Heterogenized Water Oxidation Catalysts Prepared by Immobilizing Kläui-Type Organometallic Precursors.

An efficient heterogenized water oxidation catalyst (2_TiO2 ) has been synthesized by immobilizing the Kläui-type organometallic precursor [Cp*Ir{P(O)(OH)2 }3 ]Na (2, Cp*=1,2,3,4,5-pentamethylcyclopentadienyl ligand) onto rutile TiO2 . Iridium is homogeneously distributed at the molecular and atomic/small cluster level in 2_TiO2 and 2'_TiO2 (solid catalyst recovered after the first catalytic run), respectively, as indicated by STEM-HAADF (scanning transmission electron microscopy - high angle annular dark field) studies. 2'_TiO2 exhibits TOF values up to 23.

Transformation of a Cp*-iridium(III) precatalyst for water oxidation when exposed to oxidative stress.

The reaction of [Cp*Ir(bzpy)NO3 ] (1; bzpy=2-benzoylpyridine, Cp*=pentamethylcyclopentadienyl anion), a competent water-oxidation catalyst, with several oxidants (H2 O2 , NaIO4 , cerium ammonium nitrate (CAN)) was studied to intercept and characterize possible intermediates of the oxidative transformation. NMR spectroscopy and ESI-MS techniques provided evidence for the formation of many species that all had the intact Ir-bzpy moiety and a gradually more oxidized Cp* ligand. Initially, an oxygen atom is trapped in between two carbon atoms of Cp* and iridium, which gives an oxygen-Ir coordinated epoxide, whereas the remaining three carbon atoms of Cp* are involved in a η(3) interaction with iridium (2 a).

Cationic half-sandwich quinolinophaneoxazoline-based (η6-p-cymene)ruthenium(II) complexes exhibiting different chirality types: synthesis and structural determination by complementary spectroscopic methods.

Novel, optically pure 2-{4-methyl[2]paracyclo[2](5,8)quinolinophan-2-yl}-4-aryl/alkyloxazolines (QUIPHANOX) exhibiting both planar and central chirality have been prepared by reacting (Rp)- and (Sp)-2-cyano-4-methyl[2]paracyclo[2](5,8)quinolinophane with 2-aryl/alkyl-2-aminoethanols. The reaction of each of the above N,N-ligands with [Ru(η(6)-p-cymene)Cl2]2 in methanol, in the presence of either NH4PF6 or NaBPh4, gave the corresponding half-sandwich [(η(6)-p-cymene)Ru(QUIPHANOX)Cl](+)Y(-), (Y(-) = PF6(-), BPh4(-)) as stable complex salts exhibiting planar and carbon- and metal-centered chirality. The unknown absolute configuration (AC) at the metal was determined by (1)H NMR and by theoretical calculations of electronic circular dichroism (ECD) spectra and subsequently confirmed by crystallographic X-ray analysis.

Iridium(III) molecular catalysts for water oxidation: the simpler the faster.

We report on three Ir(iii) molecular catalysts for water oxidation: 1, [Cp*Ir(ppy)Cl]; 2, [Cp*Ir(bzpy)NO(3)]; 3, [Cp*Ir(H(2)O)(3)](NO(3))(2). 2 and 3 are water-soluble and show a long-term activity ca. 2 and 3 times higher than 1.

Anion-dependent tendency of di-long-chain quaternary ammonium salts to form ion quadruples and higher aggregates in benzene.

The self-aggregation tendency of [N(CH(3))(2)(C(18)H(37))(2)]X [1X; X(-)=BF(4) (-), PF(6) (-), OTf(-), NTf(2) (-), BPh(4) (-), BTol(4) (-), BAr(F-), and B(C(6)F(5))(4) (-)] salts to form ion quadruples (IQs) and higher aggregates (HAggs) in [D(6)]benzene is investigated by means of diffusion NMR spectroscopy. The experimental results indicate that salts containing small anions (1BF(4), 1PF(6), and 1OTf) are present in solution as IQs even at the lowest investigated concentration of C=5×10(-5) M and show a limited tendency to further self-aggregate, reaching a maximum average aggregation number (N=V(H)/V(H)(0IP), where V(H)=measured hydrodynamic volume and V{H}{0IP}=hydrodynamic volume of the ion pair) of about 6-8 (C=0.050-0.

Diffusion and NOE NMR studies on multicationic DAB-organoruthenium dendrimers: size-dependent noncovalent self-assembly to megamers and ion pairing.

New multicationic organoruthenium dendrimers (RuPF(6)-Dabn, n = 2, 4, 8, 16) have been synthesized by coupling of [Ru(eta(6)-p-cymene)(kappa(3)-dpk-OCH(2)CH(2)OH)]X (1PF(6), dpk = 2,2'-dipyridyl ketone, X = PF(6)) with 1,4-diaminobutane (DAB) and polypropylenimine dendrimer DAB-dendr-(NH(2))(n) {n=4, 8, 16} mediated by 1,1'-carbonyldiimidazole (CDI). The intermediate in the synthesis, [Ru(eta(6)-p-cymene)(kappa(3)-dpk-OCH(2)CH(2)OC(O)Im]X (2PF(6), Im = imidazole, X = PF(6)) has been isolated and characterized by single-crystal XRD. The intra- and supramolecular structures in a solution of RuPF(6)-Dabn dendrimer have been investigated by multidimensional and multinuclear NMR techniques.

The effect of counterion/ligand interplay on the activity and stereoselectivity of palladium(II)-diimine catalysts for CO/p-methylstyrene copolymerization.

The catalytic activity and stereoselectivity of complexes [Pd(eta(1),eta(2)-C(8)H(12)OMe)(Ar--N==C(R')--C(R')==N--Ar)]X in the copolymerization of CO and p-methylstyrene have been correlated with their interionic structure in solution and in the solid state, as determined by (19)F,(1)H-HOESY NMR spectroscopy and X-ray diffraction studies, respectively. The highest productivity is obtained with unhindered diimine ligands bearing electron-donating substituents and with the least coordinating counterion. Copolymers with a microstructure ranging from atactic to predominantly isotactic are obtained.

Aggregation tendency and reactivity toward AgX of cationic half-sandwich ruthenium(II) complexes bearing neutral N,O-ligands.

The aggregation tendency of complexes [Ru(eta6-cymene)(N,O)Cl]X [N,O = 2-benzoylpyridine (2-bzpy), 1, and 2-acetylpyridine (2-acpy), 2, X- = BPh4- or PF6-] has been studied by means of PGSE NMR experiments. It was found that complexes with PF6- as counterion are mainly present in CD2Cl2 as ion pairs at low concentration, as a mixture of ion triples and free anions at medium concentration and as ion quadruples at elevated concentration. 19F, 1H-HOESY NMR experiments revealed that in ion triples and ion quadruples two cationic Ru-units pair up.

Structure and reactivity of trans-bis[2-(2-chloroethyl)pyridine]palladium chloride (1). A study on the elimination reaction of 1 and 2-(2-chloroethyl)pyridine induced by quinuclidine in acetonitrile.

[reaction: see text] The trans-bis[2-(2-chloroethyl)pyridine]palladium chloride (1) has been prepared and structurally characterized by X-ray spectroscopy and computational study. The X-ray structure of 1 is consistent with the trans isomer (with respect to Pd). The NMR spectrum and the computational study are in agreement with an equilibrium in CD3CN solution between two isomers of the trans structure.

PGSE and NOE NMR evidence for higher order aggregation in some cationic ruthenium complexes in both protic and aprotic solvents.

PGSE and NOE NMR measurements were carried out for complexes [Ru(eta(6)-cymene)((2-R-C(6)H(4))N=C(Me)-C(Me)=N(2-R-C(6)H(4)))Cl]X (X = BF(4) or BPh(4)) in both protic and aprotic solvents with a relative permettivity (epsilon(r)) ranging from 2.27 (benzene-d(6)) to 46.45 (dimethyl sulfoxide-d(6)).