(P-Bis(pentafluorophenyl) substituted) PCP-pincer Ru(II) complexes: A theoretical study of the molecular structure and electronic properties

The differences between the molecular structures of the PCP-pincer complex [RuCl{C₆H₃(CH₂P(C₆H₅)₂)₂-2,6}(PPh₃)] ([RuCl(PCP^H)(PPh₃)], 1) and its tetrakis-pentafluorophenyl substituted analogue [RuCl{C₆H₃(CH₂P(C₆F₅)₂)₂-2,6}(PPh₃)] ([RuCl(PCP^F20)(PPh₃)], 2) have been rationalised by performing calculations on the cations [Ru(PCP^H)(PPh₃)]⁺ (1cat) and [Ru(PCP^F20)(PPh₃)]⁺ (2cat). The molecular interactions between the chloride ligand and the axial rings, as found in 1 and 2, respectively, have been studied computationally in the model systems [(C₆X₅PH₂)₂Cl⁻] (X = H, F). The calculations on 2cat show that in 2 it is most likely the attractive electrostatic interaction between the chloride ligand and the fluorinated phenyl rings that forces the C_ipso atom to occupy an axial position rather than an equatorial one in the observed (X-ray of 2) square pyramidal arrangement. In 1, however, repulsive steric hindrance forces the PPh₃ ligand to take the apical position. The applicability of the TD-DFT method for the calculation of the electronic spectra of the PCP-pincer compounds 1 and 2 has been tested. The results indicate that the excitation energies calculated for both complexes are in a reasonable agreement with the experimental absorption maxima. However, for 1, all the calculated transition energies are underestimated.     

Novel rhenium oxocomplexes of 2-hydroxymethylbenzimidazole – Synthesis,X-ray studies,spectroscopic characterization and DFT calculations

Three novel rhenium oxocomplexes of biologically relevant ligand 2-hydroxymethylbenzimidazole: cis-[ReOCl₂(hmbzim)(PPh₃)] (1), cis-[ReOBr₂(hmbzim)(PPh₃)] and [ReO(hmbzim)₂(PPh₃)](ReO₄)·CH₃OH (3) have been synthesized and characterized spectroscopically and structurally (by single-crystal X-ray diffraction). The electronic spectra of 1 and 3 were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ. Additional information about binding in the complexes 1 and 3 was obtained by NBO analysis.     

Mono and dinuclear iridium, rhodium and ruthenium complexes containing chelating carboxylato pyrazine ligands: Synthesis, molecular structure and electrochemistry

The mononuclear complexes [(η⁵-C₅Me₅)IrCl(L¹)] (1), [(η⁵-C₅Me₅)RhCl(L¹)] (2), [(η⁶-p-PrⁱC₆H₄Me)RuCl(L¹)] (3) and [(η⁶-C₆Me₆)RuCl(L¹)] (4) have been synthesised from pyrazine-2-carboxylic acid (HL¹) and the corresponding complexes [{(η⁵-C₅Me₅)IrCl₂}₂], [{(η⁵-C₅Me₅)RhCl₂}₂], [{(η⁶-p-PrⁱC₆H₄Me)RuCl₂}₂], and [{(η⁶-C₆Me₆)RuCl₂}₂], respectively. The related dinuclear complexes [{(η⁵-C₅Me₅)IrCl}₂(μ-L²)] (5), [{(η⁵-C₅Me₅)RhCl}₂(μ-L²)] (6), [{(η⁶-p-PrⁱC₆H₄Me)RuCl}₂(μ-L²)] (7) and [{(η⁶-C₆Me₆)RuCl}₂(μ-L²)] (8) have been obtained in a similar manner from pyrazine-2,5-dicarboxylic acid (H₂L²). Compounds isomeric to the latter series, [{(η⁵-C₅Me₅)IrCl}₂(μ-L³)] (9), [{(η⁵-C₅Me₅)RhCl}₂(μ-L³)] (10), [{(p-PrⁱC₆H₄Me)RuCl}₂(μ-L³)] (11) and [{(η⁶-C₆Me₆)RuCl}₂(μ-L³)] (12), have been prepared by using pyrazine-2,3-dicarboxylic acid (H₂L³) instead of H₂L². The molecular structures of 2 and 3, determined by X-ray diffraction analysis, show the pyrazine-2-carboxylato moiety to act as an N,O-chelating ligand, while the structure analyses of 5-7, confirm that the pyrazine-2,5-dicarboxylato unit bridges two metal centres. The electrochemical behaviour of selected representatives has been studied by voltammetric techniques.     

Construction of optically active multimetallic systems of rhodium(I), palladium(II), and ruthenium(II) with a P-chiral tetraphosphine ligand

The treatment of optically P-chiral tetraphosphine, (3S,6R,9R,12S)-6,9-di-tert-butyl-2,2,3,12,13,13-hexamethyl-3,6,9,12-tetraphosphatetradecane (1), with rhodium(I), palladium(II), and ruthenium(II) complex precursors led to the selective formation of mono-, di-, or trinuclear homo- or heterometallic complexes, [Rh(1)]SbF₆ (4), [{Rh(nbd)}₂(1)](SbF₆)₂ (3), [{Pd(η³-allyl)}₂(1)](SbF₆)₂ (5), [{RuCl(η⁵-C₅(CH₃)₅)}₂(1)] (6), and [{RuCl₂(η⁶-benzene)}₂(PdCl₂)(1)] (8). These complexes were characterized by NMR and X-ray crystallographic analysis.     

Novel rhenium oxocomplexes of indazole-3-carboxylic acid – Synthesis,X-ray studies,spectroscopic characterization and DFT calculations

Three novel rhenium oxocomplexes incorporating indazole-3-carboxylate ligand: cis-[ReOCl₂(Ind-3-COO)(PPh₃)]·OPPh₃ (1a), cis-[ReOCl₂(Ind-3-COO)(PPh₃)] (1b) and cis-[ReOBr₂(Ind-3-COO)(PPh₃)]·OPPh₃ (2) have been synthesized and characterised spectroscopically and structurally (by single-crystal X-ray diffraction). The 1a and 2 are isostructural in solid state. The electronic spectrum of 1a was investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ. Additional information about binding in the complex 1a was obtained by NBO analysis.     

Structural and spectral studies of nickel(II) complexes with N(4),N(4)-(butane-1,4-diyl) thiosemicarbazones

Nickel(II) complexes of quinoline-2-carbaldehyde N(4),N(4)-(butane-1,4-diyl) thiosemicarbazone (HL¹) and 2-benzoylpyridine N(4),N(4)-(butane-1,4-diyl) thiosemicarbazone (HL²) have been synthesized and physico-chemically characterized by means of partial elemental analyses, molar conductance measurements, magnetic measurements, electronic and infrared spectral studies. Three complexes were given the formulae [Ni(HL¹)₂]Cl₂ (1), [Ni(HL²)L²]ClO₄ · 7H₂O (2) and [NiL²Cl] · 0.5H₂O (3). The structure of compound 1 has been solved by single crystal X-ray crystallography and is found to be distorted octahedral. Compound 2, when crystallized in DMSO solution, got deprotonated to form a new compound [Ni(L²)₂] (2a), with a distorted octahedral Ni(II) center. In compound 1, HL¹ coordinates to the metal in the thione form, while in compounds 2a and 3, HL² coordinates in its deprotonated thiolate form.     

Copper(II) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Crystal structure of a binuclear complex

Ten copper(II) complexes {[CuL¹Cl] (1), [CuL¹NO₃]₂ (2), [CuL¹N₃]₂ · 2/3H₂O (3), [CuL¹]₂(ClO₄)₂ · 2H₂O (4), [CuL²Cl]₂ (5), [CuL²N₃] (6), [Cu(HL²)SO₄]₂ · 4H₂O (7), [Cu(HL²)₂] (ClO₄)₂ · 1/2EtOH (8), [CuL³Cl]₂ (9), [CuL³NCS] · 1/2H₂O (10)} of three NNS donor thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL¹], pyridine-2-carbaldehyde-N(4)-2-phenethyl thiosemicarbazone [HL²] and pyridine-2-carbaldehyde N(4)-(methyl), N(4)-(phenyl) thiosemicarbazone [HL³]} were synthesized and physico-chemically characterized. The crystal structure of compound 9 has been determined by X-ray diffraction studies and is found that the dimer consists of two square pyramidal Cu(II) centers linked by two chlorine atoms.     

Rhenium chelate complexes with maltolate or kojate

Novel rhenium complexes containing the maltolate (mal) or kojate (koj) anions as chelating ligands have been synthesized: [ReOCl(mal)₂] (1), [ReOCl₂(mal)(PPh₃)] (2), [ReOBr₂(mal)(PPh₃)] (3), [ReOCl₂(koj)(PPh₃)] (4) and [ReOBr₂(koj)(PPh₃)] (5). The products have been characterized by FTIR, ¹H, ¹³C, and ³¹P NMR spectroscopies and elemental analysis. The crystal and molecular structures of all complexes were determined. Complex 1 crystallizes monoclinic, space group C2/c, Z = 8. It contains two O,O′-bidentate maltolate ligands and one chloro ligand at the (ReO)³⁺ unit, so that a distorted octahedral geometry is adopted by the six-coordinated rhenium(V) center. The chloro ligand occupies a cis position to the oxo ligand. Complexes 2 and 3 are isostructural and crystallize orthorhombic, space group Pbca and Z = 8. The isostructural complexes 4 and 5 crystallize monoclinic, space group P2₁/n and Z = 4. In complexes 2–5, the (ReO)³⁺ unit is coordinated by a monoanionic O,O-bidentate unit of the maltolate (2 and 3) or kojate (4 and 5) ligand, one triphenylphosphine and two halogeno ligands (Cl in 2 and 4; Br in 3 and 5), with the rhenium(V) center in a distorted octahedral environment. The halide ligands are in cis positions to each other.     

Synthesis,crystal structures and spectral studies of square planar nickel(II) complexes containing an ONS donor Schiff base and triphenylphosphine

Five mononuclear nickel(II) complexes, viz. [Ni(L1)(PPh₃)] (1), [Ni(L2)(PPh₃)] (2), [Ni(L3)(PPh₃)] (3), [Ni(L4)(PPh₃)] (4) and [Ni(L5)(PPh₃)] (5) (where L1, L2, L3, L4 and L5 are dianions of N-(2-mercaptophenyl)salicylideneimine, 5-methyl-N-(2-mercaptophenyl)salicylideneimine, 5-chloro-N-(2-mercaptophenyl)salicylideneimine, 5-bromo-N-(2-mercaptophenyl)salicylideneimine and N-(2-mercaptophenyl)naphthylideneimine, respectively), have been synthesized and characterized by means of elemental analysis, electronic, IR, ¹H, ¹³C and ³¹P NMR spectroscopy. Single crystal X-ray analysis of two of the complexes (1 and 5) has revealed the presence of a square planar coordination geometry (ONSP) about nickel. The crystal structures of the complexes are stabilized by intermolecular π–π stacking between the ligands (L) and by various C–H···π interactions.     

Novel hydridotris(pyrazolyl)borate ruthenium(II) complexes containing the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane: Synthesis and evaluation of DNA binding properties

A series of half-sandwich ruthenium(II) complexes containing κ³(N,N,N)-hydridotris(pyrazolyl)borate (κ³(N,N,N)-Tp) and the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA) [RuX{κ³(N,N,N)-Tp}(PPh₃)_2−n(PTA)_n] (n = 2, X = Cl (1), n = 1, X = Cl (2), I (3), NCS (4), H (5)) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)L][PF₆] (L = NCMe (6), PTA (7)) have been synthesized. Complexes containing 1-methyl-3,5-diaza-1-azonia-7-phosphaadamantane(m-PTA) triflate [RuCl{κ³(N,N,N)-Tp}(m-PTA)₂][CF₃SO₃]₂ (8) and [RuX{κ³(N,N,N)-Tp}(PPh₃)(m-PTA)][CF₃SO₃] (X = Cl (9), H (10)) have been obtained by treatment, respectively, of complexes 1, 2 and 5 with methyl triflate. Single crystal X-ray diffraction analysis for complexes 1, 2 and 4 have been carried out. DNA binding properties by using a mobility shift assay and antimicrobial activity of selected complexes have been evaluated.     

The influence of substituents (R) at the C carbon on bonding properties of thiosemicarbazones {RC(H)N-NH–C(S)–NH2} in palladium(II) complexes

Reactions of the trans-PdCl₂(PPh₃)₂ precursor with furan-2-carbaldehyde thiosemicarbazone (Hftsc) and thiophene-2-carbaldehyde thiosemicarbazone (Httsc), in 1:1 molar ratios in the presence of Et₃N base, removed one Cl and one PPh₃ group from the Pd^II center, and yielded the complexes [Pd(η²-N³,S-ftsc)(PPh₃)Cl] (1) and [Pd(η²-N³,S-ttsc)(PPh₃)Cl] (2), respectively. However, when a 1:2 molar ratio (M:L) was used, both Cl and PPh₃ ligands were removed, yielding the complexes trans-[Pd(η²-N³,S-ftsc)₂] (3) and trans-[Pd(η²-N³,S-ttsc)₂] (4). Complexes 1–4 have been characterized with the help of analytical data, spectroscopic techniques (IR, ¹H and ³¹P NMR) and single crystal X-ray crystallography. The thiosemicarbazone ligands behave as uninegative N³,S-chelating ligands in complexes 1–4. In contrast, pyrrole-2-carbaldehyde thiosemicarbazone (H₂ptsc) and salicylaldehyde thiosemicarbazone (H₂stsc) invariably formed the complexes [Pd(η³-N⁴,N³,S-ptsc)(PPh₃)] (5) and [Pd(η³–O, N³,S-stsc)(PPh₃)] (6), respectively, and the ligands acted as binegative tridentate donors (N⁴, N³, S, 5; O, N³, S, 6).     

Syntheses and properties of Re(III) complexes derived from hydrotris(1-pyrazolyl)methanes: molecular structure of [ReCl2(HCpz3)(PPh3)][BF4]

The complexes [ReCl₂{N₂C(O)Ph}(Hpz)(PPh₃)₂] (1) (Hpz = pyrazole), [ReCl₂{N₂C(O)Ph}(Hpz)₂(PPh₃)] (2), [ReCl₂(HCpz₃)(PPh₃)][BF₄] (3) and [ReCl₂(3,5-Me₂Hpz)₃(PPh₃)]Cl (4) were obtained by treatment of the chelate [ReCl₂{η²-N,O-N₂C(O)Ph}(PPh₃)₂] (0) with hydrotris(1-pyrazolyl)methane HCpz₃ (1,3), pyrazole Hpz (1,2), hydrotris(3,5-dimethyl-1-pyrazolyl)methane HC(3,5-Me₂pz)₃ (4) or dimethylpyrazole 3,5-Me₂Hpz (4). Rupture of a C(sp³)-N bond in HCpz₃ or HC(3,5-Me₂pz)₃, promoted by the Re centre, has occurred in the formation of 1 or 4, respectively. All compounds have been characterized by elemental analyses, IR and NMR spectroscopy, FAB-MS spectrometry, cyclic voltammetry and, for 1 · CH₂Cl₂ and 3, also by single crystal X-ray analysis. The electrochemical E_L Lever parameter has been estimated, for the first time, for the HCpz₃ and the benzoyldiazenide NNC(O)Ph ligands.     

New oxorhenium complexes with 2-(2′-hydroxyphenyl)-2-benzoxazolinato ligand. X-ray structure and DFT calculations for [ReOX2(hbo)(AsPh3)] and [ReOX2(hbo)(PPh3)] complexes

The reactions of [ReOX₃(AsPh₃)₂] and [ReOX₃(PPh₃)₂] with 2-(2′-hydroxyphenyl)-2-benzoxazoline (Hhbo) have been examined and [ReOX₂(hbo)(AsPh₃)] and [ReOX₂(hbo)(PPh₃)] (X = Cl, Br) complexes have been obtained. The crystal and molecular structures of [ReOCl₂(hbo)(AsPh₃)] (1) and [ReOBr₂(hbo)(PPh₃)] (4) have been determined. The electronic structures of 1 and 4 have been calculated with the density functional theory (DFT) method. The spin-allowed electronic transitions of 1 and 4 have been calculated with the time-dependent DFT method, and the UV–Vis spectra of these complexes have been discussed.     

Novel p-tolylimido rhenium(V) complexes of imidazole-derived ligand - Synthesis, X-ray studies, spectroscopic characterization and DFT calculations

Three novel imido rhenium complexes of biologically relevant ligand 2-hydroxymethylbenzimidazole: [Re(p-NC₆H₄CH₃)Cl₂(hmbzim)(PPh₃)]·CHCl₃ (1), [Re(p-NC₆H₄CH₃)Br₂(hmbzim)(PPh₃)] (2) and [Re(p-NC₆H₄CH₃)(hmbzim)₂(PPh₃)]ReO₄·MeOH (3) have been synthesized and characterized spectroscopically and structurally (by single-crystal X-ray diffraction). The electronic spectra of 1 and 3 were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ. Additional information about binding in the complexes 1 and 3 was obtained by NBO analysis, which confirms a linear coordination mode of the p-NC₆H₄CH₃ ligand and triple bond between the rhenium and imido ligand.     

Synthesis, characterization and crystal structures of palladium(II) complexes containing neutral, one and twofold deprotonated 1,2,4-triazine species

The synthesis and characterization of three new palladium(II) complexes of 4-amino-6-ethyl-1,2,4-triazine-3-thion-5-one (AETTO, H₃L), [PdCl₂(H₃L)]·H₂O (1), [Pd₂Cl₂(H₂L)(PPh₃)₃]NO₃·2CH₃CN (2) and [Pd(HL)(PPh₃)₂] (3), are reported. All the synthesized compounds are air-stable and were characterized by elemental analyses, IR, NMR spectroscopy and mass spectrometry. In addition, the molecular structures of the complexes have been determined by X-ray single crystal diffraction. On the basis of the crystallographic data, the neutral ligand in 1 and the deprotonated ligands in 2 and 3 act as bidentate NS donors. The singly deprotonated ligand in 2 acts as a bridging agent between two metal centers in the binuclear Pd^II-complex.     

Syntheses and structures of iron carbonyl complexes derived from N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine and N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine

The reaction of N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine (1) with Fe₂(CO)₉ in refluxing acetonitrile yielded di-(μ₃-thia)nonacarbonyltriiron (2), μ-[N-(5-methyl-2-thienylmethyl)-η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido]hexacarbonyldiiron (3), and N-(5-methyl-2-thienylmethylidene)amine (4). If the reaction was carried out at 45 °C, di-μ-[N-(5-methyl-2-thienylmethylidene)-η¹(N);η¹(S)-2-thiolethylamino]-μ-carbonyl-tetracarbonyldiiron (5) and trace amount of 4 were obtained. Stirring 5 in refluxing acetonitrile led to the thermal decomposition of 5, and ligand 1 was recovered quantitatively. However, in the presence of excess amount of Fe₂(CO)₉ in refluxing acetonitrile, complex 5 was converted into 2-4. On the other hand, the reaction of N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine (6) with Fe₂(CO)₉ in refluxing acetonitrile produced 2, μ-[N-(6-methyl-2-pyridylmethyl)-η¹ (N_py);η¹:η¹(N); η¹:η¹(S)-2-thiolatoethylamido]pentacarbonyldiiron (7), and μ-[N-(6-methyl-2-pyridylmethylidene)-η²(C,N);η¹:η¹(S)-2- thiolethylamino]hexacarbonyldiiron (8). Reactions of both complex 7 and 8 with NOBF₄ gave μ-[(6-methyl-2-pyridylmethyl)-η¹(N_py);η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido](acetonitrile)tricarbonylnitrosyldiiron (9). These reaction products were well characterized spectrally. The molecular structures of complexes 3, 7-9 have been determined by means of X-ray diffraction. Intramolecular 1,5-hydrogen shift from the thiol to the methine carbon was observed in complexes 3, 7, and 9.     

Cyclopalladated complexes with N-(benzoyl)-N-(2,4-dimethoxybenzylidene)hydrazine: syntheses, characterization and structural studies

Cyclopalladated complexes with the Schiff base N-(benzoyl)-N^′-(2,4-dimethoxybenzylidene)hydrazine (H₂L, 1) have been described. The reaction of 1 with Li₂[PdCl₄] in methanol yields the complex [Pd(HL)Cl] (2). [Pd(HL)(CH₃CN)Cl] (3) has been prepared by dissolving 2 in acetonitrile. In methanol-acetonitrile mixture, treatment of 2 with two mole equivalents of PPh₃ produces [PdL(PPh₃)] (4) and that with one mole equivalent of PPh₃ produces [Pd(HL)(PPh₃)Cl] (5). Crystallization of 2 from dmso-d₆ results into isolation of [Pd(HL)((CD₃)₂SO)Cl] (6). In 2, the monoanionic ligand (HL⁻) is C,N,O-donor and the Cl-atom is trans to the azomethine N-atom. In 3, 5 and 6, HL⁻ is C,N-donor and the Cl-atom is trans to the metallated C-atom. The remaining fourth coordination site is occupied by the N-atom of CH₃CN, the P-atom of PPh₃ and the S-atom of (CD₃)₂SO in 3, 5 and 6, respectively. Thus on dissolution in acetonitrile and dmso and in reaction with stoichiometric PPh₃ the incoming ligand imposes a rearrangement of the coordinating atoms on the palladium centre. On the other hand, in presence of excess PPh₃ deprotonation of the amide functionality in 2 occurs and the Cl-atom is replaced by the P-atom of PPh₃ to form 4. Here the dianionic ligand (L²⁻) remains C,N,O-donor as in 2. The compounds have been characterized with the help of elemental analysis (C, H, N), infrared, ¹H NMR and electronic absorption spectroscopy. Molecular structures of 3, 4, and 6 have been determined by X-ray crystallography.     

Microwave synthesis of bis(tetrazolato)-Pd complexes with PPh3 and water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA). The first example of C-CN bond cleavage of propionitrile by a Pd Centre

[2 + 3] Cycloaddition reactions of the di(azido)-Pd^II complex trans-[Pd(N₃)₂(PPh₃)₂] (1) with an organonitrile RCN (2), under heating for 12 h, give the bis(tetrazolato) complexes trans-[Pd(N₄CR)₂(PPh₃)₂] (3) [R = Me (3a), Ph (3b), 4-ClC₆H₄ (3c), 4-FC₆H₄ (3d), 2-NC₅H₄ (3e), 3-NC₅H₄ (3f), 4-NC₅H₄ (3g)]. The reaction of trans-[Pd(N₃)₂(PPh₃)₂] (1) with propionitrile (2h) also affords, apart from trans-[Pd(N₄CEt)₂(PPh₃)₂] (3h), the unexpected mixed cyano-tetrazolato complex trans-[Pd(CN)(N₄CEt)(PPh₃)₂] (3h′) which is derived from the reaction of the bis(tetrazolato) 3h with propionitrile, with concomitant formation of 5-ethyl-1H-tetrazole, via a suggested unusual oxidative addition of the nitrile to Pd^II. The [2 + 3] cycloadditions of [Pd(N₃)₂(PTA)₂] (4) (PTA = 1,3,5-triaza-7-phosphaadamantane) with RCN (2), under heating for 12 h, give the bis(tetrazolato) complexes trans-[Pd(N₄CR)₂(PTA)₂] (5) [R = Ph (5a), 2-NC₅H₄ (5b), 3-NC₅H₄ (5c), 4-NC₅H₄ (5d)]. All these reactions are greatly accelerated by microwave irradiation (1 h, 125 °C, 300 W). Taking advantage of the hydro-solubility of PTA, a simple liberation of 5-phenyl-1H-tetrazole from the coordination sphere of trans-[Pd(N₄CPh)₂(PTA)₂] (5a) was achieved. The complexes were characterized by IR, ¹H, ¹³C{¹H} and ³¹P{¹H} NMR spectroscopies, ESI⁺-MS, elemental analyses and, for 3b, also by X-ray structure analysis. Weak agostic interactions between the CH groups of the triphenylphosphines and the palladium(II) centre were found.     

Investigations into bis(triphenylphosphine)copper(I) complexes with cyclic derivatives of methylpyruvate thiosemicarbazones

The syntheses of four compounds, obtained by the reaction of methylpyruvate thiosemicarbazone (Hmpt) and its methyl (Me-Hmpt) and allyl (Allyl-Hmpt) derivatives with bis(triphenylphosphine)copper(I) acetate, are reported. The compounds [Cu(PPh₃)₂(pt_c)(Hpt_c)]·H₂O (1), [Cu(PPh₃)₂(Me-pt_c)] (2), [Cu₂(PPh₃)₂μ-S(Me-pt)μ-S(Me-pt_c)]·H₂O (3) and [Cu(PPh₃)₂(Allyl-pt_c)] (4) [H₂pt = pyruvic acid thiosemicarbazone and Hpt_c = cyclized pyruvic acid thiosemicarbazone, Me = methyl and Allyl are radical substituents on the amino nitrogen] were characterized by elemental analysis, IR, ¹H NMR, and by X-ray crystallography. Compound 3 was also studied by EPR because of the presence in the compound of two copper atoms in two different oxidation states. During the complexation reaction, the thiosemicarbazone ligands tend to undergo a cyclization reaction that leads to the formation of a six-member heterocyclic ring. All four compounds present the [Cu(PPh₃)₂]⁺ fragment and constant but different coordination situations. Compound 1 contains two cyclic ligand molecules, one protonated and the other deprotonated, bound as monodentate through the sulfur. Compounds 2 and 4 present a single deprotonated cyclic SN bidentate ligand molecule, while compound 3 contains copper(I) and copper(II), and two ligand molecules, one of which is linear and behaves as SNO tridentate and the other is cyclic and behaves as bridging μSN.     

Mononuclear ruthenium(II) complexes bearing the (S,S)-Pr-pybox ligand

The complexes trans-[RuCl₂(L){(S,S)-ⁱPr-pybox}] ((S,S)-ⁱPr-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′-yl]pyridine, L = PMe₃ (1), P(OMe)₃ (2), PPh₂(CH₂CHCH₂) (3), CNBn (5), CNCy (6) and MeCN (7)) have been synthesized by substitution of ethylene on the precursor trans-[RuCl₂(η²-C₂H₄){(S,S)-ⁱPr-pybox}]. This complex also reacts with cyclooctadiene (cod) or norbornadiene (nbd) and NaPF₆, in refluxing methanol, giving the coordination compounds [RuCl(η⁴-cod){(S,S)-ⁱPr-pybox}][PF₆] (8) and [RuCl(η⁴-nbd){(S,S)-ⁱPr-pybox}][PF₆] (9). The structures of complexes [RuCl(CO)(PPh₃)(H-pybox)][BF₄] (H-pybox = 2,6-bis(dihydrooxazolin-2′-yl)pyridine) (4), 6 and 8, have been resolved by X-ray diffraction methods. The catalytic activity of the new complexes in transfer hydrogenation of acetophenone has also been examined.