A facile approach for the synthesis of novel substituted 4H-chromenes and condensation reactions of 4H-chromenes leading to chromenopyrrolones and triazolylchromenopyrrolones

A facile method has been developed for the synthesis of 4H-chromene-3-carboxylates 3a–d by the nucleophilic substitution reaction of 2-hydroxy-2H-chromene-3-carboxylates 2a–d with triethylsilane in the presence of BF₃·O(C₂H₅)₂. Cyclocondensation of 4H-chromene-3-carboxylates 3a–d with benzylamines 4a–d afforded a series of 2,3-dihydrochromenopyrrolones 5a–p and with propargylamine afforded 2-propynyl-2,3-dihydrochromenopyrrolones 6a–d. Click reaction of 6a–d with benzyl azides 7a–d provided a series of 1H-1,2,3-triazolylmethyl-2,3-dihydrochromenopyrrolones 8a–p. Thus synthesized compounds 3a–d, 5a–p, 6a–d, and 8a–p are novel heterocyclic compounds and being reported for the first time.     

Half-sandwich η-arene–ruthenium(II) complexes bearing 1-alkyl(benzyl)-imidazo[4,5-f][1,10]-phenanthroline (IP) derivatives: the effect of alkyl chain length of ligands to catalytic activity

The reaction of bromoalkanes (R–Br; (3), R=C_nH_2n+1, n=4 (a), 8 (b), 12 (c),18 (d)) and bromobenzyl derivatives (R′–Br; (4), R′=CH₂C₆H₂(CH₃)₃-2,4,6 (a); CH₂C₆H(CH₃)₄-2,3,5,6 (b); CH₂C₆(CH₃)₅ (c)) with 1H-imidazo[4,5-f][1,10]-phenanthroline (IP)(L₂) gave the corresponding 1-R-imidazo[4,5-f][1,10]-phenanthroline (IPR)(L_3a–d) and 1-R′-imidazo[4,5-f][1,10]-phenanthroline(IPR')(L_4a–c) ligands, respectively. Treatment of L_3a–d and L_4a–d with [Ru(p-cymene)Cl₂]₂ led to the formation of [Ru(p-cymene)(IPR)Cl]Cl (RuL_3a–d) and [Ru(p-cymene)(IPR′)Cl]Cl (RuL_4a–c). New ruthenium(II) complexes RuL_3a–d and RuL_4a–c were characterized by elemental analysis, FTIR, UV–visible and NMR spectroscopy. In order to understand effects of these changes on the N-substituent of imidazol on IP and how they translate to catalytic activity, these new RuL₂, RuL_3a–d and RuL_4a–c were applied in the transfer hydrogenation of ketones by 2-propanol in presence of potassium hydroxide. The activities of the catalysts were monitored by NMR and GC analysis.     

New 3d–4f supramolecular systems constructed by [Fe(bipy)(CN)4] and partially blocked lanthanide cations

The reaction of acetonitrile (1–5) and mixed acetonitrile/water 1:1 (6–9) solutions containing the cyanide-bearing [Fe(bipy)(CN)₄]⁻ building block (bipy = 2,2′-bipyridine) and the partially blocked [Ln(bpym)]³⁺ cation (Ln = lanthanide trivalent cation and bpym = 2,2′-bipyrimidine) has afforded two new families of 3d–4f supramolecular assemblies of formula [Ln(bpym)(NO₃)₂(H₂O)₃][Fe(bipy)(CN)₄] · H₂O · CH₃CN [Ln = Sm (1), Gd (2), Tb (3), Dy (4) and Ho (5)] and [Ln(bpym)(NO₃)₂(H₂O)₄][Fe(bipy)(CN)₄] [Ln = Pr (6), Nd (7), Sm (8), Gd (9)]. They crystallize in the P2₁/c (1–5) and P2/c (6–9) space groups and their structures are made up of [Fe(bipy)(CN)₄]⁻ anions (1–9) and [Ln(bpym)(NO₃)₂(H₂O)_n]⁺ cations [n = 3 (1–5) and 4 (6–9)] with uncoordinated water and acetonitrile molecules (1–5) which are interlinked through an extensive network of hydrogen bonds and π–π stacking into three-dimensional motifs. Both families have in common the occurrence of the low-spin iron(III) unit [Fe(bipy)(CN)₄]⁻ where two bipy–nitrogen and four cyanide–carbon atoms build a somewhat distorted octahedral surrounding around the iron atom [Fe–N = 1.980(3)–1.988(3) Å (1–5) and 1.988(2)–1.992(2) Å (6–9); Fe–C = 1.904(5)–1.952(4) Å (1–5) and 1.911(2)–1.948(3) Å (6–9)]. The main structural difference between both families concerns the environment of the lanthanide atom which is nine- (1–5)/10-coordinated (6–9) with a chelating bpym, two bidentate nitrate and three (1–5)/four (6–9) water molecules building distorted monocapped (1–5)/bicapped (6–9) square antiprisms. This different lanthanide environment is at the origin of the different hydrogen bonding pattern of the two families of compounds.     

Synthesis of 1-indolyl substituted β-carboline natural products and discovery of antimalarial and cytotoxic activities

A series of 1-indolyl substituted β-carbolines including the natural products hyrtiosulawesine, pityriacitrin and pityriacitrin B were prepared via Pictet–Spengler condensation—oxidation strategy from the corresponding indolyl-acetaldehydes and substituted tryptamines. Efforts to prepare the C-1 methylene-linked β-carboline analogues for structure–activity relationship studies were unsuccessful. Biological evaluation revealed two analogues (5 and 41) to exhibit weak inhibition of phospholipase A₂ (IC₅₀ 171 and 131 μM, respectively), two to act as antioxidants (3 and 43), and 12 analogues with activity towards a chloroquine-resistant strain (FcB1) of Plasmodium falciparum (IC₅₀ 1.0–23 μM). Testing against a panel of 60 human tumour cell lines revealed a general lack of cytotoxic effect for most of the compounds with the exception of β-carboline 42 exhibiting modest antileukaemic activity towards the HL-60(TB) cell line (LC₅₀ 4.2 μM). In addition, two novel structures (30 and 32) resulting from aldol condensation followed by Pictet–Spengler cyclisation displayed cytotoxicity with pronounced subpanel specificities towards colon cancer (COLO 205 and HCC-2998) cell lines.     

Some new DTPA-N,N″-bis(amides) functionalized by alkyl carboxylates: Synthesis,complexation and stability properties

A new series of DTPA-N,N″-bis(amide) ligands functionalized by alkyl carboxylates on the amide side-arms (1a–1l) and their Gd(III) complexes of the type [Gd(1)(H₂O)] · xH₂O (2a–2l) were synthesized and characterized by analytical and spectroscopic techniques. Potentiality of 2a–2l as contrast agent for magnetic resonance imaging (MRI CA) was investigated by measuring some relevant physicochemical properties such as (i) the protonation constants of 1a–1l, (ii) thermodynamic and conditional stability constants of 2a–2l, (iii) the selectivity (pGd) of 1a–1l for the Gd(III) ion over the endogenous metal ions such as Zn(II), Ca(II), and Cu(II), and (iv) the relaxivities (R₁ and R₂) of 2a–2l in aqueous and aqueous HP-β-CD solutions. Comparative studies reveal that most of new Gd(III) complexes show enhanced thermodynamic stability and selectivity as compared with those of [Gd(DTPA-BMA)(H₂O)] (DTPA-BMA = N,N″-di(methylcarbamoylmethyl)diethylenetriamine-N,N′,N″-triacetate). Also enhanced with 1a–1l (except 1f and 1h) is affinity for Gd(III) as compared with [DTPA-BMA]³⁻ under physiological conditions. The relaxivities (R₁ and R₂) of aqueous solutions of 2a–2l, on the other hand, drop significantly as compared with [Gd(DTPA-BMA)(H₂O)] although they increase dramatically (6–10 fold) in aqueous hydroxypropyl-β-cyclodextrin (HP-β-CD) solutions.     

Conversion of novel palladacycles into oxopyrrolo[3,4-b]quinolines

The quinolinylcyclopalladated complexes 3a–b were synthesised in good yields (81% and 77%) by the insertion reaction of the prepared dinuclear palladium complexes [Pd(C,N-2-C₉H₄N-CHO-3-R-6)Cl(PPh₃)]₂ [(R = H (2a), R = OMe (2b)] with isonitrile XyNC (Xy = 2,6-Me₂C₆H₃). The cyclopalladated complexes 3a–b were also obtained in low yields (39% and 33.5%) via a one pot oxidative addition reaction of quinoline chloride 1a–b with isonitrile XyNC:Pd(dba)₂ (4:1). The reactions of 3a–b with Tl(TfO) (TfO = triflate, CF₃SO₃) in the presence of H₂O or EtOH causes depalladation reactions of the complexes to provide the corresponding organic compounds 4a–b, 5a–b and 6a–b in yields (41%, 27% and 18–19%). The products were characterized by satisfactory elemental analyses and spectral studies (IR, ¹H, ¹³C and ³¹P NMR). The crystal structures of 2a, 3a and 3b were determined by X-ray diffraction studies.     

Synthesis and characterization of Co(II) and Cu(II) supported complexes of 2-pyrazinecarboxylic acid for cyclohexene oxidation

The complexes [Co(N^O)₂] (1) and [Cu(N^O)₂] (2) {N^O = η²-(N,O) coordinated 2-pyrazinecarboxylic acid} have been synthesized and characterized by elemental (including metal) analyses, FT-IR spectroscopy and powder X-ray diffraction. The molecular structure of complex 2 was determined by single X-ray crystallography. In the molecule, the Cu atom occupies the center of a square planar geometry, which consists of two trans-O atoms and two trans-N atoms of two 2-pyrazinecarboxylic acid ligands. The complexes 1 and 2 were well encapsulated into zeolite–Y super-cage to yield the corresponding zeolite–Y encapsulated metal complexes, abbreviated herein as [Co(N^O)₂]–Y (3) and [Cu(N^O)₂]–Y (4). Similarly, the metal complexes 1 and 2 were immobilized on alumina and organically modified silica surfaces to lead to the formation of immobilized metal complexes [Co(N^O)₂]–Al₂O₃ (5); [Cu(N^O)₂]–Al₂O₃ (6); [Co(N^O)₂]–AMPS (7) and [Cu(N^O)₂]–AMPS (8) (AMPS = aminopropyl silica). Elemental (including metal) analyses, FT-IR spectroscopy, powder X-ray diffraction and thermal analysis have been used to characterize these materials. The catalytic activity of all the catalysts 1–8 towards the oxidation of cyclohexene into different chemically and pharmaceutically important products were evaluated under homogeneous and heterogeneous conditions. In order to obtain a maximum conversion of cyclohexene, the reaction parameters, like reaction temperature and time, were optimized. Under the optimized conditions, a maximum of 90.47% cyclohexene conversion was achieved with [Cu(N^O)₂]–Y (4) with a 1:2 molar ratio reaction of cyclohexene and H₂O₂.     

Temperature dependence on recrystallisation of the magnesium phthalocyanine (MgPc) in triethylamine

Three complexes of magnesium phthalocyaninato(2−) derivatives in the crystalline form, MgPc(H₂O)·(C₂H₅)₃N – (I), MgPc(H₂O)₂·2(C₂H₅)₃N – (II) and MgPc(H₂O)₂ – (III), depending on the thermal recrystallisation conditions were obtained and structurally characterised. In complex I, the Mg center exhibits square-pyramidal (4 + 1) coordination environment, whereas in II and III the Mg center of MgPc the biaxial (4 + 2) coordination. Owing to the interaction of the positively charged Mg center with oppositely charged oxygen atom of water molecule in an axial position in I, the Mg atom is significantly displaced (0.451(2) Å) from the plane defined by four isoindole N atoms and leads to distortion of the planar Pc(2−) macrocycle to the saucer-shape form. In II and III due to the biaxial (4 + 2) coordination of the Mg center of MgPc, the Mg atom lies on a N₄-isoindole plane. The triethylamine solvent molecules in I and II interact with mono or bis(aqua)magnesium phthalocyanine via   O–H?$?$N hydrogen bonds. The axial Mg–O bond in I is significantly shorter than that in the II and III complexes. The strength of the Mg–O bond in these complexes is correlated with their thermal stability. From among the complexes only complex I exhibits an intense near-IR absorption band in the solid-state. The spectra of I, II and III in solution are very similar.     

Synthesis and structural characterisation of five copper(I) and silver(I) complexes with 2-aminopyridine (2-APy), [Cu(μ-Cl)(2-Apy)(PPh3)]2, [Ag(μ-X)(2-Apy)(PPh3)]2 (X = Cl,Br), [Ag(μ-ONO2)(2-Apy)(EPh3)]2 (E = P,As)

Five new copper(I)/silver(I) complexes containing 2-aminopyridine, [Cu(μ-Cl)(2-Apy)(PPh₃)]₂(1), [Ag(μ-Cl)(2-Apy)(PPh₃)]₂(2), [Ag(μ-Br)(2-Apy)PPh₃)]₂(3), [Ag(μ-ONO₂)(2-Apy)(PPh₃)]₂(4), [Ag(μ-ONO₂)(2-Apy)(AsPh₃)]₂(5) have been synthesised for the first time. Complexes 1–5 are obtained by the reactions of MX (MX = CuCl for 1; M = Ag for 2–5; X = Cl, Br for 2–3; X = NO₃ for 4–5) with the monodentate ligands EPh₃ (E = P for 1–4; E = As for 5) and 2-Apy in the molar ratio of 1:1:2 in the mixed solvent of CH₂Cl₂ and MeOH. Complexes 1–5 are characterised by IR and X-ray diffraction. In 1–5, chloride, bromide and nitrate ions bridge two metal atoms to form dinuclear complexes containing the parallelogram cores M₂X₂ (M = Cu, Ag).     

Dimolybdenum complexes containing anions of N,N′-bis(pyrimidine-2-yl)formamidine and N-(2-pyrimidinyl)formamide

The reactions of Mo₂(O₂CCH₃)₄ with different equivalents of N,N′-bis(pyrimidine-2-yl)formamidine (HL1) and N-(2-pyrimidinyl)formamide (HL2) afforded dimolybdenum complexes of the types Mo₂(O₂CCH₃)(L1)₂(L2) (1) trans-Mo₂(L1)₂(L2)₂ (2) cis-Mo₂(L1)₂(L2)₂ (3) and Mo₂(L2)₄ (4). Their UV–Vis and NMR spectra have been recorded and their structures determined by X-ray crystallography. Complexes 2 and 3 establish the first pair of trans and cis forms of dimolybdenum complexes containing formamidinate ligands. The L1 ligands in 1–3 are bridged to the metal centers through two central amine nitrogen atoms, while the L2 ligands in 1–4 are bridged to the metal centers via one pyrimidyl nitrogen atom and the amine nitrogen atom. The Mo–Mo distances of complexes 1 [2.0951(17) Å], 2 [2.103(1) Å] and 3 [2.1017(3) Å], which contain both Mo?N and Mo?O axial interactions, are slightly longer than those of complex 4 [2.0826(12)–2.0866(10) Å] which has only Mo?O interactions.     

Synthesis of l-azaisotryptophan and its analogs: a general access to new 2-substituted azaindoles

l-(N-Cbz)-7-azaisotryptophan, l-(N-Cbz)-1a, a new isostere of tryptophan, was synthesized by reacting Li₂-(N-Boc)-2-amino-3-picoline, Li₂-(N-Boc)-2a, with appropriately protected l-aspartic acid followed by simple functional group manipulation. This synthetic success led us to access a set of analogs of azaisotryptophan (4a–c; 6a–c) as well as a new class of chiral amines (7a–c; 8a–c) for future application in asymmetric synthesis and design of homochiral ligands. Further, we have generalized the method substantiating a variety of new azaindol-2-yl derivatives (10aa–10lc) with functionalized substituents. In a preliminary luminescence characterization, l-(N-Cbz)-1a has exhibited about 30 nm bathochromic shifted fluorescence emission compared to tryptophan and (N-Cbz)-tryptophan.     

Dihydrofurocoumarin and dihydrofurodihydropyrid-2-one derivatives via palladium catalysed cascades involving aryl/heteroaryl/vinyl iodides and allene followed by acid catalysed cyclisation

Mono 3-(2′-arylallyl) derivatives of 4-hydroxycoumarin 1a,b, 4-hydroxy-6-methyl-pyran-2-one (3) and 6-hydroxy-1,4-dimethyl-1,2-dihydropyrid-2-one-3-carbonitrile (4) are produced in 3-component cascades involving aryl/heteroaryl/vinyl iodides and allene (1 atm) using Pd(PPh₃)₄/Cs₂CO₃/MeCN/80 °C or Pd₂(dba)₃/tris(2-furyl)phosphine/K₂CO₃/DMF/80 °C as the catalyst system. 4-Hydroxy-2-quinolone (2) afforded a mixture of mono- and bis-allylation products under these conditions. Mono C-allylation products 5a-e and 15a-e undergo facile acid catalysed cyclisation to afford dihydrofurocoumarins 11a-e and dihydrofurodihydropyrid-2-ones 16a-e in good overall yield.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Catenar bimetallomesogens derived from quinoxaline–salicylaldimine conjugates

The preparation, characterization, and mesomorphic properties of two series of tridentate N-salicylidene-2-hydroxyanilines and their metal complexes were described. The crystal and molecular structure of bis[2-hydroxy-4-propyloxy-N-(2-hydroxy-3,4-dipropyloxybenzylidene) aniline]copper(II) were determined by means of X-ray analysis. It crystallizes in the monoclinic space group P2(1)/n and a Z=4. The geometry at Cu²⁺ ions is square pyramidal with a THF solvent molecule coordinated. The core structure was nearly flat, and the intramolecular Cu–Cu atoms were separated by ca. 3.0163(6) Å. All compounds 2a formed smectic C phases, and copper complexes 1a–Cu were not mesogenic. In contrast, compound 2e and complexes 1b–Cu, 1d–Cu, 1e–Cu, and 1e–Pd exhibited columnar phases. The lack of mesomorphism in 1e–Zn was attributed to a preferred tetrahedral over square planar geometry. A N_cell equal to 2.44–2.92, calculated from powder XRD data within a 9.0 Å thick indicated that an induced structure correlated by two catenar-shaped molecules was formed in Col_h phases.     

Thieno[2,3-a]carbazole-based donor–π–acceptor organic dyes for efficient dye-sensitized solar cells

New donor–π–acceptor organic dyes K-1 and K-2 containing thieno[2,3-a]carbazole as an electron donor were designed and synthesized for dye-sensitized solar cells (DSCs). Photophysical and electrochemical properties of K-dyes were investigated. DSCs based on K-dyes showed a high conversion efficiency of 6.6–6.7% with a J_sc of 12.40–12.49 mA cm⁻² and a V_oc of 0.70–0.71 V. The molecular geometry calculation indicated that the existence of thienocarbazole donor in K-dyes enhanced the molecular planarity compared to the carbazole analogue dye MK-3. As a result, DSCs based on K-dyes showed high IPCEs, perhaps due to efficient intramolecular charge transfer and electron injection from excited dye to TiO₂ conduction band.     

Phosphorus–nitrogen compounds: Part 19. Syntheses,structural and electrochemical investigations,biological activities,and DNA interactions of new spirocyclic monoferrocenylcyclotriphosphazenes

The reactions of hexachlorocyclotriphosphazatriene, N₃P₃Cl₆, with N-alkyl-N-ferrocenylmethylethylene diamines, FcCH₂NH(CH₂)₂NHR₁ [R₁ = Me (1) and Et (2)], and sodium [3-(N-ferrocenylmethylamino)-1-propanoxide] (3) produce spirocyclic monoferrocenyl tetrachlorophosphazenes (1a–3a). The tetrapyrrolidinophosphazenes (1b–3b) are prepared from the reactions of corresponding phosphazenes (1a–3a) with excess pyrrolidine. The reaction of 1a with excess morpholine affords geminal-morpholino phosphazene (1c), whilst the reactions of 2a and 3a give diethylaminotrimorpholino (2c) and fully substituted morpholino products (3c), respectively. The structural investigations of the compounds are examined by Fourier transform IR, MS, ¹H, ¹³C, ³¹P NMR, DEPT, HETCOR, and HMBC techniques. The crystal structures of 3b and 3c are determined using X-ray crystallography. Cyclic voltammetric and chronoamperometric data show that compounds 1a–3a, 1b–3b, and 1c–3c exhibit electrochemically reversible one-electron oxidation of Fc redox centers which are hardly affected by the substituents on the phosphazene ring. The compounds 1b, 2b, 3b, and 3c are screened for antibacterial activities against Gram-positive and Gram-negative bacteria and for antifungal activities against yeast strains. In addition, the antituberculosis activities (in vitro) of these compounds are evaluated against INH-susceptible reference strain M. tuberculosis H37Rv, and six multi-drug resistant clinical M. tuberculosis isolates. Compound 2b is found to be the most active against the susceptible the reference strain. In addition, 1b, 2b, and 3c are active against all the multidrug-resistant clinical isolates at the highest concentrations. Gel electrophoresis data indicate that the compounds promote the formation of strand breaks in plasmid DNA. Almost all the concentrations lost of supercoiled DNA suggests that the compound 3b is very efficient plasmid-modifier. The compounds inhibit BamHI cleavage of pUC18 DNA while restricting HindIII.     

2-Arylnaphthoxazole-derived palladium(II) complexes as phosphine-free catalysts for Heck reactions

Four air- and moisture-stable new palladium(II) complexes 2a–2c and 4 have been synthesized from easily available 2-arylnaphthoxazole derivatives. The detailed structures of 2c and 4 have been determined by single-crystal X-ray analysis. The Pd–N, Pd–C bonds in palladacycle complexes 2a–2c and the Pd–N, Pd–O bonds in complex 4 form the basis for five- and six-membered chelate rings, respectively. These complexes were applied as efficient phosphine-free catalysts for Heck reactions with aryl bromides and ethyl acrylate. Typically, in the presence of two equivalent n-Bu₄NBr, using 0.01% of palladacycle complex 2c as catalyst and two equivalent of K₂CO₃ as base in DMF at 140 °C provided coupled products in moderate to high yields.     

Dinuclear copper(II) complexes of a novel 3-(aminomethyl)naphthoquinone Mannich base: Synthesis,structural, magnetic and electrochemical studies

A novel versatile tridentate 3-(aminomethyl)naphthoquinone proligand, 3-[N-(2-pyridylmethyl)aminobenzyl]-2-hydroxy-1,4-naphthoquinone (HL), was obtained from the Mannich reaction of 2-hydroxy-1,4-naphthoquinone (Lawsone) with 2-aminomethylpyridine (amp) and benzaldehyde. The reactions of HL with CuCl₂·2H₂O yielded two novel dinuclear copper(II) complexes, [Cu(L)(H₂O)(μ-Cl)Cu(L)Cl] (1b), [CuCl(L)(μ-Cl)Cu(amp)Cl] (2) and a polymeric compound, [Cu(L)Cl)]_n (1a), whose relative yields were sensitive to temperature, reagents concentration and presence of base. The crystalline structures of 1b and 2 were determined by X-ray diffraction studies. The two copper atoms in complex 1b are connected by a single chloro bridge with a Cu?Cu separation of 4.1342(8) Å and Cu(1)–Cl(1)–Cu(2) angle of 109.31(4)°. In complex 2 the two copper atoms are held together by a chloro and a naphthalen-2-olate bridges [Cu(1)–Cl(2)–Cu(2) and Cu(1)–O(1)–Cu(2) angles being 83.31(3) and 109.70(9)°, respectively, and the Cu?Cu separation, 3.3476(9) Å]. As expected, variable-temperature magnetic susceptibility measurements of complex 1b showed weak antiferromagnetic intramolecular coupling between the copper(II) centers, with J = −5.7 cm⁻¹, and evidenced for complex 2 strong antiferromagnetic coupling, with J ∼ −120 cm⁻¹. Furthermore, the magnetic behaviour of compound 1a suggested an infinite 1D coordination polymeric structure in which the copper(II) centers are connected by Cl–Cu–Cl bridges. Solution data (UV–Vis spectroscopy and cyclic voltammetry) indicated structural changes of 2 and 1a in CH₃CN, and evidenced conversion of polymer 1a into dimer 1b.     

Synthesis,crystal structure and spectroscopic characterization of new neutral and cationic (η-p-cymene)–ruthenium(II) complexes with phosphine–amide ligands

The dimeric starting material [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂ reacts with the phosphino-amides o-Ph₂P–C₆H₄CO–NH–R [R = ⁱPr (a), Ph (b), 4-MeC₆H₄ (c), 4-FC₆H₄ (d)] to give the mononuclear compounds 1a–d [RuCl(η⁶-p-cymene)(o-Ph₂P–C₆H₄–CO–NH–R)]Cl. The subsequent reaction of these complexes with KPF₆ produced the cationic species 2a–d [RuCl(η⁶-p-cymene)(o-Ph₂P–C₆H₄–CO–NH–R)][PF₆] in which phosphino-amides also act as rigid P,O-chelating ligands. The molecular structures of 2b–d were determined crystallographically. Amide deprotonation is achieved when complexes 2a–d were made react with 1 M aqueous solution of KOH, affording the corresponding neutral species 3a–d [RuCl(η⁶-p-cymene)(o-Ph₂P–C₆H₄–CO–N–R)] in which a P,N-coordination mode is suggested.