Syntheses of aryl- and arylethynyl-substituted N-confused porphyrins

Palladium-catalyzed cross-coupling reactions under Suzuki, Sonogashira, and Stille conditions afford 3-aryl (9-12) and 3-arylethynyl N-confused porphyrin (NCP) silver(III) complexes (13-15) from the 3-bromo NCP complex (4) in ca. 70% yields along with the transmetalated products, 3-substituted NCP palladium(II) complexes (11-Pd to 15-Pd), in 10-30% yields. Substitution at 3-position was confirmed by the single crystal X-ray structures of 9, 13-Ag, and 13-Pd. The arylethynyl groups or five-membered heterocyclic aromatic rings at 3-position largely affected the optical properties of N-confused porphyrin, in which the longest absorption maxima of the Q-bands are shifted bathochromically by 30-120 nm. The electronic effect of substituent differs largely between palladium and silver complexes reflecting the different π-electron delocalization pathway of NCP cores. 3-Aryl- and 3-arylethynyl NCP silver(III) complexes were easily demetalated to afford the corresponding free base porphyrins by the treatment of sodium borohydride.     

The influence of moisture on deprotonation mode of imidazolinium chlorides with palladacycle acetate dimer

Deprotonation of 1,3-diorganyl imidazolinium salts, 1, with N,C-type palladacyclic acetate dimer 2 afforded novel NHC coordinated complexes 3 along with ring opening hydrolysis products 4, which may coordinate to palladium center via NH group to give 5a. The hydrolysis necessitates the study of NHC complex formation in anhydrous media. The new compounds were characterized by spectroscopic methods and three of them (3c, 4c, 5a) by X-ray single-crystal diffraction studies.     

New pinene-derived pyridines as bidentate chiral ligands

A synthesis of new bidentate pyridines 8a-d, 9, and 10 has been developed, starting from triflate 14, readily available from β-pinene 11. A copper complex of the pyridine-oxazoline ligands 8a has been found to catalyze asymmetric allylic oxidation of cyclic olefins 36a-c with good conversion rates and acceptable enantioselectivity (≤67% ee). The imidazolium salt 10 has been identified as a precursor of the corresponding N,N′-unsymmetrical N-heterocyclic carbene ligand, whose complex with palladium catalyzed the intramolecular amide enolate α-arylation leading to oxindole 45 in excellent yield but with low enantioselectivity.     

Synthesis and reactivity of new functionalized Pd(II) cyclometallated complexes with boronic esters

Treatment of the functionalized Schiff base ligands with boronic esters 1a, 1b, 1c and 1d with palladium (II) acetate in toluene gave the polynuclear cyclometallated complexes 2a, 2b, 2c and 2d, respectively, as air-stable solids, with the ligand as a terdentate [C,N,O] moiety after deprotonation of the -OH group. Reaction of 1j with palladium (II) acetate in toluene gave the dinuclear cyclometallated complex 5j. Reaction of the cyclometallated complexes with triphenylphosphine gave the mononuclear species 3a, 3b, 3c, 3d and 6j with cleavage of the polynuclear structure. Treatment of 2c with the diphosphine Ph₂PC₅H₄FeC₅H₄PPh₂ (dppf) in 1:2 molar ratio gave the dinuclear cyclometallated complex 4c as an air-stable solid.Deprotection of the boronic ester can be easily achieved; thus, by stirring the cyclometallated complex 3a in a mixture of acetone/water, 3e is obtained in good yield. Reaction of the tetrameric complex 2a with cis-1,2-cyclopentanediol in chloroform gave complex 2c after a transesterification reaction. Under similar conditions complexes 3a and 3d behaved similarly: with cis-1,2-cyclopentanediol, pinacol or diethanolamine complexes 3c, 3b, 3g and 3f, were obtained. The pinacol derivatives 3b and 3g experiment the Petasis reaction with glyoxylic acid and morpholine in dichloromethane to give complexes 3h, and 3i, respectively.     

Synthesis, structure and catalytic activity of a bimacrocylic NHC palladium allyl complex

The preparation of a bimacrocyclic NHC palladium allyl complex 4 is described. The complex was obtained by transmetalation with allyl palladium chloride dimer from the NHC silver complex 2 in 85% yield. Complex 4 was fully characterized by spectroscopic methods and by single-crystal X-ray analysis. In a preliminary catalytic study, complex 4 showed high activity in the Suzuki-Miyaura cross-coupling of unactivated aryl chlorides and bromides with 1-naphthalene-boronic acid at low catalyst loading. Good results were also obtained in the Mizoroki-Heck reaction of aryl bromides with styrene, but a decrease in yield was observed when aryl chlorides were used.     

Synthesis,characterization and antitumor activity of palladium(II) complexes of monoethyl 8-quinolylmethylphosphonate

The complex-forming properties of monoethyl 8-quinolylmethylphosphonate (8-Hmqmp) towards palladium(II) ion have been investigated by reactions of the hydrochloride, 8-Hmqmp · HCl · H₂O, and sodium salt, Na(8-mqmp) · 2H₂O, of this monoester with palladium(II) halide compounds in aqueous solution over a wide pH range. Depending on pH and initial quinolinium and palladium salts, four types of complexes have been formed. Under acidic solution the ion-pair salt complexes [8-H₂mqmp]₂[PdX₄] (1 and 2, pH < 3) and [8-H₂mqmp]₂[Pd₂X₆] (3 and 4, pH ∼ 3), with protonated quinoline ligand as cation and tetrahalopalladate or hexahalodipalladate complex as anion (X = Cl, Br), were isolated. By heating in methanol the chloro complexes 1 and 3 as well as bromo complexes 2 and 4 were converted into the quinolinium salt complexes, [8-H₂mqmp][Pd(8-Hmqmp)X₃], 5 and 6, respectively, containing as anion the quinoliniummethylphosphonatetrihalopalladate complex with palladium bonded at the phosphonic acid moiety. The chelate complex 7, [Pd(8-mqmp)₂], with ligand bonded through the quinoline nitrogen and the deprotonated phosphonic acid oxygen and forming two seven-membered {N,O} chelate rings, was obtained in neutral and basic media. The complexes were identified and characterized by elemental analysis, magnetic and conductance measurements, spectroscopic studies (IR, ¹H NMR, UV–Vis, positive/negative ion FAB MS) and thermal analysis (TG, DTA). As a preliminary screening for their biological activity, complexes were investigated for their ability to inhibit the cancer growth in vitro in the human KB and murine L1210 cell lines. The results obtained were compared with those obtained for the complexes of diethyl 8-quinolylmethylphosphonate (8-dqmp) and monoethyl 2-quinolylmethylphosphonate (2-Hmqmp), and structural factors that determine the complex activity were discussed.     

Optically active cyclopentadienyl and indenyl ligands obtained from lactic acid esters

Asymmetric cyclopentadienes and indenes are easily prepared by nucleophilic attack of LiCp or LiInd on tosylate or triflate of ethyl (S)-(−) lactate. The selectivity of the reaction depends on the nature of the leaving group. This is particularly true in the case of the reaction of LiCp with sulfonates of ethyl (S)-(−) lactate. Indeed, only the monosubstituted cyclopentadiene lactate 2 is obtained from the triflate 6, whereas from the tosylate 1, besides 2 (20%) a 1,3-disubstituted cyclopentadiene lactate 3 is isolated (16.5%). From cyclopentadiene and indene lactate 2 and 7, optically active β-hydroxycyclopentadiene 10 and β-hydroxyindene 11 are obtained by reduction with LiAlH₄. Two rhodium(I) complexes 14 and 15 have been synthesized from (R,S)-2-(cyclopentadienyl)N,N-dimethylpropanamide 12 and (S)-2-(cyclopentadiene)propan-1-ol 10, respectively. The molecular structure of these complexes has been determined. Analytical and preparative chiral HPLC have been used to determine the optical purity of the ligands and to isolate enantiopure cyclopentadienyl complexes from racemic or enantiomerically enriched rhodium(I) complexes.     

Chiral C1-symmetric 2,2′:6′,2′′-terpyridine ligands: Synthesis,characterization, complexation with copper(II), rhodium(III) and ruthenium(II) ions and use of the complexes in catalytic cyclopropanation of styrene

Three new optically pure C₁-terpyridine ligands (L1–3) were prepared and the copper(II) complexes, of formula [Cu(L)Cl₂], the rhodium(III) complexes, of formula [Rh(L)Cl₃], and the ruthenium(II) complexes, of formula cis- or trans-[Ru(L)(X)Cl₂] (X = DMSO or CO), were synthesized. Structures of a chiral C₁-ligand, a copper complex, a rhodium complex and a ruthenium DMSO complex were analysed using X-ray crystal structure analysis. The copper, rhodium and ruthenium complexes were shown to be precursors of catalysts for cyclopropanation. Reaction of [Cu(L)Cl₂], [Rh(L)Cl₃] or cis- or trans-[Ru(L)(X)Cl₂] with AgOTf converted the complex to catalyst, which in the case of trans-[Ru(L)(CO)Cl₂] gave enantioselectivities of up to 67% ee for the cis-isomers of styrene cyclopropanes with t-butyl diazoacetate. Comparisons with C₂-analog of copper, rhodium and ruthenium catalysts were made.     

Gold(I) N-heterocyclic carbene based initiators for bulk ring-opening polymerization of l-lactide

Synthesis, structures, and catalysis studies of gold(I) complexes of N-heterocyclic carbenes namely, a di-O-functionalized [1-(2-hydroxy-cyclohexyl)-3-(acetophenone)imidazol-2-ylidene], a mono-O-functionalized [1-(2-hydroxy-cyclohexyl)-3-(benzyl)imidazol-2-ylidene] and a non-functionalized [1,3-di-i-propyl-benzimidazol-2-ylidene], are reported. Specifically, the gold complexes, [1-(2-hydroxy-cyclohexyl)-3-(acetophenone)imidazol-2-ylidene]AuCl (1c), [1-(2-hydroxy-cyclohexyl)-3-(benzyl)imidazol-2-ylidene]AuCl (2c), and [1,3-di-i-propyl-benzimidazol-2-ylidene]AuCl (3b), were prepared from the respective silver complexes 1b, 2b, and 3a by treatment with (SMe₂)AuCl in good yields following the commonly used silver carbene transfer route. The silver complexes 1b, 2b, and 3a were synthesized from the respective imidazolium halide salts by the reactions with Ag₂O. The N-heterocyclic carbene precursors, 1-(2-hydroxy-cyclohexyl)-3-(acetophenone)imidazolium chloride (1a) and 1-(2-hydroxy-cyclohexyl)-3-(benzyl)imidazolium chloride (2a), were synthesized by the direct reactions of cyclohexene oxide and imidazole with chloroacetophenone and benzyl chloride respectively. The gold (1c, 2c, and 3b) and the silver (3a) complexes along with a new O-functionalized imidazolium chloride salt (1a) have been structurally characterized by X-ray diffraction. The structural studies revealed that geometries around the metal centers were almost linear in these gold and silver complexes. The gold (1c, 2c, and 3b) complexes efficiently catalyze ring-opening polymerization (ROP) of l-lactide under solvent-free melt conditions producing polylactide polymer of moderate to low molecular weights with narrow molecular weight distributions.     

Rhodium(I) complexes with κP coordinated ω-phosphinofunctionalized alkyl phenyl sulfide, sulfoxide and sulfone ligands and their reactions with sodium bis(trimethylsilyl)amide and Ag[BF4]

Reactions of ω-diphenylphosphinofunctionalized alkyl phenyl sulfides Ph₂P(CH₂)_nSPh (n = 1, 1a; 2, 2a; 3, 3a), sulfoxides Ph₂P(CH₂)_nS(O)Ph (n = 1, 1b; 2, 2b; 3, 3b) and sulfones Ph₂P(CH₂)_nS(O)₂Ph (n = 1, 1c; 2, 2c; 3, 3c) with dinuclear chlorido bridged rhodium(I) complexes [(RhL₂)₂(μ-Cl)₂] (L₂ = cycloocta-1.5-diene, cod, 4; bis(diphenylphosphino)ethane, dppe, 5) afforded mononuclear Rh(I) complexes of the type [RhCl{Ph₂P(CH₂)_nS(O)_xPh-κP}(cod)]¹ (n/x = 1/0, 6a; 1/1, 6b; 1/2, 6c; 2/0, 8a; 2/1, 8b; 2/2, 8c; 3/0, 10a; 3/1, 10b; 3/2, 10c) and [RhCl{Ph₂P(CH₂)_nS(O)_xPh-κP}(dppe)] (n/x = 1/0, 7a; 1/1, 7b; 1/2, 7c; 2/0, 9a; 2/1, 9b; 2/2, 9c; 3/0, 11a; 3/1, 11b; 3/2, 11c) having the P^S(O)_x ligands κP coordinated. Addition of Ag[BF₄] to complexes 6-11 in CH₂Cl₂ led with precipitation of AgCl to cationic rhodium complexes of the type [Rh{Ph₂P(CH₂)_nS(O)_xPh-κP,κS/O}L₂][BF₄] having bound the P^S(O)_x ligands bidentately in a κP,κS (13a-18a, 15b-18b) or a κP,κO (13b, 14b, 13c-18c) coordination mode. Unexpectedly, the addition of Ag[BF₄] to 6a in THF afforded the trinuclear cationic rhodium(I) complex [Rh₃(μ-Cl)(μ-Ph₂PCH₂SPh-κP:κS)₄][BF₄]₂·4THF (12·4THF) with a four-membered Rh₃Cl ring as basic framework. Addition of sodium bis(trimethylsilyl)amide to complexes 6-11 led to a selective deprotonation of the carbon atom neighbored to the S(O)_x group (α-C) yielding three different types of organorhodium complexes: a) Organorhodium intramolecular coordination compounds of the type [Rh{CH{S(O)_xPh}CH₂CH₂PPh₂-κC,κP}L₂] (22a-c, 23a-c), b) zwitterionic complexes [Rh{Ph₂PCHS(O)_xPh-κP,κS/O}L₂] having κP,κS (21a, 21b) and κP,κO (20b/c, 21c) coordinated anionic [Ph₂PCHS(O)_xPh] ligands, and c) the dinuclear rhodium(I) complex [{Rh{μ-CH(SPh)PPh₂-κC:κP}(cod)}₂] (19). All complexes were fully characterized spectroscopically and complexes 15b, 15c, 12·4THF and 19·THF additionally by X-ray diffraction analysis. DFT calculations of zwitterionic complexes gave insight into the coordination mode of the [Ph₂PCHS(O)Ph] ligand (κP,κS versus κP,κO).     

Palladium(II) complexes containing a bulky pyridinyl N-heterocyclic carbene ligand: Preparation and reactivity

Coordination chemistry of a pyridine imidazole-2-ylidene ligand (pyN ˆC) with sterically hindered substituents toward palladium(II) metal ions has been investigated. The palladium carbene complex [(C-pyN ˆC)Pd(η³-allyl)Cl] (3) is prepared via the transmetallation from the corresponding silver carbene complexes with [ClPd(η³-allyl)]₂. Upon the abstraction of chloride, coordination of pyridinyl-nitrogen becomes feasible to form [C,N-(pyN ˆC)Pd(η³-allyl)](BF₄) (4). Ligand substitution reaction of 4 with triphenylphosphine results in the formation of [(C-pyN ˆC)Pd(PPh₃)(η³-allyl)](BF₄)], which the pyridinyl-nitrogen donor is substituted by the phosphine. This palladium complex appears to be base sensitive. Treatment of 4 with t-butoxide causes the decomposition to yield the metal nano-particles. Furthermore, de-complexation of 4 takes place under hydrogen atmosphere to generate the carbene precursor, 1-(6-mesityl-2-picolyl)-3-mesitylimidazolium salt. Nevertheless, the palladium complex 4 shows good catalytic activity on the Suzuki-Miyaura and Mizoroki-Heck reactions.     

Convenient and efficient Suzuki-Miyaura cross-coupling reactions catalyzed by palladium complexes containing N,N,O-tridentate ligands

N,N,O-Tridentate ligands 1-9 were prepared from the condensation of amines with nine aromatic aldehydes or ketones. These ligands are thermally stable and neither air- nor moisture-sensitive. Combination of either 2-methoxy-6-[(pyridine-2-ylmethylimino)-methyl]-phenol, 1 or 2-(benzothiazol-2-yl-hydrazonomethyl)-4,6-di-tert-butyl-phenol, 6 with Pd(OAc)₂ furnished an excellent catalyst precursor for the Suzuki-Miyaura cross-coupling of various aryl bromides with arylboronic acids. The effects of varying solvents, bases, and ligand/palladium ratios on the performance of the coupling reaction were investigated. The molecular structures of both free ligand 1 and its palladium acetate complex 10 were determined by single-crystal X-ray diffraction methods. The DFT studies revealed that the catalytic performance of palladium complexes involving this type of a ligand may differ greatly upon a small variation in its structure.     

Copper(I) and silver(I) complexes of 1,5-methylene- and diethylmethylene-bridged bis(oxazoline) ligands. In situ Cu(II)-catalyzed oxidation of methylene bridge

Silver(I) and copper(I) complexes of C₂-symmetric bis(oxazoline) ligands were studied by UV, NMR, IR, EPR and ES-MS spectroscopies. The stability constants of the Ag-1a and Ag-1b complexes with 1:1 and 1:2 stoichiometries in acetonitrile were determined by NMR spectrometric titrations. The evidence of tetrahedral coordination for complex (Ag(1a)₂(⁺ was obtained from the complexation induced shifts (CIS) and NOEs. Mass spectra revealed the Cu(II) mediated oxidation of methylene bridge in copper complexes of 1a and 1b, which was in accordance with the UV, NMR, IR and EPR findings. The efficiency of Cu(I) complexes of methylene-bridged 1,5-bis(oxazoline)s 1 as chiral catalysts in stereoselective cyclopropanation of styrene with ethyl diazoacetate, was compared to that of the dialkylmethylene-bridged 1,5-bis(oxazoline)s 2.     

Synthesis of palladium complexes containing 2-methoxycarbonyl-6-iminopyridine ligand and their catalytic behaviors in reaction of ethylene and norbornene

A series of palladium complexes (C1-C7) have been prepared by the reaction of PdCl₂(CH₃CN)₂ with 2-methoxycarbonyl-6-iminopyridines, L1-L7. The 2-methoxycarbonyl-6-iminopyridines and their complexes were fully characterized by FT-IR, NMR spectra and elemental analysis. Structures of C1, C2, C4, C5 and C6, C7 were determined by X-ray crystallography, and these complexes fold slightly distorted square planar structures around palladium coordinated with two nitrogen atoms and two chlorides. These palladium complexes exhibited moderate catalytic activities for ethylene dimerization and/or polymerization in the presence of methylaluminoxane, and showed remarkable catalytic activity for norbornene polymerization. The catalytic behaviors of these complexes were highly affected by both the ligand employed and reaction conditions.     

Synthesis and characterization of silver(I), gold(I), and gold(III) complexes bearing a bis-dialkylamino functionalized N-heterocyclic carbene

Bis-1,3-[2-(diisopropylamino)ethyl]-imidazolium chloride, 1, has been prepared and used as a precursor for the synthesis of the corresponding silver(I) chloride complex 2. The single crystal structure analysis reveals that the complex dimerizes in the solid state. Transmetalation of 2 with (tht)AuBr (tht = tetrahydrothiophene) yields the (NHC)Au(I)Br complex 3. By treatment with bromine it is oxidized to (NHC)AuBr₃, 4, which is obtained as a yellow, microcrystalline powder. The UV-vis spectra of 4 are dependent on the pH-value and suggest a square-pyramidal structure in solution.     

Synthesis, structure and catalytic activity of the first iridium(I) siloxide versus chloride complexes with 1,3-mesitylimidazolin-2-ylidene ligand

The first iridium(I) complex containing siloxyl and N-heterocyclic carbene ligand such as [Ir(cod)(IMes)(OSiMe₃)] (1) and [Ir(CO)₂(IMes)(OSiMe₃)] (3) have been synthesized and their structures solved by spectroscopy and X-ray methods as well as catalytic properties in selected hydrogenation reactions have been presented in comparison to their chloride analogues, i.e. [Ir(Cl)(cod)(IMes)] (2) and [Ir(Cl)(CO)₂(IMes)] (4). The attempts at synthesis of iridium(I) complex with tert-butoxyl ligand has failed as leading instead to the iridium hydroxide complex [Ir(cod)(OH)(IMes)] (5) whose X-ray structure has also been solved. All complexes (1)-(5) show square planar geometry typical of the four-coordinated iridium complexes. Catalytic activity of complexes 1 and 2 was tested in transfer hydrogenation of acetophenone and hydrogenation of olefins.     

N-heterocyclic carbene-silver complexes: Potential conductive materials for silver pastes in electronic applications

New organosilver complexes, silver(I) tetraalkylbis(benzimidazolidene) halide [1a-3a] and silver(I) dimethyl-N,N′-hexyl(imidazolyl) bromide [4a], were synthesized and incorporated into electroconductive silver pastes. Complex 3a had a 15-fold higher conductivity than conventional silver salt pastes, specifically silver(I) hexanoate, and exhibited a smooth, homogeneous surface after reductive heat-treatment of the silver paste. While the conductivity of silver(I) hexanoate can be increased by up to 33% by the addition of a supporting silver source, such as Ag₂O, the conductivity of 3a was markedly decreased by Ag₂O treatment. Thus, 3a can be used in silver pastes with moderate conductivity and can reduce the amount of conventional silver supporting materials without loss of electroconductivity.     

Novel hemi-labile pyridyl-imine palladium complexes: Synthesis, molecular structures and reactions with ethylene

Ligands (2-pyridyl-2-furylmethyl)imine, (L1), (2-pyridyl-2-thiophenemethyl)imine (L2), and (2-pyridyl-2-thiopheneethyl)imine (L3) were synthesized by condensation reactions and obtained in good yields. Reactions of L1-L3 with either [PdClMe(cod)] or [PdCl₂(cod)] gave the corresponding monometallic palladium(II) complexes 1-5 in very good yields. Molecular structures of complexes 1, 4 and 5 indicated that the ligands are bidentate and coordinate to the palladium metal through the imine and pyridine nitrogen atoms. When complexes 3-5 were treated with NaBAr₄, cationic species, 3a, 4a, and 5a were produced which catalyzed polymerization of ethylene though with very low activities. ¹H NMR spectroscopy studies showed that these cationic species were very stable in solution. DFT calculations showed high ethylene coordination barriers to the cationic species 3a, 4a and 5a.     

Phosphite ligands derived from distally and proximally substituted dipropyloxy calix[4]arenes and their palladium complexes: Solution dynamics, solid-state structures and catalysis

Two bisphosphite ligands, 25,27-bis-(2,2′-biphenyldioxyphosphinoxy)-26,28-dipropyloxy-p-tert-butyl calix[4]arene (3) and 25,26-bis-(2,2′-biphenyldioxyphosphinoxy)-27,28-dipropyloxy-p-tert-butyl calix[4]arene (4) and two monophosphite ligands, 25-hydroxy-27-(2,2′-biphenyldioxyphosphinoxy)-26,28-dipropyloxy-p-tert-butyl calix[4]arene (5) and 25-hydroxy-26-(2,2′-biphenyldioxyphosphinoxy)-27,28-dipropyloxy- p-tert-butyl calix[4]arene (6) have been synthesized. Treatment of (allyl) palladium precursors [(η³-1,3-R,R′-C₃H₄)Pd(Cl)]₂ with ligand 3 in the presence of NH₄PF₆ gives a series of cationic allyl palladium complexes (3a-3d). Neutral allyl complexes (3e-3g) are obtained by the treatment of the allyl palladium precursors with ligand 3 in the absence of NH₄PF₆. The cationic allyl complexes [(η³-C₃H₅)Pd(4)]PF₆ (4a) and [(η³-Ph₂C₃H₃)Pd(4)]PF₆ (4b) have been synthesized from the proximally (1,2-) substituted bisphosphite ligand 4. Treatment of ligand 4 with [Pd(COD)Cl₂] gives the palladium dichloride complex, [PdCl₂(4)] (4c). The solid-state structures of [{(η³-1-CH₃-C₃H₄)Pd(Cl)}₂(3)] (3f) and [PdCl₂(4)] (4c) have been determined by X-ray crystallography; the calixarene framework in 3f adopts the pinched cone conformation whereas in 4c, the conformation is in between that of cone and pinched cone. Solution dynamics of 3f has been studied in detail with the help of two-dimensional NMR spectroscopy.The solid-state structures of the monophosphite ligands 5 and 6 have also been determined; the calix[4]arene framework in both molecules adopts the cone conformation. Reaction of the monophosphite ligands (5, 6) with (allyl) palladium precursors, in the absence of NH₄PF₆, yield a series of neutral allyl palladium complexes (5a-5c; 6a-6d). Allyl palladium complexes of proximally substituted ligand 6 showed two diastereomers in solution owing to the inherently chiral calix[4]arene framework. Ligands 3, 6 and the allyl palladium complex 3f have been tested for catalytic activity in allylic alkylation reactions.     

Synthesis and X-ray structure of platinum(II), palladium(II) and copper(II) complexes with pyridine–pyrazole ligands: Influence of ligands’ structure on cytotoxic activity

The new pyrazole ligand 5-(2-hydroxyphenyl)-3-methyl-1-(2-pyridylo)-1H-pyrazole-4-phosphonic acid dimethyl ester (2a) has been used to obtain a series of platinum(II), palladium(II) and copper(II) complexes (3a–7a) as potential anticancer compounds. The molecular structures of the platinum(II) and copper(II) complexes 3a and 6a have been determined by X-ray crystallography. The cytotoxicity of the phosphonic ligand 2a and its carboxylic analog 2b as well as their complexes has been evaluated on leukemia and melanoma cell lines. Copper(II) complexes were found to be more efficient in the induction of melanoma cell death than the platinum(II) or palladium(II) complexes. Cytotoxic effectiveness of compound 7b against melanoma WM-115 cells was two times better than that of cisplatin. The reaction of compound 5b with 9-methylguanine has been studied.