Coordination chemistry of perfluoroalkylated phosphorus(III) ligands

Palladium(II), platinum(II), rhodium(I), rhodium(III) and iridium(III) complexes of the tridecafluorohexyl-derivatised diphenylethylphosphinite (PPh₂OC₂H₄R_f), phenyldiethylphosphonite {PPh(OC₂H₄R_f)₂}, triethylphosphite {P(OC₂H₄R_f)₃}, triphenylphosphinite (PPh₂OC₆H₄-4-R_f), triphenylphosphonite {PPh(OC₆H₄-4-R_f)₂}, ethyldiphenylphosphine (PPh₂C₂H₄R_f), diethylphenylphosphine {PPh(C₂H₄R_f)₂} and triethylphosphine {P(C₂H₄R_f)₃} ligands are synthesized by conventional ligand displacement and/or halide-bridge cleaved reactions, and their spectroscopic parameters are compared with those for the related ligands lacking the tridecafluorohexyl ponytails.     

Phosphorescent iridium(III) complexes with nonconjugated cyclometalated ligands

A series of blue phosphorescent iridium(III) complexes 1-4 with nonconjugated N-benzylpyrazole ligands were synthesized and their structural, electrochemical, and photophysical properties were investigated. Complexes 1-4 exhibit phosphorescence with yields of 5-45 % in degassed CH2Cl2. Of the compounds, 1 showed emission that was nearly true blue at 460 nm with a lack of vibronic progression. These photophysical data clearly demonstrate that the methylene spacer of the cyclometalated N-benzylpyrazole chelate effectively interrupts the pi conjugation upon reacting with a third L X chelating chromophore. This gives a feasible synthesis for the blue phosphorescent complexes with a sufficiently large energy gap. In another approach, these complexes were investigated for their suitability for the host material in phosphorescent OLEDs. The device was synthesized by using 1 as the host for the green-emitting [Ir(ppy)3] dopant, which exhibits an external quantum conversion efficiency (EQE) of up to 11.4 % photons per electron (and 36.6 cdA(-1)), with 1931 Commission Internationale de L'Eclairage (CIE) coordinates of (0.30, 0.59), a peak power efficiency of 21.7 lmW(-1), and a maximum brightness of 32000 cdm(-2) at 14.5 V. At the practical brightness of 100 cdm(-2), the efficiency remains above 11 % and 18 lmW(-1), demonstrating its great potential as the host material for phosphorescent organic light-emitting diodes.     

Emissive chromium(III) complexes with substituted arylethynyl ligands

Arylethynylchromium(III) complexes of the form trans-[Cr(cyclam)(CCC(6)H(4)R)(2)]OTf (where cyclam = 1,4,8,11-tetraazacyclotetradecane, R = H, CH(3), or CF(3) in the para position, and OTf = trifluoromethanesulfonate) have been prepared and characterized by IR spectroscopy and X-ray diffraction. The complexes are emissive with excited-state lifetimes in a deoxygenated fluid solution between 200 and 300 micros.     

Novel tetranuclear cubane-like Co(II) complexes involving chelate phosphoramide ligands

Interaction of cobalt(II) ions and sodium carbacylamidophosphates Na(L) (HL=PhC(O)NHP(O)(NR₂)₂; where NR₂ are morpholyl, HL¹; NMe₂, HL²; NEt₂, HL³) in methanol solution afforded polynuclear alkoxo complexes [Co₄{L¹}₃(OCH₃)₄(OH)(H₂O)₅·3H₂O] 1 and [Co₄{L}₄(OCH₃)₄(CH₃OH)₄] (L=L² 2, L³ 3). Data of spectral and TGA studies are presented. Coordination compounds 1 and 3 have been characterized by means of X-ray diffraction. Both the structures consist of tetranuclear cubane alkoxo clusters with methoxide ions bridging three metal centers (CoO 2.068(3)–2.093(4) Å) and phosphorylic ligands coordinated in a bidentatechelate fashion via the carbonyl oxygen atoms (CoO 1: 2.050(2); 3: 2.031(4) Å) and the phosphoryl groups (2.093(2) and 2.106(4) Å). Isolation of these cubane alkoxo complexes is an important proof for close resemblance in behavior of carbacylamidophosphate systems and β-diketonates towards transition metal ions.     

Luminescence of neodymium(III) carboxylate complexes with different ligands

The spectral and luminescent characteristics of neodymium(III) carboxylate complexes with different nitrogen- and phosphorus-containing neutral ligands were studied and the relationship between the intensity of luminescence and the composition of the coordination sphere was established. The most intensive luminescence of neodymium(III) compounds in the IR region was observed from the complexes with toluic and cinnamic acids.     

Sterically crowded chelate complexes of copper(II) with phenoxazinyl ligands: ESR study

A copper complex with 1-H-1-oxo-2,4,6,8-tetrakis(tert-butyl)phenoxazinyl free radical ligands was synthesized, and its magnetic properties and ESR spectra were measured at 77–290 K. It was shown that a ground electron state with one unpaired electron is typical of this complex at 77–290 K. The magnetoresonance parameters of this complex are characterized by ag-factor value (1.978) that is rather unusual for copper-containing compounds and by hyperfine coupling due to Cu nuclei. The considerable broadening of ESR spectral lines with increasing temperature is probably not due to the formation of a quartet state (S=3/2). A model of electron states of the compound investigated was developed in the framework of ligand field theory, which made it possible to explain the pattern of the ESR spectra, which were untypical of copper complexes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 894–899, May, 1995.This study was financially supported by the International Science Foundation (Grant NRT 000).     

Synthesis and catalytic properties of rhodium(I) complexes with anionic chelate nitrogen-oxygen ligands

Summary Dicarbonyl complexes of rhodium(I) [Rh(CO)₂(LL)], where LL = salicylaldoximate, 8-oxyquinolinate, glycinate, leucinate, aminophenolate or pyridine carboxylate and [Rh(COD)(LL)], where COD = 1,5-cyclooctadiene, were prepared and characterized by elemental analysis, and i.r. and n.m.r. spectra. Their activity to catalytic hydroformylation of styrene has been evaluated at atmospheric pressure of COH₂(11).     

Kinetics of replacement of bridging ligands in a diruthenium(II,III) cation

Tetrakis-μ-propionatodiruthenium(II,III) cation reacts with oxalate, in acidic aqueous solution (0.10 M LiCF₃SO₃, [H⁺] 0.01 M at 29.4°C) in a two-phase process. An initial rapid change results in a small decrease in absorbance. This is ascribed to replacement of one propionate ligand by oxalate. A subsequent slower reaction, of which the rate is proportional to added oxalate concentration (k_bi 1.3 M⁻¹ s⁻¹), corresponds to a relatively large increase of absorbance at 475 nm, the absorbance maximum of the product. The data indicate formation of a bis(μ-oxalato)bis(μ-propionato)diruthenium(II,III) anion with a formation constant K_f > 2 x 10⁴ M⁻¹ and an extinction coefficient of 1.3 x 10³ M⁻¹ cm⁻¹ at 475 nm. A third, much slower, change results in decomposition of that product. The occurrence of replacement of bridging ligands under mild conditions indicates that tris-μ-carboxylatodiruthenium(II,Ill) species (otherwise unknown) function as kinetic intermediates.     

Gaseous iron(II) and iron(III) complexes with BINOLate ligands

Electrospray ionization (ESI) of dilute solutions of 1,1'-bi-2-naphthol (BINOL) and iron(II) or iron(III) sulfate in methanol/water allows the generation of monocationic complexes of iron and deprotonated BINOL ligands with additional methanol molecules in the coordination sphere, and the types of complexes formed can be controlled by the valence of the iron precursors used in ESI. Thus, iron(II) sulfate leads to [(BINOLate)Fe(CH3OH)n]+ complexes (n=0-3), whereas usage of iron(III) sulfate allows the generation of [(BINOLdiate)-Fe(CH3OH)n]+ cations (n=0-2); here, BINOLate and BINOLdiate stand for singly and doubly deprotonated BINOL, respectively. Upon collision-induced dissociation, the mass-selected ions with n>0 first lose the methanol ligands and then undergo characteristic fragmentations. Bare [(BINOLdiate)Fe]+, a formal iron(III) species, undergoes decarbonylation, which is known as a typical fragmentation of ionized phenols and phenolates either as free species or as the corresponding metal complexes. The bare [(BINOLate)Fe]+ cation, on the other hand, preferentially loses neutral FeOH to afford an organic C20H12O+* cation radical, which most likely corresponds to ionized 1,1'-dinaphthofurane.     

Indium(III), antimony(III) and bismuth(III) dihalide complexes with tridentate, anionic thio- and selenosemicarbazonato ligands

Some indium(III), antimony(III) and bismuth(III) dihalide complexes containing deprotonated, tridentate thio- and selenosemicarbazone ligands were prepared and were fully characterized by spectroscopic methods. In addition, the crystal structures of some of the compounds were obtained. TGA and DSC analyses were carried out on selected samples to assess their suitability as single-molecule precursors for metal selenide nanomaterials.     

Aniono-pentaaminecobalt(III) complexes with polyamine ligands. Part 23. A chloropentaamine by-product from the preparation of the trans-CoCl2(en) cation

The isolation and characterisation of [CoCl(en)(L)]ZnCl₄, L = NH₂CH₂CH?NCH₂CH₂NH₂ (1,4,7-triazahept-3-ene), as a by-product (～ 8% yield) from the H₂O₂ synthesis of trans-CoCl₂(en), is described.     

Palladium(II), platinum(II), rhodium(III) and iridium(III) complexes coordinated with 2-aryl-4,5-dimethyl-1,2,3-triazoles as bidentate nitrogen-carbon chelate ligands

Summary Cyclometallations of 2-aryl-4,5-dimethyl-1,2,3-triazoles [H(C-N)] occur with palladium(II), platinum(II), rhodium(III) and iridium(III) chloride. Pallaciation and platination form [MCI(C-N)]₂, and rhodation and iridation [MCI(C-N)₂]₂ species. These complexes react with monodentate ligands, L, such as pyridine and tri-n-butylphosphine to give MCl(C-N)L and MCl(C-N)₂ L complexes. Corresponding bromo and iodo complexes are prepared by metathesis with lithium bromide and iodide. Spectroscopic data suggest that MX(C-N)L compounds (X = Cl, Br or I) have a structure withtrans-C,X andtrans-N,L, while [MX(C-N)₂ L] has atrans-N,N,cis-C,C, andcis-X,L structure.Author to whom all correspondence should be directed.     

Thermal analysis of some chromium(III) complexes with dicarboxylic ligands

The solid chromium(III) complexes with a series of dicarboxylic ligands were prepared as potassium salts and examined by TG, DTG and DSC. The results are discussed in terms of basicity by arranging the ligands in proper series.     

μ-Peroxodicobalt(III) complexes containing aromatic ligands

A series of new μ-peroxodicobalt(III) complexes have been prepared and characterized. Studies of the chemical and physical properties of these complexes were carried out using IR, electronic and NMR spectroscopy along with conductivity, magnetic susceptibility and thermogravimetric measurements. The complexes [Co₂(dpk·dien)₂ (dpk·H₂O)O₂] (ClO₄)₄·H₂O, [Co₂(dpk)₄(py)₂O₂](ClO₄)₄·4H₂O, [Co₂(dpk·H₂O₄(py)₂O₂] (ClO₄)₄, and [Co₂(dpk)₂(terpy)₂O₂](ClO₄)₄ were prepared by bubbling oxygen through a solution containing Co(NO₃)₂, NaClO₄, and the appropriate ligand mixture. Electronic spectral studies are consistent with the formulation as binuclear peroxo complexes. Thermogravimetric studies reveal the stoichiometric loss of O₂ and H₂O below 100°C. The auxiliary ligands, pyridine (py), diethylenetriamine (dien) and terpyridine (terpy) are lost at higher temperatures. Molar conductance of these complexes is indicative of a 4:1 electrolyte while magnetic susceptibility measurements indicate the diamagnetic character of the above four complexes. Three additional complexes of Co(II) containing di-2-pyridyl ketone (dpk) and terpy were prepared to compare spectral changes upon oxygenation.     

Luminescense properties of new complexes of Eu(III) and Tb(III) with heterotopic ligands

As a result of coordination between ligands L and L' and europium(III) and terbium(III) ions, the new architectures were formed. The formulae of the complexes have been assigned on the basis of the spectroscopic data in solution and microanalyses. The europium complexes show excellent luminescence properties with high quantum yield (1b-Eu(3)L(2)) and effective intramolecular energy transfer from the ligand to the Eu(III) ions.     

Oxygen catalyzed mobilization of iron from ferritin by iron(III) chelate ligands

Tridentate chelate ligands of 2,6-bis[hydroxy(methyl)amino]-1,3,5-triazine family rapidly release iron from human recombinant ferritin in the presence of oxygen. The reaction is inhibited by superoxide dismutase, catalase, mannitol and urea. Suggested reaction mechanism involves reduction of the ferritin iron core by superoxide anion, diffusion of iron(II) cations outside the ferritin shell, and regeneration of superoxide anions through oxidation of iron(II) chelate complexes with molecular oxygen.