Synthesis, multinuclear magnetic resonance and crystal structures of Pt(II) complexes containing amines and bidentate carboxylate ligands

A novel synthetic method for the synthesis of the complexes cis-Pt(amine)₂R(COO)₂ is compared to two other methods involving the use of either barium dicarboxylate or sodium carboxylate. Pt(II) compounds with monodentate and bidentate amines were studied. The reaction involves the use of a silver dicarboxylato complex, which is the intermediate in the new synthetic procedure. The crystal structure of the silver intermediate with the ligand 1,1-cyclobutanedicarboxylate (1,1-CBDCA) was determined by X-ray diffraction. The crystal Ag₂(1,1-CBDCA) has a very interesting 3-D extended structure. The complexes cis-Pt(amine)₂R(COO)₂ were studied in solution by multinuclear (¹H, ¹³C and ¹⁹⁵Pt) magnetic resonance spectroscopy, but the solubilities are very low. D₂O was found to be the best solvent. In ¹⁹⁵Pt NMR, the complexes containing bidentate amines forming five-membered chelates were observed at higher fields than those containing monodentate amines. The resonances of the NH₃ compounds were also found at lower fields than the primary amine complexes. All the dicarboxylato ligands form six-membered chelates except 1,2-CBDCA, whose Pt(II) compounds were observed at lower fields than the others. The crystal structures of Pt(en)(1,1-CBDCA), Pt(Meen)(1,1-CBDCA) and Pt(en)(benzylmalonato) were confirmed by X-ray diffraction methods. Several compounds are disordered. The crystals are stabilized by intermolecular hydrogen bonds between the -NH₂ groups and the carboxylato O atoms.     

Multinuclear NMR study and crystal structures of complexes of the types cis- and trans-Pt(amine)2I2

Complexes of the types cis- and trans-Pt(amine)₂I₂ were studied by spectroscopic methods, especially by multinuclear NMR spectroscopy. In ¹⁹⁵Pt NMR, the cis diiodo compounds with primary amines were observed between −3342 and −3357 ppm in acetone, while the trans compounds were found between −3336 and −3372 ppm. For the secondary amines, the chemical shifts were observed at lower fields. In ¹H NMR, the trans complexes were observed at higher fields than the cis compounds, while in ¹³C NMR, the reverse was observed. The ²J(¹⁹⁵Pt-¹H) and ³J(¹⁹⁵Pt-¹H) coupling constants are larger for the cis compounds (ave. 67 and 45 Hz, respectively) than for the trans isomers (ave. 59 and 38 Hz). In ¹³C NMR, the values of ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) were also found to be larger for the cis complexes (ave. 17 and 39 Hz versus 11 and 28 Hz). There seems to be a slight dependence of the pK_a values of the protonated amines or the proton affinity in the gas phase with the δ(Pt) chemical shifts. The crystal structures of eight diiodo complexes were determined. These compounds are cis-Pt(CH₃NH₂)₂I₂, cis-Pt(n-C₄H₉NH₂)₂I₂, cis-Pt(Et₂NH)₂I₂, trans-Pt(n-C₃H₇NH₂)₂I₂, trans-Pt(iso-C₃H₇NH₂)₂I₂, trans-Pt(n-C₄H₉NH₂)₂I₂, trans-Pt(t-C₄H₉NH₂)₂I₂ and trans-Pt(Me₂NH)₂I₂. The Pt-N bond distances located in trans position to the iodo ligands were compared to those located in trans position to the amines. The Pt-N bond in cis-Pt(Et₂NH)₂I₂ are much longer than the others, probably caused by the steric hindrance of the two very bulky ligands located in cis positions.     

Multinuclear nuclear magnetic resonance and X-ray crystallographic investigation of some mixed ligand alkylisocyanide platinum(II) complexes

Single crystal X-ray diffraction structure determination of tetra-n-butylammonium tricyanomethylisocyanideplatinate(II) (1) show that the complex does not feature stacking of the anions or significant Pt-Pt orbital interactions. The cis-dicyanobismethylisocyanideplatinum(II) (2) and cis-dicyanobisethylisocyanideplatinum(II) (3) complexes do crystallize with the platinum atoms collinear with one another but with a Pt-Pt separation distance on the order of 3.5 Å, which is too great for significant orbital overlap. In each of the complexes studied, the Pt-CNR bond lengths of the isocyanides are shorter than the Pt-CN bond lengths of the cyanide ligands. Additionally, each of these complexes have Pt-CNR bond distances marginally shorter than in the parent complex, [Pt(CNR)₄][BF₄]₂ (5). The shortened Pt-CNR distances in the mixed complexes are consistent with the isocyanide ligand being a stronger π-acid than the cyanide ligand, resulting in a preferred cis configuration of the mixed ligand complexes. In solution, the NMR spectra of these complexes are unusual because they display ¹⁹⁵Pt-¹⁴N and ¹H-¹⁴N coupling with high resolution. The NMR parameters of these complexes are compared with those of and (R = CH₃ or C₂H₅).     

Multinuclear magnetic resonance study of Pt(II) compounds with sulfoxide ligands and crystal structures of complexes of the types [Pt(R2SO)X3] and Pt(R2SO)2Cl2

Pt(II) complexes of the types K[Pt(R₂SO)X₃], NR₄[Pt(R₂SO)X₃] and Pt(R₂SO)₂Cl₂ (where X = Cl or Br) were characterized by multinuclear magnetic resonance spectroscopy (¹⁹⁵Pt, ¹H and ¹³C). In ¹⁹⁵Pt NMR, the chloro ionic compounds have shown signals between −2979 and −3106 ppm, while the cis disubstituted complexes were observed at higher fields, between −3450 and −3546 ppm. The signal of the compound trans-Pt(DPrSO)₂Cl₂ was found at higher field (−3666 ppm) than its cis analogue (−3517 ppm), since π-back-donation is considerably less effective in the trans geometry. In ¹H NMR, a single signal was observed for the sulfoxide in [Pt(DMSO)Cl₃]⁻, but for the other more sterically hindered ligands, two series of resonances were observed for the protons in α and β positions. The coupling constant ³J(¹⁹⁵Pt-¹H) are between 15 and 33 Hz. The ¹³C NMR results were interpreted in relation to the concept of inversed polarization of the π sulfoxide bond. The ²J(¹⁹⁵Pt-¹³C) values vary between 35 and 66 Hz, while a few ³J(¹⁹⁵Pt-¹³C) couplings were observed (13-26 Hz). The crystal structures of five monosubstituted ionic compounds N(n-Bu)₄[Pt(TMSO)Cl₃], N(Me)₄[Pt(DPrSO)Cl₃], K[Pt(EMSO)Cl₃], K[Pt(TMSO)Br₃] · H₂O and N(Et)₄[Pt(DPrSO)Br₃] and one disubstituted complex cis-Pt(DBuSO)₂Cl₂ were determined. The trans influence of the different ligands is discussed.     

Study of Pt(II)-cyclic amines complexes of the types cis- and trans-Pt(amine)2I2 and cis- and trans-Pt(amine)2(NO3)2 and their aqueous products by

Complexes of the types cis- and trans-Pt(amine)₂I₂ containing cyclic amines were synthesized and studied mainly by IR and multinuclear NMR spectroscopies. The compounds were converted to cis- and trans-Pt(amine)₂(NO₃)₂, which were also investigated. The hydrolysis and the aquation reactions of the latter compounds were then studied in D₂O in different conditions of pH. In acidic medium, the aqueous product is [Pt(amine)₂(D₂O)₂]²⁺ and for a few amines, [Pt(amine)₂(D₂O)(NO₃)]⁺ was detected. In basic pH, the main product is Pt(amine)₂(OD)₂ and Pt(amine)₂(OD)(NO₃) was detected for several compounds. In neutral pH, the cis isomers form between two and four species in fresh solutions. The most shielded species in ¹⁹⁵Pt NMR is the monoaqua-monohydroxo complex cis-[Pt(amine)₂(D₂O)(OD)]⁺ and the less shielded compound is the dihydroxo-bridged dimer [Pt(amine)₂(μ-OD)₂Pt(amine)₂]²⁺, which were observed for all the compounds. For a few amines, the monohydroxo-bridged dimer [Pt(D₂O)(amine)₂(μ-OD)Pt(OD)(amine)₂]²⁺ was detected and for cyclohexylamine, a fourth signal was assigned to a cyclic hydroxo-bridged trimer [(Pt(amine)₂(μ-OD))₃]³⁺. ¹⁹⁵Pt NMR spectroscopy has shown that the concentration of the monomer decreases with time, while the concentration of the dimers increases. Only one product was observed for the trans isomers in neutral pH. The signal was assigned to the monoaqua-monohydroxo species trans-[Pt(amine)₂(D₂O)(OD)]⁺. The ¹³C and ¹H NMR spectra of most of the complexes were measured. All the coupling constants ^2,3J(¹⁹⁵Pt-¹H) and ^2,3J(¹⁹⁵Pt-¹³C) are larger in the cis compounds than in the trans isomers.     

Synthesis and multinuclear magnetic resonance spectroscopy of the novel ionic Pt(II) mixed-ligands complexes cis- and trans-[Pt(amine)2(pyrimidine)2](NO3)2

Novel ionic mixed-ligands complexes of the types cis- and trans-[Pt(amine)₂(pm)₂](NO₃)₂ (where pm = pyrimidine) were synthesized and studied in the solid state by IR spectroscopy and in aqueous solution by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The results of the solution NMR characterization have shown that the isolated compounds are pure. In ¹⁹⁵Pt NMR, the cis RNH₂ complexes were observed at slightly lower fields (ave. −2441 ppm) than the equivalent trans analogues (ave. −2448 ppm). For Me₂NH, the difference between the two isomers is larger (29 ppm). The complexes are observed at lower fields (difference of 100 ppm) than the corresponding [Pt(amine)₄]²⁺ complexes, which might indicate the presence of π-backdonation in the Pt-pm bond. In ¹H NMR, the coupling constants ³J(¹⁹⁵Pt-¹H_amine) are larger in the cis compounds (38-48 Hz) than in the trans analogues (30-36 Hz). The ³J(¹⁹⁵Pt-¹H_pm) values are also larger for the cis isomers. In ¹³C NMR spectroscopy, the coupling constants ³J(¹⁹⁵Pt-¹³C_amine) are 36 Hz (ave.) for the cis complexes and 26 Hz (ave.) for the trans isomers, while the ²J(¹⁹⁵Pt-¹³C_amine) are 18 Hz (cis) and 14 Hz (trans), respectively. The ³J(¹⁹⁵Pt-¹³C_5(pm)) values are 36 Hz (cis) and 28 Hz (trans). A few ²J(¹⁹⁵Pt-¹³C_pm) couplings were observed (7-10 Hz).     

Synthesis, spectroscopic properties and structural characterisation of Pd(II) and Pt(II) complexes with 1,3,5-pyrazole derived ligands. Rotation around the metal-N bond

Reactions of ligands 1-ethyl-5-methyl-3-phenyl-1H-pyrazole (L¹) and 5-methyl-1-octyl-3-phenyl-1H-pyrazole (L²) with [PdCl₂(CH₃CN)₂ and K₂PtCl₄ gave complexes trans-[MCl₂(L)₂] (L = L¹, L²). The new complexes were characterised by elemental analyses, conductivity measurements, infrared, ¹H and ¹³C{¹H} NMR spectroscopies and X-ray diffraction. The NMR study of the complex [PdCl₂(L¹)₂], in CDCl₃ solution, is consistent with a very slow rotation of ligands around the Pd-N bond, so that two conformational isomers can be observed in solution (syn and anti). Different behaviour is observed for complexes [PdCl₂(L²)₂] and [PtCl₂(L)₂] (L = L¹, L²), which present an isomer in solution at room temperature (anti). The crystal structure of [PdCl₂(L¹)₂] complex is described, where the Pd(II) presents a square planar geometry with the ligands coordinated in a trans disposition.     

Multiple coordination modes of hemilabile 3-dimethylaminopropyl chalcogenolates in platinum(II) complexes: Synthesis, spectroscopy and structures

The reactions of N,N-dimethylaminopropyl chalcogenolates with platinum(II) compounds have been carried out and complexes of the types [PtCl(ECH₂CH₂CH₂NMe₂)]₂ (1) (E = S (1a) and Se (1b)), [Pt(ECH₂CH₂CH₂NMe₂)₂]_n (2) (E = S (2a) and Se (2b)), [(PtCl₂)₂{(Me₂NCH₂CH₂CH₂E)₂}]_n (3), [PtX(SeCH₂CH₂CH₂NMe₂)]₂ (4) (X = SePh (4a) and OAc (4b)) and [PtCl(ECH₂CH₂CH₂NMe₂)(PR₃)]_n (5) (E = S, Se, Te) have been isolated. These complexes have been characterized by elemental analysis, IR, UV-Vis, NMR (¹H, ¹³C, ³¹P, ⁷⁷Se, ¹⁹⁵Pt) spectroscopy and FAB mass spectral data. The structures of [PtCl(SeCH₂CH₂CH₂NMe₂)]₂ (1b) and [PtCl(SCH₂CH₂CH₂NMe₂)(PPr₃)]₂ (5a) have been established by single crystal X-ray diffraction data. Both the molecules have dimeric structures. In 1b, two platinum atoms are held together by symmetrically bridging Se atoms of the chelating selenolate groups. In 5a, two thiolates form a four-membered Pt₂S₂ bridge with dangling NMe₂ groups.     

Synthesis of new platinum(II) complexes containing hybrid thioether-pyrazole ligands: Structural analysis by H and C{H} NMR spectroscopy and X-ray crystal structures

Treatment of the ligands 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo), 1,9-bis(3,5-dimethyl-1-pyrazolyl)-3,7-dithianonane (bddn), and 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (bddh) with several platinum starting materials as K₂PtCl₄, PtCl₂, [PtCl₂(CH₃CN)₂] and [PtCl₂(PhCN)₂] was developed under different conditions. The reactions did not yield pure products. The ratio of the NSSN, NS, SS, NN, and 2NS isomers has been calculated through NMR experiments. Treatment of the mixtures of complexes with NaBPh₄ affords [Pt(NSSN)](BPh₄)₂ (NSSN = bddo, bddn). These Pt(II) complexes have been characterised by elemental analyses, conductivity measurements, IR and ¹H and ¹³C NMR spectroscopy. The X-ray structures of the complexes [Pt(NSSN)](BPh₄)₂ (NSSN = bddo, bddn) have also been determined. In these complexes, the metal atom is tetracoordinated by the two azine nitrogen atoms of the pyrazole rings and two thioether sulfur atoms. When the [Pt(NSSN)](BPh₄)₂ (NSSN = bddo, bddn) complexes were heated under reflux in a solution of Et₄NBr in CH₂Cl₂/CH₃OH (1:1), a mixture of isomers was obtained.     

Synthesis and structures of platinum(II) complexes with 5-ferrocenylpyrimidine

Reaction of platinum(II) salts with 5-ferrocenylpyrimidine (FcPM) afforded cis-[Pt(NH₃)₂(FcPM)₂](PF₆)₂ (1), trans-[Pt(NH₃)₂(FcPM)₂](PF₆)₂ (2), cis-[PtCl₂(FcPM)₂] (3), and cis-[PtCl₂(DMSO)(FcPM)] (4): their spectroscopic and electrochemical properties were investigated. Complexes 1 and 2 were structurally characterized by X-ray crystallography.     

Crystal structures of Pt(II) and Pd(II) complexes with the free radical 4-aminoTEMPO

Pt(II) and Pd(II) compounds containing the free radical 4-aminoTEMPO (4amTEMPO) were synthesized and characterised by X-ray diffraction methods. The disubstituted complexes cis- and trans-Pt(4amTEMPO)₂I₂ were studied. The trans isomer was prepared from the isomerisation of the cis analogue. The two Pd(II) compounds trans-Pd(4amTEMPO)₂X₂ (X = Cl and I) were also characterised by crystallographic methods. A mixed-ligand complex cis-Pt(DMSO)(4amTEMPO)Cl₂ was synthesized from the isomerisation of the trans isomer in hot water. Its crystal structure was also determined. In all the complexes, the 4amTEMPO ligand is bonded to the metal through the -NH₂ group, since the nitroxide O atom is not a good donor atom for the soft Pt(II) and Pd(II) metals. The conformation of the 4-aminoTEMPO ligand was compared to those of the few reported structures in the literature.     

Palladium(II) and platinum(II) monoselenocarboxylates: Synthesis, spectroscopy, structure and their use as molecular precursors for metal selenides

Treatment of MCl₂(P^∩P) or MCl₂(PⁿPr₃)₂ with two equivalents of ArCOSeK readily yields cis-[M(SeCOAr)₂(P^∩P)] and trans-[M(SeCOAr)₂(PⁿPr₃)₂], respectively (M = Pd or Pt; Ar = Ph or 4-MeC₆H₄; P^∩P = dppm, dppe, dppp). The reaction of Pd(SeCOAr)₂(dppe) with PdCl₂(dppe) in the presence of NaBPh₄ in methanol gave a tri-nuclear ionic complex, [Pd₃(μ₃-Se)₂(dppe)₃][BPh₄]₂. These complexes were characterized by UV-Vis, IR and NMR spectroscopy. The complex [Pt(SeCOPh)₂(dppp)] has been structurally characterized by X-ray crystallography. The coordination environment around square planar platinum atom is defined by chelating dppp ligand and two unidentate selenocarboxylates bonded through selenium atoms. Pyrolysis of [Pd(SeCOAr)₂(PⁿPr₃)₂] either in tri-n-butylphosphate (TBP) (at 200 °C) or in the solid state (furnace heating at 350 °C) gave Pd₁₇Se₁₅.     

Synthesis, X-ray crystal structure and NMR characterisation of mononuclear Pd(II) and Pt(II) complexes of didentate ligands with NN′-donor set

Two new 3,5-dimethylpyrazolic derived ligands that are N1-substituted by diamine chains, 1-[2-(diethylamino)ethyl]-3,5-dimethylpyrazole (L1) and 1-[2-(dioctylamino)ethyl]-3,5-dimethylpyrazole (L2) were synthesised. Reaction of the ligands, L1 and L2, with [MCl₂(CH₃CN)₂] yielded [MCl₂(L)] (M = Pd(II), Pt(II)) complexes. These complexes were characterised by elemental analyses, conductivity measurements, IR, ¹H, ¹³C{¹H} and ¹⁹⁵Pt{¹H} NMR spectroscopies. The crystal structure of [PdCl₂(L1)] was determined by single-crystal X-ray diffraction methods. The structure consists of mononuclear units. The Pd(II) atom is coordinated by a pyrazolic nitrogen, an amine nitrogen and two chlorine atoms in a cis disposition. In this structure, C-H?Cl, C-H?H-C and C-H?C-H intermolecular interactions have been identified.     

Synthesis and spectroscopy of diethyl (pyridinylmethyl)phosphates and their palladium (II) complexes: X-ray crystal structures of Pd(II) complexes

The synthesis of diethyl (pyridin-2-, -3-, -4-ylmethyl)phosphate (2-pmOpe, 3-pmOpe, 4-pmOpe) ligands and their palladium (II) complexes of general formula trans-[PdCl₂L₂] (L = 2-pmOpe, 3-pmOpe,4-pmOpe) has been described. Pyridine phosphate derivatives were synthesized via the condensation of phosphorochloridic acid diethyl ester with an appropriate pyridinylmethanol in the presence of triethylamine. The compounds have been identified and characterized by IR, far-IR, ¹H NMR, ³¹P NMR, ³¹P CP-MAS NMR and elemental analyses. The crystal and molecular structures of palladium (II) complexes, i.e., [PdCl₂(2-pmOpe)₂] and [PdCl₂(4-pmOpe)₂] determined by the X-ray diffraction method, are presented. In both structures, Pd(II) ions are four-coordinated by two chlorine atoms and two pyridine nitrogen atoms. The geometry of complexes is square-planar and adopt a trans configuration, which is consistent with preparation method.     

X-ray structure and magnetic properties of dinuclear and polymer iron(II) complexes

Five new octahedral iron(II) complexes [FeL2(4-dpa)]_n(EtOH) (1), [FeL2(bipy)]_n(DMF) (2), [FeL1(bpee)]_n (3), [Fe₂L3(1-meim)₄](1-meim)₄ (4) and [FeL1(DMAP)₂] (5), with L1 and L2 being tetradentate coordinating Schiff base like ligands (L1 = (E,E)-[{diethyl-2,2′-[1,2-phenylenebis(iminomethylidyne)]bis[3-oxobutanato](2-)-N,N′,O³,O³′}, L2 = (3,3′)-[{1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentane-dionato)(2-)-N,N′,O²,O²′}) and L3 being a octadentate dinucleating coordinating Schiff base like ligand ({tetraethyl-(E,E,E,E)-2,2′,2′′,2′′′-[1,2,4,5-phenylentetra(iminomethylidine)]tetra[3-oxobutanoato](2-)-N,N′,N′′,N′′′,O³,O³′,O³′′,O³′′′}); 4-dpa = di(4-picolyl)-amine, bipy = 4,4′-bipyridine, bpee = trans-1,2-bis(4-pyridyl)ethylene, 1-meim = 1-methylimidazole and DMAP = 4-dimethylaminopyridine, have been synthesized and characterised using X-ray structure analysis and T-dependent susceptibility measurements. Both methods indicate that all iron(II) centres are in the paramagnetic high-spin state over the whole temperature range investigated. The O-Fe-O angle, the so called bit of the equatorial ligand, is with an average of 111° in the region typical for high-spin iron(II) complexes of this ligand type. In the case of compound 1 an infinite two-dimensional hydrogen bond network can be found, for the compounds 2-4 no hydrogen bond interactions are observed between the complex molecules. A comparison of the curve progression obtained from the magnetic measurements of the mononuclear complex 5 and the polymeric complexes 1-3 leads to the conclusion that no magnetic interactions are mediated over the bridging axial ligands. For the dinuclear complex 4 weak antiferromagnetic interactions between the two iron centres are found.     

Synthesis and characterisation of new N1-alkyl-3,5-dipyridylpyrazole derived ligands. Study of their reactivity with Pd(II) and Pt(II)

Two new pyrazole-derived ligands, 1-ethyl-3,5-bis(2-pyridyl)pyrazole (L¹) and 1-octyl-3,5-bis(2-pyridyl)pyrazole (L²), both containing alkyl groups at position 1 were prepared by reaction between 3,5-bis(2-pyridyl) pyrazole and the appropriate bromoalkane in toluene using sodium ethoxide as base.The reaction between L¹, L² and [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) resulted in the formation complexes of formula [MCl₂(L)] (M = Pd(II), L = L¹ (1); M = Pd(II), L = L² (2); M = Pt(II), L = L¹ (3); M = Pt(II), L = L² (4)). These complexes were characterised by elemental analyses, conductivity measurements, infrared, ¹H, ¹³C{¹H} NMR and HMQC spectroscopies. The X-ray structure of the complex [PtCl₂(L²)] (4) was determined. In this complex, Npyridine and Npyrazole donor atoms coordinate the ligand to the metal, which complete its coordination with two chloro ligands in a cis disposition.     

Synthesis and X-ray crystal structures of dinuclear silver(I) complexes of heteroaryl thioethers

The X-ray crystal structures of four complexes, obtained by reaction of silver nitrate with four different heteroaryl thioethers, are described. In these compounds the ligands act as dinuclear bridges between silver atoms, with coordination exclusively through the nitrogen donor atoms. All ligands form dinuclear complexes, either as discrete species or as higher aggregates involving additional nitrate bridges. π–π Stacking interactions provide extra stabilisation in some of the structures.     

Chlorido-bridged polymeric and dinuclear copper(II) complexes with tridentate Schiff base: Synthesis, crystal structure and magnetic properties

Two copper(II) complexes, [Cu(qsal)Cl](DMF) (1) and [Cu₂(qsalBr)₂Cl₂](DMF) (2), with tridentate Schiff base ligands, 8-(salicylideneamino)quinoline (Hqsal) and 8-(5-bromo-salicylideneamino)quinoline (HqsalBr), respectively, were synthesised and structurally characterized. Each copper(II) ion in the two complexes is in a distorted square pyramidal N₂OCl₂ environment. Complex 1 exists as a polymeric species via equatorial-apical chloride bridges, whereas 2 is a di-chlorido-bridged dinuclear complex, where each bridging chloride simultaneously occupies an in-plane coordination site on one copper(II) ion and an apical site on the other copper(II) ion. Variable-temperature magnetical susceptibility measurements on the two complexes in the temperature range 2-300 K indicate the occurrence of intrachain ferromagnetic (J = +6.58 cm⁻¹) and intramolecular antiferromagnetical (J = −6.91 cm⁻¹) interactions.     

Synthesis of new platinum(II) compounds with several bidentate and tridentate nitrogen-donor ligands. Structural analyses by H, C{H} and Pt{H} NMR spectroscopy and X-ray crystal structure

The reaction of the N-alkylaminopyrazole (NN′) ligands 1-[2-(ethylamino)ethyl]-3,5-dimethylpyrazole (deae), 1-[2-(tert-butylamino)ethyl]-3,5-dimethylpyrazole (deat), or (NN′N) ligands bis[(3,5-dimethylpyrazolyl)methyl]ethylamine (bdmae) and bis[(3,5-dimethylpyrazolyl)ethyl]ethylamine (ddae) with [PtCl₂(CH₃CN)₂] affords a series of square-planar Pt(II) complexes with formula [PtCl₂(NN′)] (NN′ = deae (1); deat (2)), [PtCl₂(bdmae)] (3), or [PtCl(ddae)]Cl (4). Treatment of complex 4 in the presence of AgBF₄ in CH₂Cl₂/methanol (3:1) gives [PtCl(ddae)](BF₄) (5). These Pt(II) complexes have been characterised by elemental analyses, conductivity measurements and IR, ¹H, ¹³C{¹H}, and ¹⁹⁵Pt{¹H} NMR spectroscopies. The ¹H NMR spectroscopic studies of the complexes prove the rigid conformation of the ligands when they are complexed. The solid-state structure of complex 1 was determined by single crystal X-ray diffraction methods. The deae ligand is coordinated through the N_pz and N_amino atoms to the metallic centre, which completes its coordination with two chlorine atoms in cis disposition.     

Supramolecular networks of dinuclear copper(II): Synthesis, crystal structure and magnetic study

The complexes [Cu₂(ox)(phen)₂(H₂O)₂](NO₃)₂ (1), [Cu₂(sq)(pmdien)₂(H₂O)₂](ClO₄)₂ (2) and {[Cu₃(pdc)₃(4,4′-bipy)_1.5(H₂O)_2.25] · 2.5(H₂O)}_n (3) [phen = 1,10-phenanthroline; pmdien = N,N,N′,N′,N″-pentamethyldiethylenetriamine; 4,4′-bipy = 4,4′-bipyridine; ox = oxalate dianion; sq = squarate dianion and pdc = pyridine 2,6-dicarboxylate] have been synthesized and characterized by X-ray single crystal structure determination, low temperature magnetic measurement and thermal study. Structure determination reveals that 1 and 2 are dinuclear copper(II) complexes bridged by oxalate and squarate dianions, respectively, while 3 is a hexanuclear species formed by three Cu(pdc)(H₂O)-(4,4′-bipy)-Cu(pdc)(H₂O) fragments, connected through long Cu-O(pdc) bonds in a centrosymmetric arrangement. In complex 1 H-bonds occurring between the coordinated water molecules and lattice nitrate anions result in eight-membered ring clusters with the concomitant formation of 1D supramolecular chain. The adjacent chains undergo π-π stacking forming a 2D architecture. In the crystal of 3 an extensive H-bonding scheme gives rise to a 3D supramolecular network. Low temperature magnetic study shows a strong antiferromagnetic coupling in 1 (J = −288 ± 2 cm⁻¹, g = 2.21 ± 0.01, R = 1.2 × 10⁻⁶); and a very weak interaction in 2 and 3, the best-fit parameters being: J = −0.21 cm⁻¹, g = 2.12 ± 0.01, R = 1.1 × 10⁻⁶ (2) and J = −1.34 cm⁻¹ ± 0.1, g = 2.14 ± 0.01, R = 1.2 × 10⁻⁶ (3) (R defines as .