Reactions of zero-valent platinum complexes with some diacetylenes

The complexes[Pt(C₂H₄)L₂] (L = PPh₃ or PMePh₂) react with 1,4-diphenyl-buta-1,3-diyne to give, successively, mono- and di-platinum compounds [Pt-(PhC₄Ph)L₂] and [Pt₂(PhC₄Ph)L₄]. Hexa-2,4-diyne and [Pt(C₂H₄)(PPh₃)₂] react similarly. In the di-platinum compounds both acetylenic linkages are η²-bonded to platinum atoms, as also occurs in the complex [Pt₂{HC₂(CH₂)₂C₂H}(PPh₃)₄] obtained from hexa-1,5-diyne. Reaction of [Pt₃(CN-t-Bu)₆ with 1,4-diphenylbuta-1,3-diyne and hexa-2,4-diyne affords di-platinum complexes, shown by spectroscopic studies to have structures containing diplatinacyclobutene rings.     

Nickel(II)-triphenylphosphine complexes of ONS and ONN chelating 2-hydroxyacetophenone thiosemicarbazones

The complexes [Ni(L¹)(PPh₃)] (1) and [Ni(L²)(PPh₃)]·HCl (2) were synthesized by the reaction of [Ni(PPh₃)Cl₂] and dibasic 2-hydroxyacetophenone-S-R-4-R¹-thiosemicarbazones (R/R¹: H/CH₃, L¹H₂; CH₃/H, L²H₂). The ligands and the complexes were characterized using elemental analysis, IR and ¹H NMR spectra. In both complexes, the thiosemicarbazone ligands coordinate to nickel(II) by giving two protons. Complex 1 is formed through the phenolate oxygen, azomethine nitrogen and sulfur atoms of L¹ and the P atom of a triphenylphosphine ligand. In complex 2, L² is functional through an ONN donor set, containing a thioamide nitrogen instead of a sulfur atom. X-ray analysis indicated distorted square planar structures for the complexes, and the nickel atoms lie slightly above the planes structured by the donor atoms. In the crystal forms of 1 and 2, some phenyl ring protons of the phosphine ligand give intramolecular hydrogen bonds with the donor atoms of the thiosemicarbazone moiety, namely the phenolate oxygen (in complexes 1 and 2) and N⁴ nitrogen (in complex 2).     

Oxidative addition - reductive elimination sequences in the photochemistry of some bis(phosphine)platinum complexes

The photolysis of [L₂Pt(C₂H₄)] (L = PPh₃, P(p-C₆H₄CH₃)₃ complexes in halocarbon solvents (CH₂Cl₂, CH₂Br₂) gives C₂H₄ and the coordinatively unsaturated species [L₂Pt]. Photolysis of platinum metallacycles [L₂Pt(CH₂)₄] (L = PPh₃, P(n-Bu)₃) generates alkanes, alkenes and [L₂Pt]. The [L₂Pt] centers are very reactive, and under prolonged photolysis undergo oxidative addition of CH₂Cl₂ forming the trans-[L₂Pt(CH₂Cl)Cl] complexes. Under appropriately controlled conditions the trans complexes isomerize to cis species before bimolecular C₂H₄ elimination occurs and [L₂PtCl₂] is formed as the final product. The oxidative addition-reductive elimination mechanism is discussed on the basis of spin-trapping experiments, quantum yield values, and the sensitivity to radical inhibitors and to solvents.     

Palladium(II) complexes of benzaldehyde and 2-hydroxybenzaldehyde-4-H/phenyl-<Emphasis Type="Italic">S</Emphasis>-ethyl/allyl-thiosemicarbazones

The thiosemicarbazone derivatives R₁-C₆H₄-CH=N-N=(C-S-R₂)-NH-R₃ [R₁ = H, OH; R₂ = H, Ph; R₃ = C₂H₅, C₃H₅] were prepared by a modified general method. The Pd(II) complexes of the thiosemicarbazone ligands L^I–VI were isolated in the compositions [Pd(L)Cl₂], [Pd(L)Cl] and [Pd(L)₂]. The 1: 1 and 1: 2 metal complexes have non-ionic character, and the compounds were characterized by analytical data and infrared and proton resonance spectroscopy. The cis-trans and syn-anti isomers of the thiosemicarbazones were determined by means of ¹H NMR, and the coordination behavior of the polydentate thiosemicarbazone ligands towards the palladium ion were discussed.     

Synthesis,structure and electrochemical properties of some thiosemicarbazone complexes of iridium

Reaction of thiosemicarbazones of salicylaldehyde and 2-hydroxyacetophenone (H₂L¹ and H₂L²) with [Ir(PPh₃)₃Cl] affords complexes of type [Ir(PPh₃)₂(L)(H)] (L = L¹ or L²) in ethanol. A similar reaction carried out in toluene affords the [Ir(PPh₃)₂(L)(H)] complexes along with complexes of type [Ir(PPh₃)₂(L)Cl], where a chloride is coordinated to iridium instead of the hydride. The structure of the [Ir(PPh₃)₂(L²)(H)] and [Ir(PPh₃)₂(L²)Cl] complexes has been determined by X-ray crystallography. Crystal data for [Ir(PPh₃)₂(L²)(H)]: space group, P2₁/c; crystal system, monoclinic; a=12.110(2) Å, b=17.983(4) Å, c=18.437(4) Å, β=103.42(3)°, Z=4; R ₁=0.0591, wR ₂=0.1107. Crystal data for [Ir(PPh₃)₂(L²)Cl]: space group, P2₁/c; crystal system, monoclinic; a=17.9374(11) Å, b=19.2570(10) Å, c=24.9135(16) Å, β=108.145(5)°, Z=4; R ₁=0.0463, wR ₂=0.0901. In all the complexes the thiosemicarbazones are coordinated to the metal center as dianionic tridentate O, N, S-donors and the two triphenylphosphines are trans. The complexes are diamagnetic (low-spin d? ⁶, S=0) and show intense MLCT transitions in the visible region. Cyclic voltammetry on all the [Ir(PPh₃)₂(L)(H)] and [Ir(PPh₃)₂(L)Cl] complexes shows a quasi-reversible Ir(III)–Ir(IV) oxidation within 0.55–0.78 V vs. SCE followed by an irreversible oxidation of the thiosemicarbazone within 0.91–1.27 V vs. SCE. An irreversible reduction of the thiosemicarbazone is also observed within ?1.10 to ?1.23 V vs. SCE.     

Amino acid complexes of ruthenium: synthesis, characterization and cyclic voltammetric studies

Reaction of α-amino acids (HL) with [Ru(PPh₃)₃Cl₂] in the presence of a base afforded a family of complexes of type [Ru(PPh₃)₂(L)₂]. These complexes are diamagnetic (low-spin d⁶, S=0) and show ligand-field transitions in the visible region. ¹H and ³¹P NMR spectra of the complexes indicate the presence of C₂ symmetry. Cyclic voltammetry on the [Ru(PPh₃)₂(L)₂] complexes show a reversible ruthenium(II)–ruthenium(III) oxidation in the range 0.30–0.42 V vs. SCE. An irreversible ruthenium(III)–ruthenium(IV) oxidation is also displayed by two complexes near 1.5 V vs. SCE.     

Thiosemicarbazone complexes of the platinum metals. A story of variable coordination modes

Salicylaldehyde thiosemicarbazone (H₂saltsc) reacts with [M(PPh₃)₃X₂] (M = Ru, Os; X = Cl, Br) to afford complexes of type [M(PPh₃)₂(Hsaltsc)₂], in which the salicylaldehyde thiosemicarbazone ligand is coordinated to the metal as a bidentate N,S-donor forming a four-membered chelate ring. Reaction of benzaldehyde thiosemicarbazones (Hbztsc-R) with [M(PPh₃)₃X₂] also affords complexes of similar type, viz. [M(PPh₃)₂(bztsc-R)₂], in which the benzaldehyde thiosemicarbazones have also been found to coordinate the metal as a bidentate N,S-donor forming a four-membered chelate ring as before. Reaction of the Hbztsc-R ligands has also been carried out with [M(bpy)₂X₂] (M = Ru, Os; X = Cl, Br), which has afforded complexes of type [M(bpy)₂(bztsc-R)]⁺, which have been isolated as perchlorate salts. Coordination mode of bztsc-R has been found to be the same as before. Structure of the Hbztsc-OMe ligand has been determined and some molecular modelling studies have been carried out determine the reason for the observed mode of coordination. Reaction of acetone thiosemicarbazone (Hactsc) has then been carried out with [M(bpy)₂X₂] to afford the [M(bpy)₂(actsc)]ClO₄ complexes, in which the actsc ligand coordinates the metal as a bidentate N,S-donorformingafive-membered chelate ring. Reaction of H₂saltsc has been carried out with [Ru(bpy)₂Cl₂] to prepare the [Ru(bpy)₂(Hsaltsc)]ClO₄ complex, which has then been reacted with one equivalent of nickel perchlorate to afford an octanuclear complex of type [Ru(bpy)₂(saltsc-H)₄Ni₄](ClO₄)₄.     

Nickel(II) complexes of ONS and ONN chelating thiosemicarbazones with triphenylphosphine co-ligands

Reactions of 5-bromo-2-hydroxy-benzaldehyde-S-R-4-R¹-thiosemicarbazones, [R, R¹ = H,H (L¹); CH₃, H (L²); H, C₆H₅ (L³); CH₃, C₆H₅ (L⁴)] with [Ni(PPh₃)₂Cl₂] in 1:1 molar ratio yielded complexes of general formula [Ni(L)(PPh₃)]. While the complexes of L¹ and L³ involve the ONS donor set of the thiosemicarbazone, the L² complexes utilize the ONN set. The reaction of L⁴ and the nickel salt gave the L³ complex by loss of the CH₃ group from the sulphur. The complexes were characterized by physico-chemical and spectroscopic methods. The structures of the L¹ and L² complexes have been determined by single crystal X-ray diffraction and a new coordination mode (ONN) of salicylaldehyde thiosemicarbazones has been identified. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis and characterization of transition metal complexes of a new bidentate ligand {2-(diphenylphosphino)ethyl}benzylamine

A new bidentate ligand {2-(diphenylphosphino)ethyl}benzylamine(DPEBA) was synthesized and characterized based on the IR, mass and ¹H, ¹³C and ³¹P NMR spectra. Various complexes of platinum group metal ions and Ni(II) and Co(II) ions with the ligand were synthesized. Reaction of RuCl₂(PPh₃)₃ or RuCl₂(Me₂SO)₄ with the ligand DPEBA, resulted in formation of a penta-coordinate, Ru(II) species of the composition [RuCl(DPEBA)₂]Cl. Carbonylation of [RuCl(DPEBA)₂]Cl gave an octahedral carbonyl complex of the type [RuCl(CO)(DPEBA)₂]Cl. The reaction of RuCl₃·3H₂O or RuCl₃(AsPh₃)₂MeOH with a twofold excess of the ligand gave an octahedral Ru(III) cationic species [Ru(DPEBA)₂Cl₂]Cl. Carbonylation of the Ru(III) complex gave rise to a carbonyl complex [RuCl(CO)(DPEBA)₂]Cl₂. The ligand DPEBA reacts with cobalt(II) chloride in methanol to give the 1 : 1 complex [Co(DPEBA)Cl₂]. A series of Rh(I) complexes [Rh(DPEBA)₂Cl], [ RhCl(CO)(DPEBA)] and [Rh(DPEBA)₂]Cl were synthesized by the reaction of DPEBA with RhCl(PPh₃)₃, RhCl(CO)(PPh₃)₂ and [Rh(COD)Cl]₂, respectively. Reaction of [Ir(COD)Cl]₂ and IrCl(CO)(PPh₃)₂ with the ligand DPEBA, gave the square-planar complexes [Ir(DPBA)₂]Cl and [Ir(DPEBA)(CO)Cl], respectively. Octahedral cationic complexes of the type [M(DPEBA)₂Cl₂]Cl (M = Rh(III), Ir(III)) were synthesized by the reaction of the ligand DPEBA and rhodium and iridium trichlorides. Reaction of NiCl₂·6H₂O with DPEBA in 1 : 2 molar equivalents, in boiling butanol gave an octahedral neutral complex [Ni(DPEBA)₂Cl₂] which readily rearranges to the square-planar complex [Ni(DPEBA)₂]Cl₂ in methanol. Reaction of Pd(II) and Pt(II) chlorides with DPEBA gave square-planar, cationic complexes of the type [M(DPEBA)₂Cl]Cl (M = Pd, Pt). All the complexes were characterized on the basis of their analytical and spectral data.     

Chemistry of ruthenium in N2P2X2 (X = Cl, Br) coordination sphere: Synthesis, characterization and reactivities

Reaction of 2-(phenylazo)pyridine (pap) with [Ru(PPh₃)₃X₂] (X = Cl, Br) in dichloromethane solution affords [Ru(PPh₃)₂(pap)X₂]. These diamagnetic complexes exhibit a weakdd transition and two intense MLCT transitions in the visible region. In dichloromethane solution they display a one-electron reduction of pap near − 0.90 V vs SCE and a reversible ruthenium(II)-ruthenium(III) oxidation near 0.70 V vs SCE. The [Ru^III(PPh₃)₂(pap)Cl₂]⁺ complex cation, generated by coulometric oxidation of [Ru(PPh₃)₂(pap)Cl₂], shows two intense LMCT transitions in the visible region. It oxidizes N,N-dimethylaniline and [Ru^II(bpy)₂Cl₂] (bpy = 2,2′-bipyridine) to produce N,N,N′,N′-tetramethylbenzidine and [Ru^III(bpy)₂Cl₂]⁺ respectively. Reaction of [Ru(PPh₃)₂(pap)X₂] with Ag⁺ in ethanol produces [Ru(PPh₃)₂(pap)(EtOH)₂]²⁺ which upon further reaction with L (L = pap, bpy, acetylacetonate ion(acac⁻) and oxalate ion (ox²⁻)) gives complexes of type [Ru(PPh₃)₂(pap)(L)]ⁿ⁺ (n = 0, 1, 2). All these diamagnetic complexes show a weakdd transition and several intense MLCT transitions in the visible region. The ruthenium(II)-ruthenium(III) oxidation potential decreases in the order (of L): pap > bpy > acac⁻ > ox²⁻. Reductions of the coordinated pap and bpy are also observed.     

Synthesis and characterization of mononuclear palladium(II) and platinum(II), dinuclear palladium(I) and platinum(I), and heterobimetallic (Pt-Hg or Pt-Ag) complexes containing 1,1-bis-(diphenylphosphino)ethane as ligand

Summary The complex [Pd(dpmMe)₂]Cl₂ [dpmMe = 1,1-bis-(diphenylphosphino) ethane] was prepared from [PdCl₂-(PhCN)₂], whilst [Pd₂X₂(-dpmMe)₂] complexes were prepared from [PdCl₂PhCN₂] and [Pd(PPh₃)₄] (X = Cl), [PdBr( ³-C₃H₅)]₂ (X = Br), or [Pd₂Cl₂(-dpmMe)₂] (X = I). Reaction of [Pd₂Cl₂(-dpmMe)₂] with MeO₂C-C523-01CCO₂Me(L) gave the A-frame complex [PdCl₂(-L) (-dpmMe)₂]. The complexes [PtCl₂(dpmMe)] and [Pt(dpmMe)₂]Cl₂ were prepared from [PtCl₂(Bu ^t CN)₂]. Treatment of either [PtCl₂(dpmMe)] with PhC523-02CLi or [Pt(dpmMe)₂]Cl₂ with MeONa gave [Pt(Ph₂PCMe· PPh₂)₂]. Reaction of [PtCl₂(Bu ^t CN)₂] with [Pt(PPh₃)₄] and dpmMe gave a mixture of [Pt₂Cl₂(-dpmMe)₂] and [PtCl₂(dpmMe)]. The heterobimetallic complexes [Pt(C523-03CPh)₂ (-dpmMe)₂MX] (MX = HgCl₂ or AgCl) were made from the reaction of [Pt(dpmMe)₂]Cl₂ with Hg(C523-04CPh)₂ or Ag(C523-05CPh), respectively. Reaction of the Pt-Hg complex with Na₂S gave [Pt(C523-06CPh)₂ ( ¹-dpmMe)₂]. Oxidative addition of MeI to [PtMe₂· (dpmMe)] gave two Pt^IV isomers of the formula [PtMe₃I(dpmMe)].     

Side-bonded ketone complexes of platinum(0). Alloxan and diethyl oxomalonate complexes and reactions of platinum(0) complexes with isatin and benzoyl cyanide.

Reactions of alloxan (all) with [PtL(PPh₃)₂] (L′= $\text{trans}$-stilbene, L″ diphenylacetylene) afford the side-bonded ketone complex [Pt(all)(PPh₃)₂] which may also be obtained from the hydrate of alloxan and [PtL′(Pph₃)₂]. Similarly diethyl oxomalonate (dio) and [Pt(PPh₃)₄] afford a side-bonded ketone complex [Pt(dio)(PPh₃)₂]. Reaction of isatin with [Pt(PPh₃₄] gives $\text{trans}$-[PtH{$\text{NCO(}\text{o}\text{-C}{}_6\text{H}{}_4\text{)CO}$}(PPh₃)₂] and benzoyl cyanide and [PtL′(PPh₃)₂] give $\text{cis}$-[Pt(CN)(COPh₃)₂] and $\text{trans}$-[Pt(CN)₂(PPh₂)₂].     

Syntheses and structural transformations of oxorhenium(V) complexes with triazine and imidazole derivatives: mixed ligand complexes with thiocyanate, 8-hydroxyquinoline and 1,10-phenanthroline

Mononuclear oxorhenium(V) complexes [ReO(HL¹ or H₂L²)(PPh₃)(OH₂)Cl]Cl, {H₂L^{1 =} 1-(2-hydroxyphenyl)butane-1,3-dione-3-(5,6-diphenyl-1,2,4-triazine-3-ylhydrazone) and H₃L^{2 =} 1-(2-hydroxyphenyl)butane-1,3-dione-3-(1H-benzimidazol-2-ylhydrazone)}, have been synthesized by ligand exchange with trans-trichloromonooxo-bis(triphenylphosphine) rhenium(V). The reaction of a 1?:?1 mixture of either NH₄SCN, 1,10-phenanthroline (1,10-phen) or 8-hydroxyquinoline (8-OHquin) and H₂L¹ or H₃L², with trans-ReOCl₃(PPh₃)₂ yielded the mononuclear oxorhenium(V) complexes, [ReO(HL¹ or H₂L²)(PPh₃) (SCN)Cl], [ReO(HL¹)(1,10-phen)Cl]Cl, [ReO(H₂L²)(1,10-phen)(OH₂)]Cl₂·H₂O and [ReO(HL¹ or H₂L²) (8-Oquin)Cl]. Thermal studies on these complexes showed structural transformations from mononuclear into binuclear complexes. [Re₂O₃(HL¹ or H₂L²)₂(PPh₃)₂Cl₂], [Re₂O₂(μ-L¹ or L²)₂(SCN)₂] and [Re₂O₃ (H₂L²)₂(1,10-phen)₂]Cl₂, were synthesized pyrolytically in the solid state from the respective precursor rhenium complexes. The structures of all complexes and the corresponding thermal products were elucidated using elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments and ¹H NMR and TG-DSC measurements. The prepared complexes and their thermal products have octahedral configurations. The ligands H₂L¹ or H₃L² behave as monoanionic bidentate or monoanionic tetradentate ligands towards the oxorhenium ions. The antifungal activities of the metal complexes towards Alternaria alternata and Aspergillus niger were tested and showed comparable behavior with well known antibiotics.     

A ruthenium complexes of monastrol and its pyrimidine analogues: Synthesis and biological properties

Abstract

A new series of mononuclear ruthenium(II) complexes of the type [Ru(PPh₃)₂(N,S-L^1–3)₂] 2H₃O⁺.(Cl^?)_2.XH₂O, [RuCl(dmso)₃(N,S-L^1–3)], and [Ru₂(Cl^?)₂(N,S-L^1–3)₂].XH₂O, where L¹ is ethyl 4-(3-hydroxyphenyl)-6-methyl-2-thioxo-pyrimidine-5-carboxylate (monastrol), and L² and L³ are the 4-hydroxyphenyl and 4-bromophenyl analogs of monastrol have been prepared and characterized by elemental analysis, ¹H, and ¹³C NMR spectroscopy. All the complexes were assayed for their anti-HIV-1 and HIV-2 activity in MT-4 cells, and cytotoxicity was also investigated in mock-infected in MT-4 cells by using MTT assay. All the complexes exhibited no anti-HIV activity, however complexes [RuCl(dmso)₃(N,S-L¹)] (7) and [RuCl(dmso)₃(N,S-L²)] (8) showed cytotoxicity values of > 0.21 and > 2.14 µM, respectively against mock-infected MT-4 cells. In addition, complexes [Ru(PPh₃)₂(N,S-L³)₂].2H₃O⁺.2Cl^?.H₂O (4), 7, and [RuCl₂(N,S-L¹)] (10) have been selected for evaluation of their dual inhibition activity against dual-specificity tyrosine phosphorylation-regulated kinase (Dyrk1A).     

1-(2′-Pyridylazo)-2-naphtholate complexes of ruthenium: Synthesis,characterization, and DNA binding properties

Reaction of 1-(2′-pyridylazo)-2-naphthol (Hpan) with [Ru(dmso)₄Cl₂] (dmso = dimethylsulfoxide), [Ru(trpy)Cl₃] (trpy = 2,2′,2″-terpyridine), [Ru(bpy)Cl₃] (bpy = 2,2′-bipyridine) and [Ru(PPh₃)₃Cl₂] in refluxing ethanol in the presence of a base (NEt₃) affords, respectively, the [Ru(pan)₂], [Ru(trpy)(pan)]⁺ (isolated as perchlorate salt), [Ru(bpy)(pan)Cl] and [Ru(PPh₃)₂(pan)Cl] complexes. Structures of these four complexes have been determined by X-ray crystallography. In each of these complexes, the pan ligand is coordinated to the metal center as a monoanionic tridentate N,N,O-donor. Reaction of the [Ru(bpy)(pan)Cl] complex with pyridine (py) and 4-picoline (pic) in the presence of silver ion has yielded the [Ru(bpy)(pan)(py)]⁺ and [Ru(bpy)(pan)(pic)]⁺ complexes (isolated as perchlorate salts), respectively. All the complexes are diamagnetic (low-spin d⁶, S = 0) and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ru(II)–Ru(III) oxidation on the positive side of SCE. Except in the [Ru(pan)₂] complex, a second oxidative response has been observed in the other five complexes. Reductions of the coordinated ligands have also been observed on the negative side of SCE. The [Ru(trpy)(pan)]ClO₄, [Ru(bpy)(pan)(py)]ClO₄ and [Ru(bpy)(pan)(pic)]ClO₄ complexes have been observed to bind to DNA, but they have not been able to cleave super-coiled DNA on UV irradiation.     

A Ditopic Phosphane-decorated Benzenedithiol as Scaffold for Di- and Trinuclear Complexes of Group-10 Metals and Gold

The ability of 3-(diphenylphosphinomethyl)-benzene-1,2-dithiol (pbdtH₂) to act as ditopic ligand was probed in reactions with selected group-10-metal complexes. Reactions with [(cod)PdCl₂] afforded a mixture of products identified as [Pd(pbdtH)₂], [Pd₂(μ₂-pbdt)₂] and [Pd₃(μ₂-pbdt)₂Cl₂]. The polynuclear complexes could be isolated after suitably adjusting the reaction conditions, and heating of a mixture in a microwave reactor effected partial conversion into a further complex [Pd₃(μ₂-pbdt)₃]. Reaction of pbdtH₂ with [Ni(H₂O)₆Cl₂] gave rise to a complex [Ni₂(μ₂-pbdt)₂], which was shown to undergo two reversible 1e^–-reduction steps. Reaction of [Pd(pbdtH)₂] with [Au(PPh₃)Cl] afforded heterotrinuclear [PdAu₂(μ₂-pbdt)₂(PPh₃)]. All complexes were characterized by analytical, spectroscopic and single-crystal X-ray diffraction studies. Their molecular structures confirm the ability of the pbdt^2– unit to support simultaneous P,S- and S,S-chelating coordination to two metal centers.     

Novel platinum(II) and (IV) complexes of naphthaldimine schiff bases

Naphthaldimines containing N₂O₂ donor centers react with platinum(II) and (IV) chlorides to give two types of complexes depending on the valence of the platinum ion. For [Pt(II)], the ligand is neutral, [(H₂L¹)PtCl₂]·3H₂O (1) and [(H₂L³)₂Pt₂Cl₄]·5H₂O (3), or monobasic [(HL²)₂Pt₂Cl₂]·2H₂O (2) and [(HL⁴)₂Pt]·2H₂O (4). These complexes are all diamagnetic having square-planar geometry. For [Pt(IV)], the ligand is dibasic, [(L¹)Pt₂Cl₄(OH)₂]·2H₂O (5), [(L²)Pt₃Cl₁₀]·3H₂O (6), [(L³)Pt₂Cl₄(OH)₂]·C₂H₅OH (7) and [(L⁴)Pt₂Cl₆]·H₂O (8). The Pt(IV) complexes are diamagnetic and exhibit octahedral configuration around the platinum ion. The complexes were characterized by elemental analysis, UV-Vis and IR spectra, electrical conductivity and thermal analyses (DTA and TGA). The molar conductances in DMF solutions indicate that the complexes are non-ionic. The complexes were tested for their catalytic activities towards cathodic reduction of oxygen.     

The classification of trigonal bipyramidal platinum(II), rhodium(I) and iridium(I) olefin complexes

It is shown that trigonal bipyramidal platinum(II), rhodium(I) and iridium(I) olefin complexes are better classified with the platinum(O) complex [Pt(PPh₃)₂(C₂H₄)] as class T olefin complexes than with the square-planar platinum(II) complexes such as [Pt(C₂H₄)Cl₃]^- which fall in class S. The underlying reasons for this are considered to be electronic rather than steric as was previously suggested.     

Synthesis and characterization of CuII and CoII complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPT) by chemical and tribochemical reactions

Four Cu^II and Co^II complexes–[Cu(L₁)Cl₂(H₂O)]3/2H₂O · 1/2EtOH, [Cu(L₁)₂Cl₂]6H₂O, [Co(L₁)Cl₂]3H₂O · EtOH, and [Co₂(L₁)(H₂O)Cl₄]1.5H₂O · EtOH (L₁ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine; TPT)–were synthesized by conventional chemical method and used to synthesize another four metal complexes–[Cu(L₁)I₂(H₂O)]6H₂O, [Cu(L₁)₂I₂]6H₂O, [Co(L₁)I(H₂O)₂]I · 2H₂O, and [Co₂(L₁)I₄(H₂O)₃]–using tribochemical reaction, by grinding it with KI. Substitution of chloride by iodide occurred, but no reduction for Cu^II or oxidation of Co^II. Oxidation of Co^II to Co^III complexes was only observed on the dissolution of Co^II complexes in d₆-DMSO in air while warming. The isolated solid complexes (Cu^II and Co^II) have been characterized by elemental analyses, conductivities, spectral (IR, UV-Vis, ¹H-NMR), thermal measurements (TGA), and magnetic measurements. The values of molar conductivities suggest non-electrolytes in DMF. The metal complexes are paramagnetic. IR spectra indicate that TPT is tridentate coordinating via the two pyridyl nitrogens and one triazine nitrogen forming two five-membered rings around the metal in M : L complexes and bidentate via one triazine nitrogen and one pyridyl nitrogen in ML₂ complexes. In binuclear complexes, L is tridentate toward one Co^II and bidentate toward the second Co^II in [Co₂(L₁)Cl₄]2.5H₂O · EtOH and [Co₂(L₁)I₄(H₂O)₃]. Electronic spectra and magnetic measurements suggest a distorted-octahedral around Cu^II and high-spin octahedral and square-pyramidal geometry around Co^II.     

Molybdenum(VI), (V) and (IV) complexes with chiral benzoin thiosemicarbazone

The chiral (ONS) dianionic Schiff base ligand benzoin thiosemicarbazone (H₂L) reacts with MoO₂(acac)₂ to give the polymeric complex [(MoO₂L) _n ] (1) (Type 1). The reaction of MoO₂L with pyridine (py), 3-picoline (3-pic) or 4-picoline (4-pic) gives [Mo^VIO₂LD] (D = py, 3-pic or 4-pic) (Type 1). Further, the reaction of [MoO₂L] or [MoO₂LD] with PPh₃ or reaction of [MoO₂L] with PPh₃ (plus bpy or phen, D) in the presence of donor reagents D gives [Mo^IVOL] or [Mo^IVOLD] (Type 2). On the other hand, the reaction of [MoO₂L] with hydrazides (zdhH₃) such as benzoylhydrazine (bhH₃), isonicotinoylhydrazine (inhH₃), nicotinoylhydrazine (nhH₃), salicyloylhydrazine (slhH₃) and thiosemicarbazide (tscH₃) produced non-oxo–diazenido complexes [MoL(zdh)] (Type 3). The complexes have been characterized by elemental analyses, molar conductance, magnetic moment, electronic, i.r. and e.s.r. spectroscopic measurements.