Showing papers on "Denticity published in 2005"
TL;DR: In this paper, the design and preparation of stable cyanide-bearing six-coordinate complexes of formula [MIII(L)(CN)x](x+l−−m)− (M = trivalent transition metal ion and L = polydentate blocking ligand) are summarized and the appropriate choice of the end-cap ligand L whose denticity determines the number of coordinated cyanide groups in the mononuclear precursors.
405 citations
TL;DR: In this paper, the synthesis of the Schiff base ligands, 4-[(4-bromo-phenylimino)-methyl]-benzene-1,2,3-triol (A1), 4]-(3,5-di-tert-butyl-4-hydroxy-phenymalin)-methyl]benzenes- 1,2-diol (A5), and their Cd(II) and Cu(II)-metal complexes, stability constants and potentiometric studies.
382 citations
TL;DR: The new chiral bidentate N-heterocyclic carbene (NHC) ligand can be used in the preparation of highly effective Ru- and Cu-based complexes that promote enantioselective olefin metathesis and allylic alkylations with scope that is improved from previously reported protocols.
Abstract: A new chiral bidentate N-heterocyclic carbene (NHC) ligand has been designed and synthesized. The NHC ligand bears a chiral diamine backbone and an achiral biphenol group; upon metal complexation (derived from Ag(I), Ru(II), or Cu(II)), the diamine moiety induces >98% diastereoselectivity such that the biaryl unit coordinates to the metal center to afford the desired complex as a single atropisomer. Because the ligand does not require optically pure biaryl amino alcohols, its synthesis is significantly shorter and simpler than the related first generation ligands bearing a chiral binaphthyl-based amino alcohol. The chiral NHC ligand can be used in the preparation of highly effective Ru- and Cu-based complexes (prepared and used in situ from the Ag(I) carbene) that promote enantioselective olefin metathesis and allylic alkylations with scope that is improved from previously reported protocols. In many cases, transformations promoted by the chiral NHC-based complexes proceed with higher enantioselectivity and reactivity than was observed with previously reported complexes.
320 citations
TL;DR: A series of Cu(I) complexes formulated as [Cu(2)(mu-X)(2)(PPh(3))(L)(n)] were prepared with various mono- and bidentate N-heteroaromatic ligands and showed strong emission at room temperature as well as at 80 K in the solid state.
Abstract: A series of Cu(I) complexes formulated as [Cu2(μ-X)2(PPh3)(L)n] were prepared with various mono- and bidentate N-heteroaromatic ligands (X = Br, I; L = 4,4‘-bipyridine, pyrazine, pyrimidine, 1,5-naphthyridine, 1,6-naphthyridine, quinazoline, N,N-dimethyl-4-aminopyridine, 3-benzoylpyridine, 4-benzoylpyridine; n = 1, 2). Single-crystal structure analyses revealed that all the complexes have planar {Cu2X2} units. Whereas those with monodentate N-heteroaromatic ligands afforded discrete dinuclear complexes, bidentate ligands formed infinite chain complexes with the ligands bridging the dimeric units. The long Cu···Cu distances (2.872−3.303 A) observed in these complexes indicated no substantial interaction between the two Cu(I) ions. The complexes showed strong emission at room temperature as well as at 80 K in the solid state. The emission spectra and lifetimes in the microsecond range were measured at room temperature and at 80 K. The emissions of the complexes varied from red to blue by the systematic sele...
291 citations
TL;DR: In this paper, structural features of copper(I) and copper(II) complexes with bidentate, tridentate and tetradentate nitrogen based ligands commonly used in atom transfer radical polymerization (ATRP) were extensively reviewed and discussed based on several spectroscopic techniques.
263 citations
TL;DR: In this article, the enantioselective Pt(II)-catalyzed alkoxycyclization has been studied in the presence of chiral mono-and bidentate phosphines, as well as chiral bidentates N−N ligands.
246 citations
TL;DR: Polymerization of rac-lactide with [(BDI-3)MgO(t)Bu](2) shows a slight preference for heterotactic PLA in CH( 2)Cl(2) but is highly stereoselective in THF in the production of heterotact PLA.
Abstract: A series of β-diiminato complexes of the form (BDI-3)MX where (BDI-3) = [CH(CMeNC6H4-2-OMe)2]; M = Zn, Mg; X = OiPr, OtBu, or N(SiMe3)2 has been synthesized. The (BDI-3) ligand is bidentate in (BDI-3)ZnN(SiMe3)2 and tetradentate in (BDI-3)MgN(SiMe3)2. The alkoxide complexes are shown to be active for lactide polymerization. Polymerization of rac-lactide with (BDI-3)ZnOiPr gives a moderate preference for heterotactic PLA. Polymerization of rac-lactide with [(BDI-3)MgOtBu]2 shows a slight preference for heterotactic PLA in CH2Cl2 but is highly stereoselective in THF in the production of heterotactic PLA.
216 citations
TL;DR: In this article, a comprehensive study of a series four-coordinate boron compounds with the general formula of BPh 2 (N,N), where N,N are bidentate chelate ligands containing both neutral and negatively charged nitrogen donor atoms has been conducted.
Abstract: A comprehensive study of a series four-coordinate boron compounds with the general formula of BPh 2 (N,N), where N,N are bidentate chelate ligands containing both neutral and negatively charged nitrogen donor atoms has been conducted. The structures of the boron complexes were examined via single-crystal X-ray diffraction. The series of molecules display bright luminescence with emission maxima λ m a x ranging from blue to red, depending on the nature of the N,N chelate ligand. The electronic effects and their consequences on the luminescent properties of the complexes due to the CH replacement of the chelate ligand by a nitrogen atom, the increase of conjugation, or the change of substituents on the chelate ligand have been examined using electrochemical analysis, UV-visible, and fluorescence spectroscopic methods, and by molecular orbital calculations (Gaussian 98). Experimental data and MO calculation results established that the emission of this class of compounds is caused by π-π* transitions centered on the chelate ligand. Furthermore, the experimental and theoretical results consistently and conclusively established that electron withdrawing groups on the negatively charged N-donor portion of the chelate ligand causes a decrease in the highest occupied molecular orbital (HOMO) energy level, thus increasing the energy gap. The CH replacement by a nitrogen atom on the negatively charged portion of the chelate ligand causes a dramatic decrease of the HOMO energy level, and the increase of conjugation in the chelate ligand significantly decreases the energy gap. Blue and red electroluminescent (EL) devices were fabricated successfully using two representative boron compounds from the series. The new boron compounds have been found to be able to function as both emitters and electron transport materials in EL devices.
169 citations
TL;DR: Two new isostructural complexes have been synthesized and characterized by single-crystal X-ray diffraction, showing anti-ferromagnetic coupling through imidazolate bridging and magnetic susceptibilities obey the Curie-Weiss law.
Abstract: Two new isostructural complexes [M(H2biim)3][M(btc)(Hbiim)]·2H2O (M = Co, (1); M = Ni, (2)) (btc = 1,3,5-benzenetricarboxylate; H2biim = 2,2‘-biimidazole) have been synthesized and characterized by single-crystal X-ray diffraction. They present a unique structure consisting of two distinct units: the monomeric cations [M(H2biim)3]2+ and the two-dimensional (2D) anionic polymer [M(Hbiim)(btc)]2-. In the anionic moiety, the Hbiim- monoanion is simultaneously coordinated to one metal atom in a bidentate mode and further to another metal atom in a monodentate mode. The imidazolate groups bridge the two adjacent metal ions into a helical chain which is further arranged in left- and right-handed manners. These chains are bridged by btc ligands into a 2D brick wall structure. The most interesting aspect is that the [M(H2biim)3]2+ cations act as pillars and link the anionic layers via robust heteromeric hydrogen-bonded synthons (9) and (7) formed by the uncoordinated oxygen atoms of carboxylate groups and the H2...
147 citations
TL;DR: The hydrothermal synthesis, characterization, single-crystal structures, and magnetic properties of two polymorphs of trans-3(3-pyridyl)acrylate of cobalt(II) and of nickel(II), M(II)(C(8)H(6)NO(2))(2)(H(2)O)(2) are presented.
Abstract: We present the hydrothermal synthesis, characterization (IR, DT-TGA), single-crystal structures, and magnetic properties of two polymorphs of trans-3(3-pyridyl)acrylate of cobalt(II) and of nickel(II), M(II)(C(8)H(6)NO(2))(2)(H(2)O)(2). Hydrothermal reaction at 120 or 170 degrees C results exclusively in the different polymorphs. The infrared spectra and thermogravimetric analyses of the complexes are almost similar for the two polymorphs but show a difference between cobalt and nickel in energies of the vibrational modes and in the decomposition temperatures. The crystal structures of the two polymorphs are quite different; one crystallizes in a monoclinic space group and the other in a triclinic. This major difference is due to the different stereochemistry, cis or trans, of the coordination at the metal sites. When it is trans-MN(2)O(4), it results in the monoclinic cell consisting of a 3D-network of metals bridged by the ligands through single bonds (M-N and M-O). There is threading of three sublattices up to 2a x 4b x 2c, at which point the three sublattices are knotted into one infinite framework. When it is cis-MN(2)O(4), it results in the triclinic cell and consists of Zwitterionic linear chains of metals bridged by one single ligand via the pyridine and a bidentate carboxylate group and the other ligand is bonded only via the pyridine while its carboxylate end is free. All four compounds are paramagnetic with Weiss constants suggesting weak interactions.
147 citations
TL;DR: A series of zinc complexes of monodentate N-heterocyclic carbenes and a new sterically bulky bidentate pyridyl-NHC ligand have been synthesized and characterized by spectroscopic and X-ray crystallographic methods as mentioned in this paper.
TL;DR: Experimental data suggests that the anisotropic assembly is a consequence of the water-promoted desorption of the organic ligands from the {001} faces of the crystalline building blocks together with the dissociative adsorptionof water on these crystal faces.
Abstract: Nanoparticle powders composed of surface-functionalized anatase crystals with diameters of about 3 nm self-organize into different structures upon redispersion in water. The assembly is directed by a small amount of a low-molecular-weight functional ligand (the "assembler") adsorbed on the surface of the nanoparticles. The ligand functionality determines the anisotropy of the resulting structures. Multidentate ligands, such as trizma ((HOCH 2 ) 3 CNH 2 ) and serinol ((HOCH 2 ) 2 CNH 2 ), with a chargeable terminal group preferentially induce the formation of anisotropic nanostructures several hundreds of nanometers in total length, whereas all the other investigated ligands (ethanolamine H 2 N-(CH 2 ) 2 OH, glycine hydroxamate H 2 NCH 2 CONHOH, dopamine (OH) 2 C 6 H 3 (CH 2 ) 2 NH 3 Cl, tris (HOCH 2 ) 3 -CCH 3 ) mainly lead to uncontrolled agglomeration. Experimental data suggests that the anisotropic assembly is a consequence of the water-promoted desorption of the organic ligands from the {001} faces of the crystalline building blocks together with the dissociative adsorption of water on these crystal faces. Both processes induce the preferred attachment of the titania nanoparticles along the [001] direction. The use of polydentate and charged ligands to functionalize the surface of nanoparticles thus provides a versatile tool to control their arrangement on the nanoscale.
TL;DR: Reactions of the heterocyclic thione ligand 2,4,6-trimercaptotriazine (H3TMT) with copper(I) halides afforded novel three-dimensional polymers, which crystallized in the cubic space group Pa.
Abstract: Reaction of copper(I) chloride or bromide with equimolar amounts of the neutral pyrimidine-2-thione ligand (pymtH) afforded linear chain polymers [Cu(pymtH)X]n (X = Cl, Br) with the pymtH ligand acting as a bridging N, S donor. In contrast, copper(I) iodide under the same conditions gave the dimeric complex [Cu(pymtH)2I]2 with the pymtH ligand adopting monodentate coordination mode through the exocyclic sulfur atom in terminal and bridging modes. Reactions of the heterocyclic thione ligand 2,4,6-trimercaptotriazine (H3TMT) with copper(I) halides afforded novel three-dimensional polymers, which crystallized in the cubic space group Pa3. Each copper(I) ion is coordinated by three S atoms of three distinct H3TMT ligands, and each H3TMT acts as a tridentate bridging ligand linking three copper(I) ions through its sulfur atoms, thus forming two independent three-dimensional (3D) networks. The network belongs to a three-connected (10, 3)-a topology, which is enantiometric and interpenetrating. In all complexes...
TL;DR: Three new unsymmetrical compartmental dinucleating ligands, 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[{2-(1-piperidyl)ethyl}aminomethyl] phenol]phenol, have been synthesized in order to model the active site of type 3 copper proteins.
Abstract: Three new unsymmetrical compartmental dinucleating ligands, 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[{2-(1-piperidyl)ethyl}aminomethyl]phenol (HL1), 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[{2-(morpholin-4-yl)ethyl}aminomethyl]phenol (HL2), and 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[{2-(thiomorpholin-4-yl)ethyl}aminomethyl]phenol (HL3), have been synthesized in order to model the active site of type 3 copper proteins. The dicopper(II) complexes of these ligands give first hints about the influence of a thioether group close to the metal site. The bromophenol-based ligands have one piperazine arm and one other bidentate arm in positions 2 and 6 of the phenolic ring, respectively. With each ligand a dinuclear copper(II) complex was prepared and structurally characterized. The copper ions were found to have square pyramidal environments and a mixture of endogenous phenoxo and exogenous acetate bridging. The influence of a heteroatom in one arm of the ligand on catecholase activity and speciation in solution was studied by UV/Vis spectroscopy, ESI-MS experiments and, DFT calculations.
TL;DR: Two types of copper( II) and nickel(II) complexes derived from benzophenone anthranoylhydrazone and bidentate heterocyclic base with general stoichiometry [ML2] and [ML(phen)]Cl have been synthesized and characterized by elemental analysis, infrared spectra, UV-vis electronic absorption spectra and magnetic susceptibility measurements.
TL;DR: The reaction of three different 1-phenyl and 1,4-diphenyl substituted S-methylisothiosemicarbazides, H(2)[L(1-6)], with Ni(OAc)(2)O in ethanol in the presence of air yields six four-coordinate species which represent the monoanionic pi-radical forms.
Abstract: The reaction of three different 1-phenyl and 1,4-diphenyl substituted S-methylisothiosemicarbazides, H(2)[L(1-6)], with Ni(OAc)(2).4H(2)O in ethanol in the presence of air yields six four-coordinate species [Ni(L(1-6)(*))(2)] (1-6) where (L(1-6)(*))(1-) represent the monoanionic pi-radical forms. The crystal structures of the nickel complexes with 1-phenyl derivatives as in 1 reveal a square planar structure trans-[Ni(L(1)(-3)(*))(2)], whereas the corresponding 1,4-diphenyl derivatives are distorted tetrahedral as is demonstrated by X-ray crystallography of [Ni(L(5)(*))(2)] (5) and [Ni(L(6)(*))(2)] (6). Both series of mononuclear complexes possess a diamagnetic ground state. The electronic structures of both series have been elucidated experimentally (electronic spectra magnetization data). The square planar complexes 1-3 consist of a diamagnetic central Ni(II) ion and two strongly antiferromagnetically coupled ligand pi-radicals as has been deduced from correlated ab initio calculations; they are singlet diradicals. The tetrahedral complexes 4-6 consist of a paramagnetic high-spin Ni(II) ion (S(Ni) = 1), which is strongly antiferromagnetically coupled to two ligand pi-radicals. This is clearly revealed by DFT and correlated ab initio calculations. Electrochemically, complexes 1-6 can be reduced to form stable, paramagnetic monoanions [1-6](-) (S = (1)/(2)). The anions [1-3](-) are square planar Ni(II) (d,(8) S(Ni) = 0) species where the excess electron is delocalized over both ligands (class III, ligand mixed valency). In contrast, one-electron reduction of 4, 5, and 6 yields paramagnetic tetrahedral monoanions (S = (1)/(2)). X-band EPR spectroscopy shows that there are two different isomers A and B of each monoanion present in solution. In these anions, the excess electron is localized on one ligand [Ni(II)(L(4-6)(*))(L(4-6))](-) where (L(4-6))(2-) is the closed shell dianion of the ligands H(2)[L(4-6)] as was deduced from their electronic spectra and broken symmetry DFT calculations. Oxidation of 1 and 5 with excess iodine yields octahedral complexes [Ni(II)(L(1,ox))(2)I(2)] (7), [Ni(II)(L(1,ox))(3)](I(3))(2) (8), and trans-[Ni(II)(L(5,ox))(2)(I(3))(2)] (9), which have been characterized by X-ray crystallography; (L(1-)(6,ox)) represent the neutral, two-electron oxidized forms of the corresponding dianions (L(1-6))(2-). The room-temperature structures of complexes 1, 5, and 7 have been described previously in refs 1-5.
TL;DR: A novel chiral monodentate spiro phenylphospholane ligand 4 was prepared from a readily accessible, enantiomerically pure 1,1'-spirobiindane-7,7'-diol in high yield and has proven to be efficient for Pd-catalyzed enantioselective allylation of aldehydes with allylic alcohols.
TL;DR: The geometric preferences of a family of four coordinate, iron(II) d6 complexes of the general form L2FeX2 have been systematically evaluated and tetrahedral and square planar coordination has been observed upon complexation of chelating phosphine ligands.
Abstract: The geometric preferences of a family of four coordinate, iron(II) d6 complexes of the general form L2FeX2 have been systematically evaluated. Treatment of Fe2(Mes)4 (Mes = 2,4,6-Me3C6H2) with monodentate phosphine and phosphite ligands furnished square planar trans-P2Fe(Mes)2 derivatives. Identification of the geometry has been accomplished by a combination of solution and solid-state magnetometry and, in two cases (P = PMe3, PEt2Ph), X-ray diffraction. In contrast, both tetrahedral and square planar coordination has been observed upon complexation of chelating phosphine ligands. A combination of crystallographic and magnetic susceptibility data for (depe)Fe(Mes)2 (depe = 1,2-bis(diethylphosphino)ethane) established a tetrahedral molecular geometry whereas SQUID magnetometry and Mossbauer spectroscopy on samples of (dppe)Fe(Mes)2 (dppe = 1,2-bis(diphenylphosphino)ethane) indicated a planar molecule. When dissolved in chlorinated solvents, the latter compound promotes chlorine atom abstraction, forming te...
TL;DR: The coupling constant J values in the heterodinuclear Cu-Gd complexes are correlated to values of the dihedral angles alpha between the two O-Cu-O and O- Gd-O fragments of the bridging CuO2Gd networks, with the largest J value associated with the smallest alpha value.
Abstract: La(mmi) 4(NO3)2(H2O))(ClO4)‚2H2 O( 2‚La) with polydentate ligands 2-(hydroxymethyl)-pyridine and 2-hydroxymethyl- 1-methyl-imidazole. In these complexes, each pair of Cu(II) and Ln(III) ions is linked by a double I-alkoxo bridge. The temperature dependences of the magnetic susceptibilities of 1 and 2 were investigated in the range of 2 -300 K. The dinuclear and trinuclear Cu-Gd complexes exhibit ferromagnetic interaction. The coupling constant J values in the heterodinuclear Cu-Gd complexes are correlated to values of the dihedral angles R between the two O-Cu-O and O-Gd-O fragments of the bridging CuO2Gd networks, with the largest J value associated with the smallest R value. The occurrence of a ferromagnetic interaction between Cu II and Gd III ions of the trinuclear entity is supported by the field dependence of the magnetization. The field dependence of the magnetization a t2Ko f1‚Gd and 2‚Gd confirms the nature of the ground state and of the CuII -Gd III interaction, while alternating current susceptibility measurements demonstrates out-of-phase ac susceptibility signals of 1‚Tb, which is the molecule-based magnetic material of the smallest nuclearity which exhibits frequency-dependent behavior within the 3d-4f mixed-metal systems.
TL;DR: In this paper, the photoluminescence properties of the synthesized compounds were investigated in the solid state at room temperature, and it was shown that 1 is monomeric, in which IIMB acts as monodentate ligand, while the IIMB ligand in complexes 2−6 acts as bidentates ligand.
Abstract: Six novel complexes, [Zn(IIMB)4(H2O)2](NO3)2·5H2O 1, {[Ag2(IIMB)2][2,6-C10H6(COO)2]·6H2O}n 2, {[Cu(IIMB)2]Br2·0.5H2O}n 3, {[Co(IIMB)2(SCN)2]}n 4, {[Cu(IIMB)2(SO4)]·8.5H2O}n 5, and {[Co(IIMB)2(H2O)(SO4)]4·29H2O}n 6, were obtained by reactions of 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene (IIMB) with the corresponding metal salts. X-ray diffraction analyses reveal that 1 is monomeric, in which IIMB acts as monodentate ligand, while the IIMB ligand in complexes 2−6 acts as bidentate ligand. Complex 2 has a single chain structure, while complexes 3 and 4 are double stranded chains. Complexes 5 and 6 display similar 2-D polycatenated architectures formed by the inclined interpenetration of 1-D double stranded chains. This kind of 1-D → 2-D inclined interpenetration has rarely been reported until now. In addition, the photoluminescence properties of the synthesized compounds were investigated in the solid state at room temperature.
TL;DR: The first known case of a watersoluble, air-stable, heterobimetallic polymeric structure based on two metal-containing moieties, in an unprecedented N,P coordinating mode, is described.
Abstract: One of the latest trends in supramolecular chemistry is the quest for reproducible methods to achieve controlled selforganization of discrete units to form homoand heterometallic coordination networks, aggregates, and polymers. This development is based on the use of appropriate organic, inorganic, and organometallic building blocks that allow the synthesis of 1D linear or twisted chains, 2D squares and polygons, and 3D cubes and polyhedra. Among the organic spacers, nitrogen-based aromatic heterocycles are the most widely used due to their good donor properties and rigidity. These ligands can act as corner units (bipy, phen) and spacers (pyrazines, terpy, porphyrinates, tetraazamacrocycles). P-donor ligands as spacers have received less attention: P2 and P5 ligands have been studied by Scheer and co-workers, whereas the use of multidentate phosphanes has been reviewed recently. To the best of our knowledge, the use of mixed N,P ligands as metal-coordinating spacers has not been reported to date. Very few coordination polymers are water soluble, an example being the poly(ferrocenylsilane)-b-poly(aminomethacrylate) copolymer recently described by Manners and coworkers as part of their ongoing study on metallocenebased polymers, which can be prepared by ring-opening polymerization to afford either macromolecules with pendant ferrocenyl substituents in the polymer side chains or poly(ferrocenylsilane)s. Other examples of ligands that afford coordination polymers with various topologies and applications are ferrocenyl ligands bearing bipyridines or carboxylates. Herein we describe the first known case of a watersoluble, air-stable, heterobimetallic polymeric structure based on two metal-containing moieties ([CpRu] and [AgCl2] ) bridged by a cagelike, water-soluble monodentate phosphane, 1,3,5-triaza-7-phosphaadamantane (pta), in an unprecedented N,P coordinating mode. We recently reported the synthesis and characterization of the water-soluble cyclopentadienylruthenium complex [CpRuCl(pta)2] (1), which is stabilized by the phosphaadamantane-like pta ligand, and described its catalytic and biological properties. As part of our studies on new water-soluble organometallic derivatives based on the [CpRu(pta)2] + moiety, we treated 1 with one equivalent of AgOTf (OTf=OSO2CF3) in DMSO to remove the chloro ligand. Unexpectedly, noAgCl precipitated from the resulting orange solution, and neither did it contain the expected product [CpRu(OTf)(pta)2] (2), which was obtained by treatment of 1 with TlOTf. Intrigued by this apparently odd result, we repeated the experiment in an NMR tube. P{H} NMR analysis in [D6]DMSO indicated the formation of a 1:1 mixture of the new complex [CpRu(pta)2(dmso-kS)]OTf (3 ; singlet at d= 28.13 ppm) and the bimetallic neutral coordination polymer [{CpRu(pta)2(dmso-kS)}{AgCl2}]¥ (4 ; singlet at d= 23.19 ppm), as shown in Scheme 1. Quantitative formation of 4 could be attained by adding one equivalent of NH4Cl to a reaction mixture containing 1 and AgOTf. The elemental analysis and spectroscopic data are consistent with one molecule of DMSO being incorporated in the compound (see Experimental Section). Upon repetition of the latter experiment in noncoordinating CDCl3 instead of [D6]DMSO, a similar Ru–Ag polymeric structure was obtained with the coordination sphere of Ru completed by an h-O-coordinated triflate anion, as suggested by the corresponding IR stretching frequency nOSO at n= 1261 cm 1 [20] and F{H} NMR chemical shift at d= 78.77 ppm. The negative charge of the repeating unit in this coordination polymer is likely to be balanced by the ammonium cation (Scheme 2). The complex {NH4[{CpRu(OTf)(pta)2}{AgCl2}]}¥ (5) is characterized by a singlet at d= 20.85 ppm (CDCl3) in the P{H} NMR spectrum. When dissolved in DMSO, 5 is quantitatively converted into 4 with elimination of NH4OTf. [*] Dipl.-Chem. C. Lidrissi, Prof. Dr. A. Romerosa, Dr. M. Saoud, Dipl.-Chem. M. Serrano-Ruiz rea de Quimica Inorganica Universidad de Almer a 04071 Almer a (Spain) Fax: (+34)950-015-008 E-mail: romerosa@ual.es
TL;DR: A deprotonated 5, 5′, chelated palladium acetate complex, [ 5′ Pd(II)(OAc)(solv)] 8, was proposed as a precursor of a genuine catalytically active species.
TL;DR: In this article, a new concept for generation of chelating ligand libraries for homogeneous metal complex catalysis based on self-assembly is presented, and a new rhodium catalyst was identified which operated with excellent activity and regioselectivity upon hydroformylation of terminal alkenes.
Abstract: A new concept for generation of chelating ligand libraries for homogeneous metal complex catalysis based on self-assembly is presented. Thus, self-assembly of structurally simple monodentate ligands in order to give structurally more complex bidentate ligands is achieved employing hydrogen bonding. Based on this concept and on the 2-pyridone/hydroxypyridine tautomeric system, a new rhodium catalyst was identified which operated with excellent activity and regioselectivity upon hydroformylation of terminal alkenes. In order to generate defined unsymmetrical heterodimeric ligands, an A-T base pair analog—the aminopyridine/isoquinolone system—was developed which allows for comple- mentary hydrogen bonding. Based on this platform, a 4 × 4 phosphine ligand library was screened in the course of the rhodium-catalyzed hydroformylation of 1-octene. A catalyst op- erating with outstanding activity and regioselectivity in favor of the linear aldehyde was dis- covered.
Patent•
10 Jan 2005TL;DR: In this article, a process for preparing a compound having the formula L2IrL′ is provided, where L is a suitable carbene ligand precursor coordinated to Ir and L′ is a bidentate ligand or two monodentate ligands.
Abstract: A process for preparing a compound having the formula L2IrL′ is provided. The process comprises: combining and L′ in the presence of an organic solvent to form a mixture, wherein L is a suitable carbene ligand precursor coordinated to Ir; and L′ is a bidentate ligand or two monodentate ligands, and L is different from L′; Also provided is a process for preparing a compound having the formula The process comprises: (a) combining L, a carbene ligand precursor, with an organic solvent; (b) maintaining the mixture of step (a) at a temperature from about 175° C. to less than the boiling point of the organic solvent in (a). A process for preparing a compound with the formula L3Ir is also provided. This process comprises combining and L in the presence of alcohol and a base to form a mixture, wherein L is a bidentate ligand that may form a five-membered chelate ring.
TL;DR: In this article, a cadmium-acetate/NH4SCN with 4-amino-pyridine (L1), C5H4N-C(CH3) NNH2 (L2), and C5 H4N−C(NNH2)-C5 H3 NNH 2 (L3) was synthesized in methanol.
TL;DR: The organotin(IV) complexes of isatin and N-methylisatin exhibit good antibacterial activity, better than that of the corresponding N-butyl and N -pentylisatin derivatives.
TL;DR: In this article, the structure, atomic charges, natural bond orbital, and thermodynamic functions of 4-phenyl-1-(propan-2-ylidene)thiosemicarbazide have been analyzed at HF/6-311G∗∗ and B3LYP/6 -311G ∗ levels of theory for the title compound of 4 -phenyl 1-propane 2-ylidsene, and the second-order optical nonlinearity has been calculated by time-dependent density functional theory.
Abstract: Ab initio calculations of the structure, atomic charges, natural bond orbital, and thermodynamic functions have been performed at HF/6-311G∗∗ and B3LYP/6-311G∗∗ levels of theory for the title compound of 4-phenyl-1-(propan-2-ylidene)thiosemicarbazide. The calculated results show that the sulfur atom and all of the nitrogen atoms have bigger negative charges and they are the potential sites to react with the metallic ions, which make the title compound become a multidentate ligand. The coordination ability of the sulfur atom and the nitrogen atom of C=N double bond will increase with the increase of the polarity of the solvent. Electronic absorption spectra have been calculated by time-dependent density functional theory (TD-DFT) method. The calculation of the second-order optical nonlinearity also has been carried out, and the molecular hyperpolarizability is 3.068×10−30 esu.
TL;DR: A new class of monodentate phosphoramidite ligands (DpenPhos) has been developed on the basis of the modular concept for Rh(I)-catalyzed asymmetric hydrogenations of a variety of olefin derivatives, affording the corresponding optically active compounds in excellent yields and enantioselectivities.
Abstract: A new class of monodentate phosphoramidite ligands (DpenPhos) has been developed on the basis of the modular concept for Rh(I)-catalyzed asymmetric hydrogenations of a variety of olefin derivatives, affording the corresponding optically active compounds in excellent yields and enantioselectivities. The ligands have the advantages of facile preparation, tunable structure, and broad scope of substrates in their Rh(I) complex-catalyzed asymmetric hydrogenations.
TL;DR: A palladium complex bearing 1,2-diphenyl-3,4-diphosphinidenecyclobutene ligand has been used to facilitate the catalytic cyanation of aryl bromides as discussed by the authors.
TL;DR: The relative stability of these and other (mu-1,2-peroxo)diiron(III) intermediates suggests that these species may not be on the direct pathway for dioxygen activation.
Abstract: A series of complexes with [FeII2(μ-OH)2] cores has been synthesized with N3 and N4 ligands and structurally characterized to serve as models for nonheme diiron(II) sites in enzymes that bind and activate O2. These complexes react with O2 in solution via bimolecular rate-limiting steps that differ in rate by 103-fold, depending on ligand denticity and steric hindrance near the diiron center. Low-temperature trapping of a (μ-oxo)(μ-1,2-peroxo)diiron(III) intermediate after O2 binding requires sufficient steric hindrance around the diiron center and the loss of a proton (presumably that of a hydroxo bridge or a yet unobserved hydroperoxo intermediate). The relative stability of these and other (μ-1,2-peroxo)diiron(III) intermediates suggests that these species may not be on the direct pathway for dioxygen activation.