Synthesis and characterization of water-soluble palladium(II)-functionalized diphosphine complexes

Water-soluble functionalized bis(phosphine) ligands L (a–h) of the general formula CH₂(CH₂PR₂)₂, where for a: R = (CH₂)₆OH; b–g: R = (CH₂)_nP(O)(OEt)₂, n = 2–6 and n = 8; h: R = (CH₂)₃NH₂ ( Scheme 1), have been prepared photochemically by hydrophosphination of the corresponding 1-alkenes with H₂P(CH₂)₃PH₂. Water-soluble palladium complexes cis-[Pd(L)(OAc)₂] (1–8) were obtained by the reaction of Pd(OAc)₂ with the ligands a–h in a 1:1 mixture of dichloromethane:acetonitrile. The water-soluble phosphine ligands and their palladium complexes were characterized by IR, ¹H and ³¹P NMR. A crystallographic study of complex 1 shows that the Pd(II) ion has a square planar coordination sphere in which the acetate ligands and the diphosphine ligand deviate by less than 0.12 Å from ideal planar.     

Iodoetherification of unactivated alkenes catalyzed by diphosphine palladium(II) complexes

A palladium-catalyzed intramolecular iodoetherification of alkenes is reported. The reaction is efficient and highly diastereoselective for disubstituted alkenes. The tether length between the alcohol and alkene can be varied to produce tetrahydrofuran and tetrahydropyran rings. Diphosphine palladium(II) salts are highly active catalysts enabling future studies on the development of an enantioselective process.     

Manganese(II) and palladium(II) complexes containing a new macrocyclic Schiff base ligand: antibacterial properties

Complexes of tetradentate macrocyclic Schiff base ligand, L, with Mn^II and Pd^II ions have been synthesized by the template condensation of 1,10-phenanthroline-2, 9-dicarboxaldehyde, 2,3-diamino-1,4-naphthoquinone and 1,2-dibromoethane in EtOH. The complexes were characterized by physicochemical and spectroscopic methods and an octahedral geometry is suggested for their structure. They have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of penicillin.     

A simple approach to azirines containing an aldehyde functionality and their stabilization as palladium(II) complexes

A simple and useful method for the synthesis of azirines containing an aldehyde functionality, from open chain bromo/chloro-aldehydes at room temperature and their stabilization as palladium(II) complexes are reported.     

Bicyclic N-heterocyclic carbene (NHC) ligand precursors and their palladium complexes

Eight bicyclic amidinium precursors (3), prepared from R,S-tmcp (R,S-tmcp: (1R,3S)-diamino-1,2,2-trimethylcyclopentane) were described. Only five of the precursors (3a–e) could be converted to palladium complexes, (PdX₂(6,7-NHC)PEPPSI) (4) by treatment with PdCl₂, K₂CO₃, and pyridine (additional KBr was used for (PdBr₂(6,7-NHC)PEPPSI)). The salts and complexes were fully characterized by spectroscopic methods and X-ray crystallography.     

Synthesis,characterization and crystal structure of new silver(I) and palladium(II) complexes containing 1,2,4-triazole moieties

The reaction of 4-amino-5-ethyl-2H-1,2,4-triazole-3(4H)-thione (AETT, L1) with 2-thiophen carbaldehyde in methanol leads to the corresponding Schiff-base HL1a. The reaction of L1 with AgNO₃ in ethanol gives the ionic complex [{[Ag(L1)]NO₃}₂]_n (1). The ionic complex [(PPh₃)₂Ag(HL1a)₂]NO₃ · CH₃CN (2) can be obtained by the reaction of HL1a with [(PPh₃)₂Ag]NO₃ in methanol and acetonitrile solution, while its reaction with [(PPh₃)₂PdCl₂] in the presence of sodium acetate in methanol leads to the neutral complex [(PPh₃)₂Pd(L1a)₂] · 4MeOH (3). All the compounds were characterized by infrared spectroscopy, elemental analyses as well as by X-ray diffraction studies.     

Magnetic properties of a new N-TEMPO-tert-butyl substituted salicylaldimines and their biradical palladium(II) complexes

A new TEMPO bearing tert-butylated salicylaldimines 1 and 2, as well as early reported 3, and their bis(N-TEMPO-tert-butylated salicylaldiminato)palladium(II) biradical complexes 4–6 have been synthesized and characterized by elemental analyses, IR, UV/vis, ESR and an SQUID magnetometer. The solid state g-factors (2.0116–2.0168) for 4–6 suggest the existence of the significant metal-orbital contribution to the SOMO of nitroxyl radicals. The χ_mT vs. T plots for 1 and 2 indicate that the χ_mT decreases as T is lowered from 300 to 20 K, suggesting the existence of weak antiferromagnetic interactions in these radicals. Variable-temperature dependence (10–300 K) magnetic susceptibility data for biradical complexes 4–6 revealed the existence of ferromagnetic and antiferromagnetic behavior around at 10–220 K range for 4. The 1/χ_m data for 1–6 follow the Curie–Weiss law with negative θ throughout the above temperature range.     

Syndiospecific polymerization of styrene with arene titanium(II) complexes as catalyst precursors

The divalent titanium compounds [(η⁶-C₆H₅Me)Ti(Cl₂AlCl₂)₂] ( 1 ) and [(η⁶-C₆Me₆)Ti(Cl₂AlCl₂)₂] ( 2 ) are syndiospecific catalysts in the polymerization of styrene when activated with methylaluminoxane. The polystyrene is of exceptionally high molecular weight.     

Strongly luminescent palladium(0) and platinum(0) diphosphine complexes

The synthesis, structure, and photoluminescence of palladium(0) and platinum(0) complexes containing biarydiphosphines, biphep (biphep = 2,2'-bis(diphenylphosphino)-1,1'-biphenyl) and binap (binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) have been studied. X-ray structure analysis of [Pt(biphep)(2)] revealed the distorted-tetrahedral geometry of the complex. The photophysical properties of the three complexes [Pd(biphep)(2)], [Pt(biphep)(2)], and [Pd(binap)(2)] were investigated and compared with that of the previously reported [Pt(binap)(2)] complex. The [Pd(biphep)(2)] complex shows the strongest luminescence with a high quantum yield (38%) and a long lifetime (3.2 micros) in a toluene solution at room temperature. The luminescence should be due to metal-to-ligand charge transfer excited states. At room temperature, radiative rate constants of the four complexes show similar values. The difference in the luminescent properties should reflect the different nonradiative rate constants of the complexes. The temperature-dependence of the luminescence spectra and lifetime of the complexes were also discussed.     

Synthesis, spectroscopy and structures of palladium(II) and platinum(II) complexes containing mercapto-o-carborane

The reactions of [M₂Cl₂(μ-Cl)₂(PMe₂Ph)₂] with mercapto-o-carboranes in the presence of pyridine afforded mono-nuclear complexes of composition, [MCl(SCb°R)(py)(PMe₂Ph)] (M = Pd or Pt; Cb° = o-C₂B₁₀H₁₀; R = H or Ph). The treatment of [PdCl₂(PEt₃)₂] with PhCb°SH yielded trans-[Pd(SCb°Ph)₂(PEt₃)₂] (4) which when left in solution in the presence of pyridine gave another substitution product, [Pd(SCb°Ph)₂(py)(PEt₃)] (5). The structures of [PdCl(SCb°Ph)(py)(PMe₂Ph)] (1), [Pd(SCb°Ph)₂(PEt₃)₂] (4) and [Pd(SCb^oPh)₂(py)(PEt₃)] (5) were established unambiguously by X-ray crystallography. The palladium atom in these complexes adopts a distorted square-planar configuration with neutral donor atoms occupying the trans positions. Thermolysis of [PdCl(SCb°)(py)(PMe₂Ph)] (2) in TOPO (trioctylphosphine oxide) at 200 °C gave nanocrystals of TOPO capped Pd₄S which were characterized by XRD pattern and SEM.     

Synthesis of Al complexes containing phenoxy-imine ligands and their use as the catalyst precursors for efficient living ring-opening polymerisation of epsilon-caprolactone

Al complexes containing phenoxy-imine ligands of type, Me2Al[O-2-R1-6-(R2N=CH)C6H3] [R1 = Me, R2 = 2,6-iPr2C6H3 (1a), tBu (1b); R1 = tBu, R2 = 2,6-iPr2C6H3 (2a), tBu (2b), cyclohexyl (2c), adamantyl (2d), C6H5 (2e), 2,6-Me2C6H3 (2f), C6F5 (2g)] have been prepared in high yields from AlMe3 by treating with 1.0 equiv. of 2-R1-6-(R2N=CH)C6H3OH in n-hexane. Structures for 1a, 1b, 2a-e and 2g were determined by X-ray crystallography, and these complexes have a distorted tetrahedral geometry around Al; both the Al-O and the Al-N bond distances were influenced by substituents in both the aryloxo and the imino groups. Me2Al[mu2-O-2-(R2N=CH)C6H4](AlMe3) [R2 = 2,6-iPr2C6H3 (3a), tBu (3b)] were prepared exclusively by reaction of AlMe3 with 2-(R2N=CH)C6H4OH, and these complexes form a distorted tetrahedral geometry around each Al centre with additional AlMe3 coordinating to the oxygen in the phenoxy-imine ligand. Complexes 1a, 1b and 2a-g were tested as catalyst precursors for ring-opening polymerisation (ROP) of epsilon-caprolactone (CL) in the presence of (n)BuOH (1.0 equiv. to Al), and their catalytic activities were strongly influenced by the imino substituent (R2). The efficient ROP has been achieved using the C6F5 analogue (2g), with the ROP taking place in a living manner.     

Synthesis and application of palladium stearates as precursors for the preparation of palladium nanoparticles

This report successfully demonstrates the synthesis and application of palladium stearates. It was found that the branching of the carboxylate anion of metal precursors could influence the size and shape of palladium nanoparticles (PdNPs). Worm‐like nanowires were formed when using the branched isomer palladium isostearate (PdISt₂), while triangular nanoparticles were produced in a majority when using the normal form: palladium stearate (PdSt₂). Furthermore, when applying CO₂ to the system, both types of PdNPs transformed into more spherical shapes with smaller sizes. The formation of carbamates from the amine stabilizer with CO₂ could prevent the further growth and aggregation of PdNPs. The PdNPs were tested as catalysts for the hydrogenation of styrene, and higher catalytic activities were achieved with PdNPs that were prepared with the assistance of CO₂. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and characterization of square-planar palladium(II) complexes containing anti- and syn-furan-2-aldoxime

Summary Fifteen palladium(II) square-planar complexes containing monodentate and/or bidentate anti- and syn-furan-2-aldoxime (FDH) have been isolated and characterized by elemental analysis, molecular weight determination, conductance studies, magnetic moments and i.r. spectral studies. The monodentate ligand coordinates through the nitrogen atom while the bidentate ligand coordinates through the furan oxygen atom and the nitrogen atom. The C-O-C stretching frequency of the furan ring may be taken as the criterion for the denticity of this ligand and is observed at 1240 and 1270 cm^– in anti- and syn-furan-2-aldoxime respectively. A shift to lower frequency occurs (in the complex) if the ligand is bidentate, however this frequency is unaffected if the ligand is monodentate.     

New palladium (II) complexes containing phosphine‐nitrogen ligands and their use as catalysts in aminocarbonylation reaction

Aminocarbonylation of aryl halides, homogeneously catalysed by palladium, is an efficient method that can be employed for obtaining amides for pharmaceutical and synthetic applications. In this work, palladium (II) complexes containing P^N ligands were studied as catalysts in the aminocarbonylation of iodobenzene in the presence of diethylamine. Two types of systems were used: a palladium (II) complex formed in situ; and one prepared prior to the catalytic reaction. In general, the palladium complexes studied achieved high conversions in an average reaction time of less than 2 hr, which is less than that for the standard system (Pd (II)/PPh₃) used. The pre‐synthesized complexes were faster than their in situ counterparts, as the latter require an induction time to form the Pd/P^N species. The structure and electronic properties of the ligand P^N can influence both the activity and the selectivity of the reaction, stabilizing the acyl‐palladium intermediates formed in a better manner.     

Synthesis,characterization and toxicity of new heterobimetallic complexes of platinum(II) and palladium(II)

Heterobimetallic complexes of the type [M(C₆H₆N₂)₂(M′)₂(R)₄]Cl₂ have been synthesized by the direct reaction of [M(C₆H₈N₂)₂]Cl₂ with Group 4 or 14 organometallic dichlorides Ph₂M′Cl₂,Me₂M′Cl₂ or Cp₂M″Cl₂ in 1:2 molar ratio in MeOH (M = Pd or Pt, M′ = Si or Sn and M″ = Ti or Zr). The compounds were characterized by elemental analysis, molecular weight determination, electronic, ¹H NMR and IR spectra, magnetic susceptibilities and conductivity measurements. These studies showed that the compounds are monomers and dimagnetic in nature, with a square‐planar geometry around palladium and platinum metals. Both the free ligands and their metal complexes were screened for antimicrobial activity on different species of pathogenic fungi and bacteria and were found active in this respect.Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis and crystal structures of phenylalanine ester-introduced palladium(II) and platinum(II) complexes and their cytotoxicities

Research on Chemical Intermediates - Phenylalanine ester-introduced palladium(II) and platinum(II) complexes were synthesized. Taking advantage of the formation of Schiff bases by amino acids as an...     

Synthesis,characterization, and thermal behavior of palladium(II) complexes containing 4-iodopyrazole

The mononuclear pyrazolyl complexes [PdCl₂(HIPz)₂] (1), [PdBr₂(HIPz)₂] (2), [PdI₂(HIPz)₂] (3), [Pd(SCN)₂(HIPz)₂] (4), and [Pd(NHCOIPz)₂] (5) have been prepared. Compound 1 was obtained from the displacement of acetonitrile from [PdCl₂(CH₃CN)₂] precursor by the 4-iodopyrazole (HIPz) ligand, whereas 2–5 were synthesized by substitution of the chlorido in 1 by the respective anionic group. The compounds were characterized by elemental analysis, infrared spectroscopy, and ¹H NMR spectroscopy. The thermal behavior of 1–5 has been studied by TG and DTA. The thermal stability of [PdX₂(HIPz)₂] compounds varies according to the trends X = Cl^? < I^? ? SCN^?< Br^?. No stable intermediates were isolated during the thermal decompositions due to the overlap of the degradation processes. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.