Fragmentation of pyrazolecarbaldehyde thio- and dithioacetals under electron impact and chemical ionization

The mass spectra of 1-substituted 3,5-dimethyl-1H-pyrazole-4-carbaldehyde bis(2-hydroxyethyl) dithioacetals and thioacetals were studied for the first time. The main fragmentation pathways of their molecular ions generated under electron impact and chemical ionization were similar. Primary decomposition of the molecular ions of bis(2-hydroxyethyl) dithioacetals involves elimination of 2-sulfanylethanol molecule with formation of the corresponding 1,3-oxathiolane radical cation. Fragmentation of the molecular ions [M]⁺ · and [M + H]⁺ derived from 2-(3,5-dimethyl-1H-pyrazol-4-yl)-1,4,6-oxadithiocanes includes cleavage of the eight-membered heteroring and elimination of C₄H₉OS ·. Substituents in the heteroring of pyrazolecarbaldehydes inhibit decomposition processes related to the aldehyde group.     

Cationic polymerization of dimethyl-1,3-butadienes

The cationic polymerizations of dimethyl-1,3-butadienes with various catalysts in methylene chloride and toluene have been investigated. The activity of catalysts decreased in the order WCl₆ > AcClO₄ > SnCl₄·TCA > BF₃OEt₂. The homopolymerization rate of dimethyl-1,3-butadienes with WCl₆, AcClO₄, and SnCl₄·TCA decreased in the order 1,3-dimethyl-1,3-butadiene > 2,3-dimethyl-1,3-butadiene > 1,2-dimethyl-1,3-butadiene > 2,4-hexadiene. The polymers prepared with WCl₆, SnCl₄.TCA, and BF₃OEt₂ were rubberlike polymers or white powders, whereas those prepared with AcClO₄ were oily oligomers. The 1,4-propagation increased in the order 1,2-dimethyl-1,3-butadiene < 1,3-dimethyl-1,3-butadiene < 2,3-dimethyl-1,3-butadiene < 2,4-hexadiene. This order may indicate that the steric effect of methyl group determine primarily the microstructure of the polymer. The relative reactivity of dimethyl-1,3-butadienes toward a styryl cation decreased in the order 1,3-dimethyl-1,3-butadiene > 1,2-dimethyl-1,3-butadiene > 2,3-dimethyl-1,3-butadiene > 2,4-hexadiene. This order may be explained in terms of the stability of the resulting allylic cation.     

Aminobutadienes. X. Polymerization and copolymerization of 2-phthalimidomethyl-1,3-butadiene

The polymerization and copolymerization of 2-phthalimidomethyl-1,3-butadiene were investigated. This monomer was easily polymerized by benzoyl peroxide catalyst in bulk or in solvent, and by γ-radiation in the solid state to give polymers having a softening point of 135–145°C. Although these resulting polymers did not give x-ray diffraction patterns, they showed crystalline patterns by electron diffraction. On the other hand, cationic polymerization with the use of boron trifluoride diethyl etherate in chloroform was attempted, but no formation of the polymer was observed. Also, this monomer was easily copolymerized with styrene in N,N-dimethylformamide. The monomer reactivity ratios and Alfrey-Price Q and e values calculated from the copolymerization data of this monomer (M₁) with styrene (M₂) were r₁ = 2.0 ± 0.13, r₂ = 0.15 ± 0.02, and Q₁ = 2.78, e₁ = 0.30.     

Homo-and copolymerization of propylene and ethylene in the presence of titanium dichloride complexes with dioxolane dicarboxylate and bis(difurylmethanephenoxyimine) ligands

The polymerization of propylene and ethylene and the copolymerization of these olefins with postmetallocene catalysts [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol] titanium(IV) dichloride and bis{N-(3,5-ditert-butylsalicylidene)-4-[bis(5-methyl-2-furyl)methyl]aniline}titanium( IV) dichloride have been studied. The polymerization of propylene and its copolymerization with ethylene have been carried out in a liquid monomer, while the polymerization of ethylene has been performed in toluene at the constant concentration of the monomer. Polymethylaluminoxane has been used as a cocatalyst. The activity of the catalysts in the polymerization of propylene and ethylene at 50°C is ～ 10 and ～45 kg PP/mol Ti h mol C₃H₆/l and 178.5 and 2700 kg PE/mol Ti h mol C₂H₄/l, respectively. It has been established that, in the copolymerization of propylene with ethylene, the active sites of both catalysts selectively polymerize ethylene. The resulting copolymers have a block structure (r ₁ r ₂= 4.6); as a result, the crystalline phase of polyethylene is formed in them. Polypropylene and propylene-ethylene copolymers are elastomeric materials. Polypropylene samples synthesized with [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]titanium(IV) dichloride demonstrate a high melting point (150–157°C) in combination with good elastic properties. Polyethylene is a linear polymer with the degree of crystallinity varying from 37 to 45% and a melting point of 133–134°C. The mechanical properties of the polymers and copolymers have been investigated.     

The reaction of trichlorosilyltetracarbonyliron hydride (HFe(CO)4SiCl3) with conjugated dienes

Isoprene, 1,3-butadiene and 2,3-dimethyl-1,3-butadiene react with HFe(CO)₄SiCl₃ by addition of the Fe---H function to the diene. Isoprene appears to add predominantly 1,4 and 2,3-dimethyl-1,3-butadiene appears to add 1,2, while 1,3-butadiene may add both ways. In the case of isoprene and 1,3-butadiene loss of CO from the addition compound gives a stable π-allyl- Fe(Co)₃SiCl₃ product. Either cis- or trans-1,3-pentadiene is reduced to pentene by HFe(CO)₄SiCl₃.     

Reactions of 3,5-dibromo-1-(thiiran-2-ylmethyl)-1,2,4-triazole with NH-azoles

Reactions of 3,5-dibromo-1-(thiiran-2-ylmethyl)-1,2,4-triazole with 3,5-dimethylpyrazole, 1,3-dimethyl-3,7-dihydropurine-2,6-dione, 3,5-dibromo-1,2,4-triazole, 2,4,5-tribromoimidazole, and 2-chlorobenzimidazole lead to the formation of 5-azolylmethyl-2-bromo-5,6-dihydrothiazolo[3,2-b]-1,2,4-triazoles. In the case of 8-bromo-1,3-dimethyl-3,7-dihydropurine-2,6-dione the intermediate thiolate anion undergoes cyclization into 7-[(3,5-dibromo-1,2,4-triazol-1-yl)methyl]-1,3-dimethyl-6,7-dihydrothiazolo[2,3-f]purine-2,4(1H,3H)-dione. The structure of reaction products depends on the relative rate of substitution of leaving groups in the reagents.     

Reactions of 1,2,4-triazole derivatives with a “model” thiirane

Reactions of 3-mono- and 3,5-disubstituted 1,2,4-triazoles with a “model” thiirane, 8-bromo-1,3-dimethyl-7-(thiiran-2-ylmethyl)-3,7-dihydro-1H-purine-2,6-diones proceed at the positions N¹ and N² of the triazole ring and yield 7-(5-R-3-R′-1,2,4-triazol-1-yl)methyl- and/or 7-(5-R′-3-R-1,2,4-triazol-1-yl)methyl-1,3-dimethyl-6,7-dihydro[1,3]thiazolo[2,3-f]-purine-2,4-(1H,3H)-diones. 3-Methylsulfonyl-1,2,4-triazole reacted regiospecifically at the position N¹ forming 1,3-dimethyl-7-[(3-methyl-sulfonyl-1,2,4-triazole-1-yl)-methyl]-6,7-dihydro[1,3]thiazolo-[2,3-f]purine-2,4(1H,3H)-dione.     

Synthesis of New 2-[(Substituted-pyrazol-1-yl)carbonyl]-thieno[2,3b]pyridine Derivatives Using 1,3-Diketones,Alkylethoxymethylenes and Ketene Dithioacetals

The reaction of 3-amino-4,6-dimethyl-2-thieno[2,3-b]pyridine carbohydrazide ( 1 ) with appropriate 1,3-diketones 2a-2d in glacial acetic acid afforded 3-amino-2-[(3,5-disubstituted-pyrazo)-1-yl)carbonyl]-4,6-dimethylthieno[2,3-b]pyridines 3a-3d. 3-Amino-2-[(5-amino-3,4-disubstituted-pyrazol-1-yl)carbonyl]-4,6-dimethylthieno[2,3-b]pyridines 5a-5h were also prepared by treatment of carbohydrazide 1 with appropriate alkylethoxymethylenes and ketene dithioacetals 4a-4h , respectively.     

Block copolymerization of allene derivatives with 1,3-butadiene by living coordination polymerization with π-allylnickel catalyst

The block copolymerization of allene derivatives (3A–3D) with 1,3-butadiene (2) by [(allyl)NiOCOCF₃]₂ (1) is described. For instance, the living coordination polymerization of phenylallene (3A, 50 equiv) starting from the living poly(2), which was prepared by the polymerization of 2 (160 equiv) by 1, successfully gave a block copolymer of 2 and 3A in high yield. The molecular weight of the block copolymer (4A) in gel permeation chromatography shifted clearly to the higher molecular weight region and kept a unimodal distribution (M_n = 17,400, M_w/M_n = 1.23) in comparison with that of the starting living poly(2) (M_n = 5,600, M_w/M_n = 1.67). The ratio of each segment and the molecular weight of the resulting copolymers could be controlled by the feed ratio of each monomer. The block copolymerization also proceeded successfully by the inverse order of the monomer feeding (i.e., the polymerization of 3A followed by that of 2) to obtain the corresponding block copolymers in high yields. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3916–3921, 1999     

The reduction and hydrolysis of some 7,7-diethylpyrazolo[1,2-a]-pyridazine-6,8(7H)dione derivatives

The chemistry of several of the Diels-Alder adducts formed by the reaction of 4,4-diethylpyrazoline-3,5-dione ( 1 ) with conjugated dienes was studied with respect to reduction (hydride and catalytic) and reaction with base. Reaction of the 2,3-dimethyl-1,3-butadiene adduct with lithium aluminum hydride followed by hydrogenation gave 1,3,5,6,7,8-hexahydro-cis-endo-6,7-dimethyl-2,2-diethylpyrazolo[1,2-a]pyridazine ( 11 ). Attempted conversion of this compound to 3,3-diethyl-cis-7,8-dimethyl-1,5-diazacyclononane ( 12 ) gave instead a compound which has been tentatively identified as N-(2,3-dimethyl-4-aminobutyl)-2-ethyl-2-methylbutanaldimine ( 14 ). Lithium aluminum hydride reduction of 4,4-diethylpyrazolidine-3,5-dione ( 22 ) or the adducts formed from 1 and cyclopentadiene or 1,3-cyclohexadiene gave good yields of 4,4-diethylpyrazolidine ( 21 ). This later reduction gave a new and efficient synthetic route to the pyrazolidine ring system. Lithium aluminum hydride reduction of 5,6,7,8-tetrahydro-5,8-ethano-2,2-diethylpyrazolo[1,2-a]pyridazine-1,3(2H)dione ( 26 ) followed by hydrogenolysis led to a high yield of 4,4-diethyl-2,6-diazabicyclo[5.2.2]undecane ( 28 ) which is the first reported example of this ring system. Reaction of several of the adducts with ethanolic potassium hydroxide resulted in the opening of the five-membered ring.     

Anionic polymerization initiators containing protected functional groups. II

An organolithium reagent substituted with a primary amine-protecting group [i.e.,? N(TMS)₂] has been prepared and used to polymerize 1,3-butadiene and isoprene. A method is described for converting the resulting? N(TMS)₂-containing polydienes into? NH₂-containing polymers. Both ? N(TMS)₂- and ? NH₂-terminated polydienes have been characterized with regard to microstructure, M _n, and M _w/M _n data, as well as qualitative and quantitative end-group analyses. The described preparative procedures represent a convenient route to the elusive primary amine-terminated polydienes.     

Influence of Coordination Geometry on the Ring Opening of Benzoxazine: Oxidovanadium(V), Dioxidomolybdenum(VI) and Dioxidotungsten(VI) Complexes of Benzoxazine Based Ligands and their Bio Inspired Catalytic Applications

Mono benzoxazine appended N-capped amino bis(disubstitutedphenol) ligands [ II ( a–c )] upon reaction with V^VO(OEt)₃ in a 1 : 1 molar ratio in EtOH/MeOH give [{V^VO}en(3,5-dtbb)₃] ( 1 ), [{V^VO}en(3-tb,5-mb)₃] ( 2 ) and [{V^VO}en(3,5-dmb)₃] ( 3 ). During the reaction, the benzoxazine ring opens with the loss of methylene group and the newly formed ligands, N,N-bis(2-hydroxy-3,5-disubstitutedbenzyl)-N’-2-hydroxy-3,5-disubstituted benzyledene-1,2-diaminoethane [ III ( a–c )], behave as tribasic pentadentate in these complexes. Under similar conditions, when [M^VIO₂(acac)₂] (M=Mo or W; Hacac=acetylacetone) reacts with II ( a–c ), these ligands retain their identity and form cis-[M^VIO₂] complexes, [{Mo^VIO₂}{en(3,5-dtbb)₂(6,8-dtbbenzox)}] ( 4 ), [{Mo^VIO₂}{en(3-tb,5-mb)₂(6-tb,8-mbbenzox)}] ( 5 ) and [{Mo^VIO₂}{en(3,5-dmb)₂(6,8-dmbenzox)}] ( 6 ), [{W^VIO₂}{en(3,5-dtbb)₂(6,8-dtbbenzox)}] ( 7 ), and [{W^VIO₂}{en(3-tb,5-mb)₂(6-tb,8-mbbenzox)}] ( 8 ). However, the benzoxazine ring ruptures in case of ligand IIc under these conditions and form [{W^VIO₂}{en(3,5-dmb)₃}] ( 10 ), similar to complexes 1–3 . Complex [{W^VIO₂}{en(3,5-dmb)₂(6,8-dmbenzox)}] ( 9 ), having structure similar to 4–8 , could only be obtained when the reaction was carried out in toluene. Not only 9 , even complexes 4–8 can be isolated in toluene. Rupturing of both benzoxazine rings has also been experienced when ligands 1,2-bis(6,8-disubstitutedbenzo[e][1,3]oxazin-3(4H)-yl)ethane [ I ( a–c )] react with [M^VIO₂(acac)₂] (M=Mo or W) in MeOH and give salan type complexes [(M^VIO₂)en(3,5-dtbb)₂] [M=Mo ( 11 ), M=W ( 14 )], [(M^VIO₂)en(3-tb,5-mb)₄] [M=Mo ( 12 ), M=W ( 15 )] and [(M^VIO₂)en(3,5-dmb)₄] [M=Mo ( 13 ), M=W ( 16 )]. Complexes 1–9 have been used as catalyst for the multicomponent Biginelli reaction for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) and oxidative bromination of phenol derivatives.     

Well-Defined Aminophenolate Zinc and Magnesium Complexes as Excellent Inhitiators for the ROP of Lactides

A series of molecular homo and heteroleptic zinc and magnesium compounds with aminophenolate ligands [(µ,η²-L²)ZnEt]₂ ( 1 ), [(η²-L²)Zn(µ-BnO)]₂ ( 2 ), [Zn(η²-L²)₂] ( 3 ), [Zn(η²-L³)₂] ( 4 ), [Mg(η²-L³)₂] ( 5 ) (L²-H = N-[methylene(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-cyclohexylamine, L³-H = N-[methylene(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-methyl-1,3-dioxolaneamine) have been prepared and characterized. The homoleptic complexes 3–5 are most probably a mixture of diastereoisomers that in solution show an interesting dynamics which plays an important role in their catalytic behavior. The complexes 2 – 5 are efficient initiators in ring-opening polymerization (ROP) of lactides to produce polymers with desired molecular weight and narrow polydispersity.     

Direct enantioselective approach to oxazolo[4,5-e]isoindoles from [(S)R]-1-aminosubstituted-4-(p-tolylsulfinyl)-1,3-butadienes

The enantioselective construction of [3aS,5aR,8aR,8bR]-1-(p-methoxyphenyl)-3a,7-dimethyl-3a,5a,8b,8a-tetrahydro-1H-oxazolo[4,5-e]isoindole-2,6,8-trione is achieved from enantiopure [(S)R]-(1E,3E)-2-methyl-1-(p-methoxyphenyl)amino-4-(p-tolylsulfinyl)-1,3-butadiene and N-methylmaleimide through a short sequence involving a Diels–Alder reaction, a sulfoxide–sulfenate rearrangement and intramolecular cyclization.     

Synthesis and characterization of oxovanadium(IV), vanadium(IV) and oxovanadium(V) complexes of tetradentate Schiff bases. Attempted preparation of vanadium-carbon bonded compounds through desilylation

Condensation of 1,3-diaminopropane-2-ol with diacetylmonoxime, acetylacetone, salicylaldehyde and orthohydroxyacetophenone yielded the tetradentate Schiff bases N,N′-(2-hydroxy)propylenebis{(2-imino-3-oximino)butane} (H₂dampnol), N,N′-(2-hydroxy)propylenebis(acetylacetoneimine) (H₂acacpnol), N,N′-(2-hydroxy)propylenebis-(salicyalaldimine) (H₂salpnol) and N,N′-(2-hydroxy)propylenebis(7-methylsalicylaldimine) (H₂ohacpnol), respectively. The ligands form complexes with oxovanadium(IV), vanadium(IV) and oxovanadium(V) salts. Some mixed ligand complexes involving σ-bonded phenyl and benzyl radical along with tetradentate ligand, H₂L (where, H₂L stands for H₂dampnol, H₂acacpnol, H₂salpnol or H₂ohacpnol) of the types [(L)V(C₆H₅)₂]CH₃OH and [(L)V(CH₂Ph)₂]CH₃OH have been synthesized, characterized and also provide the syntheses of some new organovanadium(IV) complexes. Silylation coupled with desilylation have been employed as a route to new organovanadium(IV) complexes. All the complexes have been characterized with the help of elemental analyses, molar conductance values, molecular weights, magnetic moments and spectroscopic (IR, UV-Vis, ESR) data.     

Polymerization of 1,3‐dienes and styrene catalyzed by cationic allyl Ni(II) complexes

Polymerizations of 1,3‐dienes using in situ generated catalyst [(2‐methallyl)Ni][B(Ar_F)₄], 6 , (Ar_F = 3,5‐bis(trifluoromethyl)phenyl) as well as [(2‐methallyl)Ni(mes)][B(Ar_F)₄], 14 , (mes = mesitylene) are reported. Highly sensitive complex 6 polymerizes butadiene (BD) at –30 °C to yield polybutadiene with a M_n of ca. 10 K and 94% cis‐1,4‐enchainment while less reactive isoprene (IP) was polymerized at 23 °C to yield polyisoprene with M_n ca. 7 K. Complex 6 was also shown to polymerize a functionalized diene, 2,3‐bis(4‐trifluoroethoxy‐4‐oxobutyl)‐1,3‐BD, to polymer with M_n = 113 K. The stable and readily isolated arene complex 14 initiates BD and IP polymerizations at somewhat higher temperatures relative to 6 and delivers polymers with higher molecular weights. Complex [(allyl)Ni(mes)][B(Ar_F)₄], 13 , catalyzes polymerization of styrene to yield polystyrene with high conversion, M_n's = ca. 6 K and MWD = 2. The π‐benzyl complex [(η³‐1‐methylbenzyl)Ni(mes)] [B(Ar_F)₄], 19 , was detected as an intermediate following chain transfer by in situ NMR studies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1901–1912, 2010     

Studies on the synthesis and magnetic property of binuclear oxovanadium(IV) complexes bridged by chloranilato group

Six novel oxovanadium(IV) binuclear complexes have been synthesized and characterized, namely, [(VO)₂(CA)L₂]SO₄ [L denotes 5-methyl-1,10-phenanthroline (Me-phen); 2,9-dimethyl-1,10-phenanthroline (Me₂-phen); 5-chloro-1,10-phenanthroline (Cl-phen); diaminoethane (en); 1,3-diaminopropane (pn) and 1,2-diaminopropane (ap) respectively.], where CA represents the dianion of chloranilic acid. Based on elemental analyses, molar conductivity and room temperature magnetic moment measurements, IR and electronic spectral studies, it is proposed that there complexes have CA-bridged structures and consist of two vanadium(IV) ions in a square-pyramidal environment. The complexes [(VO)₂(CA)(Me-phen)₂]SO₄ (1) and [(VO)₂(CA)(Me₂-phen)₂]SO₄ (2) were characterized by variable temperature magnetic susceptibility measurements (4～300 K) and the observed data were fitted to the modified Bleaney-Bowers equation by the least-squares method, giving the exchange integral J=-15.8 cm^?1 for 1 and J=-10.6 cm^?l for 2. This result indicates that there is a weak antiferromagnetic spin-exchange interaction between the two VO²⁺ ions within each molecule.     

Charge-Transfer Salts of Ferrocene Derivatives with Bis(maleonitriledithiolato)metallate(III) Complexes ([M(mnt)2]−, M=Ni,Pt): A Ground-State High-Spin [(Ni(mnt)2)2]2− Dimer

New hexamethylated ferrocene derivatives containing thioether moieties (1,1′-bis[(tert-butyl)thio]-2,2′,3,3′,4,4′-hexamethylferrocene ( 3a , b )) or fused S-heteropolycyclic substituents (rac-1-[(1,3-benzodithiol- 2-yliden)methyl]-2,2′,3,3′,4,4′-hexamethylferrocene ( 5 ) and rac-1-[1,2-bis(1,3-benzodithiol-2-yliden)ethyl]-2,2′,3,3′,4,4′-hexamethylferrocene ( 14 )), as well as a series of ferrocene-substituted vinylogous tetrathiafulvalenes (1,1′-bis[1,2-bis(1,3-benzodithiol-2-yliden)ethyl]ferrocene ( 6a ), 1,1′-bis[1-(1,3-benzodithiol-2-yliden)-2-(5,6-dihydro-1,3-dithiolo[4,5-b] [1,4]dithiin-2-yliden)ethyl]ferrocene ( 6b ), [1,2-bis(1,3-benzodithiol-2-yliden)ethyl]ferrocene ( 21a ), [1-(1,3-benzodithiol-2-yliden)-2-(5,6-dihydro-1,3-dithiolo[4,5-b] [1,4]dithiin-2-yliden)ethyl]ferrocene ( 21b ), [1,2-bis(5,6-dihydro-1,3-dithiolo[4,5-b] [1,4]dithiin-2-yliden)ethyl]ferrocene ( 21c ), [1-(5,6-dihydro-1,3-dithiolo[4,5-b] [1,4]dithiin-2-yliden)-2-(1,3-benzodithiol-2-yliden)ethyl]ferrocene ( 21d )) were prepared and fully characterized. Their redox properties show that some of them are easily oxidized and undergo transformation to paramagnetic salts containing bis(maleonitriledithiolato)-metallate(III) anions [M(mnt)₂]⁻ (M=Ni, Pt; bis[2,3-dimercapto-κS)but-2-enedinitrilato(2⁻)]nickelate (1⁻) or -platinate (1⁻). The derivatives [ 3a ] [Ni(mnt)₂] ( 26 ), [ 3a ] [Pt(mnt)₂] ( 27 ), [Fe{(η⁵-C₅Me₄S)₂S}] [Ni(Mnt)₂] ( 28 ), [Fe{(η⁵-C₅Me₄S)₂S}] [Pt(mnt)₂] ( 29 ), [ 5 ] [Ni(mnt)₂]⋅ClCH₂CH₂Cl ( 30 ), [ 6a ] [Ni(mnt)₂] ( 31 ), [ 6a ] [Ni(mnt)₂]⋅ClCH₂CH₂Cl ( 31a ), [ 6a ] [Pt(mnt)₂] [ 32 ), and [ 6b ] [Ni(mnt)₂] ( 33 ) were prepared and fully characterized, including by SQUID (superconducting quantum interference device) susceptibility measurements. X-Ray crystal-structural studies of the neutral ferrocene derivatives 6a , b , 21c , d , and 1,1′-bis[1-(1,3-benzodithiol-2-yliden)-2-oxoethyl]ferrocene ( 23 ), as well as of the charge-transfer salts 26 – 28 , 30 , and 31a , are reported. The salts 28 and 30 display both a D⁺A⁻A⁻D⁺ structural motif, however, with a different relative arrangement of the [{Ni(mnt)₂}₂]²⁻ dimers, thus giving rise to different but strong antiferromagnetic couplings. Salt 26 exhibits isolated ferromagnetically coupled [{Ni(mnt)₂}₂]²⁻ dimers. Salt 27 displays a D⁺A⁻D⁺A⁻ structural motif in all three space dimensions, and a week ferromagnetic ordering at low temperature. Salt 31a , on the contrary, shows segregated stacks of cations and anions. The cations are connected with each other in two dimensions, and the anions are separated by a 1,2-dichloroethane molecule.     

Living cationic polymerization of vinyl ethers with a urethane group

To study the possibility of living cationic polymerization of vinyl ethers with a urethane group, 4‐vinyloxybutyl n‐butylcarbamate ( 1 ) and 4‐vinyloxybutyl phenylcarbamate ( 2 ) were polymerized with the hydrogen chloride/zinc chloride initiating system in methylene chloride solvent at ?30 °C ([monomer]₀ = 0.30 M, [HCl]₀/[ZnCl₂]₀ = 5.0/2.0 mM). The polymerization of 1 was very slow and gave only low‐molecular‐weight polymers with a number‐average molecular weight (M_n) of about 2000 even at 100% monomer conversion. The structural analysis of the products showed occurrence of chain‐transfer reactions because of the urethane group of monomer 1 . In contrast, the polymerization of vinyl ether 2 proceeded much faster than 1 and led to high‐molecular‐weight polymers with narrow molecular weight distributions (MWDs ≤ ～1.2) in quantitative yield. The M_n's of the product polymers increased in direct proportion to monomer conversion and continued to increase linearly after sequential addition of a fresh monomer feed to the almost completely polymerized reaction mixture, whereas the MWDs of the polymers remained narrow. These results indicated the formation of living polymer from vinyl ether 2 . The difference of living nature between monomers 1 and 2 was attributable to the difference of the electron‐withdrawing power of the carbamate substituents, namely, n‐butyl for 1 versus phenyl for 2 , of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2960–2972, 2004     

Dinuclear Schiff-base copper(II) complexes with various bridging groups

Three new centrosymmetric dinuclear copper(II) complexes, [Cu₂Cl₂(L¹)₂] (1), [Cu₂(μ _1,3-NCS)₂(L²)₂] (2), and [Cu₂(μ _1,1-N₃)₂(L³)₂] (3), where L¹, L², and L³ are the deprotonated forms of the Schiff bases 1-[(2-propylaminoethylimino)methyl]naphthalen-2-ol (HL¹), 1-[(3-methylaminopropylimino)methyl]naphthalen-2-ol (HL²), and 2-[(2-isopropylaminoethylimino)methyl]phenol (HL³), respectively, have been prepared and characterized by elemental analysis, IR spectra, and single-crystal X-ray crystallography. Each Cu is coordinated by the three donors of the Schiff bases and by two bridging groups, forming a square-pyramidal geometry.