Palladium complexes of multidentate pyrazolylmethyl pyridine ligands: Synthesis,structures and phenylacetylene polymerization

The compounds, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (_MeNˆNˆN) (L1) and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (_tBuNˆNˆN) (L2), react with either [Pd(NCMe)₂Cl₂] or [Pd(COD)ClMe] to form the mononuclear palladium complexes [Pd(_MeNˆNˆN)Cl₂] (1), [Pd(_MeNˆNˆN)ClMe] (2), [Pd(_tBuNˆNˆN)Cl₂] (3) and [Pd(_tBuNˆNˆN)ClMe] (4). Reactions of 1, 2 and 4 with the halide abstractor, NaBAr₄ (Ar = 3,5-(CF₃)₂C₆H₃), led to the formation of stable tridentate cationic species [Pd(_MeNˆNˆN)Cl]⁺(5), [Pd(_MeNˆNˆN)Me]⁺ (6) and [Pd(_tBuNˆNˆN)Cl]⁺ (7) respectively. The analogous carbonyl linker cationic species [Pd{(3,5-Me₂pz-CO)₂-py}Cl]⁺ (9) and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl]⁺ (10), prepared by halide abstraction of the neutral complexes [Pd{(3,5-Me₂pz-CO)₂-py}Cl₂] and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl₂] by NaBAr₄, were however less stable with t_1/2 of 14 and 2 days respectively. Attempts to crystallize 1 and 3 from the mother liquor resulted in the isolation of the salts [Pd(_MeNˆNˆN)Cl]₂[Pd₂Cl₆] (11) and [Pd(_tBuNˆNˆN)Cl]₂[Pd₂Cl₆] (12). Although when complexes 1–4 were reacted with modified methylaluminoxane (MMAO) or NaBAr₄, no active catalysts for ethylene oligomerization or polymerization were formed, activation with silver triflate (AgOTf) produced active catalysts that oligomerized and polymerized phenylacetylene to a mixture of cis-transoidal and trans-cisoidal polyphenylacetylene.     

The use of Cu and Zn salicylaldimine complexes as catalyst precursors in ring opening polymerization of lactides: ligand effects on polymer characteristics

A range of monomeric tetra‐coordinate copper (II) and zinc (II) complexes based on N,O‐bidentate salicylaldimine Schiff base ligands has been synthesized and characterized using various spectroscopic techniques. These complexes were then evaluated as initiators in ring‐opening polymerization of lactides at both 70 °C and 110 °C. The effect of structural changes in the complexes on the ability of these compounds to initiate lactide polymerization as well as the impact on the chemical and physical characteristics of the polymers obtained indicate that the coordination geometry of the metal complex, M? O bond length and substituents on the Schiff base ligand all play a role in the catalyst activity. Electronic factors were dominant in the case of the copper complexes while steric factors prevailed in the case of Zn initiators. Both the Zn and Cu complexes exhibit characteristics of living ring opening polymerization. Copyright © 2010 John Wiley & Sons, Ltd.     

REACTIONS BETWEEN SULFUR DIOXIDE AND PHOSPHINES

Abstract

Reaction between sulfur dioxide and trimethyl phosphine yields both phosphine oxide and sulfide. Reactions between sulfur dioxide and phosphines containing P-H bonds generally give rise to the most fully oxidized acid containing phosphorus that can be formed without cleaving P-C bonds. Thus, diphenylphosphine gives diphenylphosphinic acid (and some tetraphenyldiphosphine disulfide) and phenylphosphine gives phenylphosphonic acid.     

Styrene‐butadiene rubber synthesized by anionic polymerization

In this paper we report on the copolymerization of styrene with butadiene in cyclohexane as solvent. Some experiments were also done using toluene as a solvent in order to check the influence of this solvent on the polydispersity index of the copolymers obtained, n‐ Butyllithium (BuLi) was used as initiator, while methyl‐tert‐butyl ether (MTBE) was used as an active center modifier. Reaction parameters such as polymerization temperature, the [MTBE]/[BuLi] molar ratio and the nature of solvent were studied in relation to their effects on the copolymerization rate, the randomness of the polymer and the microstructure of the butadiene units incorporated.     

The synthesis and characterization of metal-containing vinylic monomers of iron and tungsten

A series of metal-containing vinylic monomers of the type L_nM(COC₆H₄CH=CH₂) and L_nM (COCH=CHC₆H₅) [L_nM = (η⁵-C₅H₅)Fe(CO)₂, (η⁵-C₅Me₅)Fe(CO)₂ and (η⁵-C₅H₅)W(CO)₃] were prepared by the reaction of the appropriate metal anion with either 4-vinylbenzoyl chloride or cinnamoyl chloride. (η⁵-C₅H₅)(CO)₂FeCOCH=CH₂ was prepared by the reaction of Na[(η⁵-C₅H₅)Fe(CO)₂] and acryloyl chloride, whereas the compound (η⁵-C₅H₅)(CO)₂Fe(C₆H₄CH=CH₂) was prepared via a transmetallation reaction using a palladium catalyst. All compounds were fully characterized using FTIR, ¹H and ¹³C NMR spectroscopy and mass spectrometry. Copyright © 1998 John Wiley & Sons, Ltd.     

The decomposition of ethanol vapour by infrared radiation from a pulsed HF-laser

The decomposition of ethanol vapour induced by infrared radiation from a pulsed HF-laser has been studied as a function of pressure. At high pressures, above 10 torr, the main primary processes appear to be:C₂H₅OH → H₂ + CH₃CHO,C₂H₅OH → C₂H₄ + H₂O,C₂H₅OH → CH₃ + CH₂OHin a ratio of 3:2:1 which is independent of pressure. At low pressures the process yielding C₂H₄ and H₂O becomes dominant. The results suggest that the high pressure behaviour involves a “thermal” decomposition with collisional processes dominating, whereas at low pressures the decomposition is due to multiple photon absorption which at the lowest pressures approaches a collision-free unimolecular decomposition.     

Inorganic coordination polymers. VIII. Cobalt(II) and zinc(II) phosphinate polymers and copolymers

The preparation, properties, x-ray powder patterns, and TGA curves are given for cobalt(II) dimethyl-, methylphenyl- and diphenylphosphinate. The polymeric character of cobalt(II) methylphenylphosphinate is demonstrated by its colligative properties and melt indexes. These cobalt(II) phosphinates along with hybrid copolymers of zinc(II) or cobalt(II) were prepared by the reaction of the metal acetate with the appropriate phosphinic acid or mixture of phosphinic acids. A consideration of the hybrid copolymers leads to the conclusion that both the zinc(II) and cobalt(II) dimethyl- and diphenylphosphinates are likewise polymeric. Thermal stability is discussed in terms of the structures suggested, and it is shown that crystallinity is related to polymer symmetry.     

Hydrozirconation of first-generation allyl-functionalized dendrimers and dendrimer model compounds

Several allyl-functionalized dendrimers and mono-functional model compounds have been prepared. These have been hydrozirconated using [Cp₂ZrHCl]_x to give zirconocene terminated dendrimers. These dendrimers have been characterized using spectroscopic techniques, particularly NMR.     

Consumer preference and service quality management with RFID

The importance of accurately measuring consumer preference for service quality management to firms in exceedingly competitive environments where customers have an increasing array of access to information cannot be overstated. There has been a resurgence of interest in consumer preference measurement and service quality management, specifically real-time service management, as more data about customer behavior and means to process these data to generate actionable policies become available. Recent years have also witnessed the incorporation of Radio-Frequency Identification (RFID) tags in a wide variety of applications where item-level information can be beneficially leveraged to provide competitive advantage. We propose a knowledge-based framework for real-time service management incorporating RFID-generated item-level identification data. We consider the economic motivations for adopting RFID solutions for customer service management through analysis of service quality, response speed and service dependability. We conclude by providing managerial insights on when and where managers should consider RFID-generated identification information to improve their customer services.     

Goodwill,inventory penalty,and adaptive supply chain management

Information visibility is generally useful for decision makers distributed across supply chains. Availability of information on inventory levels, price, lead times, demand, etc. can help reduce uncertainties as well as alleviate problems associated with bullwhip effect. A majority of extant literature in this area assume a static supply chain network configuration. While this was sufficient a few decades ago, advances in e-commerce and the ease with which order processing can be performed over the Internet necessitates appropriate dynamic (re)configuration of supply chains over time. Each node in the supply chain is modeled as an actor who makes independent decisions based on information gathered from the next level upstream. A knowledge-based framework is used for dynamic supply chain configuration and to consider the effects of inventory constraints and ‘goodwill,’ as well as their effects on the performance dynamics of supply chains. Preliminary results indicate that neither static nor dynamic configurations are consistently dominant. Scenarios where static configurations perform better than the modeled system are identified.