Palladium(II) coordination and cyclometallated complexes derived from 1-tert-butylpyrazole

The synthesis and characterization of a number of new coordination compounds of Pd^II with the nitrogen donor 1-tert-butylpyrazole (^tBuPzH) are described. Compounds are trans-[Pd(^tBuPzH)₂Cl₂] and the cyclometallated structures [Pd₂(^tBuPz)₂(AcO)₂] and [Pd₃(^tBuPz)₂(AcO)₄]. All these complexes are mixtures of syn and anti isomers. Also, the chloro-bridged complex [Pd₂(^tBuPz)₂Cl₂] has been isolated as an equilibrium mixture of cis and trans isomers. The compounds have been studied by variable temperature ¹H- and ¹³C-NMR spectroscopy.     

Palladium(II) halide complexes with dithioesters derived from sarcosine

Summary The compounds EtO₂CCH₂(Me)NCS₂R (R = Me, ESDTM; R = Et, ESDTE) were prepared from sarcosine ethyl ester hydrochloride, CS₂ and alkyl iodide in EtOH-H₂O. These ligands react with palladium halides in benzene to yield the benzene solvates [Pd(ESDTR)X₂]·nC₆H₆ (R = Me or Et; X = Cl or Br; n < 1), in which the dithioester molecule coordinates through both sulphur atoms. Ligands and complexes have been characterized by i.r. and ¹H n.m.r. spectroscopy and by thermal analysis (t.g., d.t.g. and d.t.a.). The low stability of the adducts in both solution and solid phase is discussed on the basis of proton n.m.r. spectra. Thermal degradation of the 1∶1 complexes has been examined up to 1000° C. The first decomposition step involves release of alkyl halide to form the [Pd(ESDT)X] _n (X = Cl or Br) intermediates, which successively decompose, finally giving palladium.     

Palladium(II) complexes containing cytokinins derived from 6-benzylaminopurine

A series of palladium(II) complexes of general formula [Pd(LH⁺)Cl₃] (1–12) containing 6-benzylaminopurine derivatives has been prepared [L?=?6-(2-methoxybenzylamino)purine (1), 6-(3-methoxybenzylamino)purine (2), 6-(4-methoxybenzylamino)purine (3), 6-(2-hydroxy-benzylamino)purine (4), 6-(3-hydroxybenzylamino)purine (5), 6-(4-hydroxybenzylamino) purine (6), 6-(2-fluorobenzylamino)purine (7), 6-(3-fluorobenzylamino)purine (8), 6-(4-fluorobenzylamino)purine (9), 6-(2-chlorobenzylamino)purine (10), 6-(3-chlorobenzylamino) purine (11) and 6-(4-chlorobenzylamino)purine (12)]. The compounds have been characterized by elemental analysis, IR, ES+ MS and ¹H- and ¹³C-NMR spectroscopy, and two of them, 6 and 12, also by TG/DSC analyses. The complexes have been screened in vitro against the four human tumour cell lines G-361, HOS, K-562 and MCF7.     

Palladium(II) Schiff base complexes derived from sulfanilamides and aminobenzothiazoles

Schiff bases (HL) derived from sulfanilamides or aminobenzothiazoles add to Pd(OAc)₂ to give complexes of the type PdL₂ (1–7) in moderate to excellent yields. Reactions of Schiff bases containing pyrimidine groups, however, gave several products arising from competing coordination of the pyrimidine nitrogen. Palladium complexes and Schiff bases have been investigated as antifungal agents against Aspergillus niger and Aspergillus flavus.     

Palladium(II) complexes with 5-methyl-5-(4-pyridyl)-2,4-imidazolidenedione

Two new palladium(II) complexes with 5-methyl-5-(4-pyridyl)-2,4-imidazolidenedione(mpyh) were synthesized: cis-[Pd(mpyh)₂Cl₂]·H₂O and cis-[Pd(mpyh)₂Br₂]·2H₂O. The molecular formulae of the complexes were confirmed by elemental analysis, IR, ¹H NMR spectra and DTA study. The ligand is coordinated to the palladium ion with N-atom of the pyridine ring. The spectroscopic data indicate a square planar geometry with two N-pyridine atoms and two halogene anions in cis position. The final product of the thermal decomposition of cis-[Pd(mpyh)₂Cl₂]·H₂O is metallic Pd, whereas for cis-[Pd(mpyh)₂Br₂]·2H₂O the residue consists of metallic Pd and C. The cytotoxic effects of the complexes were examined in vitro on some human tumor cell lines. The cis-[Pd(mpyh)₂Cl₂]·H₂O proved to be more active as compared to the cis-[Pd(mpyh)₂Br₂]·2H₂O.     

Palladium(II) complexes of Schiff bases derived from 5-amino-2,4-(1H, 3H)pyrimidinedione (5-aminouracil) and 1,2-dihydro-1,5-dimethyl-2-phenyl-4-amino-3H-pyrazol-3-one

Summary New palladium(II) complexes of Schiff bases, obtained from 5-aminouracil, (AUH), and acetylacetone (AUAcAcH₂), benzaldehyde (AUBALH), furan-2-aldehyde (AUFALH), 2-hydroxynaphthaldehyde (AUNALH₂), pyridine-2-aldehyde (AUPyALH) or salicylaldehyde (AUSALH₂) and from 1,2-dihydro-1,5-dimethyl-2-phenyl-4-amino-3H-pyrazol-3-one (AAPy) and acetylacetone (AAPyAcAcH), 2-hydroxyacetophenone (AAPyAPH), furan-2-aldehyde (AAPyFAL), pytidine-2-aldehyde (AAPyPyAL), or salicylaldehyde (AAPySALH), have been prepared. The complexes, with formulae PdL₂Cl₂ (L=AUBALH, AUFALH or AUSALH₂); PdLCl₂ (L=AUAcAcH₂, AUNALH₂, AUPyALH, AAPyFAL or AAPyPyAL) and PdLCl (L=AAPyAcAc or AAPySAL) were characterized by elemental analysis, i.r. and electronic spectral studies, thermogravimetric analyses and magnetic and conductance measurements. The x-ray powder diffraction pattern of one of the complexes was also examined. The complexes were screened for their possible antitumour activityin vitro.     

Four copper(II) pyrazolido complexes derived from reactions of 3{5}-substituted pyrazoles with CuF(2) or Cu(OH)(2)

Treatment of CuF(2) with 2 equiv of 3{5}-[pyrid-2-yl]pyrazole (Hpz(Py)), 3{5}-phenylpyrazole (Hpz(Ph)) or 3{5}-[4-fluorophenyl]pyrazole (Hpz(PhF)) in MeOH, followed by evaporation to dryness and recrystallisation of the solid residues, allows solvated crystals of [{Cu(micro-pz(Py))(pz(Py))}(2)] (1), [{Cu(micro-pz(Ph))(2)}(4)] (2) and [Cu(4)F(2)(micro(4)-F)(micro-pz(PhF))(5)(Hpz(PhF))(4)] (3) to be isolated in moderate-to-good yields. Similar reactions of these three pyrazoles with Cu(OH)(2) in refluxing MeOH respectively afford 1, 2 and [Cu(pz(PhF))(2)(Hpz(PhF))(2)] (4) in ca. 10% yield. Crystalline 1 x 1/2H(2)O x 2CHCl(3) contains two independent dinuclear molecules with a puckered di-(1,2-pyrazolido) bridge motif, linked by a bridging, hydrogen-bonding water molecule. Compound 2 x 1/2C(5)H(12), containing cyclic, square tetranuclear complex molecules, is the first homoleptic divalent metal pyrazolide to have a discrete molecular rather than polymeric structure, for a metal other than Pd or Pt. The two independent complex molecules in 3 x 3/4CH(2)Cl(2) x Hpz(PhF) contain a unique tetrahedral [Cu(4)(micro(4)-F)](7+) core, three of whose edges are spanned by bridging pyrazolido groups. Magnetic data show that the copper centres in 1 and 3 are antiferromagnetically coupled, but that dried bulk samples of 2 do not retain their molecular structure.     

Palladium(II) iminophosphine complexes

New complexes of general formula [PdCl₂(NP)] (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr, ^t Bu, NH-Me) and [Pd(NP)₂](ClO₄)₂ (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr) have been prepared by directly reacting the precursor PdCl₂(PhCN)₂ with iminophosphines (NP) in 1:1 and 1:2 molar ratios respectively. When the chloro-complex [PdCl₂(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)] was treated with CF₃SO₃Ag in MeCN, the labile complex [Pd(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)(MeCN)₂](CF₃SO₃)₂ was obtained in good yield. The reactivity of the new precursor towards a variety of neutral N- and P-donor ligands (py, PMe₂Ph, PMePh₂, PEt₃, bipy, dppe, 2-thpy) has been studied. The new complexes were characterized by partial elemental analyses and by spectroscopy (i.r., ¹H- and ³¹P-n.m.r.). The molecular structure of the aquo-complex [Pd(NP)(2-thpy)(H₂O)](CF₃SO₃)₂ has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as a chelating ligand with coordination around the palladium atom slightly distorted from square-planar geometry.     

Palladium(II) methylpyrazole complexes

Summary Pd^II complexes of the general formula PdL ₂ ⁿ Cl₂ [L¹ = 3,4,5-trimethylpyrazole, L² = l,3,4-trimethylpyrazole, L³ = 1,3,5-trimethylpyrazole, L⁴ = 1,4,5-trimethylpyrazole and L⁵ = 1,3,4,5-tetramethylpyrazole] (1)–(5) have been prepared and studied by elemental analyses, X-ray diffraction patterns, i.r., far-i.r. and n.m.r. spectroscopy, conductometry, magnetic and thermal measurements.     

Palladium(II) and platinum(II) complexes of rhodanine and 3-methylrhodanine

Summary The following palladium(II) and platinum(ll) complexes of rhodanine (HRd) and 3-methylrhodanine (MRd) have been prepared: Pd(HRd)_1.5Cl₂, Pd(HRd)₂Br₂, Pd(HRd)₂Br₂ · 0.25 EtOH, M(MRd)₂X₂ [M = Pd, X = Cl (0.25 EtOH) or Br; M = Pt, X = Cl or Br], Pd(MRd)₃Br₂, and M(MRd)₄(ClO₄)₂ (M = Pd or Pt). The ligands are coordinated to the metal through the thiocarbonylic sulphur atom. Pd(HRd)_1.5Cl₂ has presumably a structure such as (X = Cl or Br) complexes have a trans-planar coordination. Pd(MRd)₂X₂ (X = Cl or Br) complexes arecis-planar coordinated. Pd(MRd)₃Br₂ has presumably a square coordination with two MRd molecules and two CI ionscis-coordinated in the equatorial plane, and a MRd molecule and a Cl ion weakly bonded in apical position. The M(MRd)₄(ClO₄)₂ complexes have square planar coordination.Author to whom all correspondence should be addressed.     

Palladium(II)-N-heterocyclic carbene complexes derived from proline: synthesis and characterization

Pd(II)-N-heterocyclic carbene complexes derived from proline have been successfully synthesized in good yields and their structures have been characterized by X-ray single crystal diffraction. It was found that the substituents on the N-atom of the pyrrolidine skeleton dramatically affect on the coordination pattern of the palladium complexes. In a word, when an electron-rich group as benzyl group was attached on the N-atom, both of the N-atom and NHC were coordinated to the Pd(II) center; while when an electron-poor group as Ts group was attached, a dimeric mono-coordinated Pd(II)-NHC was obtained exclusively.     

New complexes derived from copper(II) salts and bis-N-(p-methoxyphenyl)-2, 5-furylideneimine

Summary Two new complexes derived from bis-N-(p-methoxyphenyl)-2, 5-furylideneimine(L) (1) and copper(II)[CuL₂](ClO₄)₂·4H₂O (2) and [(CuCl₂)₂L] (3), have been synthesized. The i.r. spectra of both complexes show that the ligand coordinatesvia oxygen and nitrogen. Spectral and magnetic properties are consistent with the formulation of (2) as an elongated tetragonal octahedral copper(II) structure and (3) as distorted square-planar copper(II) structure, where each copper atom is bonded to two chlorine, one oxygen and one nitrogen atoms, and two carbon and two copper atoms tetrahedrally surround the oxygen atom.     

Crystal structures of copper(II) and zinc(II) complexes derived from 3-(2-pyridyl)pyrazole

Two dinuclear complexes [Zn(μ-L)(NO₃)(H₂O)]₂ (1) and [Cu₂(μ-L)₂(HL)₂](NO₃)₂(C₁₂H₈Br₂)_0.5·H₂O (2), (HL = 3-(2-pyridyl)pyrazole, C₁₂H₈Br₂ = 4,4′-dibromobiphenyl) are synthesized under hydrothermal conditions and characterized by elemental analysis and X-ray single crystal diffraction. Crystal data for 1: triclinic, \(P\bar 1\), a = 8.8478(7) Å, b = 15.0550(11) Å, c = 16.4310(12) Å, α = 107.588(4)°, β = 112.498(3)°, γ = 115.595(3)°, V = 2099.8(9) ų, Z = 2; for 2: triclinic, \(P\bar 1\), a = 7.2870(15) Å, b = 8.6840(17) Å, c = 9.3290(19) Å, α = 107.588(4)°, β = 112.498(3)°, γ = 115.595(3)°, V = 528.77(18) ų, Z = 1. Complex 1 and 2 are both dinuclear structures which are further packed into a 1D supramolecular chain and a 3D supramolecular framework via weak C–H…O hydrogen bond interactions respectively.     

Palladium(II) complexes of ketimines

Summary New Pd^II complexes of biologically active ketimines containing the donor set have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The i.r. and ¹H-n.m.r. spectra indicate a square planar structure for the complexes in which the ligand is monobasic bidentate with oxygen and azomethine nitrogen coordinating sites. Representative ketimines and their respective metal complexes were found to exhibit antimicrobial properties.Author to whom all correspondence should be directed.     

Palladium(II) complexes ofN-alkyl phenothiazines

Summary Eight square-planar palladium(II) complexes, PdLCl₂ (L=N-alkyl phenothiazine) have been synthesized. Analytical, conductometric, spectral (electronic, i.r. and n.m.r.) and thermal data for the complexes have been discussed.Part of the paper presented at the International Conference The Chemistry of the Platinum Group Metals, Bristol July 20–24th, 1981.     

Palladium(II) and platinum(II) complexes with N-substituted methionines

Summary As an approach to systems containing methionine residues, 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one (HDh, dehydroacetic acid) was treated with L-methionine (MetH) or L-methionine methylester (MetM). By condensation at the acyl group and transfer of the phenolic hydrogen on the nitrogen atom, the related ligands DhMetH and DhMetM, were isolated, and form complexes of formula [MX₂(L)₂](M = Pd or Pt, L = DhMetM, X = Cl, Br or I; L = DhMetH, X = Cl or Br) and [MI₂(DhMetH)] with palladium and platinum dihalides. The reaction of the DhMetK carboxylate with MCl₂ in various media is discussed. Ligands and complexes were characterized by i.r. and n.m.r. (¹H and¹³C) spectroscopy and, in some cases, by thermogravimetric measurements. The ligands behave as monodentate sulphur donors, the 12 complexes showing atrans geometry except for [PtCl₂(DhMetH)₂], which is probably a mixture ofcis andtrans isomers.     

Synthesis and characterization of cyclometallated palladium(II) and platinum(II) complexes with amide-thiolate ligands

The redox reaction of bis(2-benzamidophenyl) disulfide (H₂L-LH₂) with [Pd(PPh₃)₄] in a 1:1 ratio gave mononuclear and dinuclear palladium(II) complexes with 2-benzamidobenzenethiolate (H₂L⁻), [Pd(H₂L-S)₂(PPh₃)₂] (1) and [Pd₂(H₂L-S)₂ (μ-H₂L-S)₂(PPh₃)₂] (2). A similar reaction with [Pt(PPh₃)₄] produced only the corresponding mononuclear platinum(II) complex, [Pt(H₂L-S)₂(PPh₃)₂] (3). Treatment of these complexes with KOH led to the formation of cyclometallated palladium(II) and platinum(II) complexes, [Pd(L-C,N,S)(PPh₃)]⁻ ([4]⁻) and [Pt(L-C,N,S) (PPh₃)]⁻ ([5]⁻). The molecular structures of 2, 3 and [4]⁻ were determined by X-ray crystallography.     

Palladium(II) complexes with primary thioamides

Summary Palladium(II) complexes of thioacetamide, thiooxamide,N ^o,N ^o-dimethylthiooxamide and ethyl thiooxamidate have been prepared and investigated by electronic and i.r. spectroscopy. It is concluded that the ligands always act as monodentate sulphur donors, and that planar [PdL₄]X₂ (X = Cl, Br or ClO₄) compounds are formed. The(PdS) frequencies and the ligand field strengths are enhanced by electron donor groups and lowered by electron withdrawing groups.