Preparation of bis(diazo) compounds incorporated into butadiyne and thiophene units, and generation and characterization of bis(carbene) from these compounds

[9-[10-(4-t-Butyl-2,6-dimethyl)phenyl]anthryl](4-bromo-2,6-dimethylphenyl)diazomethane (1-N(2)) was found to be stable enough to survive under Sonogashira and Suzuki coupling reaction conditions, and bis(diazo) compounds incorporated into the 1,4-positions of butadiyne (3-2N(2)) and the 2,5-position of thiophene (4-2N(2)) were prepared. Irradiation of those bis(diazo) compounds generated bis(carbenes), which were characterized by ESR and UV-vis spectroscopic techniques in a matrix at low temperature, as well as time-resolved UV-vis spectroscopy in solution at room temperature. These studies revealed that both of the bis(carbenes), 3 and 4, have a singlet quinoidal diradical ground state with a very small singlet-triplet energy gap of less than 1 kcal/mol. A remarkable increase in the lifetime of bis(carbenes) as opposed to that of monocarbene (1) was noted and was interpreted to indicate that bis(carbenes) are thermodynamically stabilized as a result of delocalization of unpaired electrons throughout a pi-net framework. Despite the stability, both bis(carbenes) are readily trapped by molecular oxygen to afford bis(ketones) as main products.     

Role of donor and secondary interactions in the structures and thermal properties of alkaline-earth and rare-earth metal pyrazolates

The addition of neutral coligands to reduce the aggregation and improve the volatility of potential heavy alkaline-earth metal chemical vapor deposition (CVD) precursors has typically resulted in liberation of the coligand upon heating. A new series of dinuclear alkaline-earth and rare-earth metal pyrazolates, bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)calcium] (1), bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)strontium] (2), and bis[bis(3,5-di-tert-butylpyrazolato)bis(tetrahydrofuran)barium] (3), have been obtained from our previous donor-free oligonuclear complexes [{M(3,5-tBu2pz)2}n] (5, M = Ca, n = 3; 6, M = Sr, n = 4; 7, M = Ba, n = 6) by treatment with tetrahydrofuran (THF). Compounds 1-3, as well as the europium analogue bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)europium(II)] (4), can also be prepared by direct reaction of the metals and pyrazole in THF and anhydrous liquid ammonia. Recrystallization from hexane led to single crystals of 2-4, while the powder diffraction pattern of 1 revealed it to be isostructural with the previously published bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)ytterbium(II)] (8), providing important insight into differences and similarities between the two groups of metals. Detailed structural analysis of the compounds reveals secondary interactions including pi-bonding and agostic interactions, which are considered essential in stabilizing the metal complexes. The direct comparison of structural features and thermal properties (as evaluated by thermogravimetric analysis and sublimation studies) of the donor-free oligonuclear and the donor-containing dinuclear species offers a better understanding of the role of donors and secondary interactions.     

Preparation of bis(diazo) compounds incorporated into butadiyne and thiophene units and generation and characterization of their photoproducts

(2,6-dimethyl-4-tert-butylphenyl)(2,4,6-tribromophenyl)diazomethane(-N(2)) was found to be stable enough to survive under Sonogashira coupling reaction conditions, and aryldiazomethyl substituents were introduced at the 1,4-positions of butadiyne (4-2N(2)) and the 2,5-positions of thiophene(5-2N(2)). Irradiation of those bis(diazo) compounds generated bis(carbenes), which were characterized by using ESR and UV/vis spectroscopic techniques in a matrix at low temperature as well as time-resolved UV/vis spectroscopy in solution at room temperature. These studies revealed that both of the bis(carbenes), 4 and 5, have singlet quinoidal diradical ground states with a very small singlet-triplet energy gap of less than 1 kcal mol(-1). A remarkable increase in the lifetime of bis(carbenes), as opposed to that of the monocarbene (2), was noted and was interpreted to indicate that bis(carbenes) are thermodynamically stabilized as a result of delocalization of unpaired electrons throughout the pi net framework. In spite of the stability, both bis(carbenes) are readily trapped by molecular oxygen to afford bis(ketones). Presumably, the reaction of the upper-lying localized quintet states with oxygen is much faster than that for lower-lying states.     

Ligands with Two Monoanionic N,N-Binding Sites: Synthesis and Coordination Chemistry

Polytopic ligands have become ubiquitous in coordination chemistry because they grant access to a variety of mono- and polynuclear complexes of transition metals as well as rare-earth and main-group elements. Nitrogen-based ditopic ligands, in which two monoanionic N,N-binding sites are framed within one molecule, are of particular importance and are therefore the primary focus of this review. In detail, bis(amidine)s, bis(guanidine)s, bis(β-diimine)s, bis(aminotroponimine)s, bis(pyrrolimine)s, and miscellaneous bis(N,N-chelating) ligands are reviewed. In addition to the general synthetic protocols, the application of these ligands is discussed along with their coordination chemistry, the multifarious binding modes, and the ability of these ligands to bridge two (or more) metal(loids).     

Copper(II) and nickel(II) complexes of glyoxaldehyde bis{N(3)-substituted thiosemicarbazones}

Copper(II) and nickel(II) complexes of glyoxaldehyde bis{N(3)-methyl-, bis{N(3)-ethyl-, bis{N(3)-dimethyl-, bis{piperidyl- and bis{hexamethyleneiminylthiosemicarbazone} have been prepared and studied spectroscopically. The five bis(thiosemicarbazones) have been characterized by their melting points, as well as i.r., electronic and 1H-n.m.r. spectra. The four-coordinate copper(II) complexes have been studied by e.s.r. spectroscopy, and the copper(II) and nickel(II) complexes by a number of the spectroscopic techniques mentioned above. Upon formation of these complexes, loss of protons from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazones) coordinate to the metal centres as dianionic, tetradentate N2S2 ligands. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of novel bis(chromenes) and bis(chromeno[3,4-C]pyridine) incorporating piperazine moiety

Novel bis(2-oxo-2H-chromene) as well as bis(2-imino-2H-chromene) derivatives incorporating piperazine moiety were prepared by the cyclocondensation reaction of bis(2-hydroxybenzaldehyde) with two equivalents of each of the appropriate β-ketoesters or acetonitrile derivatives. The bis(2-imino-2H-chromene-3-carbothioamide) derivative was used as a key synthon for construction of novel bis(3-(4-substituted thiazol-2-yl)-2H-chromen-2-one) derivatives via its cyclocondensation with a series of the appropriate α-halocarbonyl derivatives. Moreover, the bis(2-hydroxybenzaldehyde) reacted with four equivalents of the appropriate acetonitrile derivatives to afford the corresponding bis(3H-chromeno[3,4-c]pyridine) derivatives. Elucidation of the structure of the novel bis(chromenes) bearing piperazine nucleus was established by the spectral data and elemental analyses.     

Copper(II) and nickel(II) complexes of the bis{N(3)-substituted thiosemicarbazones} of phenylglyoxal and 1-phenylpropane-1,2-dione

Copper(II) and nickel(II) complexes of phenylglyoxal and phenylpropane-1,2-dione bis{N(3)-methyl-, bis{N(3)-dimethyl-, bis{piperidylthiosemicarbazone} have been prepared and studied spectroscopically. The six bis(thiosemicarbazones) have been characterized by their melting points, as well as i.r., electronic and 1H-n.m.r. spectra. The four-coordinate copper(II) complexes have been studied by e.s.r. spectroscopy, and the copper(II) and nickel(II) complexes by spectroscopic techniques mentioned above. Upon formation of these complexes, the loss of protons from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazones) coordinate to the metal centres as dianionic, tetradentate N2S2 ligands.     

Synthesis Efforts of Acyclic Bis(monoalkylamino)maleonitriles and Macrocyclic Bis(dialkylamino)maleonitriles as Fluorescent Probes for Cations and a New Colorimetric Copper(II) Chemodosimeter

In this article, we report on the synthesis of acyclic bis(monoalkylamino)maleonitriles and on the intended synthesis of macrocyclic bis(dialkylamino)maleonitriles to get fluorescent probes for cations. During our efforts to synthesize macrocyclic bis(dialkylamino)maleonitriles, we were only able to isolate macrocyclic bis(dialkylamino)-fumaronitriles. The synthesis of macrocyclic bis(dialkylamino)maleonitriles is challenging, due to the fact that bis-(dialkylamino)fumaronitriles are thermodynamically more stable than the corresponding bis(dialkylamino)-maleonitriles. Further, it turned out that the acyclic bis(monoalkylamino)maleonitriles and macrocyclic bis-(dialkylamino)fumaronitriles are no suitable tools to detect cations by a strong fluorescence enhancement. Further, only the bis(monoalkylamino)maleonitriles, which are bearing a 2-pyridyl unit as an additional complexing unit, are able to selectively recognize copper(II) by a color change from yellow to red.     

Copper(II) and nickel(II) complexes of pyruvaldehyde bis{N(3)-substituted thiosemicarbazones}

Copper(II) and nickel(II) complexes of pyruvaldehyde bis{N(3)-methyl-, bis{N(3)-ethyl-, bis{N(3)-dimethyl- and bis{piperidylthiosemicarbazone} have been prepared and studied spectroscopically. The four thiosemicarbazones have been characterized by their melting points, as well as i.r., electronic and n.m.r. (1H,13C) spectra. The four coordinate copper(II) complexes have been studied by e.s.r. spectroscopy, and the copper(II) and nickel(II) complexes by several of the spectroscopic techniques mentioned above. Upon formation of these complexes, loss of protons from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazones) coordinate to the metal centres as dianionic, tetradentate N2S2 ligands.     

Thio-Pybox and Thio-Phebox complexes of chromium, iron, cobalt and nickel and their application in ethylene and butadiene polymerisation catalysis

A series of bis(thiazolinyl)- and bis(thiazolyl)pyridine Thio-Pybox ligands and their metal complexes of chromium(III), iron(II), cobalt(II) and nickel(II) has been prepared, as well as a nickel(II) complex containing a monoanionic bis(thiazolinyl)phenyl Thio-Phebox ligand. These new metal complexes have been characterised and used as catalysts, in combination with the co-catalyst MAO, for the polymerisation of ethylene and for the polymerisation of butadiene. In the case of ethylene polymerisation, the Thio-Pybox and Thio-Phebox metal complexes have shown relatively low polymerisation activities, much lower compared to the related bis(imino)pyridine complexes of the same metals. In the polymerisation of butadiene, several Thio-Pybox cobalt(II) complexes show very high activities, significantly higher than the other metal complexes with the same ligand. It is the metal, rather than the ligand, that appears to have the most profound effect on the catalytic activity in butadiene polymerisation, unlike in the polymerisation of ethylene, where bis(imino)pyridine ligands provide highly active catalysts for a range of 1st row transition metals.     

On the intermediates in chiral bis(oxazoline)copper(II)-catalyzed enantioselective reactions--experimental and theoretical investigations

The intermediates in the chiral bis(oxazoline)copper(II)-catalyzed reactions have been investigated by means of experimental and theoretical investigations. It is shown that the absolute configuration of the hetero-Diels-Alder adduct obtained from the reaction of ethyl glyoxylate with 1,3-cyclohexadiene in the presence of the chiral bis(phenyloxazoline)copper(II) is dependent on the solvent. In this case, a linear relationship between the enantiomeric excess (ee) and the dielectric constant of the solvent was observed. However, the enantiomeric excess for the adduct obtained with the chiral bis(tert-butyloxazoline)copper(II) complex is independent of the solvent. The addition of different coordinating solvents to the chiral catalysts was investigated and no effect on the enantioselectivity of the reaction was observed. A series of chiral bis(tert-butyloxazoline)-, bis(phenyloxazoline)-, and bis(indaneoxazoline)copper(II) complexes has been prepared and characterized by X-ray analysis, and the similarity between the structures is discussed. For comparison, two related chiral bis(tert-butyloxazoline)- and bis(phenyloxazoline)zinc(II) complexes were also prepared and characterized. A series of chiral bis(oxazoline)copper(II)-substrate (the substrate being glyoxal or methyl glyoxylate) complexes was investigated by means of ab initio calculations. Calculation of the total energy of the optimized structure of 17-, 19-, and 21-electron bis(oxazoline)copper(II)-substrate complexes give the 17-electron complex as the most stable and the most reactive complex, while the 21-electron complex is less stable and also much less reactive. The optimized structures of both the 17-electron bis(tert-butyloxazoline)- and bis(phenyloxazoline)copper(II)-substrate complexes show that the plane of the substrate molecule is twisted by approximately 40-45 degrees out of the bis(oxazoline)copper(II) plane, in agreement with the X-ray structures. On the basis of the experimental results, X-ray structures, and ab initio calculations, the structure of the intermediate(s) and reactivity of the chiral bis(oxazoline)copper(II)-substrate complexes are discussed.     

3,4‐Bis(bromomethyl)thieno[2,3‐b]thiophene: Versatile Precursors for Novel Bis(triazolothiadiazines), Bis(quinoxalines), Bis(dihydrooxadiazoles), and Bis(dihydrothiadiazoles)

A synthesis of novel bis(triazolothiadiazines) 11 , 12 , 13 , 14 , bis(quinoxalines) 16 and 17 , bis(thiadiazoles) 24 and 25 , and bis(oxadiazole) 31 , which are linked to the thieno[2,3‐b]thiophene core via phenoxymethyl group, was reported. Thus, reaction of the bis(α‐bromoketones) 6 and 7 with the corresponding 4‐amino‐3‐mercapto‐1,2,4‐triazole derivatives 8 , 9 , 10 in ethanol–DMF mixture in the presence of a few drops of triethylamine as a catalyst under reflux afforded the novel bis(5,6‐dihydro‐s‐triazolo[3,4‐b]thiadiazines) 11 , 12 , 13 , 14 in 60–72% yields. The bis(quinoxalines) 16 and 17 were also synthesized as a sole product in high yields by the reaction of 6 and 7 with o‐phenylenediamine 15 in refluxing acetonitrile in the presence of piperidine as a catalyst. Cyclization of the bis(aldehyde thiosemicarbazones) 20 and 21 with acetic anhydride afforded the corresponding bis(4,5‐dihydro‐1,3,4‐thiadiazolyl) derivatives 24 and 25 in good yield. Bis(5‐phenyl‐2,3‐dihydro‐1,3,4‐oxadiazole) derivative 31 could be obtained in 67% yield by cyclization of the appropriate bis(N‐phenylhydrazone) 29 in refluxing acetic anhydride for 3 h.     

Synthesis of bis‐ and tris‐organophosphorus substituted amines and amino acids with PCH2N Fragments

The aminomethylation of the derivatives of trivalent organophosphorus acids, containing PH and POSiMe₃ fragments with various bis‐ and tris(alkoxymethyl)amines and bis(alkoxymethyl)amino acids, is proposed as a convenient method for the synthesis of new bis‐ and trisphosphorylated amines and amino acids as well as their derivatives with four and five coordinated phosphorus. Also the three‐components systems of phosphorous acid, paraformaldehyde, and amines are thoroughly investigated via the treatment of reaction mixtures with bis(trimethylsilyl)amine. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:430–440, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20616     

Synthesis and antitumor properties of N1-acyloxymethyl derivatives of bis(2,6-dioxopiperazines)

Many N1-acyloxymethyl derivatives VI of bis(2,6-dioxopiperazine) I, ICRF-154, were prepared and tested for antitumor activity. The treatment of I with formaldehyde gave a crystalline bis(N1-hydroxymethyl) derivative VII, which was acylated under various conditions to give bis(N1-acyloxymethyl) derivatives VI. Antitumor activity of VI against P388 leukemia in mice was studied. Several bis(N1-acyloxymethyl) compounds such as phenylacetyloxymethyl VI-6, methoxycarbonyloxymethyl VI-41, isobutoxycarbonyloxymethyl VI-44, and furancarboxymethyl VI-38 compounds were found to have potent antitumor activities. On the other hand, water-soluble esters having an amine or a carboxylic acid function in their acyl groups showed rather reduced activity. These bis(N1-acyloxymethyl) derivatives VI were presumably hydrolyzed into the parent bis(2,6-dioxopiperazine) I by nonspecific esterase in the body to exhibit their antitumor activity.     

Tuning ligand structure in chiral bis(phosphite) and mixed phosphite-phosphinite PCP-palladium pincer complexes

A range of chiral resorcinol bis(phosphite) and phosphite-phosphinite ligands were produced and their propensity to form palladium PCP-pincer complexes examined. The ease of base-assisted C-H palladation of the ligands falls in the order bis(phosphinite) > phosphite-phosphinite > bis(phosphite). The catalytic activity of the complexes in the asymmetric allylation of benzaldehyde with allyl tributyltin was examined and it was found that, contrary to expectations, ligands with 3,3'-disubstituted BINOL residues show poorer activity and stereoselectivity than unsubstituted BINOL analogues. In addition the order of activity of the pincer complexes was established as bis(phosphite) > phosphite-phosphinite > bis(phosphinite). Crystal structures of representative examples of a 3,3'-disubstituted BINOL, mono- and bis(phosphite) ligands based on 2,4-di-tert-butyl resorcinol and Pd complexes of two of the chiral complexes are presented.     

Bialkyls from dialkylmetals I. Photochemistry and mass spectra of some (2-cyanoethyl)- and [2-(methoxycarbonyl)ethyl]metals

We have studied the photolysis and the fragmentation in the mass spectrometer of bis(2-cyanoethyl)mercury, bis(2-cyanoethyl) selenide, bis(2-cyanoethyl) sulphide, dibutylbis(2-cyanoethyl)stannane, and bis[2-(methoxycarbonyl)ethyl] selenide. The mercury compound gave a high yield of adiponitrile on photolysis and in the mass spectrometer it gave the fragmentation pattern of adiponitrile, including the molecular ion, as part of the total fragmentation pattern. A low yield of bialkyl was also formed on photolysis of the bis[2-(methoxycarbonyl)ethyl] selenide but no peaks corresponding to biakyl were observed in the mass spectrum. None of the other compounds yielded alkyl dimer.

A preliminary discussion of the results in terms of orbital symmetry is presented.     

Synthesis and characterization of poly(esters) derived from diacids and diphenols containing silicon and germanium

Poly(esters) containing two heteroatoms, Si or Ge, in the main chain, derived from diphenols bis(4-hydroxyphenyl)-dimethyl-germane, bis(4-hydroxyphenyl)-diphenyl-germane, bis(4-hydroxyphenyl)-dimethyl-silane and bis(4-hydroxyphenyl)-diphenyl-silane, and the acid dichlorides bis(4-chloroformyl-phenyl)-dimethyl-germane, bis(4-chloroformyl-phenyl)-diphenyl-germane, bis(4-chloroformyl-phenyl)-dimethyl-silane and bis(4-chloroformyl-phenyl)-diphenyl-silane, were synthesized under phase transfer conditions using two phase transfer catalysts, and characterized by spectroscopic methods. This technique showed low effectivity for the synthesis of these kinds of polymers, showing a low increase of the yields and η_inh values in comparison with the interphasial process. In these experimental conditions there were no important differences neither in the studied parameters between the monomers with Si or Ge, nor between the catalysts.     

Synthesis and characterization of new platinum(II) phosphinate complexes

The syntheses of platinum(II) complexes of bis(dimethylphosphinylmethylene)amine and bis(aminomethyl)phosphinic acid were investigated. In the case of bis(dimethyl-phosphinylmethylene)amine the reaction with K₂[PtCl₄] yields the potassium amino-trichloroplatinate K[PtCl₃L] (L?=?bis(dimethylphosphinylmethylene)amine), which was characterized by multinuclear (¹H, ¹³C, ³¹P, and ¹⁹⁵Pt) NMR spectroscopy in solution. Bis(aminomethyl)phosphinic acid reacts with K₂[PtCl₄] under strictly controlled pH conditions to give colorless crystals of the cisplatin analog K[PtCl₂L′] (L′?=?bis(aminomethyl)phosphinate). This complex was characterized by multinuclear NMR spectroscopy in solution as well as by single-crystal X-ray diffraction in the solid state. The bis(aminomethyl)phosphinate coordinates to platinum via both amino functions, thus acting as a chelating ligand.     

The first metal complexes of bis(diisopropylamino)carbene: synthesis, structure and ligand properties

The synthesis of rhodium(I) and iridium(I) complexes of the bis(diisopropylamino)carbene is described for the first time. The formamidinium chloride and the free bis(diisopropylamino)carbene (L) were used as consecutive precursor compounds to form the metal complexes. Spectroscopic and, for LRh(cod)Cl, crystallographic data are presented for the complexes LRh(cod)Cl and LIr(cod)Cl (L=bis(diisopropylamino)carbene). The ligand properties of the acyclic bis(diisopropylamino)carbene are compared with imidazolin-2-ylidenes and imidazolidin-2-ylidenes as ligands in related rhodium(I) carbonyl complexes. Bis(diisopropylamino)carbene is the most basic known carbene ligand to date.     

聚乙二醇(PEG)桥连的新型双N-杂环卡宾-膦的合成及其在水相Suzuki反应中的应用

通过乙酸1-(2-二苯膦基二茂铁基)乙基酯与PEG-400衍生的双咪唑化合物反应,制得新型PEG桥连的双咪唑盐-膦配体,其结构经1HNMR,<31>PNMR和MS鉴定.初步催化研究表明,该PEG桥连的双咪唑盐一膦可作为支持配体在有机和水相中高产率地实现Pd催化的溴代芳烃和苯硼酸的Suzuki偶联反应.