Chloride Ligands (chloride + ligand)

Distribution by Scientific Domains


Selected Abstracts


Pyrazole and Pyrazolyl Complexes of cis -Bis(2,2,-bipyridine)chlororuthenium(II): Synthesis, Structural and Electronic Characterization, and Acid-Base Chemistry

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2009
Hershel Jude
Abstract Complexes of the type cis -[Ru(bpy)2(Cl)(L)]+ [bpy = 2,2,-bipyridine; with L = pyrazole (1H), 4-methylpyrazole (2H), and 3,5-dimethylpyrazole (3H)] were synthesized and isolated as hexafluorophosphate salts. The molecular structures of these new complexes were fully characterized by 1H NMR spectroscopy and ESI mass spectrometry, and the crystal structure of 3H·PF6 was determined by X-ray crystallography. Compound 3H·PF6 (C25H24ClF6N6PRu) crystallizes in the monoclinic space group P21/n with a = 12.102(2) Å, b = 16.826(3) Å, c = 13.016(2) Å, , = 92.606(2)°, V = 2647.6(8) Å3, and Z = 4. The crystal structure of 3H reveals the formation of an intramolecular hydrogen bond (2.562 Å) between the pyrazole N(2),H site and the chloride ligand. The redox and electronic absorption properties of 1H, 2H, and 3H, as well as their deprotonated counterparts [L = pyrazolate (1), 4-methylpyrazolate (2), and 3,5-dimethylpyrazolate (3)], were investigated by cyclic voltammetry and UV/Vis spectroscopy. For detailed analysis of the electronic nature of this series of pyrazolyl ligands, the results are discussed along with other relevant cis -[Ru(bpy)2(X)(Y)]n+ complexes. From spectrophotometric pH titrations, the basicity associated with the coordinated pyrazole/pyrazolate couple in water was found in all three cases to be unusually high, partly owing to the N,H···Cl hydrogen bond that stabilizes the protonated, azole state. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Poly[bis(,-4-benzoyl-1-isonicotinoylthiosemicarbazide-,2N:S)dichloridocadmium(II)]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010
Yu-Bo Wang
The asymmetric unit of the title complex, [CdCl2(C14H12N4O2S)2]n, consists of one CdII ion located on the crystallographic inversion centre, one 4-benzoyl-1-isonicotinoylthiosemicarbazide ligand and one chloride ligand. The central CdII ion adopts a distorted octahedral coordination geometry formed by two pyridyl N atoms of two ligands, two S atoms of two other ligands and two chloride ligands. The thiosemicarbazide ligands act as bridges, linking the metal ions into a two-dimensional layered structure parallel to the bc plane. Intermolecular N,H...O hydrogen bonds and C,H..., interactions exist between adjacent layers. [source]


Pincer-Type Heck Catalysts and Mechanisms Based on PdIV Intermediates: A Computational Study

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2010
Olivier Blacque Dr.
Abstract Pincer-type palladium complexes are among the most active Heck catalysts. Due to their exceptionally high thermal stability and the fact that they contain PdII centers, controversial PdII/PdIV cycles have been often proposed as potential catalytic mechanisms. However, pincer-type PdIV intermediates have never been experimentally observed, and computational studies to support the proposed PdII/PdIV mechanisms with pincer-type catalysts have never been carried out. In this computational study the feasibility of potential catalytic cycles involving PdIV intermediates was explored. Density functional calculations were performed on experimentally applied aminophosphine-, phosphine-, and phosphite-based pincer-type Heck catalysts with styrene and phenyl bromide as substrates and (E)-stilbene as coupling product. The potential-energy surfaces were calculated in dimethylformamide (DMF) as solvent and demonstrate that PdII/PdIV mechanisms are thermally accessible and thus a true alternative to formation of palladium nanoparticles. Initial reaction steps of the lowest energy path of the catalytic cycle of the Heck reaction include dissociation of the chloride ligands from the neutral pincer complexes [{2,6-C6H3(XPR2)2}Pd(Cl)] [X=NH, R=piperidinyl (1,a); X=O, R=piperidinyl (1,b); X=O, R=iPr (1,c); X=CH2, R=iPr (1,d)] to yield cationic, three-coordinate, T-shaped 14e, palladium intermediates of type [{2,6-C6H3(XPR2)2}Pd]+ (2). An alternative reaction path to generate complexes of type 2 (relevant for electron-poor pincer complexes) includes initial coordination of styrene to 1 to yield styrene adducts [{2,6-C6H3(XPR2)2}Pd(Cl)(CH2CHPh)] (4) and consecutive dissociation of the chloride ligand to yield cationic square-planar styrene complexes [{2,6-C6H3(XPR2)2}Pd(CH2CHPh)]+ (6) and styrene. Cationic styrene adducts of type 6 were additionally found to be the resting states of the catalytic reaction. However, oxidative addition of phenyl bromide to 2 result in pentacoordinate PdIV complexes of type [{2,6-C6H3(XPR2)2}Pd(Br)(C6H5)]+ (11), which subsequently coordinate styrene (in trans position relative to the phenyl unit of the pincer cores) to yield hexacoordinate phenyl styrene complexes [{2,6-C6H3(XPR2)2}Pd(Br)(C6H5)(CH2CHPh)]+ (12). Migration of the phenyl ligand to the olefinic bond gives cationic, pentacoordinate phenylethenyl complexes [{2,6-C6H3(XPR2)2}Pd(Br)(CHPhCH2Ph)]+ (13). Subsequent ,-hydride elimination induces direct HBr liberation to yield cationic, square-planar (E)-stilbene complexes with general formula [{2,6-C6H3(XPR2)2}Pd(CHPhCHPh)]+ (14). Subsequent liberation of (E)-stilbene closes the catalytic cycle. [source]


Unprecedented Solvent-Assisted Reactivity of Hydrido W3CuS4 Cubane Clusters: The Non-Innocent Behaviour of the Cluster-Core Unit

CHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2009
Andrés
Abstract Opening the cluster core: Substitution of the chloride ligand in the novel cationic cluster [W3CuS4H3Cl(dmpe)3]+ (see figure; dmpe=1,2-bis(dimethylphosphino)ethane) by acetonitrile is promoted by water addition. Kinetic and density functional theory studies lead to a mechanistic proposal in which acetonitrile or water attack causes the opening of the cluster core with dissociation of one of the CuS bonds to accommodate the entering ligand. Reaction of the incomplete cuboidal cationic cluster [W3S4H3(dmpe)3]+ (dmpe=1,2-bis(dimethylphosphino)ethane) with CuI compounds produces rare examples of cationic heterodimetallic hydrido clusters of formula [W3CuClS4H3(dmpe)3]+ ([1]+) and [W3Cu(CH3CN)S4H3(dmpe)3]2+ ([2]2+). An unexpected conversion of [1]+ into [2]2+, which involves substitution of chloride by CH3CN at the copper centre, has been observed in CH3CN/H2O mixtures. Surprisingly, formation of the acetonitrile complex does not occur in neat acetonitrile and requires the presence of water. The kinetics of this reaction has been studied and the results indicate that the process is accelerated when the water concentration increases and is retarded in the presence of added chloride. Computational studies have also been carried out and a mechanism for the substitution reaction is proposed in which attack at the copper centre by acetonitrile or water causes disruption of the cubane-type core. ESI-MS experiments support the formation of intermediates with an open-core cluster structure. This kind of process is unprecedented in the chemistry of M3M,Q4 (M=Mo, W; Q=S, Se) clusters, and allows for the transient appearance of a new coordination site at the M, site which could explain some aspects of the reactivity and catalytic properties of this kind of clusters. [source]


Metal-Induced Tautomerization of p - to o -Quinone Compounds: Experimental Evidence from CuI and ReI Complexes of Azophenine and DFT Studies

CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2004
Stéphanie Frantz
Abstract Azophenine (7,8-diphenyl-2,5-bis(phenylamino)- p -quinonediimine, Lp) reacts with [Cu(PPh3)4](BF4) or [Re(CO)5Cl] to yield the (Ph3P)2Cu+ or [(OC)3ClRe] complex of the tautomeric form 7,8-diphenyl-4,5-bis(phenylamino)- o -quinonediimine, Lo, as evident from structure determinations and from very intense metal-to-ligand charge transfer (MLCT) transitions in the visible region. Time-dependent DFT (TD-DFT) calculations on model complexes [(N,N)Re(CO)3Cl] confirm the spectroscopic results, showing considerably higher oscillator strengths of the MLCT transition for the o -quinonediimine complexes in comparison to compounds with N,N=1,4-dialkyl-1,4-diazabutadiene. The complexes are additionally stabilized through hydrogen bonding between two now ortho -positioned NHPh substituents and one fluoride of the BF4, anion (Cu complex) or the chloride ligand (Re complex). DFT Calculations on the model ligands p -quinonediimine or 2,5-diamino- p -quinonediimine and their ortho -quinonoid forms with and without Li+ or Cu+ are presented to discuss the relevance for metal-dependent quinoproteins. [source]


Characterization by NMR Spectroscopy, X-ray Analysis and Cytotoxic Activity of the Ruthenium(II) Compounds [RuL3](PF6)2(L = 2-Phenylazopyridine or o -Tolylazopyridine) and [RuL'2L"](PF6)2(L', L" = 2-Phenylazopyridine, 2,2'-Bipyridine)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2005
Anna C. G. Hotze
Abstract Tris(ligand) complexes [RuL3](PF6)2 (L = 2-phenylazopyridine or o -tolylazopyridine) and mixed ligand [RuL'2L"](PF6)2 (L' and L" are 2-phenylazopyridine or 2,2'-bipyridine) have been synthesized, structurally characterized and investigated for cytotoxic activity. These complexes are important to study the hypothesis that the compound ,-[Ru(azpy)2Cl2] (azpy = 2-phenylazopyridine) exhibits a high cytotoxicity due to its two cis chloride ligands, which might be exchanged for biological targets as DNA. Molecular structures of mer -[Ru(azpy)3](PF6)2 (1) and mer -[Ru(tazpy)3](PF6)2 (5) (tazpy = o -tolylazopyridine) have been determined by X-ray diffraction. Series of complexes [RuL3](PF6)2 and [RuL'2L"](PF6)2 show interesting NMR spectroscopic data; e.g. the spectrum of mer -[Ru(azpy)3](PF6)2 (1) shows extremely broadened resonances at room temp. but sharpened resonances at low temperature. In the 1H NMR spectra of compounds [Ru(azpy)2(bpy)]2+ and [Ru(bpy)2(azpy)]2+ (bpy = 2,2-bipyridine), respectively, less broadened (room temp.) or completely sharp resonances (room temp.) occur in comparison to 1 (under same conditions). By selecting the right temperature and/or concentration, NMR spectra of these series of compounds have been resolved using 2D COSY and NOESY NMR spectroscopy. Remarkably, the cytotoxicity data against a series of human tumor cell lines (A498, EVSA-T, H226, IGROV, M19, MCF-7 and WIDR) show a moderate cytotoxicity for these series of tris(ligand) complexes. So, even though no chloride ligands are present in these tris(ligand) complexes, a considerable cytotoxic activity is observed. This would imply that the 2-phenylazopyridine ruthenium(II) complexes act by a completely different mechanism than the well-known cisplatin. This finding is important, because an anticancer compound acting via a different mechanism is a prerequisite in designing new anticancer drugs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]


Bis(salicylaldiminato)titanium Complexes Containing Bulky Imine Substituents: Synthesis, Characterization and Ethene Polymerization Studies

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005
Antti Pärssinen
Abstract A series of titanium complexes bearing two anionic [N, O,] bidentate salicylaldiminato ligands, namely bis[(N -salicylidene)anilinato]titanium(IV) dichloride (1), bis[(N -salicylidene)-2,6-dimethylanilinato]titanium(IV) dichloride (2), bis[(N -salicylidene)-2,6-di- i - propylanilinato]titanium(IV) dichloride (3), bis[(N -salicylidene)-(1-naphthalenylimino)]titanium(IV) dichloride (4), bis[(N -salicylidene)-2,6-difluoroanilinato]titanium(IV) dichloride (5), and bis[(N -3-fluorosalicylidene)-2,6-difluoroanilinato]titanium(IV) dichloride (6) have been synthesized with good yields by a two-step procedure. The X-ray structure analysis reveals that in complex 2, titanium has a distorted octahedral coordination sphere in which the oxygen atoms and the chloride ligands form the basal plane. Both the chloride and the phenoxy moieties have a cis orientation and the angle between the chloride ligands is 93.05°. The imine nitrogen atoms complete the octahedral coordination of the Ti center by occupying the axial positions. The newly synthesized (2 and 4,6) and already known complexes (1 and 3) were introduced in detailed ethene-polymerization studies. The activities achieved were low to moderate depending on the size and nature of the imino substituents. The polyethenes (PEs) produced had high molar masses, and the modalities of the molecular weight distributions varyied with polymerization temperature. Based on the results of ab initio calculations and on the experimental data obtained, an explanation for uni- and bimodal polymerization behavior and the differences in catalytic activities are given. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]


Poly[bis(,-4-benzoyl-1-isonicotinoylthiosemicarbazide-,2N:S)dichloridocadmium(II)]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010
Yu-Bo Wang
The asymmetric unit of the title complex, [CdCl2(C14H12N4O2S)2]n, consists of one CdII ion located on the crystallographic inversion centre, one 4-benzoyl-1-isonicotinoylthiosemicarbazide ligand and one chloride ligand. The central CdII ion adopts a distorted octahedral coordination geometry formed by two pyridyl N atoms of two ligands, two S atoms of two other ligands and two chloride ligands. The thiosemicarbazide ligands act as bridges, linking the metal ions into a two-dimensional layered structure parallel to the bc plane. Intermolecular N,H...O hydrogen bonds and C,H..., interactions exist between adjacent layers. [source]


Potassium yttrium hexaniobium octadecachloride, KYNb6Cl18

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2003
Thirumalai Duraisamy
The structure of potassium yttrium hexaniobium octadeca­chloride is built of anionic [Nb6Cl12iCl6a]4, cluster units (where `i' and `a' denote inner and outer ligands, respectively), linked together by K+ and Y3+ cations. The K+ cations occupy half of the tetrahedral vacancies in the face-centered cubic lattice of cluster units, and are coordinated by 12 chloride ligands. The Y atom is located in an octahedral site and is bonded to six outer chloride ligands. [source]


Cadmium copper tetrachloride tetrahydrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2000
Ulrich Kortz
The double salt [CuCl2(H2O)2{CdCl2}]·2H2O crystallizes in the triclinic rather than the monoclinic system as reported previously. The structure consists of sheets in the ac plane with slightly distorted octahedral CdCl6 [Cd,Cl 2.5813,(8),2.6943,(8),Å] connected by Cd,Cl,Cd bridges in the Cd equatorial plane along a, and by Cd,Cl,Cu bridges to layers of square-planar CuCl2(H2O)2 along c. There are long axial Cu,Cl interactions of 2.8623,(7),Å and additional water of hydration is hydrogen bonded to coordinated water and chloride ligands. The additional water connects the ac sheets into a three-dimensional network. Both Cd and Cu occupy different sites. The Cu,Cu and Cd,Cd distances are 3.8274,(6),Å. [source]


Pincer-Type Heck Catalysts and Mechanisms Based on PdIV Intermediates: A Computational Study

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2010
Olivier Blacque Dr.
Abstract Pincer-type palladium complexes are among the most active Heck catalysts. Due to their exceptionally high thermal stability and the fact that they contain PdII centers, controversial PdII/PdIV cycles have been often proposed as potential catalytic mechanisms. However, pincer-type PdIV intermediates have never been experimentally observed, and computational studies to support the proposed PdII/PdIV mechanisms with pincer-type catalysts have never been carried out. In this computational study the feasibility of potential catalytic cycles involving PdIV intermediates was explored. Density functional calculations were performed on experimentally applied aminophosphine-, phosphine-, and phosphite-based pincer-type Heck catalysts with styrene and phenyl bromide as substrates and (E)-stilbene as coupling product. The potential-energy surfaces were calculated in dimethylformamide (DMF) as solvent and demonstrate that PdII/PdIV mechanisms are thermally accessible and thus a true alternative to formation of palladium nanoparticles. Initial reaction steps of the lowest energy path of the catalytic cycle of the Heck reaction include dissociation of the chloride ligands from the neutral pincer complexes [{2,6-C6H3(XPR2)2}Pd(Cl)] [X=NH, R=piperidinyl (1,a); X=O, R=piperidinyl (1,b); X=O, R=iPr (1,c); X=CH2, R=iPr (1,d)] to yield cationic, three-coordinate, T-shaped 14e, palladium intermediates of type [{2,6-C6H3(XPR2)2}Pd]+ (2). An alternative reaction path to generate complexes of type 2 (relevant for electron-poor pincer complexes) includes initial coordination of styrene to 1 to yield styrene adducts [{2,6-C6H3(XPR2)2}Pd(Cl)(CH2CHPh)] (4) and consecutive dissociation of the chloride ligand to yield cationic square-planar styrene complexes [{2,6-C6H3(XPR2)2}Pd(CH2CHPh)]+ (6) and styrene. Cationic styrene adducts of type 6 were additionally found to be the resting states of the catalytic reaction. However, oxidative addition of phenyl bromide to 2 result in pentacoordinate PdIV complexes of type [{2,6-C6H3(XPR2)2}Pd(Br)(C6H5)]+ (11), which subsequently coordinate styrene (in trans position relative to the phenyl unit of the pincer cores) to yield hexacoordinate phenyl styrene complexes [{2,6-C6H3(XPR2)2}Pd(Br)(C6H5)(CH2CHPh)]+ (12). Migration of the phenyl ligand to the olefinic bond gives cationic, pentacoordinate phenylethenyl complexes [{2,6-C6H3(XPR2)2}Pd(Br)(CHPhCH2Ph)]+ (13). Subsequent ,-hydride elimination induces direct HBr liberation to yield cationic, square-planar (E)-stilbene complexes with general formula [{2,6-C6H3(XPR2)2}Pd(CHPhCHPh)]+ (14). Subsequent liberation of (E)-stilbene closes the catalytic cycle. [source]


In vitro Ruthenation of Human Breast Cancer Suppressor Gene 1 (BRCA1) by the Antimetastasis Compound RAPTA-C and Its Analogue CarboRAPTA-C

CHEMISTRY & BIODIVERSITY, Issue 5 2010
Adisorn Ratanaphan
Abstract The interaction of two ruthenium,arene,1,3,5-triaza-7-phosphaadamantane compounds ([Ru(,6 - p -cymene)Cl2(pta)] and [Ru(,6 - p -cymene)(C6H6O4)(pta)], termed RAPTA-C (3) and carboRAPTA-C (4), resp.) with the DNA sequence of the human breast-cancer suppressor gene 1 (BRCA1) has been studied using a range of techniques that probe conformation, cross-linking, base specificity, restriction analysis, and in vitro inhibition of DNA polymerization. The study demonstrates that substitution of the two labile chloride ligands in 3 by the more stable cyclobutane-1,1-dicarboxylate ligand onto the RAPTA framework reduces the rate of reaction with DNA in a similar manner to the analogous Pt-based drug pair cisplatin (1) and carboplatin (2), suggesting that hydrolysis may be a prerequisite to DNA binding with the Ru compounds. Moreover, the rate of DNA interaction for 3 is in a similar range to that of 2, despite the fact that these compounds have a different therapeutic profile. The similar rates of reaction contrasting with the different modes of activity suggests that the RAPTA compounds may be clinically useful against cancer cells that have developed resistance to Pt-based therapies, particularly involving excision,repair mechanisms. [source]