TL;DR: In this paper, four new Pd(II) complexes containing sulfonate-functionalized N-heterocyclic carbene ligands have been synthesized, in which the ligands adopt a monodentate, bis-chelating, and pincer coordination form.
TL;DR: The ruthenium complex 7 generally leads to a faster conversion into ketones with respect to the osmium complex 13, which displays better activity in the dehydrogenation of 5-en-3β-hydroxy steroids.
Abstract: The ruthenium and osmium complexes [MCl(2)(diphosphane)(L)] (M=Ru, Os; L=bidentate amino ligand) and [MCl(CNN)(dppb)] (CNN=pincer ligand; dppb=1,4-bis-(diphenylphosphino)butane), containing the N−H moiety, have been found to catalyze the acceptorless dehydrogenation of alcohols in tBuOH and in the presence of KOtBu. The compounds trans-[MCl(2)(dppf)(en)] (M=Ru 7, Os 13; dppf=1,1'-bisdiphenylphosphino)ferrocene; en=ethylenediamine) display very high activity and different substrates, including cyclic and linear alcohols, are efficiently oxidized to ketones by using 0.8-0.04 mol % of catalyst. The effect of the base and the comparison of the catalytic activity of the Ru versus Os complexes are reported. The ruthenium complex 7 generally leads to a faster conversion into ketones with respect to the osmium complex 13, which displays better activity in the dehydrogenation of 5-en-3β-hydroxy steroids. The synthesis of new Ru and Os complexes [MCl(2)(PP)(L)] (PP=dppb, dppf; L=(±)-trans-1,2-diaminocyclohexane,2-(aminomethyl)pyridine, and 2-aminoethanol) of trans and cis configuration is also reported.
TL;DR: Protonation constants of (ATS) ligand and stability constants of its Cu2+, Co2+, Mn2+ and Ni2+ complexes were determined by potentiometric titration method in 50% (v/v) DMSO-water solution at ionic strength of 0.1 M NaNO3.
TL;DR: In this article, four octamolybdate hybrid materials based on a new flexible multidentate ligand have been synthesized at different pH values under hydrothermal conditions.
Abstract: Four octamolybdate hybrid materials based on a new flexible multidentate ligand, namely, H4L(γ-Mo8O26)·2H2O (1), [Cu(H2L)(β-Mo8O26)(H2O)2]·3H2O (2), [Cu(H2L)(γ-Mo8O26)]·3H2O (3), and Cu(HL)2(β-Mo8O26) (4), where L is 1,1′-(1,4-butanediyl)bis[2-(4-pyridyl)benzimidazole], have been synthesized at different pH values under hydrothermal conditions. Compound 1, which is hydrothermally prepared at pH ≈ 1, exhibits a rare one-dimensional (1D) molybdenum oxide chain. Compounds 2 and 3 are hydrothermally obtained at pH ≈ 2.5. In 2, CuII cations are bridged by H2L2+ ligands and (β-Mo8O26)4– anions to form an interesting two-dimensional (2D) layer. In 3, the H2L2+ ligands and (γ-Mo8O26)4– clusters bridge adjacent CuII cations to form a 3D framwork. When the pH value is adjusted to 3.5, compound 4 is obtained. Because the HL+ cation acts as a monodentate ligand, compound 4 only exhibits a 1D chain structure. The structural diversities of 1–4 reveal that the pH value of the reaction system plays a crucial role in the ...
TL;DR: Direct metalation of bis(1,2,3-triazolium) salts affords mononuclear rhodium(I) complexes, which feature a 1,4-bidentate bis( 1,2-3-Triazol-5-ylidene) (i-bitz) ligand, which paves the way for various applications.
TL;DR: It is shown that mild one-pot "click" methods can be used to readily and rapidly synthesize a family of functionalized bidentate 2-pyridyl-1,2,3-triazole ligands, containing electrochemically, photochemically, and biologically active functional groups in good to excellent yields.
Abstract: The Cu(I)-catalyzed 1,3-cycloaddition of organic azides with terminal alkynes, the CuAAC “click” reaction is currently receiving considerable attention as a mild, modular method for the generation of functionalized ligand scaffolds. Herein we show that mild one-pot “click” methods can be used to readily and rapidly synthesize a family of functionalized bidentate 2-pyridyl-1,2,3-triazole ligands, containing electrochemically, photochemically, and biologically active functional groups in good to excellent yields (47–94%). The new ligands have been fully characterized by elemental analysis, HR-ESI-MS, IR, 1H and 13C NMR and in three cases by X-ray crystallography. Furthermore we have demonstrated that this family of functionalized “click” ligands readily form bis-bidentate Pd(II) complexes. Solution studies, X-ray crystallography, and density functional theory (DFT) calculations indicate that the Pd(II) complexes formed with the 2-(1-R-1H-1,2,3-triazol-4-yl)pyridine series of ligands are more stable than tho...
TL;DR: In this paper, an ammonium-functionalized water-soluble bidentate nitrogen-containing ligand and its palladium chelating complex (4) have been easily prepared from the commercial available starting materials in high overall yields.
TL;DR: A novel class of luminescent dialkynylgold(III) complexes containing various phenylpyridine and phenylisoquinoline-type bidentate ligands has been successfully synthesized and characterized and the structures of some of them have been determined by X-ray crystallography.
Abstract: A novel class of luminescent dialkynylgold(III) complexes containing various phenylpyridine and phenylisoquinoline-type bidentate ligands has been successfully synthesized and characterized. The structures of some of them have also been determined by X-ray crystallography. Electrochemical studies demonstrate the presence of a ligand-centered reduction originating from the cyclometalating C^N ligand, whereas the first oxidation wave is associated with an alkynyl ligand-centered oxidation. The electronic absorption and photoluminescence properties of the complexes have also been investigated. In dichloromethane solution at room temperature, the low-energy absorption bands are assigned as the metal-perturbed π-π* intraligand (IL) transition of the cyclometalating C^N ligand, with mixing of charge-transfer character from the aryl ring to the pyridine or isoquinoline moieties of the cyclometalating C^N ligand. The low-energy emission bands of the complexes in fluid solution at room temperature are ascribed to originate from the metal-perturbed π-π* IL transition of the cyclometalatng C^N ligand. For complex 4 that contains an electron-rich amino substituent on the alkynyl ligand, a structureless emission band, instead of one with vibronic structures as in the other complexes, was observed, which was assigned as being derived from an excited state of a [π(C≡CC(6) H(4) NH(2) )→π*(C^N)] ligand-to-ligand charge-transfer (LLCT) transition.
TL;DR: In this tutorial review of metallatriangles and metallasquares containing predominantly cis-square-planar metal entities and a range of bidentate bridging ligands, it is demonstrated how complexity increases as the symmetry of the bridges ligands is lowered from D(∞h) and D(2h) to C( ∞v, C(2v), C( 2h, and C(s).
Abstract: Reports on spontaneous self-assembly processes between metal fragments and organic ligands frequently tend to ignore the fact that the product isolated and structurally characterized in most cases is only one out of a more or less large series of feasible ones. This is true even for rings containing as few as three or four metal ions. Here we shall review metallatriangles and metallasquares containing predominantly cis-square-planar metal entities and a range of bidentate bridging ligands. The most significant features contributing to the number of possible stereoisomers appear to be ligand symmetry and flexibility, viz. rotation of two halves of a ligand about a single bond, or rotation of the whole ligand about the metal–donor atom bonds. With low-symmetry bidentate ligands the number of isomers increases dramatically with ring size as a consequence of an increase in possible connectivity patterns, hence linkage isomers, and an increase in possible rotamer states of the bridging ligands. In this tutorial review it is demonstrated how complexity increases as the symmetry of the bridging ligands is lowered from D∞h and D2h to C∞v, C2v, C2h and Cs. Special attention will be paid to cyclic tri- and tetranuclear complexes of substituted pyrimidine ligands (C2v and Cs symmetries) as well as the flexible 2,2′-bipyrazine, which can adopt states of either C2v or C2h symmetry. Uses of these complexes and ways to reduce the number of isomers will be pointed out.
TL;DR: By careful inspection of the structures of 1-6, it can be seen that the ttb ligand, the metal ion and the coordination mode of the octamolybdate anion play important roles in the formation of the POM-based MOFs.
Abstract: Six polyoxometalate-based (POM) hybrid materials based on octamolybdate building blocks and metal–organic fragments with flexible multidentate ligand, namely [CuII2(ttb)2(β-Mo8O26)(H2O)2]·2H2O (1), CuI4(ttb)2(β-Mo8O26)(H2O) (2), [CuI4(ttb)3(β-Mo8O26)] (3), [Ni2(ttb)2(β-Mo8O26)(H2O)6]·2H2O (4), [Zn2(ttb)2(α-Mo8O26)(H2O)2] (5), and [Ag4(ttb)2(β-Mo8O26)] (6), where ttb = 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethyl benzene, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, TGA, IR spectra, and electrochemistry. Compounds 1 and 2 exhibit three-dimensional (3D) 2-fold interpenetrating frameworks with (3,6)-connected (41·62)(42·610·103) and (3,4)-connected (62·81)2(62·84) topologies, respectively. We are not aware of any other examples of interpenetrating (3,6)- and (3,4)-connected frameworks which involves the octamolybdates. Compound 3 shows a rare two-dimensional (2D) 2-fold interpenetrating network structure. In compound 4, a 3D supramolecular framework with the channels is constructed by the hydrogen-bonding interactions between (β-Mo8O26)4−polyanions and the Ni-ttb double layers, in which the guest (β-Mo8O26)4− anions are included. If Zn⋯O interactions are considered, the structure of 5 is a 3D (3,4)-connected framework with (4·82)(4·82·103) topology. In 6, the ttb ligand as a tetradentate ligand links the Ag atoms to yield a 2D POM-based network. By careful inspection of the structures of 1–6, it can be seen that the ttb ligand, the metal ion and the coordination mode of the octamolybdate anion play important roles in the formation of the POM-based MOFs.
TL;DR: A range of fac-[Re(CO)(3)(Phen)(H(2)O)](n) (L,L'-Bid = neutral or monoanionic bidentate ligands with varied L,L' donor atoms, N,N', N,O, or O,O') has been synthesized and the aqua/methanol substitution has been investigated.
Abstract: A range of fac-[Re(CO)3(L,L′-Bid)(H2O)]n (L,L′-Bid = neutral or monoanionic bidentate ligands with varied L,L′ donor atoms, N,N′, N,O, or O,O′: 1,10-phenanthroline, 2,2′-bipydine, 2-picolinate, 2-quinolinate, 2,4-dipicolinate, 2,4-diquinolinate, tribromotropolonate, and hydroxyflavonate; n = 0, +1) has been synthesized and the aqua/methanol substitution has been investigated. The complexes were characterized by UV–vis, IR and NMR spectroscopy and X-ray crystallographic studies of the compounds fac-[Re(CO)3(Phen)(H2O)]NO3·0.5Phen, fac-[Re(CO)3(2,4-dQuinH)(H2O)]·H2O, fac-[Re(CO)3(2,4-dQuinH)Py]Py, and fac-[Re(CO)3(Flav)(CH3OH)]·CH3OH are reported. A four order-of-magnitude of activation for the methanol substitution is induced as manifested by the second order rate constants with (N,N′-Bid) < (N,O-Bid) < (O,O′-Bid). Forward and reverse rate and stability constants from slow and stopped-flow UV/vis measurements (k1, M–1 s–1; k–1, s–1; K1, M–1) for bromide anions as entering nucleophile are as follows: fac-[R...
TL;DR: Magnetic studies reveal that both Dy(3) and Tb(2) clusters exhibit significant ferromagnetic interactions and that the Dy( 3) species behave as single-molecule magnets, expanding upon the recent reports of the pure 4f type SMMs.
Abstract: A family of linear Dy(3) and Tb(3) clusters have been facilely synthesized from the reactions of DyCl(3), the polydentate 3-methyloxysalicylaldoxime (MeOsaloxH(2) ) ligand with auxiliary monoanionic ligands, such as trichloroacetate, NO(3)(-), OH(-), and Cl(-). Complexes 1-5 contain a nearly linear Ln(3) core, with similar Ln···Ln distances (3.6901(4)-3.7304(3) A for the Dy(3) species, and 3.7273(3)-3.7485(5) A for the Tb(3) species) and Ln···Ln···Ln angles of 157.036(8)-159.026(15)° for the Dy(3) species and 157.156(8)-160.926(15)° for the Tb(3) species. All three Ln centers are bridged by the two doubly-deprotonated [MeOsalox](2-) ligands and two of the four [MeOsaloxH](-) ligands through the N,O-η(2)-oximato groups and the phenoxo oxygen atoms (Dy-O-Dy angles=102.28(16)-106.85(13)°; Tb-O-Tb angles=102.00(11)-106.62(11)°). The remaining two [MeOsaloxH](-) ligands each chelate an outer Ln(III) center through their phenoxo oxygen and oxime nitrogen atoms. Magnetic studies reveal that both Dy(3) and Tb(3) clusters exhibit significant ferromagnetic interactions and that the Dy(3) species behave as single-molecule magnets, expanding upon the recent reports of the pure 4f type SMMs.
TL;DR: The speciation profiles for the denaturation reactions demonstrate that intermediate species are not significantly populated and that these equilibria are well described by a highly cooperative two-state model.
Abstract: Complexes of zinc porphyrin oligomers with multivalent ligands can be denatured by adding a large excess of a monodentate ligand, such as quinuclidine. We have used denaturation titrations to determine the stabilities of the complexes of a cyclic zinc–porphyrin hexamer with multidentate ligands with two to six pyridyl coordination sites. The corresponding complexes of linear porphyrin oligomers were also investigated. The results reveal that the stepwise effective molarities (EMs) for the third through sixth intramolecular coordination events with the cyclic hexamer are extremely high (EM = 102–103 M), whereas the values for the linear porphyrin oligomers are modest (EM ≈ 0.05 M). The speciation profiles for the denaturation reactions demonstrate that intermediate species are not significantly populated and that these equilibria are well described by a highly cooperative two-state model.
TL;DR: The mechanism of the tert-butylhydroperoxide-mediated, Pd(Quinox)-catalyzed Wacker-type oxidation was investigated to evaluate the hypothesis that a selective catalyst-controlled oxidation could be achieved by rendering the palladium coordinatively saturated using a bidentate amine ligand.
Abstract: The mechanism of the tert-butylhydroperoxide-mediated, Pd(Quinox)-catalyzed Wacker-type oxidation was investigated to evaluate the hypothesis that a selective catalyst-controlled oxidation could be achieved by rendering the palladium coordinatively saturated using a bidentate amine ligand. The unique role of the Quinox ligand framework was probed via systematic ligand modifications. The modified ligands were evaluated through quantitative Hammett analysis, which supports a "push-pull" relationship between the electronically asymmetric quinoline and oxazoline ligand modules.
TL;DR: The spin state of 2, which showed paramagnetically shifted NMR signals in the range of 60 to -20 ppm, was determined to be an intermediate spin (S = 1) by the Evans' method with (1)H NMR spectroscopy in acetone-d(6).
Abstract: A coordinatively saturated ruthenium(II) complex having tetradentate tris(2-pyridylmethyl)amine (TPA) and bidentate 2,2'-bipyridine (bpy), [Ru(TPA)(bpy)](2+) (1), was oxidized by a Ce(IV) ion in H(2)O to afford a Ru(IV)-oxo complex, [Ru(O)(H(+)TPA)(bpy)](3+) (2). The crystal structure of the Ru(IV)-oxo complex 2 was determined by X-ray crystallography. In 2, the TPA ligand partially dissociates to be in a facial tridentate fashion and the uncoordinated pyridine moiety is protonated. The spin state of 2, which showed paramagnetically shifted NMR signals in the range of 60 to -20 ppm, was determined to be an intermediate spin (S = 1) by the Evans' method with (1)H NMR spectroscopy in acetone-d(6). The reaction of 2 with various oraganic substrates in acetonitrile at room temperature afforded oxidized and oxygenated products and a solvent-bound complex, [Ru(H(+)TPA)(bpy)(CH(3)CN)], which is intact in the presence of alcohols. The oxygenation reaction of saturated C-H bonds with 2 proceeds by two-step processes: the hydrogen abstraction with 2, followed by the dissociation of the alcohol products from the oxygen-rebound complexes, Ru(III)-alkoxo complexes, which were successfully detected by ESI-MS spectrometry. The kinetic isotope effects in the first step for the reaction of dihydroanthrathene (DHA) and cumene with 2 were determined to be 49 and 12, respectively. The second-order rate constants of C-H oxygenation in the first step exhibited a linear correlation with bond dissociation energies of the C-H bond cleavage.
TL;DR: The anticancer activity of the synthesized metallodrugs was checked against DU145 human prostate carcinoma (HTB-81) cells, the IC(50) values indicate that the compounds are highly active against these cells.
TL;DR: In this paper, three Cu(II) coordination polymers have been synthesized solvothermally, employing enantiopure l-amino acids and bidentate N-donor ligands, 1,4-bis(imidazol-1-ylmethyl)benzene (1, 4-Bix) and 4,4′-bipyridyl(4, 4′-Bpy) respectively, to yield 1-D, 2-D and 3-D helical polymers, respectively.
Abstract: Three Cu(II) coordination polymers, {[Cu(l-cysteate)(1,4-Bix)(H2O)]·H2O}n (1), {[Cu(l-aspartate)(1,4-Bix)0.5]·H2O}n (2), and {[Cu(l-aspartate)(4,4′-Bpy)0.5]H2O}n (3), have been synthesized solvothermally, employing enantiopure l-amino acids and bidentate N-donor ligands, 1,4-bis(imidazol-1-ylmethyl)benzene (1,4-Bix) and 4,4′-bipyridyl(4,4′-Bpy), to yield 1-D, 2-D, and 3-D helical coordination polymers, respectively. All the three neutral frameworks are well-characterized by various physicochemical methods (C,H,N analysis, IR, TGA) including the single crystal X-ray diffraction technique. The chiral nature of complexes 2 and 3 was established using solid state CD spectra. Structural investigation of complex 1 revealed 1-D helical chains, whereas that of complex 2 confirms a chiral and helical two-dimensional 63-hcb net, with helicity propagating in both the dimensions. Cu(II) nodes with the mixed ligands in complex 3 generate a three-dimensional framework by the pillaring of Cu(l-aspartate) 2-D helical lay...
TL;DR: In this article, the N-alkyphosphine-substituted benzimidazoles have been obtained and crystallographically characterized and they react with [RhCl(P∧C)PR3] depending on the steric demand of the PR3, the phosphines of the P∧c ligands, and on the spacer linking the benziminidazole ring nitrogen atom to the alkylphosphines.
TL;DR: These are the first primary amine- or amido-NHC complexes of Rh and Ir, pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity.
Abstract: Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine-NHC and amido-NHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [(p-cymene)RuCl(2)](2) and [Cp*MCl(2)](2) (M = Rh, Ir). Treating 2a with [Cp*MCl(2)](2) and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3; M = Ir, 4), resulting from aromatic C-H activation. In contrast, treating 2b with [(p-cymene)RuCl(2)](2), Ag(2)O and KI gave the amine-NHC complex [(p-cymene)Ru(C,NH(2))I]I (5). The reaction of 2b with [Cp*MCl(2)](2) (M = Rh, Ir), NaO(t)Bu and KI gave the amine-NHC complex [Cp*Rh(NH(2))I]I (6) or the amido-NHC complex Cp*Ir(C,NH)I (7); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amine-NHC complex [Cp*Ir(C,NH(2))I][CF(3)CO(2)] (8). These are the first primary amine- or amido-NHC complexes of Rh and Ir. Solid-state structures of the complexes 3-8 have been determined by single crystal X-ray diffraction. Complexes 5, 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity.
TL;DR: The 1,4-disubstituted 1,2,3-triazole ligand was investigated as novel chelating ligand for Ru(II) complexes with potential antitumor activity and was found to be more cytotoxic than cisplatin against human lung squamose carcinoma cell line (A-549).
Abstract: The 1,4-disubstituted 1,2,3-triazole ligand prepared by click chemistry 1-(2-picolyl)-4-phenyl-1H-1,2,3-triazole (ppt) was investigated as novel chelating ligand for Ru(II) complexes with potential antitumor activity. The preparation and structural characterization, mainly by NMR spectroscopy in solution and by X-Ray crystallography in the solid state, of four new Ru(II) complexes is reported: two isomeric Ru-dmso compounds, trans,cis-[RuCl2(dmso-S)2(ppt)] (1) and cis,cis-[RuCl2(dmso-S)2(ppt)] (2), and two half-sandwich Ru-[9]aneS3 coordination compounds, [Ru([9]aneS3)(dmso-S)(ppt)][CF3SO3]2 (3) and [Ru([9]aneS3)Cl(ppt)][CF3SO3] (4). In all compounds ppt firmly binds to ruthenium in a bidentate fashion through the pyridyl nitrogen atom and the triazole N2, thus forming a puckered six-membered ring. The chemical behavior in aqueous solution of the water-soluble complexes 3 and 4 was studied by UV-Vis and NMR spectroscopy and compared to that of the previously described organometallic analogue [Ru(η6-p-cymene)Cl(ppt)][Cl] (5) in view of their potential antitumor activity. Compounds 3–5 were tested also in vitro for cytotoxic activity against two human cancer cell lines, one sensitive and one resistant to cisplatin, in comparison with cisplatin. Compound 4, the one that aquates faster, was found to be more cytotoxic than cisplatin against human lung squamose carcinoma cell line (A-549).
TL;DR: The Schiff base hydrazone ligand HL was prepared by the condensation reaction of 7-chloro-4-quinoline with o-hydroxyacetophenone and its metal complexes were characterized by elemental analyses, IR, NMR, Mass, and UV-Visible spectra.
Abstract: The Schiff base hydrazone ligand HL was prepared by the condensation reaction of 7-chloro-4-quinoline with o-hydroxyacetophenone. The ligand behaves either as monobasic bidentate or dibasic tridentate and contain ONN coordination sites. This was accounted for be the presence in the ligand of a phenolic azomethine and imine groups. It reacts with Cu(II), Ni(II), Co(II), Mn(II), UO(2) (VI) and Fe(II) to form either mono- or binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, NMR, Mass, and UV-Visible spectra. The magnetic moments and electrical conductance of the complexes were also determined. The Co(II), Ni(II) and UO(2) (VI) complexes are mononuclear and coordinated to NO sites of two ligand molecules. The Cu(II) complex has a square-planar geometry distorted towards tetrahedral, the Ni(II) complex is octahedral while the UO(2) (VI) complex has its favoured heptacoordination. The Co(II), Mn(II) complexes and also other Ni(II) and Fe(III) complexes, which were obtained in the presence of Li(OH) as deprotonating agent, are binuclear and coordinated via the NNNO sites of two ligand molecules. All the binuclear complexes have octahedral geometries and their magnetic moments are quite low compared to the calculated value for two metal ions complexes and thus antiferromagnetic interactions between the two adjacent metal ions. The ligand HL and metal complexes were tested against a strain of Gram +ve bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli), and fungi (Candida albicans). The tested compounds exhibited high antibacterial activities.
TL;DR: The curcumin complexes 5 and 6, as well as their intermediate aqua complex 4, were successfully tested for selective staining of β-amyloid plaques of Alzheimer's disease and prompted for further exploration of their chemistry and biological properties as radioimaging probes.
Abstract: The synthesis and characterization of “2 + 1” complexes of the [M(CO)3]+ (M = Re, 99mTc) core with the β-diketones acetylacetone (complexes 2, 8) and curcumin (complexes 5, 10 and 6, 11) as bidentate OO ligands, and imidazole or isocyanocyclohexane as monodentate ligands is reported. The complexes were synthesized by reacting the [NEt4]2[Re(CO)3Br3] precursor with the β-diketone to generate the intermediate aqua complex fac-Re(CO)3(OO)(H2O) that was isolated and characterized, followed by replacement of the labile water by the monodentate ligand. All complexes were characterized by mass spectrometry, NMR and IR spectroscopies, and elemental analysis. In the case of complex 2, bearing imidazole as the monodentate ligand, X-ray analysis was possible. The chemistry was successfully transferred at 99mTc tracer level. The curcumin complexes 5 and 6, as well as their intermediate aqua complex 4, that bear potential for radiopharmaceutical applications due to the wide spectrum of pharmacological activity of curc...
TL;DR: The coordination mode of a monodentate phosphoroamidite ligand in a rhodium complex can be switched from equatorial to axial by a unique supramolecular pseudo encapsulation as mentioned in this paper.
Abstract: The coordination mode of a monodentate phosphoroamidite ligand in a rhodium complex can be switched from equatorial to axial by a unique supramolecular pseudo encapsulation (see scheme). The axial complex has higher activity and selectivity in the challenging asymmetric hydroformylation of internal alkenes.
TL;DR: Electronic structure calculations show that bond elongation in the lowest energy triplet metal-to-ligand charge transfer ((3)MLCT) state compared to the ground state is greater for complexes containing bisthioether ligands than those with coordinated bidentate nitrogen atoms.
Abstract: The series of complexes [Ru(bpy)(2)(L)](2+), where bpy = 2,2'-bipyridine and L = 3,6-dithiaoctane (bete, 1), 1,2-bis(phenylthio)ethane (bpte, 2), ethylenediamine (en, 3), and 1,2-dianilinoethane (dae, 4), were synthesized, and their photochemistry was investigated. Photolysis experiments show that the bisthioether ligands in 1 and 2 are more easily photosubstituted by chloride ions, bpy, and H(2)O than the corresponding diammine complexes in 3 and 4 to generate the bis-substituted products. Electronic structure calculations show that bond elongation in the lowest energy triplet metal-to-ligand charge transfer ((3)MLCT) state compared to the ground state is greater for complexes containing bisthioether ligands than those with coordinated bidentate nitrogen atoms. This elongation in the excited state is attributed to Ru-S π-bonding character of the highest occupied molecular orbitals, which is not present in the diamine complexes. In the Ru→bpy (3)MLCT state, the lower electron density on the metal-centered highest occupied molecular orbital (HOMO) weakens the Ru-S bond and results in the greater photoreactivity of 1 and 2 relative to that of 3 and 4. The more efficient photoinduced ligand exchange of the complexes possessing thioether ligands results in binding of 1 and 2 to DNA upon irradiation.
TL;DR: The analysis that the Ru!Cl coordination bond is too weak to provide good selectivity towards cancer cells led us to look for protective groups, that is, ligands that would hold more strongly to ruthenium than chlorides, but that could also be cleaved in a controlled way in vivo.
Abstract: Over the last decades the large therapeutic success of cisplatin-like anticancer drugs, combined to its recognized limitations (such as acquired resistance and general toxicity), have stimulated the scientific community to find other metal-based drugs with anticancer properties. Ruthenium-based molecules, and among them those containing polypyridyl ligands, have emerged as a vast family of active compounds. However, clinical studies have shown that general toxicity remains an important issue, and ruthenium-based chemotherapy is still a heavy burden for the cancer patient. Although several mechanisms might explain their anticancer properties in vivo, the thermal aquation of ruthenium–chloride bonds, followed by coordination to DNA 16–18] and/or proteins is, like for platinum-based anticancer drugs, a highly plausible mode of action (see Figure 1, route 1). 21] However, as thermal breaking of Ru!Cl bonds in aqueous solution might happen anywhere in a human body, this mechanism is thought to be the basis of both antitumor activity and general toxicity. Our analysis that the Ru!Cl coordination bond is too weak to provide good selectivity towards cancer cells, led us to look for protective groups, that is, ligands that would hold more strongly to ruthenium than chlorides, but that could also be cleaved in a controlled way in vivo. In the ideal case, such ligands would avoid the formation of aqua complexes, and thus prevent the coordination of competing biological ligands in vivo. Thioether ligands are ideal candidates because ruthenium(II) likes binding to their soft sulfur atom. Secondly, unlike nitrogen-based ligands, thioethers are only weakly basic in water, which might make their ruthenium complexes less sensitive to pH changes. Finally, visible-light irradiation leads to the controlled release of thioether ligands, which feature might be used to deliver locally the cytotoxic form of the ruthenium complex at the desired location (Figure 1, route 2). The use of light to cure cancer, which has notably led to the clinical development of photodynamic therapy, has also been proposed as an interesting development in metal-based anticancer drug research, in which the presence of oxygen is not required. To investigate this concept, we selected two monodentate thioether ligands of natural origin: N-acetyl-l-methionine and d-biotin, and synthesized their ruthenium complexes [Ru ACHTUNGTRENNUNG(terpy) ACHTUNGTRENNUNG(bpy)(N-acetyl-l-methionine)]Cl2 (compound [3]Cl2) and [RuACHTUNGTRENNUNG(terpy)ACHTUNGTRENNUNG(bpy) ACHTUNGTRENNUNG(d-biotin)]Cl2 (compound [4]Cl2, see Scheme 1). The synthesis is straightforward: it does not require any silver salts to remove the chloride anions, but simply requires mixing in water, at 80 8C and in the dark, the chlorido complex [Ru ACHTUNGTRENNUNG(terpy) ACHTUNGTRENNUNG(bpy)Cl]Cl (compound[1]Cl, see Scheme 1) and one equivalent of the thioether ligand. The course of the reaction can be nicely monitored using H NMR spectroscopy, since each different ruthenium species present in solution gives a distinct A6 [a] R. E. Goldbach, I. Rodriguez-Garcia, S. Bonnet Leiden Institute of Chemistry, Gorlaeus Laboratories Leiden University, P.O. Box 9502 2300 RA Leiden (The Netherlands) E-mail : bonnet@chem.leidenuniv.nl [b] J. H. v. Lenthe Theoretical Chemistry Group Debye Institute for Nanomaterial Science Faculty of Science, Utrecht University Padualaan 8, 3584 CH Utrecht (The Netherlands) [c] M. A. Siegler Small Molecule X-ray Facility Department of Chemistry, Johns Hopkins University Baltimore, MD 21218 (USA) Supporting information for this article (including synthetic procedures, full characterization and high-resolution ES-MS spectra of complexes [3]Cl2 and [4]Cl2; notations for the assignments of the NMR spectra and H NMR spectra; X-ray crystallography resolution method and data; ferrioxalate actinometry, quantum yield measurement procedures, H NMR and kinetic data for irradiation experiments; calculation procedure and x,y,z coordinates for the DFT-minimized species [3A] , [3B] , [4A], and [4B]) is available on the WWW under http://dx.doi.org/10.1002/chem.201101541. Figure 1. One of the modes of action of ruthenium polypyridyl anticancer drugs (reaction 1), and a new photochemotherapy strategy using analogous complexes “protected” by thioethers ligands and “deprotected” by visible light irradiation (reaction 2).
TL;DR: The RuCp complex of a new chiral bidentate sp2-N ligand was shown to catalyze a variety of intra- and inter-molecular enantioselective dehydrative C-, N-, and O-allylation reactions without the need of extra additives.
Abstract: The RuCp complex of a new chiral bidentate sp2-N ligand is shown to catalyze a variety of intra- and inter-molecular enantioselective dehydrative C-, N-, and O-allylation reactions without the need of extra additives.
TL;DR: A series of neutral and cationic Ru(II) complexes were synthesized by starting from [RuCl2(DMSO)4] and [RuCL2(p-cymene)]2 precursors as mentioned in this paper.
TL;DR: The combination of copper acetate and a chiral monodentate ligand was used for the enantioselective hydrogenation of various carbonyl compounds as mentioned in this paper.
Abstract: The combination of copper acetate and a chiral monodentate ligand is used for the enantioselective hydrogenation of various carbonyl compounds.
TL;DR: The preparation, single-crystal X-ray diffraction study, and surprising reactivity of a room-temperature-stable [(CAAC)CuH]2 complex are reported.
Abstract: Discovered as early as 1844,[1] copper(I) hydride complexes have attracted considerable interest. In combination with a hydrosilane, as a hydride source, they promote the hydrosilylation of ketones and aldehydes, and they are efficient catalysts in the regioselective conjugate reduction of a number of carbonyl derivatives, including unsaturated ke-tones, aldehydes, and esters.[2] The most extensively studied copper hydride is certainly the hexameric [(Ph3P)CuH]6, first described by Osborn et al.[3] and then developed as a useful synthetic tool by Stryker et al.[4] Despite the numerous applications of the Stryker reagent, several studies have focused on the synthesis of copper hydride complexes of lower nuclearity. Huang et al.[5] reported the synthesis and X-ray crystal structure of the trinuclear (μ3-H) dicationic complex A (
TL;DR: The combination of 2 (0.005 mmol) with hydrogen peroxide in acetonitrile is found to be an active catalyst for the oxidation of primary and secondary alcohols to their corresponding acids and ketones, respectively, at room temperature.
Abstract: New four-coordinated tetrahedral copper(I) complexes have been synthesized from the reactions between [CuCl2(PPh3)2] and N-(diphenylcarbamothioyl)benzamide (HL1) or N-(diethylcarbamothioyl)benzamide (HL2) in benzene. These complexes have been characterized by elemental analyses, IR, UV/Vis, 1H, 13C and 31P NMR spectroscopy. The molecular structure of both the complexes, [CuCl(HL1)2(PPh3)] (1) and [CuCl(HL2)(PPh3)2] (2) were determined by single-crystal X-ray diffraction, which reveals distorted tetrahedral geometry around each Cu(I) ion. The combination of 2 (0.005 mmol) with hydrogen peroxide (2.5 mmol) in acetonitrile is found to be an active catalyst for the oxidation of primary and secondary alcohols (0.5 mmol) to their corresponding acids and ketones, respectively, at room temperature.
