Olefin metathesis of the aligned assemblies of conjugated polymers constructed through supramolecular bundling

The ordered structures constructed from an aligner molecule 1o and conjugated polymers (CPs) were efficiently converted into the poly-pseudo-rotaxane structures by the template-assisted ring-closing olefin metathesis (RCM) of olefinic groups at the peripheral positions of 1o. Moreover, the poly-pseudo-rotaxane structures permitted the separation of the crystalline ordered assemblies of CP by size exclusion chromatography and the preservation of the sheet morphologies after the treatment with trifluoroacetic acid. The morphologies and the periodicities of assemblies were also maintained after the retrieving treatments.     

Olefin metathesis of alkenyltrimethylsilanes

WCl₆ has been used as a catalyst for the metathesis of various alkenylsilanes and the degree of conversion found to be dependent on the distance between the olefinic bond and the silyl group. The first observation of metathetical conversion of allyltrimethylsilane in the absence of a co-catalyst is reported     

Olefin metathesis in room temperature ionic liquids using imidazolium-tagged ruthenium complexes

New recyclable imidazolium-tagged ruthenium catalysts have been developed to perform olefin metathesis in room temperature ionic liquids (RTILs). High level of recyclability combined with a high reactivity were obtained in the ring-closing metathesis (RCM) of a variety of di- or tri-substituted and/or oxygen-containing dienes. Extremely low residual ruthenium levels were detected in the RCM products (average of 7.3 ppm per run). Several examples of olefin cross-metathesis (CM) have been also studied.     

Olefin metathesis featuring ruthenium indenylidene complexes with a sterically demanding NHC ligand

The synthesis and characterization of two new ruthenium indenylidene complexes [RuCl(2)(SIPr)(Py)(Ind)] 6 and [RuCl(2)(SIPr)(3-BrPy)(Ind)] 7 featuring the sterically demanding N-heterocyclic carbene 1,3-bis(2,6-di isopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr) are reported. Remarkable activity was observed with these complexes in ring closing, enyne, and cross metathesis of olefins at low catalyst loadings. The performance of SIPr-bearing complexes 6 and 7 as well as [RuCl(2)(SIPr)(PCy(3))(Ind)] 5 in ring opening metathesis polymerization is also disclosed. This work highlights the enormous influence of the neutral "spectator" ligands on catalyst activity and stability.     

Olefin metathesis as an inorganic synthetic tool: cross and ring closing metathesis reactions of diruthenium-bound omega-alkene-alpha-carboxylates

Diruthenium compounds containing one omega-alkene-alpha-carboxylate ligand, Ru2Cl(D(3,5-Cl2Ph)F)3(O2C(CH2)nCH=CH2) (n=1 (1a) and 2 (1b)), were prepared from the reaction between Ru2Cl(D(3,5-Cl2Ph)F)3(O2CCH3) (D(3,5-Cl2Ph)F=N,N'-bis(3,5-dicholorophenyl)formamidinate) and the corresponding omega-alkene-alpha-carboxylic acid. Compounds 1a and 1b both underwent olefin cross metathesis reactions catalyzed by (Cy3P)2Cl2Ru(=CHPh) to afford the dimerized compounds [Ru2Cl(D(3,5-Cl2Ph)F)3]2(mu-O2C(CH2)nCH=CH(CH2)nCO2) (n=1 (2a) and 2 (2b)). Similarly, diruthenium compounds containing two omega-alkene-alpha-carboxylate ligands, cis-Ru2Cl(D(3,5-Cl2Ph)F)2(O2C(CH2)nCH=CH2)2 (n=1 (3a), 2 (3b), and 3 (3c)), were prepared by substituting the acetate ligands in cis-Ru2Cl(D(3,5-Cl2Ph)F)2(O2CCH3)2 with the corresponding omega-alkene-alpha-carboxylate ligands. Compounds 3 exhibited different reactivity under olefin metathesis conditions: both 3b and 3c underwent the intramolecular ring closing reaction quantitatively to afford compounds cis-Ru2(D(3,5-Cl2Ph)F)2(mu-O2C(CH2)nCH=CH2(CH2)nCO2)Cl with n=2 (4b) and 3 (4c), respectively, but 3a displayed no metathesis reactivity. Molecular structures of compounds 1a/1b, 2a/2b, 3a/3b, and 4b were established via X-ray diffraction studies, confirming the formation of cross and ring closing metathesis products. Voltammograms of compounds 2 are nearly identical to those of compounds 1, indicating the absence of electronic interactions mediated by the tether derived from olefin metathesis.     

Hydroamination of conjugated dienes catalyzed by transition metal complexes

The review summarizes published data on the hydroamination of 1,3-dienes with various primary and secondary amines, ammonia, and ammonium salts of mineral acids in the presence of transition metal complexes under homogeneous conditions. The effects of the nature of metal, ligand, initial diene, and amine and reaction conditions on the selectivity of hydroamination are considered, and possible reaction mechanisms are discussed.     

Macromolecules containing bipyridine and terpyridine metal complexes: towards metallosupramolecular polymers

The ability of a broad range of N-heterocycles to act as very effective and stable complexation agents for several transition metal ions, such as cobalt(II), copper(II), nickel(II), and ruthenium(II), has long been known in analytical chemistry. This behavior was later utilized in supramolecular chemistry for the construction of highly sophisticated architectures, such as helicates, racks, and grids. The discovery of macromolecules by Staudinger in 1922 opened up avenues towards sophisticated materials with properties hitherto completely unknown. In the last few decades, the combination of macromolecular and supramolecular chemistry has been attempted by developing metal-complexing and metal-containing polymers for a wide variety of applications that range from filtration to catalysis. The stability of the polymer-metal complex is a fundamental requirement for such applications. In this respect, the use of bi- and terpyridines as chelating ligands is highly promising, since these molecules are known to form highly stable complexes with interesting physical properties with transition-metal ions. A large number of different structures have been designed for many different applications, but polymers based on the application of coordinative forces have been prepared in a few cases only. Furthermore, the synthetic procedures applied frequently resulted in low yields. During the last few years, strong efforts have been made in the direction of self-assembling and supramolecular polymers as novel materials with "intelligent" and tunable properties. In this review, an overview of this active area at the interface of supramolecular and macromolecular chemistry is given.     

Synthesis and characterization of some conjugated ketoanilides and their metal complexes

The reaction between acetoacetanilide and aromatic aldehydes (2,4-dimethoxybenzaldehyde, veratraldehyde and piperonal) under specified conditions yielded two types of conjugated ketoanilides in which the keto-groups are attached to olefinic linkages. The existence of these compounds predominantly in the intramolecularly hydrogen-bonded enol form has been well demonstrated from their IR, ¹H NMR, and mass spectral data. Details on the formation of their complexes with Ni(II), Cu(II), and Zn(II) and their nature of bonding are discussed on the basis of analytical, IR, ¹H NMR, and mass spectral data. The text was submitted by the authors in English.     

Ruthenium-indenylidene complexes: powerful tools for metathesis transformations

Ruthenium-indenylidene complexes represent a class of robust and efficient pre-catalysts for olefin metathesis reactions. In this feature article, we provide an overview of the various complexes belonging to this family and summarise their use in various applications. The relation between the nature of ancillary ligands around the metal coordination sphere of these complexes and their catalytic activity is also discussed.     

Stability of transition metal complexes with sulfonated polymers

Stability constants of macromolecular metallocomplexes of transition metal ions (Ag⁺, Cu²⁺, Ni²⁺, Fe³⁺) with sulfonated polymers in water and aqueous HCl and NaCl solutions were determined from quenching by transition metal ions of the luminescence of macromolecules labeled with luminescent groups.     

Water‐soluble anionic conjugated polymers for metal ion sensing: Effect of interchain aggregation

Three sulfonato‐containing fluorene‐based anionic water‐soluble conjugated polymers, which are specially designed to link fluorene with alternating moieties such as bipyridine ( P1 ), pyridine ( P2 ), and benzene ( P3 ) have been synthesized via the Pd‐catalyzed Sonogashira‐coupling reaction, respectively. These polymers had good solubility in water and showed different responses for transition metal ions with different valence in aqueous environments: the fluorescence of bipyridine‐containing P1 can be completely quenched by addition of all transition metal ions selected and showed a good selectivity for Ni²⁺; the pyridine‐containing P2 had a little response for monovalent and divalent metal ions while showed good quenching with the addition of trivalent metal ions (with a special selectivity for Fe³⁺); P3 had responses only for the trivalent metal ions within the ionic concentration we studied. After investigation of the UV‐vis absorption spectra, PL emission spectra, DLS, and fluorescence lifetime of P1 – P3 in aqueous solution when adding transition metal ions, we found that the different spectrum responses of these polymers are attributed to the different coordination ability of the units linked with fluorene in the main chain. The energy or electron‐transfer reactions were the main reason for fluorescence quenching of P1 and P2 . On the other hand, interchain aggregation caused by trivalent metal ions lead to fluorescence quenching for P3 and also caused partly fluorescence quenching of P1 and P2 . These results revealed the origin of ionochromic effects of these polymers and suggested the potential application for these polymers as novel chemosensors with higher sensing sensitivity in aqueous environments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5057–5067, 2009     

Monoamineplatinum (II) complexes conjugated to water-soluble carrier polymers for chemotherapeutic applications

In the light of the observed carcinostatic activity of the monoamineplatinum complexes K[PtCl₃(NH₃)] and K[PtCl₃(t-butylamine)], it has been of interest in this laboratory to develop water-soluble, antineoplastic conjugates in which square-planar platinum complex structures of the monoamineplatinum type are linked to suitable carrier polymers possessing water solubility for improved pharmacokinetics. In the present paper the synthesis is described of conjugates in which each platinum atom is coordinated to a single, primary amine ligand provided by a water-soluble polyaspartamide-type carrier. Microanalytical data suggest the remaining three coordination sites on the metal center to be occupied on average by one aquo and two chloro ligands. The carriers, prepared by a known method from polysuccinimide by stepwise aminolytic ring-opening, are designed so as to feature randomly placed hydrosolubilizing units and metal-binding units in a ratio of 3:1, thus providing spatial insulation between the latter and minimize intramolecular interaction between the platinum complexes incorporated subsequently. Platination of the carriers is brought about by treatment with K₂PtCl₄ in aqueous solution at 25–60 °C in the pH range 5–6, and the polymer–platinum conjugates are purified and isolated in 50–70% yield by aqueous-phase dialysis and freeze-drying. The extent of platination attained depends inter alia on the Pt/NH₂ feed ratio (equivalents of tetrachloroplatinate per carrier base unit); in optimal cases complete metal coordination to the carrier-attached primary-amine ligands is achieved with a feed ratio of 1.4:1. The conjugates, initially showing complete solubility in water, tend to undergo an ageing process on storage believed to involve intermolecular solid-state interaction of the bound platinum complexes with proximate amine sites, resulting in gradual loss of solubility. In frozen aqueous solution, however, the conjugates are stable for extended periods of time.     

Olefin metathesis catalyst: stabilization effect of backbone substitutions of N-heterocyclic carbene

Ruthenium olefin metathesis catalysts bearing an N-phenyl-substituted N-heterocyclic carbene (NHC) ligand that are resistant to decomposition through C-H activation have been prepared and tested in ring closing metathesis (RCM), cross metathesis (CM), and ROMP reactions. The N, N'-diphenyl-substituted NHC complex proved to be one of the most efficient catalysts in RCM to form tetrasubstituted olefins.     

Olefin metathesis: remote substituents governing the stereoselectivity of 11-membered-ring formation

[reaction: see text] Stereospecific RCM reaction of 7 (R1 = Me) results in the formation of (Z)-11-membered macrocycle 9c. Cascade RCM/ROM/RCM transformation of 7 (R1 = H) affords the thermodynamically more stable spirocycle product 12.