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Cationic Complexes (cationic + complex)
Selected AbstractsReaction of 1,3,5-Triazacyclohexanes with TiCl4: Formation of Cationic ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2005Randolf D. Köhn Abstract N -substituted 1,3,5-triazacyclohexanes [R3TAC; R = cyclohexyl, p -fluorobenzyl or Ph(CH2)n (n = 1, 2, 3)] react with excess TiCl4 to give the corresponding cationic ,3 complexes [(R3TAC)TiCl3][Ti2Cl9]. Attempts to prepare complexes with titanium-free anions at lower Ti:R3TAC ratio or with added Me3SiOTf lead to the same cations with [Ti2Cl10]2, and [Ti2Cl8(OTf)], anions. Five complexes as well as (p -fluorobenzyl)3TAC have been characterised by X-ray crystallography. The ring C,H bonds engage in hydrogen bonding interactions in the crystals and strongly solvent and anion dependent 1H NMR signals are detected in solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Chiral Fluorous Dialkoxy-Diamino Zirconium Complexes: Synthesis and Use in Stereospecific Polymerization of 1-HexeneCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2007Evgueni Kirillov Dr. Abstract New catalysts for the isospecific polymerization of 1-hexene based on cationic zirconium complexes incorporating the tetradentate fluorous dialkoxy-diamino ligands [OC(CF3)2CH2N(Me)(CH2)2N(Me)CH2C(CF3)2O]2, [(ON2NO)2,] and [OC(CF3)2CH2N(Me)(1R,2R -C6H10)N(Me)CH2C(CF3)2O]2, [(ONCyNO)2,] have been developed. The chiral fluorous diamino-diol [(ONCyNO)H2, 2] was prepared by ring-opening of the fluorinated oxirane (CF3)2COCH2 with (R,R)- N,N, -dimethyl-1,2-cyclohexanediamine. Proligand 2 reacts cleanly with [Zr(CH2Ph)4] and [Ti(OiPr)4] precursors to give the corresponding dialkoxy complexes [Zr(CH2Ph)2(ONCyNO)] (3) and [Ti(OiPr)2(ONCyNO)] (4), respectively. An X-ray diffraction study revealed that 3 crystallizes as a 1:1 mixture of two diastereomers (,- 3 and ,- 3), both of which adopt a distorted octahedral structure with trans -O, cis -N, and cis -CH2Ph ligands. The two diastereomers ,- 3 and ,- 3 adopt a C2 -symmetric structure in toluene solution, as established by NMR spectroscopy. Cationic complexes [Zr(CH2Ph)(ON2NO)(THF)n]+ (n=0, anion=[B(C6F5)4],, 5; n=1, anion=[PhCH2B(C6F5)3],, 6) and [Zr(CH2Ph)(ONCyNO)(THF)]+[PhCH2B(C6F5)3], (7) were generated from the neutral parent precursors [Zr(CH2Ph)2(ON2NO)] (H) and [Zr(CH2Ph)2(ONCyNO)] (3), and their possible structures were determined on the basis of 1H, 19F, and 13C NMR spectroscopy and DFT methods. The neutral zirconium complexes H and 3 (,- 3/,- 3 mixture), when activated with B(C6F5)3 or [Ph3C]+[B(C6F5)4],, catalyze the polymerization of 1-hexene with overall activities of up to 4500,kg,PH,mol,Zr,1,h,1, to yield isotactic-enriched (up to 74,% mmmm) polymers with low-to-moderate molecular weights (Mw=4800,47,200) and monodisperse molecular-weight distributions (Mw/Mn=1.17,1.79). [source] Unprecedented Stereoselective Synthesis of Catalytically Active Chiral Mo3CuS4 ClustersCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2006Marta Feliz Dr. Abstract Cluster excision of polymeric {Mo3S7Cl4}n phases with chiral phosphane (+)-1,2-bis[(2R,5R)-2,5-(dimethylphospholan-1-yl)]ethane ((R,R)-Me-BPE) or with its enantiomer ((S,S)-Me-BPE) yields the stereoselective formation of the trinuclear cluster complexes [Mo3S4{(R,R)-Me-BPE}3Cl3]+ ([(P)- 1]+) and [Mo3S4{(S,S)-Me-BPE}3Cl3]+ ([(M)- 1]+), respectively. These complexes posses an incomplete cuboidal structure with the metal atoms defining an equilateral triangle and one capping and three bridging sulfur atoms. The P and M symbols refer to the rotation of the chlorine atoms around the C3 axis, with the capping sulphur atom pointing towards the viewer. Incorporation of copper into these trinuclear complexes affords heterodimetallic cubane-type compounds of formula [Mo3CuS4{(R,R)-Me-BPE}3Cl4]+ ([(P)- 2]+) or [Mo3CuS4{(S,S)-Me-BPE}3Cl4]+ ([(M)- 2]+), respectively, for which the chirality of the trinuclear precursor is preserved in the final product. Cationic complexes [(P)- 1]+, [(M)- 1]+, [(P)- 2]+, and [(M)- 2]+ combine the chirality of the metal cluster framework with that of the optically active diphosphane ligands. The known racemic [Mo3CuS4(dmpe)3Cl4]+ cluster (dmpe=1,2-bis(dimethylphosphanyl)ethane) as well as the new enantiomerically pure Mo3CuS4 [(P)- 2]+ and [(M)- 2]+ complexes are efficient catalysts for the intramolecular cyclopropanation of 1-diazo-5-hexen-2-one (3) and for the intermolecular cyclopropanation of alkenes, such as styrene and 2-phenylpropene, with ethyl diazoacetate. In all cases, the cyclopropanation products were obtained in high yields. The diastereoselectivity in the intermolecular cyclopropanation of the alkenes and the enantioselectivity in the inter- or intramolecular processes are only moderate. La reacción de escisión de la fase polimérica {Mo3S7Cl4}ncon la fosfina quiral (+)-1,2-bis[(2R,5R)-2,5-(dimetilfosfolan-1-il)]etano, (R,R)-Me-BPE, o con su enantiómero, (S,S)-Me-BPE, conduce a la formación estereoselectiva de los complejos clúster trinucleares [Mo3S4(R,R -Me-BPE)3Cl3]+([(P)- 1]+) y [Mo3S4(S,S -Me-BPE)3Cl3]+([(M)- 1]+), respectivamente. Estos complejos poseen una estructura de cubo incompleto, dónde los átomos metálicos definen un triángulo equilátero, con un azufre unido a tres átomos de molibdeno y tres azufres puente. Los símbolos P y M hacen referencia a la rotación de los átomos de cloro alrededor del eje C3, con el azufre apuntado dirigido hacia el observador. La incorporación de cobre a estos complejos trinucleares conduce a compuestos heterodimetálicos con estructura tipo cubano de fórmula [Mo3CuS4(R,R -Me-BPE)3Cl4]+([(P)- 2]+) y [Mo3CuS4(S,S -Me-BPE)3Cl4]+([(M)- 2]+) donde la quiralidad del precursor trinuclear se mantiene en el producto final. Los complejos catiónicos [(P)- 1]+, [(M)- 1]+, [(P)- 2]+y [(M)- 2]+combinan la quiralidad del esqueleto clúster con la de los ligandos difosfina. El clúster racémico [Mo3CuS4(dmpe)3Cl4]+(dmpe=1,2-bis(dimetilfosfino)etano), así como los complejos Mo3CuS4 enantioméricamente puros [(P)- 2]+o [(M)- 2]+son catalizadores eficaces para la reacción de ciclopropanación intramolecular de 1-diazo-5-hexen-2-ona (3) y para la ciclopropanación intermolecular de alquenos, estireno y 2-fenilpropeno, con etil diazoacetato. En todos los casos los productos de ciclopropanación se obtienen con rendimientos elevados. La diastereoselectividad en la ciclopropanación intermolecular de alquenos y la enantioselectividad en los procesos tanto inter- como intramoleculares son únicamente moderadas. [source] Linear Coinage Metal Complexes Stabilized by a Group 13 Metalloid LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2010Ganesan Prabusankar Abstract The synthesis and structural characterization of the linear, cationic complex [{(DDP)Ga}2Cu][OTf]·2C6H5F (2, Tf = O2SCF3) stabilized by the monodentate, gallium-based ligand Ga(DDP) (DDP = [HC{(CMe)N(2,6- iPr2C6H3)}2],), as well as NMR spectroscopic evidence for the formation of the corresponding silver compound [{(DDP)Ga}2Ag][Al(hfip)4] (3, hfip = [OC(H)(CF3)2]), are reported. The remarkable steric properties of this gallium-based ligand permit the stabilization of 2, which exhibits an unusual linear geometry and a coordination number of two. [source] An Atropo-Stereogenic Diphosphane Ligand with a Proximal Cationic Charge: Specific Catalytic Properties of a Palladium Complex ThereofEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2008Nathalie Debono Abstract A class of cationic diphosphane ligands combining phosphane and amidiniophosphane moieties is illustrated on the N -methyl,N -naphthylbenzimidazolium framework. The palladium(II) complex thereof is described and compared to the corresponding complex of the analogous neutral diphosphane. Contrary to first-level expectations, the N2C,P and N2CP,Pd bonds in the cationic diphosphane complex are not longer than those occurring in its neutral counterpart. In the cationic ligand, the proximal positive charge is indeed conjugated to one phosphanyl group, and the coordination scheme is tentatively interpreted by resonance of the phosphane,metal dative bond (+N2C,P:,[Pd]) with a carbene,phosphenium dative bond (N2C:,[+P:,Pd]). Despite this peculiar structural feature, the electronic , donation (vs. , acceptation) towards the palladium centre remains lowered in the cationic ligand. This specific property can be a priori valuable in a catalytic process where oxidative addition is not the limiting step. It is indeed shown that although the neutral complex is more active in Suzuki coupling reactions, the cationic complex is more active in Sonogashira-type coupling reactions involving predissociated halide substrates, namely an acyl chloride. These likely atropo-chiral ligands deserve to be resolved for application in asymmetric catalysis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Multiple Reaction Pathways in Rhodium-Catalyzed Hydrosilylations of KetonesCHEMISTRY - A EUROPEAN JOURNAL, Issue 43 2009Nathanaëlle Schneider Dr. Abstract A detailed density functional theory (DFT) computational study (using the BP86/SV(P) and B3LYP/TZVP//BP86/SV(P) level of theory) of the rhodium-catalyzed hydrosilylation of ketones has shown three mechanistic pathways to be viable. They all involve the generation of a cationic complex [LnRhI]+ stabilized by the coordination of two ketone molecules and the subsequent oxidative addition of the silane, which results in the Rh,silyl intermediates [LnRhIII(H)SiHMe2]+. However, they differ in the following reaction steps: in two of them, insertion of the ketone into the RhSi bond occurs, as previously proposed by Ojima et,al., or into the SiH bond, as proposed by Chan et,al. for dihydrosilanes. The latter in particular is characterized by a very high activation barrier associated with the insertion of the ketone into the SiH bond, thereby making a new, third mechanistic pathway that involves the formation of a silylene intermediate more likely. This "silylene mechanism" was found to have the lowest activation barrier for the rate-determining step, the migration of a rhodium-bonded hydride to the ketone that is coordinated to the silylene ligand. This explains the previously reported rate enhancement for R2SiH2 compared to R3SiH as well as the inverse kinetic isotope effect (KIE) observed experimentally for the overall catalytic cycle because deuterium prefers to be located in the stronger bond, that is, CD versus MD. [source] Magneto,Structural Correlations in Discrete MnII -WV Cyano-Bridged Assemblies with Polyimine LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2010Robert Podgajny Abstract We present the magneto,structural correlations for two novel discrete cyano-bridged assemblies based on cationic complexes of manganese(II) with diimine ligands and octacyanotungstate(V) ions. The crystal structure of [MnII(terpy)(dmf)(H2O)2][MnII(terpy)(H2O)(dmf)(,-NC)WV(CN)7]2·6H2O (1) (terpy = 2,2,;6,,2,-terpyridine, dmf = dimethylformamide) contains dinuclear {MnIIWV}, cyano-bridged anions, while the crystal structure of [MnII(phen)3]2[MnII(phen)2(,-NC)2WV(CN)6]2(ClO4)2·9H2O (2) (phen = 1,10-phenanthroline) is built of tetranuclear {MnII2WV2}2, square anions. Intramolecular Mn,W magnetic interactions through the cyano bridges are represented by magnetic coupling constants J = ,39 cm,1 for the {MnIIWV}, unit in 1 and J1 = ,25.7 and J2 = ,16.7 cm,1 for the {MnII2WV2}2, unit in 2. J and J1 represent relatively strong W,CN,Mn interactions and are ascribed to the bridges in b positions of TPRS-8 (trigonal prism square-face bicapped) of [W(CN)8]3, polyhedra, favoring the strongest electronic interactions between the d,d orbital of W and the ,* orbitals of CN,, whereas J2 is related to the m vertex of [W(CN)8]3,. The magnetic properties of 1 and 2 are compared with reference compounds and discussed in the context of the type of coordination polyhedra of [W(CN)8]3, as well as the metric parameters of cyano-bridged W,CN,Mn linkages. We found the type of coordination polyhedra and bridging mode of [W(CN)8]3, to be the most important factors influencing the magnitude of the Mn,W magnetic interaction. [source] Synthesis and Characterization of Semiconductive Dichloridobis(thianthrene)gold(1+) Tetrachloridoaurate(1,)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2009Rachmat Triandi Tjahjanto Abstract A new (thianthrene)gold(III) complex has been synthesized in liquid SO2 as the solvent from thianthrene (TA) andAuCl3. [AuCl2(TA)2][AuCl4] [triclinic, P, a = 9.9832(2) Å, b = 10.3404(2) Å, c = 15.0798(4) Å, , = 75.038(1)°, , = 81.610(1)°, , = 68.409(1)°, V = 1396.15(5) Å3, Z = 2] has a salt-like structure consisting of [AuCl2(TA)2]+ and [AuCl4], ions, both with square-planar coordinated gold atoms of oxidation state +3. In the cation, two bent TA molecules are coordinated to Au each through one sulfur atom. The title compound is thermally stable up to 425 K and is semiconducting with a conductivity reaching 25 mSm,1 at 380 K and a low activation energy of 0.43 eV. A model for the charge transport along the stacked cationic complexes is discussed. When dissolved in chloroform [AuCl2(TA)2][AuCl4] is converted into the already known uncharged, mononuclear complex [AuCl3(TA)], which shows that a polymerization isomerism exists between the two forms.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Aiding Factors in the Formation of Azaplatinacyclobutane Rings , X-ray and Crystal Structure of [Pt{CH(Ph)CH2NEt2 -,C,,N}(N,N,N,,N, -tetramethylethylenediamine)]+ and of Its Open-Chain PrecursorEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2007Giuseppe Lorusso Abstract The addition products 2 of a secondary amine to a coordinated olefin, in the cationic complexes [PtCl(,2 -CH2=CHR)(tmeda)]+ (tmeda = N,N,N,,N, -tetramethylethylenediamine; R = Me, 1a; Ph, 1b, H, 1c), undergo in basic medium an intramolecular nucleophilic substitution with elimination of the chlorido ligand and formation of an azaplatinacyclobutane ring 3. The ring-closing process occurs notwithstanding the absence of a labilizing ligand trans to the leaving chlorido ligand and of bulky substituents on the amino,ethanide chain. If the addition product 2 is a mixture of Markovnikov and anti-Markovnikov isomers, the ring-closing reaction is faster for the anti-Markovnikov form, and this leads to an increase of the relative amount of the anti-Markovnikov isomer in the cyclized species 3. The difference in the rate of formation of the azaplatinacyclobutane ring between the two isomers has been interpreted on the basis of a more favorable stereochemistry in the case of the anti-Markovnikov form. The X-ray crystal structures of [Pt{CH(Ph)CH2NEt2 -,C,,N}(tmeda)]+ (3bn) and of its open-chain precursor, [PtCl{CH(Ph)CH2NHEt2}(tmeda)]+ (2bn) fully support this hypothesis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Diastereopure Cationic NCN-Pincer Palladium Complexes with Square Planar ,4 - N,C,N,O CoordinationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2006Silvia Gosiewska Abstract Neutral NCN-pincer palladium bromide complex 2 containing the monoanionic, enantiopure pincer ligand 2,6-bis{[(S)-2-hydroxymethyl-1-pyrrolidinyl]methyl}phenyl bromide (1) with bis- ortho -(S)-prolinol substituents was synthesized and isolated as a mixture of three stereoisomers [(SN,SN,SC,SC), (RN,SN,SC,SC), and (RN,RN,SC,SC)] in a 1:1:1 ratio. Upon abstraction of the bromide ion from the unresolved mixture of 2, single diastereoisomers of the cationic complexes [3]BF4 and [3]PF6, respectively, were formed with a unique,4 - N,C,N,O coordination mode of ligand 1. X-ray crystal structure determination established the intramolecular,4 - N,C,N,O coordination of 1 to palladium where the typical mer -,3 - N,C,N pincer coordination is accompanied by coordination of one of the hydroxy groups of the (S)-prolinol moieties. The water molecule that was cocrystallized in the crystal structure of [3]PF6 does not coordinate to palladium, but instead is involved in a hydrogen bonding network. The catalytic potential of both cationic complexes, [3]BF4 and [3]PF6, was tested in an aldol reaction of aldehydes with methyl isocyanoacetate to yield the oxazoline products as racemic mixtures.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] New Polar Pyrazolylborate Ligands and Their Basic Zinc Complex ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Cristina Pérez Olmo Abstract By refinement of Trofimenko's procedures, four new tris(pyrazolyl)borate (Tp) ligands bearing pyridyl and carboxamide substituents at the 3-positions of the pyrazole rings, were obtained. Two of them were identified by structure determinations of their potassium salts. Their coordinative properties were explored by preparing Tp*Zn-X complexes, with X = Cl, Br, I, NO3, OAc, phenolate, thiophenolate and diorganophosphate, including the cationic complexes [Tp*Zn·L]+ with L = methanol and pyrazole. From the spectra and structure determinations of these complexes it has become evident that the polar Tp* ligands favor coordination numbers higher than four for zinc, either by inducing bidentate coordination of the coligands X and L, using the carboxamide oxygen atoms for coordination, or by linking two Tp*Zn-X units through the pyridyl nitrogen atoms. As a result, the structural chemistry of these complexes is quite varied, and includes coordination dimers and polymers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Water-Soluble Arene Ruthenium Complexes Containing a trans -1,2-Diaminocyclohexane Ligand as Enantioselective Transfer Hydrogenation Catalysts in Aqueous SolutionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005Jérôme Canivet Abstract The cationic chloro complexes [(arene)Ru(H2N,NH2)Cl]+ (1: arene = C6H6; 2: arene = p -MeC6H4iPr; 3: arene = C6Me6) have been synthesised from the corresponding arene ruthenium dichloride dimers and enantiopure (R,R or S,S) trans -1,2-diaminocyclohexane (H2N,NH2) and isolated as the chloride salts. The compounds are all water-soluble and, in the case of the hexamethylbenzene derivative 3, the aqua complex formed upon hydrolysis [(C6Me6)Ru(H2N,NH2)OH2]2+ (4) could be isolated as the tetrafluoroborate salt. The molecular structures of 3 and 4 have been determined by single-crystal X-ray diffraction analyses of [(C6Me6)Ru(H2N,NH2)Cl]Cl and [(C6Me6)Ru(H2N,NH2)OH2][BF4]2. Treatment of [Ru2(arene)2Cl4] with the monotosylated trans -1,2-diaminocyclohexane derivative (TsHN,NH2) does not yield the expected cationic complexes, analogous to 1,3 but the neutral deprotonated complexes [(arene)Ru(TsN,NH2)Cl] (5: arene = C6H6; 6: arene = p -MeC6H4iPr; 7: arene = C6Me6; 8: arene = C6H5COOMe). Hydrolysis of the chloro complex 7 in aqueous solution gave, upon precipitation of silver chloride, the corresponding monocationic aqua complex [(C6Me6)Ru(TsHN,NH2)(OH2)]+ (9) which was isolated and characterised as its tetrafluoroborate salt. The enantiopure complexes 1,9 have been employed as catalysts for the transfer hydrogenation of acetophenone in aqueous solution using sodium formate and water as a hydrogen source. The best results were obtained (60 °C) with 7, giving a catalytic turnover frequency of 43 h,1 and an enantiomeric excess of 93,%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Insertion of Molecular Oxygen in Transition-Metal Hydride Bonds, Oxygen-Bond Activation, and Unimolecular Dissociation of Metal Hydroperoxide Intermediates.HELVETICA CHIMICA ACTA, Issue 3 2008Short Communication Abstract Thermal activation of molecular oxygen is observed for the late-transition-metal cationic complexes [M(H)(OH)]+ with M=Fe, Co, and Ni. Most of the reactions proceed via insertion in a metalhydride bond followed by the dissociation of the resulting metal hydroperoxide intermediate(s) upon losses of O, OH, and H2O. As indicated by labeling studies, the processes for the Ni complex are very specific such that the O-atoms of the neutrals expelled originate almost exclusively from the substrate O2. In comparison to the [M(H)(OH)]+ cations, the ionmolecule reactions of the metal hydride systems [MH]+ (M=Fe, Co, Ni, Pd, and Pt) with dioxygen are rather inefficient, if they occur at all. However, for the solvated complexes [M(H)(H2O)]+ (M=Fe, Co, Ni), the reaction with O2 involving OO bond activation show higher reactivity depending on the transition metal: 60% for the Ni, 16% for the Co, and only 4% for the Fe complex relative to the [Ni(H)(OH)]+/O2 couple. [source] Synthesis, structure and reactivity of cationic base-stabilized gallyleneiron complexes,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 6-7 2003Keiji Ueno Abstract Addition of 2,2,-bipyridine (bpy) to an acetonitrile solution of dichlorogallyliron complex FpGaCl2 (1: Fp = (,-C5H5)Fe(CO)2) afforded almost quantitatively a salt consisting of a cationic base-stabilized gallylene complex [FpGaCl·bpy]+ ([3a]+) and an anionic complex [FpGaCl3], ([4],). Reaction of Fp,GaCl2 (Fp, = Fp (1), Fp* (2); Fp* = (,-C5Me5)Fe(CO)2) with NaBPh4 in the presence of a bidentate donor (Do2) gave [Fp,GaCl·Do2]BPh4 where Do2 was bpy or 1,10-phenanthroline (phen). These cationic complexes may be useful precursors for the synthesis of gallyleneiron complexes with various substituents on the gallium atom. Indeed, reaction of [Fp*GaCl·phen]BPh4 ([5b]BPh4) with NaSpTol or Me3SiSpTol afforded the gallyleneiron complex [Fp*GaSpTol·phen]BPh4 ([6]BPh4), the first example of a gallium,transition metal complex having a thiolate group on the gallium atom. The molecular structures of [5b]BPh4 and [6]BPh4 were determined by single crystal X-ray diffraction. Copyright © 2003 John Wiley & Sons, Ltd. [source] Insights into CO/Styrene Copolymerization by Using PdII Catalysts Containing Modular Pyridine,Imidazoline LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004Amaia Bastero Dr. Abstract Continuing our studies into the effect that NN, ligands have on CO/styrene copolymerization, we prepared new C1 -symmetrical pyridine,imidazoline ligands with 4,,5,- cis stereochemistry in the imidazoline ring (5) and 4,,5,- trans stereochemistry (6,10) and compared them with our previously reported ligands (1,4). Their coordination to neutral methylpalladium(II) (5,a,10,a) and cationic complexes (5,b,10,b), investigated in solution by NMR spectroscopy, indicates that both the electronic and steric properties of the imidazolines determine the stereochemistry of the palladium complexes. The crystal structures of two neutral palladium precursors [Pd(Me)2,nCln(NN,)] (n=1 for 8,a; n=2 for 9,a,) show that the PdN coordination distances and the geometrical distortions in the imidazoline ring depend on the electronic nature of the substituents in the imidazoline fragment. Density functional calculations performed on selected neutral and cationic palladium complexes compare well with NMR and X-ray data. The calculations also account for the formation of only one or two stereoisomers of the cationic complexes. The performance of the cationic complexes as catalyst precursors in CO/4- tert -butylstyrene copolymerization under mild pressures and temperatures was analyzed in terms of the productivity and degree of stereoregularity of the polyketones obtained. Insertion of CO into the PdMe bond, which was monitored by multinuclear NMR spectroscopy, shows that the N ligand influences the stereochemistry of the acyl species formed. [source] Water-soluble Organometallic Analogues of Oxaliplatin with Cytotoxic and Anticlonogenic ActivityCHEMMEDCHEM, Issue 1 2010Michele Benedetti Dr. Pt prodrugs: We synthesized new cationic complexes [PtCl(,2 -C2H4)(R,R -chxn)]Cl (1) and [PtCl(,2 -C2H4)(S,S -chxn)]Cl (2), which are organometallic analogues of the drug oxaliplatin. Complexes 1 and 2 can be considered antitumor prodrugs, as we demonstrate that they can decompose to give the same metabolites as those of oxaliplatin. [source] | ||||||||||