Monitoring of the synthesis ofcis andtrans ruthenium macrocyclic complexes by reversed-phase high-performance liquid chromatography

Summary The synthesis of the complex [Ru(cyclam)Cl₂]Cl (cyclam=1,4,8,11-tetraazacyclotetradecane) has been monitored by reversed-phase high-performance liquid chromatography. The analytical results obtained during the reaction have shown that it is feasible to identify and isolate the two isomerscis- andtrans- [Ru(cyclam)Cl₂]Cl. The use of an octadecylsiloxy preparative column enabled the separation and purification of these two isomers and the compounds have been obtained in high purity. The use of reversed-phase high-performance liquid chromatography has afforded complete analytical control of the syntheses of saturated nitrogendonor macrocyclic complexes of ruthenium, enabling identification of thecis andtrans isomers of the complex [Ru(cyclam)Cl₂]Cl.     

Electropolymerization of [Ru(bpy)(CO)2Cl2] (bpy=2,2′-bipyridine: a revisited trans versus cis(Cl) isomeric influence study

The mono-bipyridine bis carbonyl complex [Ru(bpy)(CO)₂Cl₂] exists in two stereoisomeric forms having a trans(Cl)/cis(CO) (1) and cis(Cl)/cis(CO) (2) configuration. In previous work we reported that only the trans(Cl)/cis(CO) isomer 1 leads by a two-electron reduction to the formation of [Ru(bpy)(CO)₂]_n polymeric film on an electrode surface. This initial statement was overstated, as both isomers allowed the build up of polymers. A detailed comparison of the electropolymerization of both isomers is reported here, as well as the reduction into dimers of parent stereoisomer [Ru(bpy)(CO)₂(C(O)OMe)Cl] complexes 3 and 4 obtained as side products during the synthesis of 1 and 2.     

Crystal structure,electrochemical and photochemical studies of the trans-[Fe(cyclam)(NO)Cl]Cl2 complex (cyclam = 1,4,8,11-tetraazacyclotetradecane)

The trans-[Fe(cyclam)(NO)Cl]Cl₂ complex was synthesized by the reaction of cis-[Fe(cyclam)Cl₂]Cl with NO gas. The X-ray structure of the complex showed that the [Fe–NO] moiety is linear, consistent with the NO⁺ character of the nitric oxide ligand. This suggestion was reinforced by the IR data, which showed the νNO at 1888 cm⁻¹. The cyclic voltammogram of the trans-[Fe(cyclam)(NO)Cl]²⁺ complex presented three electrochemical processes at −0.70, 0.08 and 0.40 V versus Ag/AgCl. The first and last redox processes are centered at the NO ligand, whereas the second is characteristic of the generated aqua species, trans-[Fe(cyclam)Cl(H₂O)]²⁺. Upon irradiation at 330 nm, pH 3.4, the title complex releases the NO moiety with the concomitant generation of the trans-[Fe(cyclam)(H₂O)Cl]⁺ complex as suggested by electronic and IR spectroscopy as well as by cyclic voltammetry technique.     

Synthesis,Structures, Ligand Substitution Reactions,and Electrochemistry of the Nitrile Complexes cis‐[Ru(dppm)2Cl(NCR)]+ PF6– (dppm = Bis(diphenylphosphino)methane,R = CH3, C2H5, tBu,Ph)

Isomerically pure nitrile complexes cis‐[Ru(dppm)₂Cl(NCR)]⁺ ( 2 a – d ) are formed upon chloride displacement from cis‐[Ru(dppm)₂Cl₂] ( 1 ) or, alternatively, by ligand substitution from the acetonitrile complex 2 a . This latter approach does also allow for the introduction of pyridine ( 3 a , b ), heptamethyldisilazane ( 4 ) or isonitrile ligands ( 5 ). All complexes are obtained as the configurationally stable cis‐isomers. Only cis‐[Ru(dppm)₂Cl(CN^tBu)]⁺ slowly isomerizes to the trans from. The solid state structures of the CH₃CN, C₂H₅CN and the trans‐^tBuNC complexes were established by X‐ray crystallography. Electrochemical investigations of the nitrile complexes 2 a – d show in addition to a chemically reversible one‐electron oxidation an irrversible reduction step. In CH₂Cl₂ solution, cis‐ and trans‐[Ru(dppm)₂Cl₂] have been identified as the final products of the electrochemically induced reaction sequence.     

The trans influence in mer‐tri­chloro­nitridobis­(tri­phenyl­arsine)­ruthenium(VI)

The title compound, mer‐[RuCl₃N(C₁₈H₁₅As)₂], is the first structurally characterized example of a nitride complex in which ruthenium is six‐coordinated to monodentate ligands only. The Ru[triple‐bond]N bond length [1.6161 (15) Å] is relatively long, and the trans influence of the nitride ligand is reflected by the difference between the Ru—Cl_trans and Ru—Cl_cis bond lengths [0.1234 (4) Å]. The N—Ru—Cl_trans axis is sited on a twofold axis.     

Beitrag zur Kenntnis der Pt(II)-Verbindungen mit Acetoxim

Zusammenfassung Es wurde die thermische Zersetzung dercis-undtrans-Isomeren des [PtAox ₂Cl₂] sowie des [PtAox ₃Cl]Cl mit Hilfe derTG-undTD-Kurven im Falle des reinen Komplexes sowie im Falle einer Mischung mit Al₂O₃ (1:3) geklärt. Dietrans-Form ist stabiler als diecis-Form, die Zersetzung wird durch Al₂O₃ nicht beeinflu\t. [PtAox ₃Cl]Cl wird infolge der Erhitzung in die stabileretrans-Form [PtAox ₂Cl₂] umgewandelt und verhält sich auch weiterhin wie diese.

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A contribution to the study of the compounds of Pt(II) with acetoxime

The thermal decomposition ofcis- andtrans-[PtAox ₂Cl₂] and of [PtAox ₃Cl]Cl was studied by means ofTGA andTDA on pure substances as well as on mixtures with Al₂O₃ (1:3). Thetrans form is more stable then thecis form, the presence of Al₂O₃ has no influence on its decomposition. The [PtAox ₃Cl]Cl is transformed by heating into the more stabletrans-isomer and its further behaviour is identical with that of thetrans isomer.

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Mit 4 Abbildung     

Inclusion compounds of cucurbit[8]uril with noble metal polyamine complexes

Inclusion compounds of the macrocyclic cavitand cucurbit[8]uril (CB[8]) with the ruthenium(iii) bis(ethylenediamine) complex {trans-[Ru(en)₂Cl₂]@CB[8]}Cl·27.5H₂O (1), the gold(iii) diethylenetriamine complex {[Au(dien)Cl]@CB[8]}Cl₂·11H₂O (2), and the gold(iii) and platinum(ii) cyclam complexes (H₃O)₅{[Au(cyclam)]@CB[8]}Cl₈·18H₂O (3) and {[Pt(cyclam)]_0.11(H₂cyclam)_0.89@CB[8]}Cl₂·16H₂O (4), respectively, where cyclam is the tetraazamacrocyclic ligand, were synthesized. The inclusion compounds were synthesized both directly starting from CB[8] and the metal complexes with polyamines (en or dien) and by the two-step method with the use of the cyclic polyamine ligand (cyclam) pre-included into the cavity of the macrocycle. The inclusion compounds were characterized by X-ray diffraction (1, 2, and 4), IR spectroscopy, electrospray ionization mass spectrometry, UV-Vis spectroscopy, and thermogravimetric analysis.     

Synthesis and Characterization of Some Ru( tmeda ) Complexes Containing Chloride, Hydride, and Vinylidene Ligands

 The polymeric compound [Ru(cod)Cl₂] _x (cod = cyclooctadiene) reacts with 2 equivalents of tmeda (N,N,N′,N′-tetramethylethylenediamine) in refluxing MeOH to afford trans-[Ru(cod)(tmeda)(Cl)(H)] (1), which upon treatment with CHCl₃ is readily converted to the dichloro complex trans-[Ru(cod)(tmeda)Cl₂] (2). When [Ru(cod)Cl₂] _x is reacted with tmeda under an atmosphere of H₂ (3 bar), the bis-tmeda complex trans-[Ru(tmeda)₂Cl₂] (3) is obtained in 80% yield. DFT calculations revealed that 3 is by 52 kJ/mol more stable than the corresponding cis isomer. Attempts to prepare the coordinatively unsaturated complex [Ru(tmeda)₂Cl]⁺ by reacting 1 with TICF₃SO₃ were unsuccessful. According to DFT calculations, however, such a complex should be stable and, interestingly, should adopt a square pyramidal rather than a trigonal bipyramidal structure. If halide abstraction of 3 is performed in the presence of terminal alkynes HC*CR (R*t-Bu, n-Bu), the cationic vinylidene complexes [Ru(tmeda)₂(Cl)(*C*CHR)]⁺ (4a,b) are obtained.     

Preparation and photochemistry of macromolecular bound ruthenium(II) complexes in aqueous solutions

Ruthenium(II) polypyridyl complexes with macromolecular ligands poly(methylolacrylamide-co-vinylpyridine) and poly (acrylamide-co-vinylpyridine) have been synthesized. The macromolecular ruthenium (II) complexes which are soluble in water have been characterized and their absorption and emission properties have been studied in aqueous solution. Photolysis of the complex in aqueous solution leads to photoaquation reactions with release of coordinated pyridines of the polymer. In the case of monomeric complex, cis-[Ru(bpy)₂(py)₂]Cl₂, photolysis in water in presence of Cl^? ions produces only the substitution of the pyridine by water whereas in the polymeric complexes, [Ru(bpy)₂(MAAM-co-VP)₂]Cl₂ photolysis in the presence of chloride produces [Ru(bpy)₂(MAAM-co-VP)Cl]Cl and [Ru(bpy)₂(AM-co-VP)Cl]Cl, respectively. Quantum yields for the photosubstitution reactions have been determined and mechanistic details are outlined.     

High-Performance liquid chromatographic separation of enantiomers of unusual amino acids possessing cycloalkane or cycloalkene skeletons on a chiral crown ether containing stationary phase

Summary Direct reversed-phase high-performance liquid chromatographic methods were developed for the separation and identification of the enantiomers of mono- and bicyclic racemic β-amino acids:cis- andtrans-2-aminocyclopentane-1-carboxylic acids,cis- andtrans-2-aminocyclohexane-1-carboxylic acids,cis- andtrans-2-amino-4-cyclohexene-1-carboxylic acids,diendo- anddiexo-3-aminobicyclo[2.2.1]heptane-2-carboxylic acids anddiendo- anddiexo-3-amino-5-bicyclo[2.2.1]heptene-2-carboxylic acids. Enantioseparation was carried out by the application of a chiral stationary phase, Crownpak CR(+). The conditions of separation were optimized by changing the temperature, the flow rate and the pH of the mobile phase. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Quantum-Chemical Calculations of Ruthenium Nitrosyl Complexes with Tetradentate Macrocyclic Ligands

The geometric structure of the ground state and of metastable isomers of nitrosyl complexes trans-[Ru(P)(NO)(Cl)] (P = porphinate dianion) and trans-[Ru(NO)(salen)(X)]^q [salen = N,N'-ethylenebis(salicylideniminate) dianion; X = Cl^- (q = 0), H₂O (q = +1)] was optimized within the framework of the density functional method (SVWN/LanL2DZ+6-31G). The local minima corresponding to metastable isomers with a linear NO coordination through the oxygen atom and with a side ² NO coordination were found on the potential energy surfaces of these compounds. The second metastable states of all the three complexes have a lower energy. The difference in energies between the stable and metastable isomers is the least in the case of the complex trans-[Ru(NO)(salen)(Cl)].     

Syntheses and Characterization of a Pair of Isomers of Heteroleptic Bis(Bidentate) Ruthenium(II) Complexes with Two Different Monodentate Ligands

Two isomers of heteroleptic bis(bidentate) ruthenium(II) complexes with dimethyl sulfoxide (dmso) and chloride ligands, trans(Cl,N_bpy)- and trans(Cl,N_Hdpa)-[Ru(bpy)Cl(dmso-S)(Hdpa)]⁺ (bpy: 2,2′-bipyridine; Hdpa: di-2-pyridylamine), are synthesized. This is the first report on the selective synthesis of a pair of isomers of cis-[Ru(L)(L′)XY]ⁿ⁺ (L≠L′: bidentate ligands; X≠Y: monodentate ligands). The structures of the ruthenium(II) complexes are clarified by means of X-ray crystallography, and the signals in the ¹H NMR spectra are assigned based on ¹H–¹H COSY spectra. The colors of the two isomers are clearly different in both the solid state and solution: the trans(Cl,N_bpy) isomer has a deep red color, whereas the trans(Cl,N_Hdpa) isomer is yellow. Although both complexes have intense absorption bands at λ≈440–450 nm, only the trans(Cl,N_bpy) isomer has a shoulder band at λ≈550 nm. DFT calculations indicate that the LUMOs of both isomers are the π* orbitals in the bpy ligand, and that the LUMO level of the trans(Cl,N_bpy) isomer is lower than that of the trans(Cl,N_Hdpa) isomer due to the trans effect of the Cl ligand; thus resulting in the appearance of the shoulder band. The HOMO levels are almost the same in both isomers. The energy levels are experimentally supported by cyclic voltammograms, in which these isomers have different reduction potentials and similar oxidation potentials.     

Cucurbit[8]uril-based inclusion compounds containing iron(II), cobalt(III), and nickel(II) complexes with cyclam and cyclen as guest molecules: Synthesis and crystal structures

New inclusion compounds containing iron(II), cobalt(III), and nickel(II) complexes with the cyclic polyamine ligands cyclam and cyclen in the macrocyclic cavitand cucurbit[8]uril (CB[8]) were obtained: {trans-[Fe(Cyclam)(CO)(OCHO)]@CB[8]}Cl · 15H₂O, {cis-[Co(Cyclen)(H₂O)Cl]@CB[8]}Cl₂ · 20H₂O, and {cis-[Ni(Cyclen)(H₂O)Cl]@CB[8]}Cl · 12H₂O. According to X-ray diffraction data, the complexes are in the cavity of each CB[8] molecule. The complexes of the above molecular formulas were isolated in the solid state as supramolecular compounds with CB[8] and structurally characterized for the first time.     

Synthesis and Characterization of Some Ru(tmeda) Complexes Containing Chloride, Hydride, and Vinylidene Ligands

Summary.  The polymeric compound [Ru(cod)Cl₂] _x (cod = cyclooctadiene) reacts with 2 equivalents of tmeda (N,N,N′,N′-tetramethylethylenediamine) in refluxing MeOH to afford trans-[Ru(cod)(tmeda)(Cl)(H)] (1), which upon treatment with CHCl₃ is readily converted to the dichloro complex trans-[Ru(cod)(tmeda)Cl₂] (2). When [Ru(cod)Cl₂] _x is reacted with tmeda under an atmosphere of H₂ (3 bar), the bis-tmeda complex trans-[Ru(tmeda)₂Cl₂] (3) is obtained in 80% yield. DFT calculations revealed that 3 is by 52 kJ/mol more stable than the corresponding cis isomer. Attempts to prepare the coordinatively unsaturated complex [Ru(tmeda)₂Cl]⁺ by reacting 1 with TICF₃SO₃ were unsuccessful. According to DFT calculations, however, such a complex should be stable and, interestingly, should adopt a square pyramidal rather than a trigonal bipyramidal structure. If halide abstraction of 3 is performed in the presence of terminal alkynes HC*CR (R*t-Bu, n-Bu), the cationic vinylidene complexes [Ru(tmeda)₂(Cl)(*C*CHR)]⁺ (4a,b) are obtained. Received March 26, 2001. Accepted April 26, 2001     

trans‐Di­chloro­tetrakis(4‐methylpyrimidine‐N1)­ruthenium(II)

The title compound, trans‐[Ru^IICl₂(N¹‐mepym)₄] (mepym is 4‐methylpyrimidine, C₅H₆N₂), obtained from the reaction of trans,cis,cis‐[Ru^IICl₂(N¹‐mepym)₂(SbPh₃)₂] (Ph is phenyl) with excess mepym in ethanol, has fourfold crystallographic symmetry and has the four pyrimidine bases coordinated through N¹ and arranged in a propeller‐like orientation. The Ru—N and Ru—Cl bond distances are 2.082 (2) and 2.400 (4) Å, respectively. The methyl group, and the N³ and Cl atoms are involved in intermolecular C—H?N and C—­H?Cl hydrogen‐bond interactions.     

CHARACTERIZATION OF CIS- AND TRANS-DINITROBIS-(l-CYCLOHEXANEDIAMINE)-COBALT(III) CHLORIDE1

Abstract

Two geometrical isomers of [Co(l-chxn)₂(No₂)₂]Cl have been isolated. The trans-isomer is eluted first from a cellulose ion exchange column as a single isomer. The cis-isomer corresponds to the complex previously reported as the trans-isomer. The cis-isomer with the same CD sign pattern as for the trans-isomer is stereoselectively favored, but a small amount of the second cis-isomer separates using Cellex CM ion exchange cellulose. The CD spectra of the cis- and trans- isomers are similar to those of the corresponding isomers of the l-pn complex.     

Synthesis and DFT calculations of oxido and phenylimido-rhenium(V) complexes incorporating the N,O donor ligand 2-[(2-hydroxyethylimino)methyl]phenol

The reactions of equimolar amounts of trans-[ReOC1₃(PPh₃)₂] or trans-[Re(NPh)(PPh₃)₂Cl₃] with a Schiff base formed by condensation of 2-hydroxy-4-methoxybenzaldehyde and ethanolamine (H₂L) result in the formation of cis-[ReO(HL)PPh₃Cl₂] (1a) and trans-[Re(NPh)(HL)(PPh₃)Cl₂] (2b), respectively, in good yields. 1a and 2b have been characterized by a range of spectroscopic and analytical techniques. The X-ray crystal structures of 1a and 2b reveal that 1a is an octahedral cis-Cl,Cl oxorhenium(V) complex, while 2b is a trans-Cl,Cl phenylimidorhenium(V) complex. The complexes are weakly emissive at room temperature with quantum yields of 10^?4. Density functional theory calculations of the electronic properties of the complexes were performed and are in agreement with the experimental results. The complexes display quasi-reversible Re(V)/Re(VI) redox couples in acetonitrile. There is reasonable agreement between the experimental and calculated redox potentials of 1a and 2b.     

Stereospecific synthesis and redox properties of ruthenium(II) carbonyl complexes bearing a redox-active 1,8-naphthyridine unit

Two stereoisomers of cis-[Ru(bpy)(pynp)(CO)Cl]PF₆ (bpy = 2,2′-bipyridine, pynp = 2-(2-pyridyl)-1,8-naphthyridine) were selectively prepared. The pyridyl rings of the pynp ligand in [Ru(bpy)(pynp)(CO)Cl]⁺ are situated trans and cis, respectively, to the CO ligand. The corresponding CH₃CN complex ([Ru(bpy)(pynp)(CO)(CH₃CN)]²⁺) was also prepared by replacement reactions of the chlorido ligand in CH₃CN. Using these complexes, ligand-centered redox behavior was studied by electrochemical and spectroelectrochemical techniques. The molecular structures of pynp-containing complexes (two stereoisomers of [Ru(bpy)(pynp)(CO)Cl]PF₆ and [Ru(pynp)₂(CO)Cl]PF₆) were determined by X-ray structure analyses.     

A PROTON NMR STUDY OF THE STEREOCHEMISTRY AND KINETICS OF THE REACTIONS OF DIMETHYL SULFOXIDE WITH POTASSIUM DICLOROGLYCINATOPLATINATE(II) AND ITS METHYL DERIVATIVES

Abstract

Amino acid complexes of general formula K[Pt(NO)Cl₂], where NO denotes the metal bonded atoms of the amino acid, react completely with solvent DMSO to yield two products, cis- and trans-Pt(NO) (DMSO)Cl, where cis and trans refer to positions of DMSO relative to coordinated nitrogen. The products were identified and kinetic data were obtained from changes in the proton nmr spectra of the amino acid, when DMSO-d₆ was the solvent, or of both amino acid and coordinated DMSO, when ordinary DMSO was the solvent. For glycine and π-aminoisobutyric acid complexes, the rate of displacement of trans chloride exceeds that of cis chloride by a factor of 3. However, subsequent equilibration favors the cis isomer over the trans isomer by a factor of 10. By contrast, for the corresponding N, N-dimethyl derivatives, the rates of formation of the two isomers are more nearly the same and the equilibrium ratio does not differ from the kinetic ratio. In addition to providing a sensitive technique for evaluating small differences in kinetic trans-effects, these observations strongly suggest that the stereochemistry of Pt(NO) (DMSO)Cl for the corresponding alanine complex described by Kukushkin and Guryamava should be denoted cis, rather than the trans reported.     

Oxomolybdenum(VI) complexes with glycine bisphenol [O,N,O,O′] ligand: synthesis and catalytic studies

The oxomolybdenum(VI) complex [MoOCl(L)] with a tetradentate glycine bisphenol ligand (H₃L) was prepared by reaction of [MoO₂Cl₂(DMSO)₂] with a ligand precursor in hot toluene. The product was isolated in moderate yield as separable cis and trans isomers along with the third minor component, [MoO₂(HL)]. The solid-state structure of trans-[MoOCl(L)] was determined by X-ray diffraction. The ligand has tetradentate coordination through three oxygens and one nitrogen, which is located trans to the terminal oxo whereas the sixth coordination site is occupied by a chloride. Both cis and trans isomers of [MoOCl(L)] are active catalysts for epoxidation of cis-cyclooctene and sulfoxidation of tolyl methyl sulfide. The cis isomer gave higher activity in epoxidation and sulfoxidation reactions at room temperature than the trans isomer but they performed identically at 50?°C.