages are different, S atoms for 1 and O atoms for 2. The discrete clusters of 1 and 2 are connected to form 2-D supramolecular layers through hydrogen bonds C–H···S, C–H···π for 1 and C–H···O for 2. The different supramolecular interactions may be caused by the different terminal atoms, which also result in different fluorescence emissions and oxidation potentials.

Synthesis, characterization and properties of a μ–η2:η2-carbonato-bridged bis(phosphinoferrocenyl) copper(I) complex from CO2 fixation

Abstract A μ–η2:η2-carbonato-bridged copper(I) dinuclear complex 3, of formula [Cu2(μ-CO3)(dppf)2]·[PhCONPh]·[Na(H2O)4]·CH2Cl2·2H2O (dppf = 1,1′-bis(diphenylphosphino)ferrocene) was synthesized and characterized by IR, 1HNMR and X-ray diffraction method. When chloride-bridged copper(I) complex reacted with N-phenyl benzamide with sodium methoxide as base under air or carbon dioxide atmosphere, the carbonate-bridged copper(I) complex from CO2 fixation was obtained. Cyclic voltammetry experiments of dppf ligand and complex 3 illustrate that the oxidation occurs only at the ferrocene(II) center, but complex 3 oxidizes at more negative potential than the uncoordinated dppf ligand. The thermal stability of complex 3 was also reported and discussed.

A cyclometalated diplatinum complex containing 1,1′-bis(diphenylphosphino)ferrocene as spacer ligand: Antitumor study

Cyclometalated platinum(II) complex [Pt(C^N)Cl(dmso)], 1, in which C^N = N(1),C(2′)-chelated deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, was reacted with 1 equiv of 1,1′-bis(diphenylphosphino)ferrocene, dppf, to give the cyclometalated diplatinum(II) complex [Pt 2(C^N) 2Cl 2(μ-dppf)], 2, along with 0.5 equiv of unreacted dppf. However, the related reaction with 0.5 equiv of dppf produced complex 2 in pure form. Complex 2 in solution was fully characterized by using multinuclear NMR spectroscopy ( 1H, 13C, 31P, and 195Pt) and a number of 2D NMR experiments. The structure of complex 2 in solid state was determined by X-ray crystallography showing that the bridging dppf ligand is arranged close to “antiperiplanar staggered” conformation. Cytotoxicity of the complex 2 was studied in three human cancer cell lines derived from ovarian carcinoma(CH1), lung carcinoma(A549), and colon carcinoma (SW480) by means of the MTT assay (MTT = 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide).

ChemInform Abstract: Nickel‐Catalyzed, Base‐Mediated Amination/Hydroamination Reaction Sequence for a Modular Synthesis of Indoles.

Abstract A catalytic system consisting of [Ni(cod)2] and ligand dppf enabled an efficient synthesis of differently substituted indoles through a modular reaction sequence, which consists of intermolecular aminations and intramolecular hydroaminations with ortho-alkynylhaloarenes.

Assembly of Cyclometalated Platinum(II) Complexes via 1,1′-Bis(diphenylphosphino)ferrocene Ligand: Kinetics and Mechanisms

The kinetics and mechanism of the reaction of the cyclometalated complexes [PtAr(C−N)(SMe2)], 1, in which Ar is Ph, p-MeC6H4, or p-MeOC6H4, and C−N is either ppy (deprotonated 2-phenylpyridine) or bhq (deprotonated benzo[h]quinoline), with 1,1′-bis(diphenylphosphino)ferrocene, dppf, were studied using UV−visible and 31P NMR spectroscopies. When 0.5 equiv of dppf was added, the binuclear Pt(II) complex [Pt2Ar2(C−N)2(μ-dppf)], 2, was formed in a good yield. The complexes were fully characterized using multinuclear (1H, 31P, and 195Pt) NMR spectroscopy, and the structure of complex [Pt2(p-MeOC6H4)2(bhq)2(μ-dppf)], 2c′·CH2Cl2, was further identified by X-ray crystallography. On the basis of low-temperature 31P NMR studies involving the starting complex [Pt(p-MeC6H4)(ppy)(SMe2)], 1b, we suggest that dppf displaces the labile ligand SMe2 to give an uncommon complex, [Pt(p-MeC6H4)(ppy)(dppf-κ1P)], A, in which dppf-κ1P is a monodentate dppf ligand, which rapidly forms an equilibrium with the chelating dppf isomer...

2‐Pyridyl Tosylate Derivatives—Building Blocks for Structural Diversity via Transition Metal Catalysis

Abstract2‐Pyridyl tosylate derivatives have proved to be highly reactive electrophiles in palladium‐catalyzed Mizoroki–Heck reactions with electron‐rich olefins. These results suggest that the tosylate anion is able to dissociate from the catalyst’s metal center subsequent to the oxidative addition step, providing a tricoordinated cationic complex mandatory for a high degree of α‐regioselectivity. Further development of the 2‐pyridyl electrophiles as counterparts in palladium catalysis led to the development of several efficient protocols including amidation, amination, aminocarbonylations, Suzuki–Miyaura, and a fast iron‐catalyzed Kumada–Tamao–Curriu cross coupling. Interestingly, in all but one of the palladium‐catalyzed reactions, the optimized conditions employed the ligand DPPF (1,1′‐bis(diphenylphosphino)ferrocene) or the diisopropyl analog DiPrPF (1,1′‐bis(diisopropylphosphino)ferrocene) in dioxane. As with the Mizoroki–Heck couplings, the existence of the cationic tricoordinated complex in dioxane was speculated to play an important role, facilitating steps such as transmetallation and CO incorporation. The mild conditions developed in all of the catalytic reactions described in this overview can be applied to the pyridine/pyrimidine core, providing highly functionalized heteroaromatic compounds in a few steps.

Nickel-catalyzed, base-mediated amination/hydroamination reaction sequence for a modular synthesis of indoles

A catalytic system consisting of [Ni(cod) 2] and ligand dppf enabled an efficient synthesis of differently substituted indoles through a modular reaction sequence, which consists of intermolecular aminations and intramolecular hydroaminations with ortho-alkynylhaloarenes.

ChemInform Abstract: A Highly Catalytic Robust Palladium-Catalyzed Cyanation of Aryl Bromides.

Abstract A dependable high yielding palladium catalyzed aryl bromide cyanation procedure has been developed. The optimized cyanation features extremely low levels of palladium and DPPF ligand.

A Tetramethylplatinum(IV) Complex with 1,1′‐Bis(diphenylphosphanyl)ferrocene Ligands: Reaction with Trifluoroacetic Acid

AbstractA new tetramethylplatinum(IV) complex [PtMe4(dppf)] [2; dppf = 1,1′‐bis(diphenylphosphanyl)ferrocene], as the first platinum(IV) complex to contain a chelating dppf ligand, was prepared by the reaction of the known dimeric tetramethylplatinum(IV) complex cis,cis‐[Me4Pt(μ‐SMe2)2PtMe4] (1) with the biphosphane ligand dppf (2 equiv.) at room temperature by replacement of the SMe2 ligands with the P ligating atoms of dppf. The single‐crystal X‐ray structure of complex 2 revealed that the dppf chelating ligand is arranged close to the “synperiplanar–eclipsed” conformation, with a Cp(centroid)···Fe···Cp(centroid) twist angle of 17.6° and a dppf bite angle, P1–Pt1–P2, of 95.77(3)°. This is in contrast to the usually preferred “synclinal–staggered” conformation, in which the Cp(centroid)···Fe···Cp(centroid) twist angle is close to 36° as found in PtII complexes with chelating dppf ligands, like for example [PtMe2(dppf)] exhibiting a dppf bite angle close to 100°. When complex 2 was treated with the strong acid CF3COOH (1 equiv.) first evolution of methane was observed, followed by a C–C coupling reaction to give ethane and the methylplatinum(II) complex [PtMe(OCOCF3)(dppf)] (3). The reaction of complex 2 with the nucleophile HgCl2 (1 equiv.) similarly gave MeHgCl, ethane, and the methylplatinum(II) complex [PtMeCl(dppf)] (11). The structure of complex 3 was also determined by X‐ray crystallography. The geometry around the platinum center is best described as distorted square‐planar and the dppf is arranged in the usually preferred “synclinal–staggered” conformation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Methoxycarbonylation of Styrene Catalyzed by Palladium Complexes with Ferrocene Derivatives Containing Nitrogen and Phosphine Ligands

The catalytic behaviour of different complexes of Palladium(II) containing mono or bidentate phosphorus or nitrogen ligands in the methoxycarbonylation reaction is examined. The pre-catalysts containing either a diphosphine ligand possessing a ferrocenyl backbone or a naphthyridine ligand attached to the same ferrocenyl backbone showed different catalytic activity for the reaction. Complexes containing the 1,1-bis(diphenylphosphino)ferrocene (dppf) ligand showed a better catalytic activity than the complex having the naphthyridine ligand in its structure. Various effects of the addition of triphenylphosphine to these pre-catalysts were observed. More than 99% conversion was achieved in the methoxycarbonylation of styrene using Pd(II) catalysts with ferrocenyl chelate derivatives, mostly with the Pd(dppf)Cl2, [Pd(dppf)(MeCN)2](BF4)2 and [Pd(dppf)PPh3](BF4)2 complexes without the presence of triphenylphosphine as is usual in this reaction. The reactions were carried out under mild pressure and temperature conditions. Complexes of the type Pd(dppf)Cl2, [Pd(dppf)(MeCN)2](BF4)2 and [Pd(dppf)PPh3](BF4)2 were used as catalysts for the Methoxycarbonylation of styrene using mild pressure and temperature condition. The catalysts system showed more than 99% conversion in reactions without the presence of triphenylphosphine.

Novel Types of Tetra-, Hexa-, Octa-, and Dodecanuclear Silver Clusters Containing (2,7-Di-tert-butylfluoren-9-ylidene)methanedithiolate†

The reaction of AgClO(4) with piperidinium 2,7-di-tert-butyl-9H-fluorene-9-carbodithioate (pipH)[S(2)C(t-Bu-Hfy)] (1) (t-Bu-Hfy = 2,7-di-tert-butylfluoren-9-yl) afforded [Ag(n){S(2)C(t-Bu-Hfy)}(n)] (2), which reacted with phosphines to give [Ag{S(2)C(t-Bu-Hfy)}L(2)] [L = PPh(3) (3a); L(2) = bis(diphenylphosphino)ethane (dppe, 3b), 1,1'-bis(diphenylphosphino)ferrocene (dppf, 3c). By reacting complex 2 with AgClO(4) and piperidine in a 1:1:1 molar ratio, the dodecanuclear cluster [Ag(12){S(2)C(t-Bu-fy)}(6)] (4) (t-Bu-fy = 2,7-di-tert-butylfluoren-9-ylidene) was obtained. Compound 4 can also be directly prepared from the reaction of 1 with AgClO(4) and piperidine in a 1:2:1 molar ratio. The reactions of 1 with AgClO(4), phosphines, and piperidine afforded the compounds [Ag(6){S(2)C(t-Bu-fy)}(3)L(5)] [1:2:2:1 molar ratio; L = PPh(3) (5a), P(p-To)(3) (5b)], [Ag(4){S(2)C(t-Bu-fy)}(2)(dppf)(2)] (6) (1:2:1:1 molar ratio), [Ag(n){S(2)C(t-Bu-fy)}(n/2){P(i-Pr)(3)}(n)] (7) (1:2:2:1 molar ratio), or [Ag(8){S(2)C(t-Bu-fy)}(4){P(i-Pr)(3)}(4)] (8) (1:2:1:1 molar ratio). Complexes 5a,b, 6, 7, and 8 can be also obtained by reacting 4 with the corresponding phosphine in the appropriate molar ratio. The crystal structures of 4, 5b, and 8 have been determined by X-ray diffraction studies. The nuclearity of complex 6 was established from its (31)P{(1)H} NMR data, which reveal a very fast dynamic process leading to an average coupling of each of the P atoms of the dppf ligands with four Ag atoms.

1,1′-Bis(diphenylphosphino)ferrocene]carbonyl[dihydrobis(pyrazol-1-yl)borato]hydridoruthenium(II) acetone solvate

In the title compound, [FeRu(C17H14P)2(C6H8BN4)H(CO)]·C3H6O, the RuII ion is coordinated in a distorted octa­hedral environment involving a hydride ligand, a carbonyl ligand and two bidentate ligands. Of the two bidentate ligands, the bulky 1,1′-bis­(diphenyl­phosphino)ferrocene (dppf) ligand chelates with a larger bite angle of 101.90 (2)°, whereas the bite angle of the [H2Bpz2]− ligand (pz = pyrazol­yl) is 85.67 (7)°. The latter ligand creates an RuN4B six-membered ring with a boat conformation, which puckers towards the site of the small hydride ligand. The hydride ligand is cis with respect to the carbonyl ligand and trans to one of the P atoms of the dppf ligand. In the crystal structure, there are weak inter­molecular C—H⋯O hydrogen bonds between complex mol­ecules and acetone solvent mol­ecules.

Chelate and Bridge Diphosphine Isomerization: Triosmium and Triruthenium Clusters Containing 1,1‘-Bis(diphenylphosphino)ferrocene (dppf)

The coordination mode of dppf {dppf = 1,1'-bis(diphenylphosphino)ferrocene} at triosmium and triruthenium carbonyl clusters has been studied. Heating [Os3(CO)12] with dppf in the presence of Me3NO in benzene at 60 C furnishes three triosmium compounds, [Os3(CO)11(1-dppf)] (1), [Os3(CO)10(2-dppf)] (2), and [Os3(CO)10(-dppf)] (3) in 10, 20, and 30% yields, respectively. Reaction of the labile cluster [Os3(CO)10(MeCN)2] with dppf at room temperature also gives 1, 2, and 3 (5, 10, and 35% yields). Treatment of 1, which contains a pendant diphosphine, with Me3NO at room temperature affords 2 via a ring closure reaction, whereas heating 2, in which the dppf ligand is chelating, at 110 C affords the thermodynamically stable bridging isomer 3, in which phosphorus atoms are bound at equatorial positions. Reaction of the unsaturated cluster [Os3(CO)10(-H)2] (4) with dppf in refluxing THF affords the bridging complex [Os3(CO)8(-dppf)(-H)2] (6) in high yield as the sole product. Hydrogenation of 3 with H2 at 110 C at 1 atm also yields 6. Reactions of both the saturated [Os3(CO)10(-dppm)] (7) and electron-deficient [Os3(CO)8{3-Ph2PCH2P(Ph)C6H4}(-H)] (8) with dppf at 110 C and at room temperature respectively yield [Os3(CO)9(-dppm)(1-dppf)] (9) and [Os3(CO)8(-dppm)(2-dppf)] (10). Compound 9 converts to 10 at 110 C via CO loss and phosphorus coordination. Reaction of [Ru3(CO)12] with dppf in the presence of Me3NO affords the dihydroxy-bridged complex, [Ru3(CO)8(-dppf)(-OH)2] (13), together with the previously reported compounds [Ru3(CO)10(-dppf)] (11) and [Ru3(CO)8(-dppf)2] (12). (Less)

C—H...F, C—F...π and C—F...F—C interactions in a palladium(II) benzenethiolate complex

The title compound, [1,1′-bis­(diphenyl­phosphino)ferrocene-κ2P,P′]bis­(2,3,4,5,6-penta­fluoro­benzene­thiol­ato-κS)palladium(II­), [FePd(C6F5S)2(C17H14P)2], crystallizes with two independent mol­ecules in the asymmetric unit. The complex has the palladium metal center in a slightly distorted square-planar environment with the 1,10-bis(diphenylphosphino)ferrocene (dppf) ligand coordinated in a bidentate fashion and, completing the coordination environment, the two –SC6F5 thiol­ates in a cis configuration. The mol­ecules are linked by weak C—F⋯π, C—F⋯F—C and C—H⋯F stacking inter­actions.

Synthesis, characterization, X-ray structure and preliminary in vitro antitumor activity of the nitrosyl complex fac-[RuCl 3(NO)(dppf)], dppf = 1,1′-bis(diphenylphosphine)ferrocene

The reaction of RuCl 3NO · 2H 2O with stoichiometric amount of dppf, 1,1′-bis(diphenylphosphino)ferrocene, afforded the new neutral nitrosyl complex fac-[RuCl 3(NO)(dppf)] which was characterized by spectroscopical, electrochemical and X-ray crystallography techniques as well as elemental analysis. The ν NO band in the IR spectrum is at 1860 cm −1 (CH 2Cl 2 solution) and in the cyclic voltammogram an irreversible wave was observed at −1.35 V, both are characteristics of a nitrosonium (NO +) character for the coordinated NO. Additionally, preliminary in vitro antitumor activity against the MDA-MB-231 breast tumor cell line was carried out for the new complex. The initial results indicated an important activity for fac-[RuCl 3(NO)(dppf)] (IC 50 = 10 ± 3 μM ). The complex has a higher cytotoxicity than the precursor complex RuCl 3NO · 2H 2O, the free dppf ligand as well as the reference metallodrug cisplatin.

1,1′-Bis(diphenylphosphino)ferrocene-κ2P,P′]bis(2,3,4,5,6-pentafluorobenzenethiolato)platinum(II)

The title compound, [PtFe(C6F6S)2(C17H14P)2], was obtained from the metathesis reaction of [Pt(dppf)Cl2] and [Pb(SC6F5)2] in CH2Cl2 [dppf is 1,1′-bis­(diphenyl­phosphino)ferrocene]. Two independent mol­ecules are found in the asymmetric unit. The PtII centers have a distorted square-planar environment with the P atoms of the dppf ligand coordinating to the metal centers in a bidentate fashion. The coordination of each Pt atom is completed by two –SC6F5 ligands in an anti conformation. The crystal packing exhibits inter­esting C—H⋯π stacking.

Transition Metal Cluster Chalcogenide Ligated by Multiple Redox Active Organometallic Centers: [Ni6(μ3-Se)2(μ4-Se)3(dppf)3]Br2and Its Electrocatalysis

One of the current trends in molecular material science concerns the preparation and the study of materials combining several physical properties in a synergistic way. Organic/inorganic hybrids, in which organicor organometallicmoieties having a special physicochemical property are incorporated into a transition-metal cluster, may exhibit certain coupling phenomena between the d-electrons of inorganic transition-metal networks and the mobile πelectrons of the organic conjugated networks. Such coupling effects should provide us with rich opportunities to design and study molecular systems exhibiting special material characteristics, such as superconductivity, magnetism, electrical conductivity, optical properties, electrochromism, and catalytic activity. On the other hand, there is a considerable interest in the chemistry of multi-metallocenyl assemblies, particularly multi-ferrocenyl assemblies. Such compounds can be viewed as excellent candidates for multielectron reservoir systems, electron-transfer mediators, redox active materials for the modification of electrodes, ion sensors and/or materials for electronic devices. In this respect, if one hybridizes the multi-ferrocenyl moieties onto a transitionmetal cluster, the electrical and magnetic properties of both components will be probably combined in a synergistic way, leading to new properties applicable to the material science. However, the chemistry of the transition-metal clusters into which organic and/or organometallic moieties are incorporated, would be difficult to achieve a true advance mainly due to the poorly settled synthetic methods for such molecular assemblies. It is nearly impossible to prepare inorganic clusters having special functionalities in a bondby-bond fashion. One of the most plausible strategies for constructing such systems with their unique architecture will involve one-pot spontaneous self-assembly of components with required functionalities already in place. Such a strategy has been popularly utilized in organic chemistry and supramolecular inorganic chemistry. As an example of the related synthetic efforts, [Ni6(μ3Se)2(μ4-Se)3(dppf)3]Br2·3/2CHCl3 (1) was obtained by the self-assembly reaction of Ni(dppf)Br2 with Li2Se in the presence of Li[PhNC(O)Me] in THF. The first example of the [Ni6(μ3-Se)2(μ4-Se)3] cluster was prepared by the reaction of (NBu3)[NiCl3(PPh3)] with Se(SiMe3)2 and the similar reaction of [NiCl2(PPh3)2] with Se(SiMe3)2 produced [Ni12Se11Cl][NiCl3(PPh3)]2. 13 The structure of the cluster 1 is shown in Figure 1. The production of 1 from the present reaction is ascribed to the directional-bonding influence of the dppf ligand. During the course of the reaction, the fixed distance between the two phosphine atom of the ferrocene bridge may force the selective construction of the present prismatic structure. The existence of Li[PhNC(O)Me] was essential for an effective reaction. Without this anion it takes more than 14 days for the production of 1 to be detected by TLC. It is known that the addition of the [PhNC(O)Me]− ion suppresses the formation of an intractable polymer by complexing to the metal center and the more reactive anion temporarily displaces the less reactive bromide of the nickel before the attack of selenide, leading to the easy production of the cluster. 1 is soluble in THF and CHCl3, moderately soluble in hexane and sparingly soluble in polar solvents. It appears to be stable on exposure to moisture and air. X-ray

Palladium‐Catalyzed Coupling of Pyrazole Triflates with Arylboronic Acids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Palladium‐Catalyzed C–S Bond Formation: Rate and Mechanism of the Coupling of Aryl or Vinyl Halides with a Thiol Derived from a Cysteine

AbstractThe mechanism of the palladium‐catalyzed coupling reaction of aryl or vinyl halides with a thiol derived from a protected chiral cysteine 1 (RSH), leading to C–S bond formation, has been investigated in the context of catalytic reactions. All palladium complexes involved in the catalytic cycle have been characterized, successively, as PhPdI(dppf), PhPdI(SHR)(η1‐dppf) and PhPd(SR)(dppf). The oxidative addition reaction which generates PhPdI(dppf) is followed by the metallation of 1 whose mechanism has been investigated. In the case of the weakly acidic cysteine 1 (RSH) studied here, the anions RS– are not generated in detectable concentrations in the reaction with the NEt3 base. Even if the classical transmetallation reaction of PhPdI(dppf) by RS–, present at a very low concentration, cannot be entirely excluded, we propose that an alternative mechanism, complexation of the thiol, leads to the previously unreported PhPdI(SHR)(η1‐dppf) (observed by 31P NMR spectroscopy) after decomplexation of one of the phosphorus atoms of the dppf ligand, followed by the easier deprotonation of the coordinated RSH by the base, which generates PhPd(SR)(dppf). A classical reductive elimination reaction delivers the coupling product PhSR. The kinetics of all the steps have been investigated independently, one after the other, starting from Pd2(dba)3 and dppf, using the initial concentrations of the reagents used in the catalytic reaction. Under the experimental conditions used in the catalytic reaction involving phenyl iodide and NEt3 as the base, the reductive elimination reaction is the slowest step which mainly limits the rate of the catalytic cycle up to approximately 80 % conversion. The metallation reaction of RSH is very slow when propylene oxide was used as the probase. The reductive elimination is the slowest step in the cross‐coupling of a vinyl iodide. Diastereoisomers of the vinyl‐PdX(dppf) (X = I, SR) complexes were observed as a result of the atropisomerism induced by the bulkiness of the investigated vinyl group and the chiral center present on the vinyl or on the SR group. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Palladium-Catalyzed Coupling of Pyrazole Triflates with Arylboronic Acids

[reaction: see text] A general protocol for the palladium-mediated Suzuki coupling reaction of pyrazole triflates and aryl boronic acids has been developed. The use of additional dppf ligand was determined to increase product yields allowing for the use of a broad range of reaction substrates.