Synthesis,characterization, and aqueous self‐assembly of amphiphilic poly(ethylene oxide)‐functionalized hyperbranched fluoropolymers

Complex amphiphilic polymers were synthesized via core‐first polymerization followed by alkylation‐based grafting of poly(ethylene oxide) (PEO). Inimer 1‐(4′‐(bromomethyl)benzyloxy)‐2,3,5,6‐tetrafluoro‐4‐vinylbenzene was synthesized and subjected to atom transfer radical self‐condensing vinyl polymerization to afford hyperbranched fluoropolymer (HBFP) as the hydrophobic core component with a number‐averaged molecular weight of 29 kDa and polydispersity index of 2.1. The alkyl halide chain ends on the HBFP were allowed to undergo reaction with monomethoxy‐terminated poly(ethylene oxide) amine (PEO_x‐NH₂) at different grafting numbers and PEO chain lengths to afford PEO‐functionalized HBFPs [(PEO_x)_y‐HBFPs], with x = 15 while y = 16, 22, or 29, x = 44 while y = 16, and x = 112 while y = 16. The amphiphilic, grafted block copolymers were found to aggregate in aqueous solution to give micelles with number‐averaged diameters (D_av) of 12–28 nm, as measured by transmission electron microscopy (TEM). An increase of the PEO:HBFP ratio, by increase in either the grafting densities (y values) or the chain lengths (x values), led to decreased TEM‐measured diameters. These complex, amphiphilic (PEO_x)_y‐HBFPs, with tunable sizes, might find potential applications as nanoscopic biomedical devices, such as drug delivery vehicles and ¹⁹F magnetic resonance imaging agents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3487–3496, 2010     

Associative block copolymers comprising poly(N‐isopropylacrylamide) and poly(ethylene oxide) end‐functionalized with a fluorophilic or hydrophilic group. Synthesis and aqueous solution properties

A series of block copolymers comprising poly(N‐isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (PEO) end‐functionalized with a quaternary ammonium group (R_Q) was synthesized by free‐radical polymerization of N‐isopropylacrylamide with well‐defined R_QPEO macroazoinitiators. The radical termination occurred mainly by disproportionation, as confirmed by combining the data from size exclusion chromatography (SEC) and rheology measurements. The copolymers denoted R_QE_xN_y differ in type of the terminal group [F_Q = C₈F₁₇(CH₃)₂N⁺ or M_Q = (CH₃)₃N⁺] and in the length of the PEO (E_x; x = 4, 6, or 10 K) and PNIPAM (N_y; y = 7 or 17–19 K) blocks. The type of the terminal group determined the behavior of the block copolymers in the dilute and semidilute regime. Self‐assembled species formed by both F_Q and M_Q modified block copolymers were detected by static light scattering measurements at 25 °C and above the lower critical solution temperature (LCST). The LCST of the block copolymers depended on the type of the R_Q group and the length of the blocks. F_Q‐modified copolymers form elastic gels below and above the LCST. It was inferred that the F_Q groups and the PNIPAM blocks form segregated microdomains that serve as junctions to maintain a viscoelastic network. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5736–5744, 2004     

Copolymers of vinyl chloride and vinylidene chloride with some acid chlorides

Vinyl chloride and vinylidene chloride were copolymerized with 10-acryloxydecanoyl chloride and 12-acryloxystearoyl chloride by use of free-radical initiator in solution to obtain copolymers with active chlorine groups. Alternative routes for making such copolymers which consisted of making the corresponding acrylic acid or acrylyl chloride copolymers, followed by reaction with hydroxy acid and finally conversion to the acid chloride by treatment with thionyl chloride, were investigated. The monomer reactivity ratios for the radical copolymerization of vinyl chloride (VCI) and vinylidene chloride (VCl₂) with acrylic acid (AA) and acrylyl chloride (ACI) were determined: VCI–AA, r₁ = 0.025, r₂ = 6.40; VCl–ACl, r₁ = 0.017, r₂ = 2.65; VCl₂–AA, r₁ = 0.46, r₂ = 1.26; VCl–ACl, r₁ = 0.50, r₂ = 1.12.     

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [FeII2] Supramolecular Helicates

A new bis(pyrazolylpyridine) ligand (H₂L) has been prepared to form functional [Fe₂(H₂L)₃]⁴⁺ metallohelicates. Changes to the synthesis yield six derivatives, X@[Fe₂(H₂L)₃]X(PF₆)₂?xCH₃OH ( 1 , x=5.7 and X=Cl; 2 , x=4 and X=Br), X@[Fe₂(H₂L)₃]X(PF₆)₂?yCH₃OH?H₂O ( 1 a , y=3 and X=Cl; 2 a , y=1 and X=Br) and X@[Fe₂(H₂L)₃](I₃)₂?3 Et₂O ( 1 b , X=Cl; 2 b , X=Br). Their structure and functional properties are described in detail by single‐crystal X‐ray diffraction experiments at several temperatures. Helicates 1 a and 2 a are obtained from 1 and 2 , respectively, by a single‐crystal‐to‐single‐crystal mechanism. The three possible magnetic states, [LS–LS], [LS–HS], and [HS–HS] can be accessed over large temperature ranges as a result of the structural nonequivalence of the Fe^II centers. The nature of the guest (Cl^? vs. Br^?) shifts the spin crossover (SCO) temperature by roughly 40 K. Also, metastable [LS–HS] or [HS–HS] states are generated through irradiation. All helicates (X@[Fe₂(H₂L)₃])³⁺ persist in solution.     

A temperature‐dependent kinetics study of the reaction of O(3PJ) with (CH3)2SO

A laser flash photolysis–resonance fluorescence technique has been employed to investigate the kinetics of the reaction of ground state oxygen atoms, O(³P_J), with (CH₃)₂SO (dimethylsulfoxide) as a function of temperature (266–383 K) and pressure (20–100 Torr N₂). The rate coefficient (k_R1) for the O(³P_J) + (CH₃)₂SO reaction is found to be independent of pressure and to increase with decreasing temperature. The following Arrhenius expression adequately describes the observed temperature dependence: k_R1(T) = (1.68 ± 0.76) × 10_?12 exp[(445 ± 141)/T] cm³ molecule^?1 s^?1, where the uncertainties in Arrhenius parameters are 2σ and represent precision only. The absolute accuracy of each measured rate coefficient is estimated to be ±30%, and is limited predominantly by the uncertainties in measured (CH₃)₂SO concentrations. The observed temperature and pressure dependencies suggest that, as in the case of O(³P_J) reactions with CH₃SH and (CH₃)₂S, reaction occurs by addition of O(³P_J) to the sulfur atom followed by rapid fragmentation of the energized adduct to products. The O(³P_J) + (CH₃)₂SO reaction is fast enough so that it could be a useful laboratory source of the CH₃SO₂ radical if this species is produced in significant yield. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 156–161, 2002; DOI 10.1002/kin.10040     

Novel Copolymers of Trisubstituted Ethylenes and Styrene. 7. Dihalogen Ring-Substituted Ethyl 2-Cyano-1-oxo-3-phenyl-2-propenylcarbamates

Electrophilic trisubstituted ethylenes, dihalogen ring-substituted ethyl 2-cyano-1-oxo-3-phenyl-2-propenylcarbamates, RC₆H₃ CH = C(CN)CONHCO₂C₂H₅(where R is 2,3-diCl, 2,4-diCl, 2,6-diCl, 3,4-diCl, 3,5-diCl, and 2-Cl-6-F, were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and N-cyanoacetylurethane, and characterized by CHN analysis, IR, ¹H- and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H- and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers 2,4-diCl (4.4) > 2,6-diCl (3.6) > 2,3-diCl (3.4) = 3,4-diCl (3.4) > 2-Cl-6-F (2.7) > 3,5-diCl (2.0). High T _g of the copolymers in comparison with that of polystyrene indicates decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene structural unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 270–420°C with residue (5–13% wt), which then decomposed in the 420–650°C range.     

An Improved Synthetic Method for Preparing Polyoxyethylene Macromers and a Study of Their Copolymerization with Alkyl Acrylates

Polyoxyethylene macromers were synthesized by polymerization of ethylene oxide in dimethylsulfoxide by using potassium napthalide in tetrahydrofuran as initiator, followed by termination with methacroyl chloride. Potassium naphthalide is more active as an initiator than sodium naphthalide. The initiator in this case was confirmed to be of the monoanionic type. The molecular weight of the macromers can be varied from 2 × 10³ to 1.2 × 10⁴with M_w/M_n = 1.07-1.12. The macromers were characterized by UV, IR, and ¹H NMR, and copolymerized with butyl acrylate, methyl acrylate, or methyl methacrylate. The grafting efficiency can reach about 90%. The graft copolymers were purified by extractions and characterized by GPC, IR, and a Bruss membrane osmometer. The average grafting number of the copolymers varied from 10 to 15.     

Ultrathin self-assembled polymeric films on solid surfaces. I. Synthesis and characterization of acrylate copolymers containing alkyl disulfide side chains

Copolymers of 2-hydroxyethyl acrylate and 2-methoxyethyl acrylate with variable compositions were synthesized, fractionated, and characterized by ¹H-NMR, IR, GPC, and viscometry. These copolymers were further modified via polymer analog esterification of copolymer hydroxy groups by a series of disulfide-containing carboxylic acids including lipoic acid and (n-pentyldithio) alkyl carboxylic acids (n-C₅H₁₁SS(CH₂)m? COOH, m = 10, 15, 22) in the presence of 1,3-dicyclohexylcarbodiimide (DCC). Esterification reactions were quantitative for copolymers possessing hydroxy monomer contents ≤ 40% when excess acid and DCC were present for sufficiently long reaction times (2–4 days) at room temperature. Copolymer DSC analysis demonstrates a systematic variation of T_g with copolymer composition in good agreement with ideal mixing theory. These disulfide-bearing copolymers spontaneously yield two-dimensional ultrathin polymer films with side chain-dependent layer thicknesses of 20–45 Å by solution adsorption onto freshly deposited gold surfaces. Such ultrathin polymer films are expected to have diverse applications as bound polymeric surface modification reagents. © 1993 John Wiley & Sons, Inc.     

Syntheses and characterization of Zn(II), Cd(II) and Hg(II) complexes with 5-methyl-1-(2′-pyridyl)pyrazole-3-carboxamide (MP y P z CA) ligand

From the reaction between Zn(II), Cd(II) and Hg(II) with 5-methyl-1-(2′-pyridyl)pyrazole-3-carboxamide (MP _y P _z CA) in ethanol, the complexes [Zn(MP _y P _z CA)₂(NO₃)]⁺ [(NO₃)_0.60(ClO₄)_0.40]^?·H₂O, Cd(MP _y P _z CA)₂Cl₂ and Hg(MP _y P _z CA)(SCN)₂ were obtained. These compounds have been characterized by IR and CHN analyses. The structure of [Zn(MP _y P _z CA)₂NO₃]⁺[(NO₃)_0.60(ClO₄)_0.40]^?·H₂O has been solved by X-ray crystallography. The coordination environment around the Zn(II) may be described as a trigonal bipyramid in which the ligands are both bidentate, but coordinated differently. The coordination sphere is completed with the oxygen atom of a nitrate anion as a unidentate ligand.     

Novel Copolymers of 4-Fluorostyrene. 11. Some Ring-substituted 1,1-dicyano-2-(1-naphthyl)ethylenes

Novel copolymers of trisubstituted ethylene monomers, ring-substituted 1,1-dicyano-2-(1-naphthyl)ethylenes, RC₁₀H₆CH?C(CN)₂ (where R is H, 2-OCH₃, 4-OCH₃) and 4-fluorostyrene were prepared by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is (5.86) > 2-CH₃O (4.28) > 4-CH₃O (2.87). Relatively high T_g of the copolymers in comparison with that of poly(4-fluorostyrene) indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (7.3–7.7% wt.), which then decomposed in the 500–800°C range.     

Bildung und Struktur des iso-Tetraphosphans P(PtBu2)3: ein Molekül mit einem planaren,dreibindigen P-Atom

Formation and Structure of the iso -Tetraphosphane P(P^tBu₂)₃: a Molecule with a Planar Three-coordinated P Atom The iso-tetraphosphane P(P^tBu₂)₃ ( 1 ) was obtained by irradiating ^tBu₂P–P=P(Me)^tBu₂ ( 3 ). 1 forms hexagonal crystals (space group P6₃/m) with a = 1005,63(8), c = 1621,4(2) pm, Z = 2. The P(P^tBu₂)₃ molecules are arranged in a hexagonally close packed lattice. The four P atoms in each molecule are coplanar with P–P bond distances 219.08(4) pm and P–P–P angles 120°. The observed planar geometry is in accordance with ab initio calculations.     

Ionic complexes of 1,1′‐dimethyltitanocene(IV) dichloride with simple α‐amino acids: synthesis,structural characterisation and investigation on hydrolytic stability in aqueous solution

Five cationic complexes of the general formula [Cp′₂Ti(A)₂]²⁺ [Cl^?]₂ [Cp′ = η⁵‐(CH₃)C₅H₄ and A = glycine, 1 ; 2‐methylalanine, 2 ; N‐methylglycine, 3 ; L ‐alanine, 4 ; and D ‐alanine 5 ] were prepared by the reaction of Cp′₂TiCl₂ and the appropriate α‐amino acid in 1:2 molar ratio from methanol–water solution in high yield. Air‐stable crystalline solids, highly soluble in water, were characterized by means of elemental analysis, IR, Raman, ¹H, ¹³C and ¹⁴N NMR spectroscopy. The structure of compound 3 was determined by single crystal X‐ray crystallography: orthorhombic Pbca No. 61, a = 9.5310(3), b = 18.2980(5), c = 26.6350(5) Å, V = 4654 ų, Z = 8. Hydrolytic stability of all compounds in D₂O was investigated using ¹H NMR spectroscopy within the pD interval of 2.9–6.5. All compounds slowly decomposed during 24 h at pD = 2.94, forming a mixture of hydrolytic products [Cp′₂Ti(A)(D₂O)]²⁺, [Cp′₂Ti(D₂O)₂]²⁺ and respective α‐amino acids. By elevating pD to 4.0 and up to 6.5, a yellowish precipitate was formed, which indicates decomposition of the complexes. These compounds were characterized using elemental analyses, IR and Raman spectroscopy and attributed to oligomeric and/or polymeric structures described empirically by the formula Ti(Cp′)_xO_y(OH)_z (x = 0.65; y = 0.3, z = 1.9). Copyright © 2005 John Wiley & Sons, Ltd.     

Three‐arm star block copolymers of ε‐caprolactone and acrylic acid: Synthesis and micellization behavior

A series of well‐defined three‐arm star poly(ε‐caprolactone)‐b‐poly(acrylic acid) copolymers having different block lengths were synthesized via the combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). First, three‐arm star poly(ε‐caprolactone) (PCL) (M_n = 2490–7830 g mol^?1; M_w/M_n = 1.19–1.24) were synthesized via ROP of ε‐caprolactone (ε‐CL) using tris(2‐hydroxyethyl)cynuric acid as three‐arm initiator and stannous octoate (Sn(Oct)₂) as a catalyst. Subsequently, the three‐arm macroinitiator transformed from such PCL in high conversion initiated ATRPs of tert‐butyl acrylate (^tBuA) to construct three‐arm star PCL‐b‐P^tBuA copolymers (M_n = 10,900–19,570 g mol^?1; M_w/M_n = 1.14–1.23). Finally, the three‐arm star PCL‐b‐PAA copolymer was obtained via the hydrolysis of the PtBuA segment in three‐arm star PCL‐b‐P^tBuA copolymers. The chain structures of all the polymers were characterized by gel permeation chromatography, proton nuclear magnetic resonance (¹H NMR), and Fourier transform infrared spectroscopy. The aggregates of three‐arm star PCL‐b‐PAA copolymer were studied by the determination of critical micelles concentration and transmission electron microscope. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Novel Copolymers of 4-Fluorostyrene. 2. Alkoxy Ring-Substituted 2-Phenyl-1,1-dicyanoethylenes

Novel copolymers of trisubstituted ethylene monomers, alkoxy ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC₆H₄CH = C(CN)₂ (where R is 2-methoxy, 3-methoxy, 4-methoxy, 2-ethoxy, 3-ethoxy, 4-ethoxy, 4-propoxy, 4-buthoxy, 4-hexyloxy) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 2-methoxy (1.5) > 4-ethoxy (1.0) > 4-methoxy (0.8) > 3-ethoxy (0.7) = 3-methoxy (0.7) > 4-hexyloxy (0.6) = 2-ethoxy (0.6) > 4-butoxy (0.5) = 4-propoxy (0.5). High T _g of the copolymers, in comparison with that of poly(4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 284–500°C range with residue (5–9% wt), which then decomposed in the 500–800°C range.     

The preparation,characterization, and application of cellulose–MMA graft copolymers. I. The aqueous-based preparation of cellulose–MMA graft copolymers

Cellulose-MMA graft copolymers have been produced using aqueous-based, Ce(IV)-initiated and periodate-initiated systems and also photochemical initiation. The reaction variables studied include the effect on grafting of varying the MMA monomer concentration, the initiator type and concentration, and also the reaction time. Of the three initiator types examined, the Ce (IV)-initiated and the photochemically-initiated systems are comparable in their effects on graft copolymer formation. Concurrent homopolymer formation was in the region of 50% by weight. Periodate-initiation leads to less efficient grafting of MMA onto cellulose, although homopolymer formation is also lower (typically <20% by weight). The characterization of the copolymeric products through their properties as solids and, as their carbanilated derivatives, through their solution properties has been undertaken. Values of the activation onergy of decomposition (E_A) of the cellulose-MMA graft copolymers decrease with increasing MMA content, ranging between 227 and 155kJ mol^?1. There is also a dependence on initiator type and grafting reaction conditions used (E_A (cellulose wood pulp) = 239 kJ mol^?1; E_A (PMMA) = 115 kJ mol^?1). Quantitative zeta-potential (ζ) determinations for cellulose-MMA graft copolymer samples produce negative surface charge density (σ) values. At a comparable MMA grafting level of 70–80%, values are of the order: photochemical (?730 esu/cm²) > periodate (?470 esu/cm²) > Ce (IV)-initiation (?351 esu/cm²). Characterization of carbanilate solutions (by rheological examination) and of dry, carbanilate films (by study of surface wetting behavior) highlighted differences in the physical conformation of copolymers prepared by the different initiation routes. The highly degradative effect on cellulose of a periodate initiator, in comparison with the Ce (IV)-initiation system, is reflected in significantly reduced molar mass values (typically, M_n 65,000 as opposed to 130,000 for Ce (IV)-initiated graft copolymer carbanilates).     

Novel Copolymers of Styrene. 17. Ring-Trisubstituted Methyl 2-Cyano-3-Phenyl-2-Propenoates

Electrophilic trisubstituted ethylenes, ring-trisubstituted methyl 2-cyano-3-phenyl-2-propenoates, RPhCH = C(CN)CO₂CH₃ (where R is 2,4,6-trimethyl, 3,5-dimethoxy-4-hydroxy, 3,5-dimethyl-4-hydoxy, 3,4,5-trimethoxy, 2-bromo-3-hydroxy-4-methoxy, 5-bromo-2,3-dimethoxy, 5-bromo-2,4-dimethoxy, 6-bromo-3,4-dimethoxy were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-trisubstituted benzaldehydes and methyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 5-bromo-2,3-dimethoxy (2.69) > 3,4,5-trimethoxy (1.86) > 6-bromo-3,4-dimethoxy (0.84) > 5-bromo-2,4-dimethoxy (0.39) > 4-hydoxy-3,5-dimethyl (0.31) = 2-bromo-3-hydroxy-4-methoxy (0.31) > 3,5-dimethoxy-4-hydroxy (0.24) > 2,4,6-trimethyl (0.22). Relatively high T_g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500ºC range with residue (1–6% wt), which then decomposed in the 500–800ºC range.     

Kinetics of the reactions of Cl(2PJ) and Br(2P3/2) with O3

A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the important stratospheric reactions Cl(²P_J) + O₃ → ClO + O₂ and Br(²P_3/2) + O₃ → BrO + O₂ as a function of temperature. The temperature dependence observed for the Cl(²P_J) + O₃ reaction is nonArrhenius, but can be adequately described by the following two Arrhenius expressions (units are cm³ molecule^?1 s^?1, errors are 2σ and represent precision only): ??₁(T) = (1.19 ± 0.21) × 10^?11 exp [(?33 ± 37)/T] for T = 189–269K and ??₁(T) = (2.49 ± 0.38) × 10^?11 exp[(?233 ± 46)/T] for T = 269–385 K. At temperatures below 230 K, the rate coefficients determined in this study are faster than any reported previously. Incorporation of our values for ??₁(T) into stratospheric models would increase calculated ClO levels and decrease calculated HCl levels; hence the calculated efficiency of ClO_x catalyzed ozone destruction would increase. The temperature dependence observed for the (²P_3/2) + O₃ reaction is adequately described by the following Arrhenius expression (units are cm³ molecule^?1 s^?1, errors are 2σ and represent precision only): ??₂(T) = (1.50 ± 0.16) × 10^?1 exp[(?775 ± 30)/T] for T = 195–392 K. While not in quantitative agreement with Arrhenius parameters reported in most previous studies, our results almost exactly reproduce the average of all earlier studies and, therefore, will not affect the choice of ??₂(T) for use in modeling stratospheric BrO_x chemistry.     

Novel Copolymers of Styrene. 1. Alkyl Ring-Substituted Butyl 2-Cyano-3-Phenyl-2-Propenoates

Novel trisubstituted ethylenes, alkyl ring-substituted butyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂C₄H₉ (where R is 2-methyl, 3-methyl, 4-methyl, 2-ethyl, 4-ethyl, 4-butyl, 4-t-butyl, 4-i-butyl) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and butyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 4-ethyl (4.69) > 3-methyl (4.18) > 4-t-butyl (2.98) > 2-ethyl (2.52) > 4-butyl (2.47) > 4-methyl (1.86) > 4-i-butyl (0.94) > 2-methyl (0.87). Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (3–8% wt), which then decomposed in the 500–800°C range.     

Reactions of tBu2P–PLi–PtBu2 with [(Et3P)2MCl2] (M = Ni,Pd, Pt). Synthesis and Properties of [(1,2‐η‐tBu2P=P–PtBu2)M(PEt3)Cl] (M=Ni,Pd)

^tBu₂P–PLi–P^tBu₂·2THF reacts with [cis‐(Et₃P)₂MCl₂] (M = Ni, Pd) yielding [(1,2‐η‐^tBu₂P=P–P^tBu₂)Ni(PEt₃)Cl] and [(1,2‐η‐^tBu₂P=P–P^tBu2)Pd(PEt₃)Cl], respectively. ^tBu₂P– PLi–P^tBu₂ undergoes an oxidation process and the ^tBu₂P–P–P^tBu₂ ligand adopts in the products the structure of a side‐on bonded 1,1‐di‐tert‐butyl‐2‐(di‐tert‐butylphosphino)diphosphenium cation with a short P–P bond. Surprisingly, the reaction of ^tBu₂P–PLi–P^tBu₂·2THF with [cis‐(Et₃P)₂PtCl₂] does not yield [(1,2‐η‐^tBu₂P=P–P^tBu₂)Pt(PEt₃)Cl].     

Mechanism of the Formation of Molybdenum Metallocarbene Complexes in the Gas Phase

The reactions of Mo⁺ ions and Mo _x O _y ⁺ oxygen-containing molybdenum cluster ions (x = 1-3; y = 1-9) with methane, ethylene oxide, and cyclopropane were studied using ion cyclotron resonance. The formation of a number of organometallic ions, including the metallocarbene MoCH₂ ⁺ , as well as molybdenum oxometallocarbenes Mo _x O _y CH₂ ⁺ (x = 1-3; y = 2, 4, 5, or 8) and Mo _x O _y (CH₄)⁺ ions (x = 1-3; y = 2, 5, or 8), was detected. The upper and lower limits of bond energies in oxometallocarbene complexes were evaluated: 111 > D ⁰ (Mo _x O _y ⁺-CH₂) > 82 kcal/mol (x = 1-3; y = 2, 5, 8).