Mixed-ligand complexes of osmium(III/IV)8-quinolinolates with one ketoximate ligand

Summary A group of mixed-tris chelates of type [OsAQ₂] [A = isonitrosoacetophenonate (A¹) and isonitroso-propiophenonate (A²); Q = deprotonated 8-quinolinol (Q¹) and 2-methyl-8-quinolinol (Q²)] have been prepared by two distinct synthetic approaches. [OsAQ₂]⁺, obtained by Ce^IV oxidation of [OsAQ₂], can be regenerated by hydrazine hydrate reduction of the former. The complexes, characterized by physico-chemical, magnetic and spectroscopic methods, exhibit several spin-allowed and spin-forbidden charge transfer transitions in their electronic spectra. In MeCN solution the OsN₃O₃ unit displays a nearly-reversible Os^IV-Os^III change and an Os^III-Os^II couple in the ca. -1.0– + 0.3V range versus s.c.e. The stability of the metal oxidation levels is discussed in terms of the chemical and electrochemical results.     

Mixed-ligand complexes of osmium(III/II)8-quinolinolates with one diimine/azoimine ligand

Summary Paramagnetic [Os^IIIDQ₂]⁺ and diamagnetic [Os^IIAQ₂] (Q = deprotonated 8-quinolinols, D = diimines and A = azoimines) complexes were prepared and characterised by physicochemical, magnetic and spectroscopic methods. The complexes exhibit several spin-allowed and spinforbidden charge-transfer transitions in the visible region. In MeCN solution the OsN₄O₂ unit displays nearly reversible Os^IV-Os^III and Os^III-Os^II couples in the ca. -0.4 to +1.1 V range versus SCE. An anodic shift of these responses is seen in going from diimines to azoimines. The stability of metal oxidation levels is correlated on the basis of -acceptor properties of these ligands.     

Heteroleptic tris-complexes of osmium(III/IV)8-quinolinolates: synthesis,characterization and link-up of oxidation levels

Summary A series of mixed-tris chelates of Os^III and Os^IV of the general formula [OsDQ₂]^0/1+ [D =-ketoenolates (D¹-D³) or tropolonate (D⁴); Q = deprotonated 8-quinolinol] has been prepared and characterized by physico-chemical and spectroscopic methods. In MeCN solution the OsN₂O₄ unit displays reversible Os^IV-Os^III and Os^III-Os^II couples in the ca. - 1.2 to + 0.3 V range versus s.c.e. An irreversible oxidative response corresponding to a higher degree of oxidation is also observed at ca. 1.6 V. The chemistry in different oxidation states is discussed in terms of the electrochemical results.     

Mixed-ligand uranyl(V) beta-diketiminate/beta-diketonate complexes: synthesis and characterization

The reaction of [UO 2(Ar 2nacnac)Cl] 2 [Ar 2nacnac = (2,6- (i)Pr 2C 6H 3)NC(Me)CHC(Me)N(2,6- (i)Pr 2C 6H 3)] with Na(RC(O)CHC(O)R) (R = Me, Ph, CF 3) in tetrahydrofuran results in the formation of UO 2(Ar 2nacnac)(RC(O)CHC(O)R) (R = Me, 1; Ph, 2; CF 3, 3), which can be isolated in moderate yields. The structures of 1 and 2 have been confirmed by X-ray crystallography, while the solution redox properties of 1- 3 have been measured by cyclic voltammetry. Complexes 1- 3 exhibit reduction features at -1.82, -1.59, and -1.39 V (vs Fc/Fc (+)), respectively, at a scan rate of 100 mV.s (-1). The decrease in the reduction potential follows the electron-withdrawing ability of each beta-diketonate ligand. Chemical reduction of 1 and 2 with Cp* 2Co in toluene yields [Cp* 2Co][UO 2(Ar 2nacnac)(RC(O)CHC(O)R)] (R = Me, 4; Ph, 5), while reduction of 3 with Cp 2Co provides [Cp 2Co][UO 2(Ar 2nacnac)(CF 3C(O)CHC(O)CF 3)] ( 6). Complexes 4- 6 have been fully characterized, while the solid-state molecular structure of 5 has also been determined. In contrast to the clean reduction that occurs with Cp* 2Co, reduction of 1 with sodium ribbon, followed by cation exchange with [NEt 4]Cl, produces [NEt 4][UO 2(Ar 2nacnac)(H 2CC(O)CH(O)CMe)] ( 7) in modest yield. This product results from the formal loss of H (*) from a methyl group of the acetylacetonate ligand. Alternately, complex 7 can be synthesized by deprotonation of 1 with NaNTMS 2 in good yield.     

Mixed-ligand and binuclear complexes of oxovanadium(IV)

Summary Mixed ligand complexes of the type [VOLA]ClO₄ where L=5-bromosalicylaldehyde (L) or 5-nitrosalicylaldehyde (L) and A=2, 2-dipyridyl (A) or 1, 10-phenanthroline (A) have been prepared. Treatment of the mononuclear complexes, [VOLA]ClO₄, withp-phenylenediamine (ppd) orm-phenylenediamine (mpd) yielded homobinuclear [VOLA-NC₆H₄N-LAVO](ClO₄)₂, complexes, which were characterised by elemental analyses, spectra, magnetic susceptibility and molar conductance measurements.     

Mixed-ligand copper(II) complexes with positive redox potentials

Summary Mixed-ligand complexes formed by reaction of Cu(ClO₄)₂ with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (dppt) as primary ligand and 2,2-bipyridine (bipy), 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (dmp), N,N-bis(pyrid-2-ylmethyl)amine (dipica), N,N-bis(benzimidazol-2-ylmethyl)amine (bba), 1,3-bis(2-benzimidazolyl)-2-thiapropane (bbms) and 1,5-bis(benzimidazolyl)-3-thiapentane (bbes) as the secondary ligands have been isolated. They are of the type [Cu(dppt)L](ClO₄)₂·nH₂O, where n = 0 or 2. All complexes exhibit only one ligand field band and their cryogenic solution e.p.r. spectra are axial, with v_max and g values diagnostic of a square-based geometry. The spectral and redox data are consistent with facial coordination of the tridentate ligands. All the complexes exhibit a positive redox potential (versus n.h.e.). The weak -bonding of dppt, caused by the highly electron-withdrawing phenyl rings, the strong -back bonding involving phen and dmp, and interligand repulsions appear to be responsible for the relatively positive Cu^II/Cu^I redox potentials.     

Mixed-ligand complexes of Ru(III) and Rh(III): ESR studies on some Ru(III) complexes

Reactions of 2-mercapto-3-phenyl-4-quinazolinone (LH) with RuCl₃·xH₂O and RhCl₃·xH₂O afforded the compounds [RuL₂Cl(H₂O)]H₂O, [RuL₂Cl·DMFI and RhL(LH)Cl₂·2H₂O. Reactions of LH with RuCl₃·xH₂O in the presence of N-heterocyclic bases led to the formation of complexes of type [RuL₂ClB]·H₂O (B = pyridine, 3-picoline or imidazole) and [RuLCl₂(o-phen)] H₂O (o-phen = 1, 10-phenanthroline). These complexes were characterized on the basis of analytical, conductivity, magnetic, IR and electronic spectral and ESR studies. Tentative structures for the complexes are proposed.     

Mixed-ligand iridium(IV) complexes with amino acids,adenine and hypoxanthine

The complexation in iridium(IV)-purine base (adenine, hypoxanthine)-amino acid (α-alanine, aspartic acid, lysine) systems was studied by pH titration. The stability constants of 1: 1: 1 complexes were determined. The stability of 1: 1: 1 mixed-ligand complexes with hypoxanthine and adenine increases in the series Ala < Lys < Asp. Reactions between aqueous solutions gave the following coordination compounds: [Ir(C₅H₄N₄O)(C₃H₆NO₂)Cl]Cl₂, [Ir(C₅H₄N₄O)(C₄H₅NO₄)]Cl₂, [Ir(C₅H₄N₄O)(C₆H₁₃N₂O₂)]Cl₃, [Ir(C₅H₅N₅)(C₃H₆NO₂)]Cl₃, [Ir(C₅H₅N₅)(C₄H₅NO₄)]C_l2, and [Ir(C₅H₅N₅)(C₆H₁₃N₂O₂)]Cl₃. The individual character of the complexes was established by chemical and thermogravimetric analyses and powder X-ray diffraction. The complexes were characterized by NMR, IR, and X-ray photoelectron spectroscopy. Alanine and lysine in mixed-ligand iridium(IV) complexes are bidentate (α-NH₂ and COO⁻ groups), aspartic acid is tridentate, and purine bases function as polydentate ligands through heterocycle N atoms and functional groups (NH₂ in adenine and C=O in hypoxanthine).     

Organotin(IV) complexes of thiohydrazones: synthesis, characterization and antifungal study

Some new organotin(IV) complexes with salicylaldehyde aniline-N-thiohydrazone (L1) and cinamaldehyde aniline-N-thiohydrazone (L2) of the type (p-ClC6H4)3Sn[L] Cl and (p-ClC6H4)2Sn[L]Cl2 have been synthesized (where L = L1 and L2). The complexes and ligands were characterized by elemental analysis and spectral (UV-vis, IR and 1H NMR) studies. In all the complexes, ligands act as bidentate, coordination through sulphur and azomethane nitrogen. Complexes are 1:1 metal ligands complexes. Antifungal studies of some complexes against Rhizoctonia bataticola fungal strain have been carried out.     

Mixed-ligand platinum(IV) complexes with amino acids and cytosine

Complex formation in platinum(IV)-cytosine-amino acid (glycine, α-alanine, lysine, or histidine) systems is studied using pH titration. Stability constants for 1:1:1 stoichiometry of complexes are determined. The stability of the mixed-ligand complexes varies in the following order: Lys < Ala < Gly < His. Reactions of aqueous solutions yields the following complexes: Pt(Cyt)(Gly^?)Cl₃ · 3H₂O (I), pt(Cyt)(Ala^?)Cl₃ · 3H₂O (II), Pt(Cyt)(Hist)Cl₄ · 2H₂O (III), and Pt(Cyt)(Lys)Cl₄ · 2H₂O (IV). ¹³C NMR, IR, and XPS spectra show that glycine and alanine are complexed via amino and carboxy groups, lysine via its α-amino group exclusively, and histidine via its amino group and heterocyclic N3 atom. Cytosine in these complexes is bidentate (it is complexed via C=O oxygen and N3 heterocyclic atoms).     

Mixed-ligand platinum(IV) complexes with amino acids and adenine

Complexing in platinum(IV)-adenine-amino acid (α-alanine (Ala), lysine (Lys), or histidine (His)) systems was studied by pH titration. The stability constants of 1: 1: 1 complexes were determined. The stability of these mixed-ligand complexes changes in the following order: Lys < Ala < His. Reactions between aqueous solutions of H₂PtCl₆ and amino acids produced the following coordination compounds: Pt(C₃H₆NO₂)(C₅H₅N₅)Cl₃ · 2H₂O, or Pt(Ala^?)(Ade)Cl₃ · 2H₂O (I); Pt(C₅H₅N₅)(C₆H₁₄N₂O₂)Cl₄ · 2H₂O, or Pt(Ade)(Lys)Cl₄ · 2H₂O (II); and Pt(C₅H₅N₅)(C₆H₉N₃O₂)Cl₄ · 3H₂O or Pt(Ade)(Hist)Cl₄ · 3H₂O (III). These complexes were characterized by ¹³C NMR, IR, and X-ray photoelectron spectroscopy. Alanine is complexed via both amino and carboxy groups; lysine, via α-amino group exclusively; and histidine, via the amino group and the N3 heterocyclic atom. Adenine in these complexes is monodentate due to the N7 heterocyclic atom. The adenine amino group is apparently H-bonded to a water oxygen atom.     

Mixed-ligand praseodymium(III) complexes with glycine,methionine, and tartaric acid

Mixed-ligand inner complexes of praseodymium(III) containing coordinated glycine or methionine ions and tartaric acid were synthesized. The compositions of the complexes were determined, and their spectral and thermal properties were studied. The coordination modes of the ligands were determined based on the results.     

New homoleptic organometallic derivatives of vanadium(III) and vanadium(IV): synthesis, characterization, and study of their electrochemical behaviour

The arylation of [VCl3(thf)3] with LiR(Cl), where R(Cl) is a polychlorinated phenyl group [C6Cl5, 2,4,6-trichlorophenyl(tcp), or 2,6-dichlorophenyl (dcp)] gives four-coordinate, homoleptic organovanadium(III) derivatives with the formula [Li(thf)(4)][V(III)(R(Cl))(4)] (R(Cl) = C(6)Cl(5) (1), tcp (2), dcp (3)). The anion [V(III)(C6Cl5)4]- has an almost tetrahedral geometry, as observed in the solid-state structure of [NBu4][V(C6Cl5)4] (1') (X-ray diffraction). Compounds 1-3 are electrochemically related to the neutral organovanadium(IV) species [V(IV)(R(Cl))4] (R(Cl) = C6Cl5 (4), tcp (5), dcp (6)). The redox potentials of the V(IV)/V(III) semisystems in CH2Cl2 decrease with decreasing chlorination of the phenyl ring (E(1/2) = 0.84 (4/1), 0.42 (5/2), 0.25 V (6/3)). All the [V(IV)(R(Cl))4] derivatives involved in these redox couples could also be prepared and isolated by chemical methods. The arylation of [VCl(3)(thf)(3)] with LiC6F5 also gives a homoleptic organovanadium(III) compound, but with a different stoichiometry: [NBu4]2[V(III)(C6F5)5] (7). In this five-coordinate species, the C6F5 groups define a trigonal bipyramidal environment for the vanadium atom (X-ray diffraction). EPR spectra for the new organovanadium compounds 1-6 are also given and analysed in terms of an elongated tetrahedral structure with C(2v) local symmetry. It is suggested that the R(Cl) groups exert a protective effect towards the vanadium centre.     

Platinum(IV) complexes with N-alkylphenothiazines: synthesis,characterization, and antibacterial activity

Two new platinum(IV) complexes (1, trifluoperazinehydrochloride-aquapentachloridoplatinate(IV) and 2, chlorpromazine-chlorpromazinehydrochloridepentachloridoplatinate(IV)) were synthesized in the reaction of K₂[PtCl₆] with trifluoperazine dihydrochloride (TF·2HCl) or chlorpromazine hydrochloride (CP·HCl). The complexes were characterized by elemental analysis, molar conductivity measurement, and spectral (IR, ¹H, ¹³C, 2D ¹H–¹³C heteronuclear correlation spectra, ¹⁹⁵Pt NMR, and MS) methods. Outer-coordination sphere was proposed for 1; while in 2, the ligand was coordinated to the metal. The complexes exhibit antibacterial effect on strains of Bacillus subtilis, Bacillus cereus, Bacillus pumilus, and methicillin-resistant Staphylococci as Gram-positive bacteria and an Escherichia coli as Gram-negative bacteria, as well as the reference strains.     

Divalent osmium complexes: synthesis,characterization, strong red phosphorescence,and electrophosphorescence

We report new divalent osmium complexes that feature strong red metal-to-ligand-charge-transfer (MLCT) phosphorescence and electrophosphorescence. The general formula of the complexes is Os(II)(N-N)(2)L-L, where N-N is either a bipyridine or a phenanthroline and L-L is either a phosphine or an arsine. New polypyridyl ligands synthesized are 4,4'-di(biphenyl)-2,2'-bipyridine (15) and 4,4'-di(diphenyl ether)-2,2'-bipyridine (16), and the 1,10-phenanthroline derivatives synthesized are 4,7-bis(p-methoxyphenyl)-1,10-phenanthroline (17), 4,7-bis(p-bromophenyl)-1,10-phenanthroline (18), 4,7-bis(4'-phenoxybiphen-4-yl)-1,10-phenanthroline (19), and 4,7-bis(4-naphth-2-ylphenyl)-1,10-phenanthroline (20). 4,4'-Diphenyl-2,2'-bipyridine (21) and 4,7-diphenyl-1,10-phenanthroline (22) were also used in these studies. Strong pi-acid ligands used were 1,2-bis(diphenylarseno)ethane (23), cis-1,2-bis(diphenylphosphino)ethylene (24), and cis-1,2-vinylenebis(diphenylarsine) (25). Ligand 25 is used for the first time in these types of luminescent osmium complexes. These compounds feature strong MLCT absorption bands in the visible region and strong red phosphorescent emission ranging from 611 to 651 nm, with quantum efficiency up to 45% in ethanol solution at room temperature. Red organic light-emitting diodes (OLEDs) were successfully fabricated by doping the Os(II) complexes into blend of poly(N-vinylcarbazole) (PVK) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD). Brightness over 1400 cd/m(2) for a double-layer device has been reached, with a turn-on voltage of 8 V. The maximum external quantum efficiency was 0.64%. Commission Internationale de l'Eclairage (CIE) chromaticity coordinates (x, y) of the red electrophosphorescence from the complexes are (0.65, 0.34), which indicates pure red emission.     

Syntheses,characterization, and crystal structures of ruthenium(II)/(III) complexes with tridentate salicylaldiminato ligands

Treatment of [Ru(PPh₃)₃Cl₂] with one equivalent of tridentate Schiff base 2-[(2-dimethylamino-ethylimino)-methyl]-phenol (HL) in the presence of triethylamine afforded a ruthenium(III) complex [RuCl₃(κ²-N,N-NH₂CH₂CH₂NMe₂)(PPh₃)] as a result of decomposition of HL. Interaction of HL and one equivalent of [RuHCl(CO)(PPh₃)₃], [Ru(CO)₂Cl₂] or [Ru(tht)₄Cl₂] (tht = tetrahydrothiophene) under different conditions led to isolation of the corresponding ruthenium(II) complexes [RuCl(κ³-N,N,O-L)(CO)(PPh₃)] (2), [RuCl(κ³-N,N,O-L)(CO)₂] (3), and a ruthenium(III) complex [RuCl₂(κ³-N,N,O-L)(tht)] (4), respectively. Molecular structures of 1·CH₂Cl₂, 2·CH₂Cl₂, 3 and 4 have been determined by single-crystal X-ray diffraction.     

Imidomolybdenum(IV) porphyrin complexes: synthesis, characterization, and intermetal imido transfer reactivity

The imido(meso-tetra-p-tolylporphyrinato)molybdenum(IV) complexes, (TTP)Mo=NR, where R = C6H5 (1a), p-CH3C6H4 (1b), 2,4,6-(CH3)3C6H2 (1c), and 2,6-(i-Pr)2C6H4 (1d), can be prepared by the reaction of (TTP)MoCl2 with 2 equiv of LiNHR in toluene. Upon treatment of the imido complexes with pyridine derivatives, NC5H4-p-X (X = CH3, CH(CH3)2, C[triple bond]N), new six-coordinate complexes, (TTP)Mo=NR.NC5H4-p-X, were observed. The reaction between the molybdenum imido complexes, (TTP)Mo=NC6H5 or (TTP)Mo=NC6H4CH3, and (TTP)Ti(eta2-PhC[triple bond]CPh) resulted in complete imido group transfer and two-electron redox of the metal centers to give (TTP)Mo(eta2-PhC[triple bond]CPh) and (TTP)Ti=NC6H5 or (TTP)Ti=NC6H4CH3.     

Coordinatively saturated cyclometallated Pt(IV) azobenzene complexes: synthesis and mesomorphic behaviour

The mesomorphic 4,4-bis[4-n-octyloxybenzoyloxy]azobenzene dinuclear chloro-bridged cycloplatinated complex [(Azo)Pt(mu;-Cl)]2 (smectic C between 263 and 342 C) has been reacted with different chelating ligands, giving rise to a family of square-planar ortho-platinated derivatives, [(Azo)Pt(L)] (L = tropolonate, 8-hydroxyquinolinate and 1,1,1,5,5,5-hexafluoro2,4-pentanedionate). Thermotropic mesomorphism is preserved for these mononuclear complexes which exhibit at least a nematic mesophase and transition temperatures lower by over 100° C than that of the corresponding dimeric precursor. Oxidative addition to the Pt(II) [(Azo)Pt(L)] species of electrophilic substrates such as I₂ or CH₃I eventually led to the corresponding octahedral [(Azo)Pt(L)(I)(X)] products. The introduction of two further ligands leads to Pt(IV) derivatives showing smectic and nematic mesophases for all L ligands. For the hexacoordinated [(Azo)Pt(L)(I)(CH₃)] complexes it has been verified that the oxidative addition of methyl iodide is a thermally reversible process, indicating that these species have potential applications as switchable systems.     

Manipulation of reaction pathways in redox transmetallation-ligand exchange syntheses of lanthanoid(II)/(III) aryloxide complexes

Redox transmetallation/ligand exchange reactions of lanthanoid metals (Ln), Hg(C6F5)2 and HOAr(OMe) (Ar(OMe) = C6H2-2,6-Bu(t)-4-OMe), in thf (tetrahydrofuran) gave, for Ln = Yb, [Yb(OAr(OMe))2(thf)3], and for Ln = Sm, a mixture of [Sm(II)(OAr(OMe))2(thf)3] and mainly [Sm(III)(Ar(OMe))3(thf)] x thf. X-Ray structure determinations show the divalent complexes to have distorted square-pyramidal stereochemistry with transoid thf and OAr(OMe) ligands in the basal plane. Treatment of [Yb(OAr(OMe))2(thf)3] with diethyl ether or PhMe at room temperature gave [Yb(OAr(OMe))2] or [Yb(OAr(OMe))2] x 0.5 PhMe. For lanthanoids Ln = Nd, Er or Y, the reactions with Hg(C6F5)2 and HOAr(OMe) yielded complex product mixtures, from one of which the novel erbium aryloxide fluoride cage [Er3(OAr(OMe))4(mu2-F)3(mu3-F)2(thf)4] x thf x 0.5 C6H14 was isolated. The cage core consists of a triangle of Er atoms joined to two mu3-fluoride ligands and three further mu2-fluorides bridge adjacent Er atoms. One of the Er atoms is six-coordinate with additionally two OAr(OMe) ligands whilst the other two have one OAr(OMe) and two thf ligands and are seven coordinate. Substitution of Hg(C6F5)2 by Hg(CCPh)2 in the redox transmetallation/ligand exchange reactions gave the new derivatives [Ln(OAr(OMe))3(thf)] x thf (Ln = La, Pr, Nd, Sm, Gd, Ho) in good yields whilst Ln = Yb gave [Yb(OAr(OMe))2(thf)3]. Recrystallisation of [Sm(OAr(OMe))3(thf)] x thf from dme (1,2-dimethoxyethane) yielded [Sm(OAr(OMe))3(dme)]. Structural characterisation of [Ln(OAr(OMe))3(thf)] x thf (Ln = Nd, Ho) and [Sm(OAr(OMe))3(dme)] showed monomeric four-coordinate distorted tetrahedral and five-coordinate distorted square-pyramidal complexes respectively. For the smaller lanthanoids Ln = Y, Er or Lu, reactions with Hg(CCPh)2 and HOAr(OMe) gave the mixed aryloxide/alkynide complexes [Ln(OAr(OMe))2(CCPh)(thf)2]. Oxidation of the divalent ytterbium aryloxide [Yb(OAr(OMe))2(thf)3] by Hg(CCPh)2 in thf gave the analogous [Yb(OAr(OMe))2(CCPh)(thf)2]. The erbium alkynide [Er(OAr(OMe))2(CCPh)(thf)2] x 0.25 C6H14 has distorted square-pyramidal stereochemistry with transoid OAr(OMe) and thf ligands in the basal plane and a rare (for Ln) terminal alkynide ligand in the apical position. The reactive Lu-C bond in the [Lu(OAr(OMe))2(CCPh)(thf)2] complexes could be slowly cleaved by free HOAr(OMe) in hydrocarbon solvents, yielding Lu(OAr(OMe))3 species and fortuitous partial hydrolysis of [Er(Ar(OMe))2(CCPh)(thf)2] gave the dimeric [Er(OAr(OMe))2(mu-OH)2]2.