Trinuclear silver(I) complexes of fluorinated pyrazolates

Silver pyrazolates [[3-(CF3)Pz]Ag]3, [[3-(CF3),5-(CH3)Pz]Ag]3, [[3-(CF3),5-(Ph)Pz]Ag]3, [[3-(CF3),5-(But)Pz]Ag]3, and [[3-(C3F7),5-(But)Pz]Ag]3 have been synthesized by treatment of the corresponding pyrazole with a slight molar excess of silver(I) oxide. This economical and convenient route gives silver pyrazolates in high (>80%) yields. X-ray crystal structures of [[3-(CF3),5-(CH3)Pz]Ag]3, [[3-(CF3),5-(But)Pz]Ag]3, and [[3-(C3F7),5-(But)Pz]Ag]3 show that these molecules have trinuclear structures with essentially planar to highly distorted Ag3N6 metallacycles. [[3-(CF3),5-(CH3)Pz]Ag]3 forms extended columns via intertrimer argentophilic contacts (the closest Ag...Ag separation between the neighboring trimers are 3.355 and 3.426 A). The trinuclear [[3-(CF3),5-(But)Pz]Ag]3 units crystallize in pairs, basically forming "dimers of trimers", with the six silver atom core of the adjacent trimers adopting a chair conformation. However, in these dimers of trimers, even the shortest intertrimer Ag...Ag distance (3.480 A) is slightly longer than the van der Waals contact of silver (3.44 A). [[3-(C3F7),5-(But)Pz]Ag]3, which has two bulky groups on each pyrazolyl ring, shows no close intertrimer Ag...Ag contacts (closest intertrimer Ag...Ag distance = 5.376 A). The Ag-N bond distances and the intratrimer Ag...Ag separations of the silver pyrazolates do not show much variation. However, their N-Ag-N angles are sensitive to the nature (especially, the size) of substituents on the pyrazolyl rings. The pi-acidic [[3,5-(CF3)2Pz]Ag]3 and [[3-(C3F7),5-(But)Pz]Ag]3 form adducts with the pi-base toluene. X-ray data show that they adopt extended columnar structures of the type [[Ag3]2.[toluene]]infinity and [[Ag3]'.[toluene]]infinity ([[3,5-(CF3)2Pz]Ag]3 = [Ag3],[[3-(C3F7),5-(But)Pz]Ag]3 = [Ag3]'), in which toluene interleaves and makes face-to-face contacts with [[3-(C3F7),5-(But)Pz]Ag]3 or dimers of [[3,5-(CF3)2Pz]Ag]3.     

An unprecedented, figure-of-eight, dinuclear iridium(I) dicarbene and new iridium(III) 'pincer' complexes

An unusual dinuclear Ir(i) complex bridged by two N-heterocyclic biscarbene ligands, forming a 20-membered, figure-of-eight dimetallacycle, and new C(NHC)CC(NHC) pincer complexes of Ir(iii) have been obtained directly from the bis(imidazolium) precursors and [Ir(mu-Cl)(cod)](2).     

A cyclometallated iridium(III) dimethylphenylphosphine complex

[Ir(cod)Cl]₂ (cod = 1,5-cyclooctadiene) reacts with PMe₂Ph in CH₃CN to give the red cation [Ir(PMe₂Ph)₄]⁺. This complex in CH₃CN reacts with H₂ to give cis-[IrH₂(PMe₂Ph)₄]⁺, but on reflux for 6 h in the absence of H₂, it gives the first example of a cyclometallated PMe₂Ph complex fac-[IrH(PMe₂C₆H₄)(PMe₂Ph)₃]⁺, as shown by PMR spectroscopy and preliminary X-ray crystallographic data.     

A bright tetranuclear iridium(III) complex

A cyclic tetranuclear cyclometallated iridium(III) complex using cyanide anions as bridging ligands and displaying a tetrahedrally distorted square geometry has been obtained with high yield; photo- and electrochemical characterizations show that most interesting properties of mononuclear cyclometallated iridium complexes are retained in the tetranuclear assembly.     

Cationic rhodium(I) and iridium(I,III) complexes of cinnamonitrile and their catalytic activities

Summary Reactions of cinnamonitrile (trans-PhCH=CHCN) with [M(ClO₄)(CO)(PPh₃)₂] (M=Rh or Ir) produce hydrogenation oftrans-PhCH=CHCN to PhCH₂CH₂CN at 100°C under 3 atm of hydrogen.     

Ruthenium(III) and iridium(III) complexes with nicotine

A new chloride-dimethylsulfoxide-ruthenium(III) complex with nicotine trans-[Ru^IIICl₄(DMSO)[H-(Nicotine)]] (1) and three related iridium(III) complexes; [H-(Nicotine)]trans-[Ir^IIICl₄(DMSO)₂] (2), trans-[Ir^IIICl₄(DMSO)[H-(Nicotine)]] (3) and mer-[Ir^IIICl₃(DMSO)(Nicotine)₂] (4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction (1, 2, and 4). Protonated nicotine at pyrrolidine nitrogen is present in complexes 1 and 3 while two neutral nicotine ligands are observed in 4. In these three inner-sphere complexes coordination occurs through the pyridine nitrogen. Moreover, in the outer-sphere complex 2, an electrostatic interaction is observed between a cationic protonated nicotine at the pyrrolidine nitrogen and the anionic trans-[Ir^IIICl₄(DMSO)₂]^¯ complex.     

Trifluoromethyl and mixed hydrido trifluoromethyl complexes of iridium(III) as potential precursors of an iridium(I) trifluoromethyl complex

Abstraction of iodide from Ir(CF₃)ClI(CO)(PPh₃)₂ (1) by AgSbF₆ in the presence of acetonitrile yields the cationic complex [Ir(CF₃)Cl(MeCN)(CO)(PPh₃)₂]⁺ [SbF₆]⁻ (2). The acetonitrile group of 2 is readily displaced, and 2 reacts with para-tolyl isocyanide to yield [Ir(CF₃)Cl(CN-p-tolyl)(CO)(PPh₃)₂]⁺ [SbF₆]⁻ (3). The addition of NaOMe to 3 results in the methoxyester complex Ir(CF₃)(COOMe)Cl(CN-p-tolyl) (PPh₃)₂ (4). The acetonitrile ligand of 2 is also displaced by anions, including H⁻. Thus, 2 reacts with LiEt₃BH to give Ir(CF₃)HCl(CO)(PPh₃)₂ (5), in which the hydrido and trifluoromethyl ligands are mutually trans. In contrast, the addition of excess NaBH₄ to 2 affords the novel dihydrido complex trans-Ir(CF3)H₂(CO)(PPh₃)₂ (6). Investigations into the potential use of 5 and 6 as precursors of an iridium(I) complex such as Ir(CF₃)(CO)(PPh₃)₂ are also described.     

Photosensitized generation of singlet oxygen from rhenium(I) and iridium(III) complexes

Photophysical properties in dilute acetonitrile solution are reported for a number of iridium(III) and rhenium(I) complexes. The nature of the lowest excited state of the complexes under investigation is either metal-to-ligand charge transfer ((3)MLCT) or a ligand centred ((3)LC) state. Rate constants, k(q), for quenching of the lowest excited states by molecular oxygen are in the range 1.5 x 10(8) to 1.4 x 10(10) M(-1) s(-1). Efficiency of singlet oxygen production, f(Delta)(T), following oxygen quenching of the lowest excited states of these complexes, are in the range of 0.27-1.00. The rate constants and the efficiency of singlet oxygen formation are quantitatively reproduced by a model that assumes the competition between a non-charge transfer (nCT) and a CT deactivation channel. The balance between CT and nCT deactivation channels, which is described by the relative contribution p(CT) of CT induced deactivation, is discussed. The kinetic model is found to be successfully applied in the case of quenching of the excited triplet states of coordination compounds by oxygen in acetonitrile, as was proposed for the quenching of pi-pi* triplet states by oxygen.     

1,3-diaryltriazenido complexes of ruthenium(I), (II) and (III), and of osmium(III), rhodium(III) and iridium(III)

The synthesis and characterization of the platinum metal—1,3-diaryltriazenido complexes [Ru(ArNNNAr)(CO)₃]₂, [Ru(ArNNNAr)₂]₂, cis-Ru(ArNNNAr)₂(CO)₂, MX₂(ArNNNAr)(PPh₃)₂ (M = Ru, Os; X = Cl, Br) and M′(ArNNNAr)₃ (M′= Ru, Os, Rh and Ir) are reported. Axial ligand substitution in [Ru(ArNNNAr)(CO)₃]₂ and adduct formation by [Ru(ArNNNAr)₂]₂ are described. In contrast to other known Ru(II)/Ru(II) “lantern” molecules, the species [Ru(ArNNNAr)₂]₂ have measured magnetic moments equivalent to ca one unpaired electron per dimer, which are presumably due to population of the spin states σ²π⁴δ²π^*4 and σ²π⁴δ²π^*3σ^*1.     

Highly efficient phosphorescent iridium (III) diazine complexes for OLEDs: Different photophysical property between iridium (III) pyrazine complex and iridium (III) pyrimidine complex

The synthesis and luminescence of four new iridium (III) diazine complexes (1-4) were investigated. HOMO and LUMO energy levels of the complexes were estimated according to the electrochemical performance and the UV-Vis absorption spectra, showing the pyrimidine complexes have a larger increase for the LUMO than the HOMO orbital in comparison with the pyrazine complexes. Several high-efficiency yellow and green OLEDs based on phosphorescent iridium (III) diazine complexes were obtained. The devices emitting yellow light based on 1 with turn-on voltage of 4.1 V exhibited an external quantum efficiency of 13.2% (power efficiency 20.3 lm/W), a maximum current efficiency of 37.3 cd/A. The electroluminescent performance for the green iridium pyrimidine complex of 3 is comparable to that of the iridium pyridine complex (PPY)₂Ir(acac) (PPY = 2-phenylpyridine), which is among the best reported.     

Voltammetric behaviour of dichlorobis(2,2′-bipyridine) iridium(III) and dichlorobis(1,10-phenanthroline) iridium(III) complexes

The electrochemical behaviour of [Ir(bipy)₂Cl₂]⁺ and [Ir(phen)₂Cl₂]⁺ (bipy = 2,2′-bipyridine; phen = 1,10-phenanthroline) has been investigated in N,N-dimethylformamide (DMF). In potential sweep voltammetry [Ir(bipy)₂Cl₂]⁺ exhibits four reduction peaks. The first two processes involve one electron and are reversible in our conditions. The third reduction step is irreversible and has been attributed to the addition of three electrons to [Ir(bipy)₂Cl₂]⁺ followed by fast liberation of ligands. The data obtained for the fourth peak are consistent with a one-electron reversible process. The behaviour of [Ir(phen)₂Cl₂]⁺ is more complicated than that found for the bipy complex. In this case in fact, in addition to the four peaks observed in the case of the bipy complex, two other peaks appear. The latter have been attributed to the reduction of phen molecules liberated by the reduction of the complex. A qualitative MO discussion of the nature of the molecular levels involved in the reduction processes is also reported.     

Supramolecular assembly of trimeric gold(I) pyrazolates through aurophilic attractions

The supramolecular architecture of trinuclear gold(I) pyrazolato aggregates is held together by intermolecular aurophilic attractions, sterically governed by the substituents on the pyrazole rings. A two-dimensional network of [Au(mu-pz)]3 complexes, 1 (pz = pyrazolato anion, C3H3N2-), and a large intricate aggregate of 16 [Au(mu-4-Me-pz)]3 complexes in 2 have been determined crystallographically. Under UV irradiation at ambient temperature, solid samples of 1 and 2 luminesce with lambda max = 626 and 631 cm-1, respectively, attributed to intermolecular Au...Au aurophilic contacts.     

Studies on ruthenium(III), rhodium(III) and iridium(III) complexes of indazoles

Summary New complexes of the general formula M(L)₃Cl₃ and M(5-AInz)₂Cl₃ · n H₂O (where M = Ru^III, Rh^III and Ir^III; L = indazole and 5-nitroindazole; n=1–2) have been synthesized and characterised by elemental analysis, molar conductance, magnetic susceptibility and i.r. and electronic spectral measurements. All the complexes are covalent and apparently have an octahedral geometry. The ligands are monocoordinated through the pyrrole nitrogen. From the far i.r. spectra amer configuration has been assigned to the indazole and 5-nitroindazole complexes.     

Electrochemiluminescence of cyclometalated iridium (III) complexes

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Bright electrochemiluminescence of iridium(III) complexes

Electrochemiluminescence (ECL) of four bright iridium(III) complexes containing aryltriazole cyclometallated ligands is reported. The ECL mechanisms, spectra and high efficiencies via annihilation and coreactant paths have been investigated.