Complexes of acid amides with polar aprotic solvents. I

Complexes of bis(N-phenyl)-pyromellitic acid diamide with dimethylformamide were synthetized and studied by thermal mass-spectrometry. It was found that, depending on the precipitating agent applied, the composition of the complexes corresponded to 1 acid amide: 2 dimethylformamide or to 1 acid amide: 1 dimethylformamide. The effects of complex formation on the thermal cyclodehydration of bis(N-phenyl)-pyromellitic acid diamide and on the accompanying degradation processes are discussed.     

Specific features of ethylene polymerization on self-immobilizing catalytic systems based on titanium bis(phenoxy imine) complexes

The kinetics of ethylene polymerization on six methylalumoxane-activated self-immobilizing bis(phenoxy imine) complexes of titanium chloride with allyloxy groups in the m- and p-positions of the N-phenyl ring and with various substituents in the salicylaldehyde fragment was studied. The activity of the complexes in the temperature range 20–60°C and ethylene pressure of 0.4 MPa was evaluated.     

The chemistry of nitrogen coordinated tertiary carboxamides: a spectroscopic study on bis(picolyl)amidecopper(II) complexes

Metal coordination of the electrically neutral nitrogen atom of a tertiary carboxamide reduces the barrier to C-N-bond rotation and activates the amide towards methanolysis. X-Ray crystallographic studies indicate that this reactivity is correlated to a lifting of the amide resonance structure and concurrent pyramidalization at nitrogen. However, mechanistic data in solution have not been obtained. It became evident that structural mobility is characteristic of the complexes and the crystallographic data do not fully account for relevant reactive species. In this report we summarize IR, UV-vis, and EPR spectra of amide nitrogen coordinated bis(picolyl)amide complexes with copper(II) triflate and copper(II) chloride. A comparison between spectra sampled in the aprotic solvents dichloromethane and acetonitrile, as well as under methanolysis conditions reveals the nature of several species formed in solution. The key reactions are (I) ligand exchange involving either CH3CN or CH3OH, or, in IR experiments, bromide ions from KBr, (II) coordination-dissociation equilibria involving the urethane protecting groups of amino acid substituted ligands Boc-Xaa-bpa (Boc = tert-butoxycarbonyl, Xaa = glycine, alanine, and leucine, respectively, bpa = bis(picolyl)amine), (III) dissociation of a chloro ligand from LCuCl2 complexes and formation of square-pyramidal complex cations [LCuCl]+, and finally (IV) complete dissociation of the polydentate tertiary amide ligand to produce free copper ions in solution. Taken together, the results provide a fairly detailed qualitative picture of the processes which accompany the amide bond methanolysis.     

Rhenium tricarbonyl core complexes of thymidine and uridine derivatives

Thymidine and uridine were modified at the C2' and C5' ribose positions to form amine analogues of the nucleosides (1 and 4). Direct amination with NaBH(OAc)3 in DCE with the appropriate aldehydes yielded 1-{5-[(bis(pyridin-2-ylmethyl)amino)methyl]-4-hydroxytetrahydrofuran-2-yl}-5-methyl-1H-pyrimidine-2,4-dione (L1), 1-{5-[(bis(quinolin-2-ylmethyl)amino)methyl]-4-hydroxytetrahydrofuran-2-yl}-5-methyl-1H-pyrimidine-2,4-dione (L2), and 1-[3-(bis(pyridin-2-ylmethyl)amino)-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl]-1H-pyrimidine-2,4-dione (L5), while standard coupling procedures of 1 and 4 with 5-(bis(pyridin-2-ylmethyl)amino)pentanoic acid (2) and 5-(bis(quinolin-2-ylmethyl)amino)pentanoic acid (3) in the presence of HOBT-EDCI in DMF provided a second novel series of bifunctional chelators: 5-(bis(pyridin-2-ylmethyl)amino)pentanoic acid [(3-hydroxy-5-(5-methyl-4-oxo-3,4-dihydro-2H-pyrimidin-1-yl)tetrahydrofuran-2-yl)methyl] amide (L3), 5-(bis(quinolin-2-ylmethyl)amino)pentanoic acid [(3-hydroxy-5-(5-methyl-4-oxo-3,4-dihydro-2H-pyrimidin-1-yl)tetrahydrofuran-2-yl)methyl] amide (L4), 5-(bis(pyridin-2-ylmethyl)amino)pentanoic acid [2-(2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-3-yl] amide (L6), and 5-(bis(quinolin-2-ylmethyl)amino)pentanoic acid [2-(2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-3-yl] amide (L7). The rhenium tricarbonyl complexes of L1-L4, L6, and L7, [Re(CO)3(LX)]Br (X=1-4, 6, 7: compounds 5-10, respectively), have been prepared by reacting the appropriate ligand with [NEt4][Re(CO)3Br3] in methanol. The ligands and their rhenium complexes were obtained in good yields and characterized by common spectroscopic techniques including 1D and 2D NMR, HRMS, IR, cyclic voltammetry, UV, and luminescence spectroscopy and X-ray crystallography. The crystal structure of complex 6.0.5NaPF6 displays a facial geometry of the carbonyl ligands. The nitrogen donors of the tridentate ligand complete the distorted octahedral spheres of the complex. Crystal data: monoclinic, C2, a = 24.618(3) A, b = 11.4787(11) A, c = 15.5902(15) A, beta = 112.422(4) degrees , Z = 4, D(calc) = 1.562 g/cm3.     

Benzene C-H activation by platinum(II) complexes of bis(2-diphenylphosphinophenyl)amide

The amido diphosphine complexes [PNP]PtMe and [PNP]PtOTf, where [PNP]- is bis(2-diphenylphosphinophenyl)amide, effectively activate the benzene C-H bond in the presence of an appropriate Lewis acid or base, leading to the formation of [PNP]PtPh quantitatively.     

Gas-phase anionic complexes of alkali metal ions and peptides: Structure and collision activated decompositions

Alkali metal ions and anionic peptides can be desorbed into the gas phase to give metal-bound peptides and bis(peptide) complexes bearing a ? 1 charge. Although amide nitrogens of peptide bonds are deprotonated in the gas phase by alkali metal ions, this reacion does not occur in solution. Metal-bound dipeptide anions exist as a single structure, whereas those of tripeptide complexes have three structures as revealed by tandem mass spectrometric studies. Ions of bis(peptide) complexes of alkali metals decompose upon collisional activation principally to form deprotonated peptides, in contrast to bis(peptide) complexes of alkaline earth metal ions, which undergo elimination of a neutral peptide.     

Synthesis and Properties of Bis(2,5-dimethylpyrrolo[3,4-d])tetrathiafulvalenes, a Class of Annelated Tetrathiafulvalene Derivatives with Excellent Electron Donor Properties

The synthesis of the first derivatives of bis(pyrrolo[3,4-d])tetrathiafulvalene has been studied in detail. Starting from the readily available 2,5-dimethylpyrrole (11) and N-phenyl-2,5-dimethylpyrrole, bis(2,5-dimethylpyrrolo[3,4-d])tetrathiafulvalene (8) and the N,N'-disubstituted derivatives 6, 7, 9, and 10 were prepared in good yields by practical procedures. In contrast to the other types of aromatic annelated tetrathiafulvalenes (TTFs), which have appreciably higher oxidation potentials than TTF, the redox behavior of the pyrrolo tetrathiafulvalenes (TTFs) is very close to that of TTF itself. The potential of pyrrolotetrathiafulvalenes as a new series of organic metal building blocks is shown by the two-probe conductivities of the tetracyanoquinodimethane (TCNQ) complexes of the N-phenyl compound 7 and the N-methyl compound 9, which give higher values than TTF-TCNQ under similar conditions.     

Direct enolization chemistry of 7-azaindoline amides: A case study of bis(tetrahydrophosphole)-type ligands

7-Azaindoline amides are particularly useful in direct enolization chemistry due to their facilitated enolization in soft Lewis acid/Brønsted base cooperative catalysis. The Cu(I) complex of (R,R)-Ph-BPE, a bis(tetrahydrophosphole)-type chiral bisphosphine ligand, exhibits consistently high catalytic performance and stereoselectivity irrespective of the nature of the α-substituent of the amides. Unexpectedly, however, alkyl-substituted bis(tetrahydrophosphole)-type ligands have substantially inferior catalytic performance. Evaluation of the optimized structures of Cu(I)/amide and Cu(I)/enolate complexes provided clues to dissecting the diverted reaction outcomes.     

Recyclable and selective Lewis acid catalysts for transesterification and direct esterification in a fluorous biphase system: tin(IV) and hafnium(IV) bis(perfluorooctanesulfonyl)amide complexes

Tin(IV) and hafnium(IV) bis(perfluorooctanesulfonyl)amide complexes were shown to give excellent yield and selectivity for highly practical transesterification and direct esterification, respectively, with an equimolar ratio of the reactants in a fluorous biphase system. It was found that these metal complexes were completely recovered and reused in the immobilized fluorous phase without loss of their catalytic activities.     

Rare earth metal bis(amide) complexes bearing amidinate ancillary ligands: synthesis, characterization, and performance as catalyst precursors for cis-1,4 selective polymerization of isoprene

A family of rare earth metal bis(amide) complexes bearing monoanionic amidinate [RC(N-2,6-Me(2)C(6)H(3))(2)](-) (R = cyclohexyl (Cy), phenyl (Ph)) as ancillary ligands were synthesized and characterized. One-pot salt metathesis reaction of anhydrous LnCl(3) with one equivalent of amidinate lithium [RC(N-2,6-Me(2)C(6)H(3))(2)]Li, following the introduction of two equivalents of NaN(SiMe(3))(2) in THF at room temperature afforded the neutral and unsolvated mono(amidinate) rare earth metal bis(amide) complexes [RC(N-2,6-Me(2)C(6)H(3))(2)]Y[N(SiMe(3))(2)](2) (R = Cy (1); R = Ph (2)), and the "ate" mono(amidinate) rare earth metal bis(amide) complex [CyC(N-2,6-Me(2)C(6)H(3))(2)]Lu[N(SiMe(3))(2)](2)(μ-Cl)Li(THF)(3) (3) in 61-72% isolated yields. These complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray single crystal diffraction. Single crystal structural determination revealed that the central metal in complexes 1 and 2 adopts a distorted tetrahedral geometry, and in complex 3 forms a distorted trigonal bipyramidal geometry. In the presence of AlMe(3), and in combination with one equimolar amount of [Ph(3)C][B(C(6)F(5))(4)], complexes 1 and 2 showed high activity towards isoprene polymerization to give high molecular weight polyisoprene (M(n) > 10(4)) with good cis-1,4 selectivity (>90%).     

二胍基钛配合物的合成及其催化性能

胍上有三个具有给电子能力的氮原子,胍基负离子[(RN)2C(NR2)]-具有多种共振结构,可以多种方式与金属配位;同时它的空间位阻和电荷效应可以很容易通过氮原子上的取代基进行调控。近年来胍基作为辅助配体在主族和过渡金属配合物的合成中的应用引起了人们的广泛关注,而且发现一些胍基金属配合物显示出了不同于茂基金属配合物的独特的反应性质。但是有关胍基钛配合物的合成与反应性能方面的文献报道还很少。本文报道两个胍基钛的配合物的合成,并对它们的催化聚合活性作了初步研究。     

Synthesis and electronic properties of a pentafluoroethyl-derivatized nickel pincer complex

The synthesis of a bis(amino)amide nickel pincer complex bearing a perfluoroethyl ligand was effected by reaction of the corresponding nickel chloride complex with cesium fluoride and trimethyl(pentafluoroethyl)silane. Electrochemical experiments revealed that the oxidation of the LNi-C(2)F(5) complex occurs at the same potential as the LNi-Cl derivative, but reduction of the LNi-C(2)F(5) complex occurs at slightly more positive potentials. The similarity of the electrochemical data was corroborated by density functional theory (DFT), which predicts that the energies of the HOMOs (HOMO = highest occupied molecular orbital) and LUMOs (LUMO = lowest unoccupied molecular orbital) of the LNi-C(2)F(5) and LNi-Cl complexes are equal in magnitude. DFT also revealed that the HOMOs of the bis(amino)amide nickel pincer complexes are primarily ligand in character, while the LUMOs are predominantly metal in character, supporting redox-activity with this ligand.     

Bis(phosphonate)‐Building Blocks Modified with Fluorescent Dyes

Preparation of two benzylic bis(phosphonic acids) modified with primary amine or carboxylic acid groups on the benzene ring is described. These compounds were prepared and characterized in the form of both bis(phosphonate) tetraesters and corresponding free acids. The phosphonic acid esters are suitable for further derivation, mainly for conjugation through the amide bond. Mild conversion of the bis(phosphonate) esters to free acids using trimethylsilylbromide allowed to work with functional groups sensitive to conditions of acidic and/or alkaline hydrolysis. Three bis(phosphonate)‐containing fluorescent probes were prepared from the building blocks, utilizing amide and sulfamide bonds as spacers. Dyes containing the dansyl group, rhodamine B, and fluorescein were chosen due to their common availability and low cost. The prepared bis(phosphonate)‐building blocks and modified fluorescent probes were used for adsorption studies with hydroxyapatite, the commonly used model of bone tissue. Sorption ability of the prepared bis(phosphonate) compounds was similar to that of pamidronate.     

Dinuclear zinc(II) double-helicates of homochirally substituted bis(dipyrromethene)s

[structure: see text] A series of bis(dipyrromethene)s substituted with aromatic amide and aliphatic ester homochiral auxiliaries have been prepared and complexed with zinc(II) ions to form double-helical dinuclear complexes. CD analysis of the crude complexes revealed that the helicates formed in a diastereoselective manner. The helicates have been resolved into their constituent M and P helices by HPLC, indicating that the helical sense of the complexes is stable to racemization.     

π-cyclohexadienyliron complexes bearing exocyclic double bonds

Sodium amide and sodium bis(trimethylsilyl)amide abstract α protons from certain π-arene-π-cyclopentadienylixon(II) cations to produce neutral π-cyclohexadienyl complexes bearing exocyclic CC or CN bonds. Also reported are the first examples of π-arene-π-cyclopentadienyliron(II) cations of aromatic amines synthesized by direct reaction of the amine, ferrocene and AlCl₃.     

Ruffling-induced chirality: synthesis, metalation, and optical resolution of highly nonplanar, cyclic, benzimidazole-based ligands

Expedient five-step syntheses of a cyclic bis(benzimidazole)-based amide 5 and two sterically more hindered analogues 23-24 have been developed. These amides are chiral due to the inherent ruffling of the macrocyclic plane. Racemization of the optical antipodes of these compounds has been studied using dynamic chiral stationary phase HPLC. These studies reveal that, while the parent amide 5 racemizes rapidly, for the sterically more hindered amides 23-24, the rate of racemization is significantly reduced. Bis(benzimidazole)-based amides 5 and 23-24 form stable Ni(II) complexes 25-27, respectively. Like their parent ligands, complexes 25-27 are chiral due to their highly ruffled geometry. Studies of these complexes by chiral stationary phase HPLC reveal that metalation leads to a much lower rate of racemization. Incorporation of a strap can slow racemization even further. A series of strapped cyclic amides 54-57, along with their corresponding dimers 58-61, have been prepared. The rate of racemization for amides 54-57 is strongly dependent on the length of the strap. X-ray single-crystal structure analysis of the Ni(II) complex of strapped amide 54 reveals that the bis(benzimidazole) core retains its highly ruffled shape, with the two phenyl rings of the macrocycle located anti to the strap. Chiral separation of strapped ligands 54-57 and their corresponding Ni(II) complexes is shown to be facile by chiral stationary phase HPLC.     

Stereochemically stable double-helicate dinuclear complexes of bis(dipyrromethene)s: a chiroptical study

Helical zinc(II) complexes of bis(dipyrromethene)s bearing homochiral amide substituents were synthesized. Analysis of the products by chiral HPLC showed two diastereomeric major products and showed that dipyrromethene double-nuclear helicates are stereochemically stable and do not interconvert. Circular dichroism (CD) studies showed that the complexation reactions had proceeded with modest diastereomeric excesses. Analysis of an analogous symmetric zinc(II) bis(dipyrromethene) lacking homochiral substituents that could act as chromophores discounted induced CD by the chiral auxiliaries.     

Aufbau von Erdalkalimetall‐Arsen‐Käfigstrukturen durch die Metallierung von Triisopropylsilylarsan mit Calcium‐, Strontiumund Barium‐bis[bis(trimethylsilyl)amid] in Tetrahydrofuran

Formation of Alkaline Earth Metal‐Arsenic Cages via the Metalation of Triisopropylsilylarsane with Calcium, Strontium, and Barium Bis[bis(trimethylsilyl)amide] in Tetrahydrofuran The metalation of triisopropylsilylarsane with the alkaline earth metal bis[bis(trimethylsilyl)amides] in tetrahydrofuran yields the THF complexes of calcium ( 1 ), strontium ( 2 ), and barium‐bis(triisopropylsilylarsanide) ( 3 ). Dissolving of these compounds in toluene leads to the elimination of triisopropylsilylarsane and the formation of the THF complexes of tetraalkaline earth metal hexakis(triisopropylsilylarsanide)‐triisopropylsilylarsanediide of calcium ( 4 ), strontium ( 5 ), and barium ( 6 ), respectively. The central polyhedron of compound 4 can be described as two trigonal bipyramids with the metal atoms in apical positions, connected via the arsanediide substituent as a common corner. The central moieties of the compounds 5 and 6 consist of four trigonal bipyramids which are connected by common edges as well as common faces.     

Ytterbium amides of linked bis(amidinate): synthesis, molecular structures, and reactivity for the polymerization of L-lactide

The steric effect of an amide group on the synthesis, molecular structures and reactivity of ytterbium amides supported by linked bis(amidinate) L (L = [Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3]) is reported. Reaction of LYbCl(THF)2 with equimolar NaNHAr' and NaNHAr (Ar' = 2,6-Me2C6H3; Ar = 2,6-iPr2C6H3), respectively, gave the corresponding monometallic amide complexes LYb(NHAr')(DME) 1 and LYb(NHAr)(DME) 2, in which the linked bis(amidinate) is coordinated to the metal center as a chelating ligand. The similar reaction with NaN(SiMe3)2 afforded a bimetallic amide complex (TMS)2NYb(L)2YbN(TMS)2 3 formed through the rearrangement reaction of L induced by the bulky N(SiMe3)2 group. In complex 3 the two linked bis(amidinate)s act as bridging ancillary ligands to link two YbN(TMS)2 species in one molecule. The definite molecular structures of 1-3 were provided by single-crystal X-ray analysis. Complexes 1-3 are efficient initiators for the polymerization of L-lactide, and their catalytic performance is highly dependent on the amido groups and molecular structures. The polymerizations initiated by complexes 1 and 2 proceeded in a living fashion as evidenced by the narrow polydispersities of the resulting polymers, together with the linear natures of the number average molecular weight versus conversion plots, while the polymerization system with complex 3 provided polymers with rather broad molecular weight distributions.     

Synthesis and properties of novel aromatic poly(ester amide)s derived from 1,5-bis(4-aminobenzoyloxy)naphthalene and aromatic dicarboxylic acids

A new naphthalene ring-containing bis(ester amine), 1,5-bis(4-aminobenzoyloxy)naphthalene (2), was synthesized from the condensation of 1,5-dihydroxynaphthalene with 4-nitrobenzoyl chloride followed by catalytic hydrogenation. A series of naphthalene-containing poly(ester amide)s having inherent viscosities of 0.34-0.82 dl/g were prepared by the direct phosphorylation polyamidation from bis(ester amine) 2 with various aromatic dicarboxylic acids. The poly(ester amide)s derived from terephthalic acid, 4,4′-biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-oxydibenzoic acid were semicrystalline and showed less solubility. The other polymers were amorphous and readily soluble in polar organic solvents and gave flexible and tough films via solution casting. Except for four examples, the poly(ester amide)s displayed discernible glass transitions between 190 and 227 °C by differential scanning calorimetry. These poly(ester amide)s did not show significant decomposition below 400 °C in nitrogen or air.