Highly active new α-diimine nickel catalyst for the polymerization of α-olefins

A new silylated α-diimine ligand, bis[N,N′-(4-tert-butyl-diphenylsilyl-2,6-diisopropylphenyl)imino]acenaphthene 3, and its corresponding Ni(II) complex, {bis[N,N′-(4-tert-butyl-diphenylsilyl-2,6-diisopropylphenyl)imino]acenaphthene}dibromonickel 4, have been synthesized and characterized. The crystal structures of 3 and 4 were determined by X-ray crystallography. In the solid state, complex 4 is a dimer with two bridging Br ligands linking the two nickel centers, which have square pyramidal geometries. Complex 4, activated either by diethylaluminum chloride (DEAC) or methylaluminoxane (MAO) produces very active catalyst systems for the polymerization of ethylene and moderately active for the polymerization of propylene. The activity values are in the order of magnitude of 10⁷ g PE (mol Ni [E] h)⁻¹ for the polymerization of ethylene and of 10⁵ g PP (mol Ni [P] h)⁻¹ for the polymerization of propylene. NMR analysis shows that branched polyethylenes (PE) are obtained at room or higher temperatures and almost linear PE is obtained at 0 °C with 4/DEAC.     

{Bis[N,N′-(2-alkyl-6-para-methylphenyl)phenyl)imino]acenaphthene}dibromonickel catalysts bearing bulky methylphenyl groups: synthesis,characterization, crystal structures and application in catalytic polymerization of ethylene and styrene

Two new Ni(II) complexes containing methylphenyl groups, {bis[N,N′-(2,6-dimethyl-4-p-methylphenylphenyl)imino]acenaphthene}dibromonickel 4a and {bis[N,N′-(2-ethyl-4,6-di(p-methylphenyl)phenyl)imino]acenaphthene}dibromonickel 4b, were synthesized and characterized. The molecular structures of both complexes were determined by single-crystal X-ray diffraction. Both complexes have pseudo-tetrahedral geometry about the nickel center, showing pseudo C _2v and C ₂ molecular symmetry, respectively. Complex 4c, {bis[N,N′-(2,4,6-trimethylphenyl)imino]acenaphthene}dibromonickel, was also synthesized for comparison. These complexes were tested as catalysts for the polymerization of ethylene and styrene under mild conditions using diethylaluminum chloride. The precatalyst 4b bearing one ortho-ethyl group and two bulky p-methylphenyl groups in the ortho- and para-aryl position of the ligand, displayed highly catalytic activity for the polymerization of ethylene [4.70 × 10⁶ g PE/(mol Ni h bar)], and produced branched polyethylene (76 methyl, 8 ethyl, 5 propyl and 22 butyl or longer branches/1,000 C at 60 °C). Interestingly, complex 4b also displays high catalytic activity [5.46 × 10⁵ g polystyrene/(mol Ni·h)] for styrene polymerization and produces nearly atactic polystyrene at 70 °C (stereo-triad distributions: rr, 39.9 %; mr, 30.4 %; mm, 29.8 %; stereo-diad distributions: r, 55.1 %; m, 44.9 %).     

New octahedral bis-α-diimine nickel(II) complexes containing chloro-substituted aryl groups: Synthesis, characterization and testing as ethylene polymerisation catalysts

Three new 20-electron bis-α-diimine nickel (II) complexes containing chloro-substituted ligands, bis{bis[N,N′-(3-chloro-2-methylphenyl)imino]-1,2-dimethylethane}dibromonickel 2a, bis{bis[N,N′-(3-chloro-2,6-dimethylphenyl)imino]-1,2-dimethylethane}dibromonickel 2b and bis{bis[N,N′-(4-chloro-2,6-dimethyl-phenyl)imino]-1,2-dimethylethane}dibromonickel 2c, were synthesized and characterized. The molecular structure of complex 2a was determined by X-ray crystallography. In the solid state, complex 2a has a pseudo-octahedral geometry about the nickel center, containing two α-diimine ligands in the pseudo-equatorial plane and two trans bromide ligands occupying the axial positions. These complexes, activated by diethylaluminum chloride (DEAC) were tested in the polymerization of ethylene under mild conditions. NMR analysis shows that highly branched polyethylenes are obtained using these bis-α-diimine nickel(II) complexes containing electron-withdrawing Cl groups in the aryl groups (e.g. 84 branches/1000 C, at 20 °C). The catalytic activity, polymer molecular weight and polymer degree of branching were significantly affected by the number of methyl substituents in the ortho-aryl position and the chlorine substituent position in the aryl rings of the coordinated α-diimine ligands.     

Synthesis and crystal structures of dinuclear zinc complexes with the 1,3-bis(2-pyridylmethyl)acetamidinato ligand

The reaction of an equimolar mixture of N,N′-bis(2-pyridylmethyl)acetamidine (1) and di(tert-butyl)phosphane with dimethylzinc yields dinuclear bis(methylzinc) bis(2-pyridylmethyl)acetamidinate di(tert-butyl)phosphanide (2). A similar protocol allows the preparation of bis(alkylzinc) bis(2-pyridylmethyl)acetamidinate tert-butylamide [zinc-bound methyl (3) or trimethylsilylmethyl group (4)]. The reactions of 3 and 4 with diphenylsilane lead to the formation of insoluble dimeric bis(alkylzinc) N,N′-bis(2-pyridylmethyl)acetamidinate hydrides [zinc-bound methyl (5) or trimethylsilylmethyl group (6)]. These zinc hydrides decompose once dissolved under formation of elemental zinc thus hampering catalytic applications. Molecular structures of [(1)ZnCl₂] as well as of the zinc complexes 2 to 6 are discussed.     

Polymerization of methyl methacrylate in the presence of iron(II) complex with tetradentate nitrogen ligands under conditions of atom transfer radical polymerization

Four tetradentate nitrogen ligands, viz. dichloro{[N,N^′-diphenyl-N,N^′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (1), {[N,N^′-dioctyl-N,N^′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (2), {[N,N^′-dibenzyl-N,N^′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (3), and (1R,2R)-(−)-N,N^′-di(quinoline-2-methyl) di-iminocyclohexane (4), were investigated as novel complexing ligands in iron-mediated atom transfer radical polymerization (ATRP) of methyl methacrylate where ethyl-2-bromoisobutyrate was the initiator in o-xylene at 90 °C. With ligands 1 and 2 the experimental molecular weights increased gradually with monomer conversion. High to moderate conversions (87%, 43%) were obtained in relatively short times (90 min for 1 and 30 min for 2), which indicates an efficient catalyst system, but after these times a dramatic increase in viscosity of the polymerization medium led to loss of control. It is noteworthy that polymerization proceeded in a controlled manner with ligand 1, which has two rather bulky substituents on the N-atom. Such bulky ligands did not work for a copper-based system, where they led to excessive terminations or other side reactions. When the bulkiness of the substituents was significantly increased, as in ligand 3, a decrease in polymerization rate and loss of control occurred. Ligand 4 was less efficient than the other ligands, probably because the ethylene bridge was replaced by cyclohexane bridge.     

Synthesis and structures of some sterically hindered zinc complexes containing 6-membered and rings

Zinc β-diketiminates containing the N,N′-chelating ligand [{N(SiMe₃)C(Ph)}₂CH]⁻ (≡LL⁻) [Zn(LL)(μ-Cl)]₂ (1) and [ZnEt(LL)thf] (2) were prepared from 2ZnCl₂ + [Li(LL)]₂ and ZnEt₂ + H(LL), respectively. The new phenols 2-(N-R-piperazinyl-N′-methyl)-4,6-di-tert-butylphenol [R = Ph (3a), Me (3b)] and 2,2-[μ-N,N′-piperazindiyldimethyl]-bis(4,6-di-tert-butylphenol) (4) were obtained from 2,4-tBu₂C₆H₃OH, (CH₂O)_n and the appropriate piperazine. Zinc phenoxides 5, 7 and 8 were derived from 2ZnEt₂ with 2(3a), 2(3b) and 4, respectively. Controlled methanolysis of 5 furnished the bis(phenoxo)zinc compound Zn[OC₆H₂tBu₂-2,4-{CH₂N(CH₂CH₂)₂NPh}-6]₂ (6). The X-ray structures of the crystalline zinc compounds 1, 2, 5, 6, 7 and 8, are presented; each of 5-8 contains two six-membered rings. The centrosymmetric molecule 1 has a rhomboidal (ZnCl)₂ core with exceptionally different Zn-Cl and Zn-Cl′ bond lengths of 2.248(1) and 2.509(1) Å, respectively. None of 1, 2 or 5-8 was an effective catalyst for the copolymerisation of an oxirane and CO₂.     

Synthesis and structural characterization of η-allyl(α-diimine)nickel(II) complexes bearing trimethylsilyl groups

A set of isomeric para- and meta-trimethylsilylphenyl ortho-substituted N,N-phenyl α-diimine ligands [(Ar-NC(Me)-(Me)CN-Ar) Ar=2,6-di(4-trimethylsilylphenyl)phenyl (16); Ar=2,6-di(3-trimethylsilylphenyl)phenyl (17)] have been synthesized through a two-step procedure. The palladium-catalysed cross-coupling reaction between 2,6-dibromophenylamine (7) and 4-trimethylsilylphenylboronic acid (8), 3-trimethylsilylphenylboronic acid (9) was used to prepare 4,4^′-bis(trimethylsilyl)-[1,1^′;3^′,1″]terphenyl-2^′-ylamine (10) and 3,3^′-bis(trimethylsilyl)-[1,1^′;3^′,1″]terphenyl-2^′-ylamine (11). The di-1-adamantylphosphine oxide Ad₂P(O)H (13) and di-tert-butyl-trimethylsilylanylmethylphosphine tert-Bu₂P-CH₂-SiMe₃ (14) were used for the first time as ligands for the Suzuki coupling. The condensation of 2,2,3,3-tetramethoxybutane (15) with anilines 10 and 11 afforded α-diimines 16 and 17. The reaction of π-allylnickel chloride dimer (18), α-diimines (16), (17) and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BAF) (19) or silver hexafluoroantimonate (20) led to two sets of isomeric complexes [η³-allyl(Ar-NC(Me)-(Me)CN-Ar)Ni]⁺ X⁻, [Ar=2,6-di(4-trimethylsilylphenyl)phenyl, X=BAF (3), X=SbF₆ (4); Ar=2,6-di(3-trimethylsilylphenyl)phenyl, X=BAF (5), X=SbF₆ (6)]. The steric repulsion of closely positioned trimethylsilyl groups in 4 caused the distortion of the nickel square planar coordination by 17.6° according to X-ray analysis.     

Synthesis, crystal structure and antibacterial activity of a group of mononuclear manganese(II) Schiff base complexes

Five mononuclear complexes of manganese(II) of a group of the general formula, [MnL(NCS)₂] where the Schiff base L = N,N′-bis[(pyridin-2-yl)ethylidene]ethane-1,2-diamine (L¹), (1); N,N′-bis[(pyridin-2-yl)benzylidene]ethane-1,2-diamine (L²), (2); N,N′-bis[(pyridin-2-yl)methylidene]propane-1,2-diamine (L³), (3); N,N′-bis[(pyridin-2-yl)ethylidene]propane-1,2-diamine (L⁴), (4) and N,N′-bis[(pyridin-2-yl)benzylidene]propane-1,2-diamine (L⁵), (5) have been prepared. The syntheses have been achieved by reacting manganese chloride with the corresponding tetradentate Schiff bases in presence of thiocyanate in the molar ratio of 1:1:2. The complexes have been characterized by IR spectroscopy, elemental analysis and other physicochemical studies, including crystal structure determination of 1, 2 and 4. Structural studies reveal that the complexes 1, 2 and 4 adopt highly distorted octahedral geometry. The antibacterial activity of all the complexes and their respective Schiff bases has been tested against Gram(+) and Gram(−) bacteria.     

From N,N-diphenyl-N-naphtho[2,1-b]thieno[2,3-b:3′,2′-d]dithiophene-5-yl-amine to propeller-shaped N,N,N-tri(naphtho[2,1-b]thieno[2,3-b:3′,2′-d]dithiophene-5-yl)-amine: syntheses and structures

Three unique propeller-shaped helicenyl amines compounds: N,N-diphenyl-N-naphtho[2,1-b]thieno[2,3-b:3′,2′-d]dithiophene-5-yl-amine (1), N-phenyl-N,N-di(naphtho[2,1-b]thieno[2,3-b:3′,2′-d]dithiophene-5-yl)amine (2), and N,N,N-tri(naphtho[2,1-b]thieno[2,3-b:3′,2′-d]dithiophene-5-yl)amine (3) were efficiently synthesized by Wittig reaction and oxidative photocyclization. The crystal structures of 1, 2 and molecular configuration optimization (DFT-B3LYP/6-31+G(d)) of 3 reveal that the steric hindrance from the moiety of trithia[5]helicene effectively forces the nitrogen atom and the three bonded carbon atoms to coplanar and the interplanar angles of the facing terminal thiophene ring and benzene ring becoming larger when the helical arm increased from 1 to 3. Electrochemical properties and UV–vis absorption behaviors of 1, 2, 3 were primarily determined by the moiety of trithia[5]helicene.     

Magnesium complexes based on an amido-bis(pyrazolyl) ligand: Synthesis,crystal structures,and use in lactide polymerization

The coordination chemistry of the tridentate N,N,N pro-ligand bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine (1, LH) with dialkylmagnesium and monoalkyl magnesium halides has been studied. Reaction of 2 equiv of 1 with Mg(nBu)₂ gave bis(amido) complex [L]₂Mg (3), which is monomeric in the solid state. Alkane elimination reactions from iPrMgCl and MeMgI with 1 equiv of 1 afforded the corresponding halide complexes {[L]MgCl}₂ (4) and {[L]MgI}₂ (5), which both feature dimeric structures in the solid state, with a chelating and spanned coordination mode of the tridentate ligand, respectively. Additionally, bis(amido) complex 3 was shown to be active for the ring-opening polymerization of racemic lactide at room temperature to yield atactic polylactides with high initiation efficiencies and relatively narrow polydispersities (M_w/M_n = 1.28–1.34).     

Preparation and structures of 6- and 7-coordinate salen-type zirconium complexes and their catalytic properties for oligomerization of ethylene

A series of salen-type zirconium complexes of the general formula LZrCl₂ (L = N,N′-ethylenebis(salicylideneiminate), 3a; N,N′-ethylenebis(3,5-di-tert-butylsalicylideneiminate), 3b; N,N′-ethylenebis(5-methoxysalicylideneiminate), 3c; N,N′-ethylenebis(5-chlorosalicylideneiminate), 3d; N,N′-ethylenebis(5-nitrosalicylideneiminate), 3e; N,N′-o-phenylenebis(salicylideneiminate), 4a; N,N′-o-phenylenebis(3,5-di-tert-butylsalicylideneiminate), 4b; N,N′-o-phenylenebis(5-methoxysalicylideneiminate), 4c; N,N′-o-phenylenebis(5-chloro-salicylideneiminate), 4d) were prepared. The crystal structures of 6- and 7-coordinate zirconium complexes 4b and [4b · OCMe₂] were determined by X-ray crystallography, which reveals that a salen-type zirconium complex possesses a labile coordination site on the Zr center with a relatively stable framework and that the coordination and the dissociation of O-donor molecules occur readily at this site. The catalytic properties of 3(a-e) and 4(a-d) were studied for ethylene oligomerization in combination with Et₂AlCl as co-catalyst. Complex 3c featuring a methoxy-substituted salen ligand displayed higher activity than its analogous precursors having chloro and nitro groups as substituents. The catalytic reactions by 3(a-e) and 4(a-d) gave C₄-C₁₀ olefins and low-carbon linear α-olefins in good selectivity.     

Synthesis and structural characterization of 1′-(diphenylphosphino)ferrocene-1-carboxamide, its corresponding hydrazide, some heterocycles derived from the hydrazide and palladium(II) complexes with these functional phosphinoferrocene ligands

Two polar phosphinoferrocene ligands, 1′-(diphenylphosphino)ferrocene-1-carboxamide (1) and 1′-(diphenylphosphino)ferrocene-1-carbohydrazide (2), were synthesized in good yields from 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) via the reactive benzotriazole derivative, 1-[1′-(diphenylphosphino)ferrocene-1-carbonyl]-1H-1,2,3-benzotriazole (3). Alternatively, the hydrazide was prepared by the conventional reaction of methyl 1′-(diphenylphosphino)ferrocene-1-carboxylate with hydrazine hydrate, and was further converted via standard condensation reactions to three phosphinoferrocene heterocycles, viz 2-[1′-(diphenylphosphino)ferrocen-1-yl]-1,3,4-oxadiazole (4), 1-[1′-(diphenylphosphino)ferrocen-1-carbonyl]-3,5-dimethyl-1,2-pyrazole (5), and 1-[1′-(diphenylphosphino)ferrocene-1-carboxamido]-3,5-dimethylpyrrole (6). Compounds 1 and 2 react with [PdCl₂(cod)] (cod = η²:η²-cycloocta-1,5-diene) to afford the respective bis-phosphine complexes trans-[PdCl₂(L-κP)₂] (7, L = 1; 8, L = 2). The dimeric precursor [(L^NC)PdCl]₂ (L^NC = 2-[(dimethylamino-κN)methyl]phenyl-κC¹) is cleaved with 1 to give the neutral phosphine complex [(L^NC)PdCl(1-κP)] (9), which is readily transformed into a ionic bis-chelate complex [(L^NC)PdCl(1-κ²O,P)][SbF₆] (10) upon removal of the chloride ligand with Ag[SbF₆]. Pyrazole 5 behaves similarly affording the related complexes [(L^NC)PdCl(5-κP)] (12) and [(L^NC)PdCl(5-κ²O,P)][SbF₆] (13), in which the ferrocene ligand coordinates as a simple phosphine and an O,P-chelate respectively, while oxadiazole 4 affords the phosphine complex [(L^NC)PdCl(4-κP)] (11) and a P,N-chelate [(L^NC)PdCl(4-κ²N³,P)][SbF₆] (14) under similar conditions. All compounds were characterized by elemental analysis and spectroscopic methods (multinuclear NMR, IR and MS). The solid-state structures of 1⋅½AcOEt, 2, 7⋅3CH₃CN, 8⋅2CHCl₃, 9⋅½CH₂Cl₂⋅0.375C₆H₁₄, 10, and 14 were determined by single-crystal X-ray crystallography.     

Synthesis of novel piperazine based building blocks: 3,7,9-triazabicyclo[3.3.1]nonane, 3,6,8-triazabicyclo[3.2.2]nonane, 3-oxa-7,9-diazabicyclo[3.3.1]nonane and 3-oxa-6,8-diazabicyclo[3.2.2]nonane

The preparation of four novel bridged piperazine building blocks is described: 3,7,9-triazabicyclo[3.3.1]nonane 1, 3-oxa-7,9-diazabicyclo[3.3.1]nonane 2, 3,6,8-triazabicyclo[3.2.2]nonane 3 and 3-oxa-6,8-diazabicyclo[3.2.2]nonane 4. The scaffold of 1 was synthesized from N,N′-dibromobenzenesulfonamide and ethyl acrylate. Compound 2 may be prepared from identical starting materials or alternatively from α,α′-diglycerol. Compounds 3 and 4 were identified as side products from possible aziridinium intermediates.     

Novel titanocene anti-cancer drugs derived from fulvenes and titanium dichloride

Starting from 6-(p−N,N-dimethylanilinyl)fulvene (1a) or 6-(pentamethylphenyl)fulvene (1b) [1,2-di(cyclopentadienyl)-1,2-di(p−N,N-dimethylaminophenyl)ethanediyl] titanium dichloride (2a) and [1,2-di(cyclopentadienyl)-1,2-bis(pentamethylphenyl)ethanediyl] titanium dichloride (2b) and their corresponding dithiocyanato complexes (3a, 3b) were synthesized. Titanocene 2b did not show a cytotoxic effect, but when 2a was tested against pig kidney carcinoma cells (LLC-PK) or human ovarian carcinoma cells (A2780/cp70) inhibitory concentrations (IC₅₀) of 2.7 × 10⁻⁴ and 1.9 ×  10⁻⁴ M, respectively, were observed.     

High-pressure NMR study of migratory CO-insertion in palladium-methyl complexes modified with Cs-symmetrical 1,4-diphosphines

Carbonylation of the palladium complexes [PdCH₃(P^∧P′)Cl] (P^∧P′ = 1a, 1b, 1c, 1d, 1e) and [PdCH₃(P^∧P′)(CH₃CN)](OTf) was investigated by means of high-pressure NMR with the determination of the half-life times t_1/2. The results were rationalized on the basis of the electronic properties of the diphosphines and the nature of the solvento ligand in the first coordination sphere. The crystal structures of the complexes [Pd(1b)Cl₂] and [Pd(1b)(H₂O)₂](OTf)₂ are described (1b = 1-(diphenylphosphinomethyl)-2-[bis(3- trifluoromethylphenyl)phosphinomethyl]benzene).     

Synthesis of new condensed nitrogen heterocyclic systems

A cotarnine alkaloid-based synthesis was developed for new heptacyclic condensed diisoquinolines via the double intramolecular pseudosalt bis[1,3]dioxolo[4,5-g;4′,5′-g′][1,3,4]oxadiazolo[2,3-a;5,4-a′]diisoquinoline 6. Substitution of the central O atom in 6 by C, S, or N nucleophiles afforded the first representatives of the new ring systems bis[1,3]dioxolo[4,5-g:4,5-g′]pyrazolo[3,2-a:5,1-a′]diisoquinoline (7a-d), bis[1,3]dioxolo[4,5-g:4,5-g′][1,3,4]thiadiazolo[2,3-a:5,4-a′]diisoquinoline (8), and bis[1,3]dioxolo[4,5-g:4,5-g′][1,2,4]triazolo[3,2-a:5,1-a′]diisoquinoline (9a-d) under simple reaction conditions.     

Synthesis, characterization, and spectrophotometric studies of novel fluorescent arachno decaborane and nonaborane clusters containing aza-distyrylbenzene derivatives

Two aza-analogues of distyrylbenzene namely: 1,4-bis[β-(4-quinolyl)vinyl]benzene (PhQ) and 1,4-bis[β-(4-pyridyl)vinyl]benzene (PhPy) containing arachno-decaborane or arachno-nonaborane clusters have been isolated: 6,9-(PhQ)₂-arachno-B₁₀H₁₂ (1), N,N′-bis[9-Me₂S-arachno-B₁₀H₁₂-6-yl]PhQ (2), 6,9-(PhPy)₂-arachno-B₁₀H₁₂ (3), N,N′-bis[(9-Me₂S)-arachno-B₁₀H₁₂-6-yl]PhPy (4), N,N′-bis[arachno-B₉H₁₃-4-yl]PhQ (5), 4-PhQ-arachno-B₉H₁₃ (6), N,N′-bis[arachno-B₉H₁₃-4-yl]PhPy (7), and 4-PhPy-arachno-B₉H₁₃ (8). These boronated compounds were easily prepared from the displacement reactions of weaker ligand (SMe₂) of bis (dimethyl sulfide) arachno-decaborane(14) {6,9-(Me)₂SB₁₀H₁₂}or dimethyl sulfide-arachno-nonaborane {4-(Me)₂SB₉H₁₃} by the stronger bidentate ligands of PhQ or PhPy in ratio (1:2). The electronic interaction between decaborane or nonaborane arachno-type unit and the bonded pyridine units has been investigated by UV-Vis spectroscopy and by AM1 molecular orbital calculations. The resulting compounds undergo trans-cis photoisomerization upon excitation. The connection of boron clusters to PhQ and PhPy led to enhancing of the photoreactivity and decreasing of the fluorescence quantum yield of the products.     

Application of the aza-Wittig reaction to the synthesis of pyrazinothienotriazolopyrimidinones: a new tetracyclic ring system

A simple one-pot and efficient method is described for the synthesis of pyrazinothienopyrimidines 6 by domino processes involving aza-Wittig/intermolecular nucleophilic addition/intramolecular cyclization. A tandem aza-Wittig reaction of phosphazenes 7, derived from 6, with heterocumulenes (isocyanates, carbon disulfide or carbon dioxide) generates the pyrazinothienotriazolopyrimidinones 9, 11 and 12, respectively. Pyrazino[2′,3′:4,5]thieno[3,2-d]-1,2,4-triazolo[1,5-a]pyrimidin-4(3H)-ones 15 and bis(pyrazinothienotriazolopyrimidinones) 17 were synthesized by the intermolecular aza-Wittig reaction of phosphazenes 7 with acyl chlorides or α,ω-dichlorides followed by heterocyclization via imidoyl chloride intermediate 16. Further S-alkylation of 11 and reaction of 6 with phosgeniminium chloride produce 2-alkylthio- and 2-N,N-dimethylaminopyrazinothienotriazolopyrimidinones 13 and 19, respectively.     

Syntheses and studies of flexible amide ligands: a toolkit for studying metallo-supramolecular assemblies for anion binding

The syntheses of seven flexible bidentate bis-pyridyl diamide and four monodentate pyridyl amide ligands containing central amide units are described. The bis-pyridyl ligands were prepared in one step from commercially available compounds in moderate to good yield. These compounds all possess external metal coordinating pyridyl groups and internal amide functionalities, with the potential to bind anions. Crystal structures of six of the bis-pyridyl diamide ligands are described. The four compounds with xylene cores N,N′-[1,3-phenylenebis(methylene)]bis-3-pyridinecarboxamide 1, N,N′-[1,3-phenylenebis(methylene)]bis-4-pyridinecarboxamide 2, N,N′-[1,4-phenylenebis(methylene)]bis-3-pyridinecarboxamide 3 and N,N′-[1,4-phenylenebis(methylene)]bis-4-pyridinecarboxamide 4 crystallize with extensive amide N-H?OC hydrogen bonding between the diamide compounds, giving rise to two and three dimensional hydrogen bonded networks. N,N′-Bis(3-pyridylmethyl)benzene-1,3-dicarboxamide 5, the only compound with the amide groups directly attached to a central benzene core, was not able to be crystallised. N,N′-2,6-Bis(3-pyridylmethyl)pyridine dicarboxamide 6 and N,N′-2,6-bis(4-pyridylmethyl)pyridine dicarboxamide 7 have a mismatch of hydrogen bond donor and acceptor regions preventing ready involvement of the amide NH groups in network formation. For comparison we also prepared compounds N,N′-2′-propyl-6-(3-pyridylmethyl)pyridine dicarboxamide 10 and N,N′-2′-propyl-6-(4-pyridylmethyl)pyridine dicarboxamide 11 with two amide groups but only the one external donor pyridyl moiety, and compounds N-6-[(3-pyridylmethylamino)carbonyl]-2-pyridinecarboxylic acid methyl ester 8 and N-6-[(4-pyridylmethylamino)carbonyl]-2-pyridinecarboxylic acid methyl ester 9, which have only the one amide.     

Synthesis and characterisation of six Fe(II or III), Co(II) or Zr(IV) complexes containing the ligand [CH(SiMe2R)P(Ph)2NSiMe3] (R = Me, NEt2) and of [Co{N(SiMe3)C(Ph)C(H)P(Ph)2NSiMe3}2]

The C,N-(trimethylsilyliminodiphenylphosphoranyl)silylmethylmetal complexes [Fe(L)₂] (3), [Co(L)₂] (4), [ZrCl₃(L)]·0.83CH₂Cl₂ (5), [Fe(L)₃] (6), [Fe(L′)₂] (7) and [Co(L′)₂] (8) have been prepared from the lithium compound Li[CH(SiMe₂R)P(Ph)₂NSiMe₃] [1a, (R = Me) {≡ Li(L)}; 1b, (R = NEt₂) {≡ Li(L′)}] and the appropriate metal chloride (or for 7, FeCl₃). From Li[N(SiMe₃)C(Ph)C(H)P(Ph)₂NSiMe₃] [≡ Li(L″)] (2), prepared in situ from Li(L) (1a) and PhCN, and CoCl₂ there was obtained bis(3-trimethylsilylimino- diphenylphosphoranyl-2-phenyl-N-trimethylsilyl-1-azaallyl-N,N′)cobalt(II) (9). These crystalline complexes 3-9 were characterised by their mass spectra, microanalyses, high spin magnetic moments (not 5) and for 5 multinuclear NMR solution spectra. The X-ray structure of 3 showed it to be a pseudotetrahedral bis(chelate), the iron atom at the spiro junction.