Industrial methods[ edit ] Alkenes are produced by hydrocarbon cracking. Raw materials are mostly natural gas condensate components principally ethane and propane in the US and Mideast and naphtha in Europe and Asia. Alkanes are broken apart at high temperatures, often in the presence of a zeolite catalyst, to produce a mixture of primarily aliphatic alkenes and lower molecular weight alkanes. The mixture is feedstock and temperature dependent, and separated by fractional distillation.
Multimetallic Polymerization Catalysis Research in the Agapie laboratory is targeted toward developing new, practical catalysts by using inspiration from biological systems. Some of the most fascinating catalysts in Nature display complex inorganic cofactors, sometimes in combination with organic cofactors, and perform chemical transformations water reduction and oxidation, carbon dioxide reduction, dinitrogen reduction, dioxygen reduction that are arguably prerequisites for the advance of society in the current context of limiting energy resources and environmental concerns.
Given the scale of the potential applications, we focus on studies of inexpensive and abundant first-row transition metals. To these ends we have developed new methodologies for the synthesis of complex inorganic targets and have performed mechanistic studies to understand the properties and reactivity of these compounds.
Our research focuses on three general topics: With mixed metal oxides as catalysts for water oxidation and O2 reduction in heterogeneous and biological systems, fundamental Mechanism for olefin polymerization of the effects of redox inactive metals on the chemistry of mixed metal oxide clusters is important for the rational development of effective catalysts.
Prior to our work, a single high oxidation state complex displaying an oxo bridged redox active — redox inactive heterometallic core had been structurally characterized and studied for redox chemistry, though examples of in situ modulation of reactivity by metal Lewis acids had been reported.
We have developed rational strategies for the synthesis of a series of well-defined heterometallic oxide clusters that have allowed for systematic structure-property studies. The reduction potentials of these clusters were found to depend linearly on the Lewis acidity of the redox inactive metal.
This finding has applications in rationally tuning the reduction potentials of metal oxide clusters to match the thermodynamic requirements of the desired redox transformations.
Mechanistic studies have provided insights into the mechanism of cluster assembly and O- and H-atom transfer. Synthesized complexes have been studied by collaborators for spectroscopic benchmarking relative to the biological system. In the context of small molecule activation, the ability of protein active sites to transfer electrons and protons is instrumental for selectivity and high reaction rates.
We have developed new molecular architectures for multimetallic complexes of redox active metals and monometallic complexes of non-innocent ligands.
Although non-innocent ligands have often been employed to transfer electrons or protons, pendant groups that transfer both are relatively rare, despite the biological precedent.
Moieties such as catechol and hydroquinone are envisioned to act as reservoirs of both electrons and protons, if placed in proximity of metals orthogonally to the arene plane. Toward that end, hemi-labile arene ligands with pendant donors have been employed for their versatility and potential to lower reaction barriers by accommodating several metal binding modes.
New types of bimetallic reactivity C-C coupling with Nicatalysts Mo catalyzed ammonia-borane dehydrogenationand mechanistic insights metal mediated aryl C-O bond activation, H-transfer to arene have been achieved.
The functionalized versions of these systems, with catechol and hydroquinone moieties, bind metals while retaining the protonated state. Therefore, they can deliver not only electrons, but also protons to substrates such as O2, clearly showing the potential of such motifs for metal mediated multi-electron and multi-proton chemistry.
The insertion polymerization of polar monomers has been a significant challenge in polyolefin synthesis. Bimetallic catalysts have been proposed as candidates to address this problem, but the molecular design of many of the known systems has provided limited insight into the reaction mechanism due to high flexibility or distant placement of metals.
We have prepared bimetallic complexes with rigid organic linkers that lock the metals centers at well-defined positions. Our studies have revealed a mechanism of bimetallic cooperativity that contrasts with other proposals in the literature, with reactivity being affected by the steric interaction between coordinated ligands.
Due to these interactions, the catalytic activity and the stereocontrol are increased, and deactivation by polar groups such as amines is lowered.
These mechanistic insights are expected to allow for the development of catalysts with better functional group tolerance. Lopez, and Theodor Agapie. Reed and Theodor Agapie. VanderVelde, and Theodor Agapie.
Buss, Christine Cheng, and Theodor Agapie. Chalkley, and Theodor Agapie. Buss, and Theodor Agapie. Hirscher and Theodor Agapie. Oyala, and Theodor Agapie. Yachandra, Junko Yano, and Philippe Wernet.
Takase, and Theodor Agapie. Peters, and Theodor Agapie.Recent results for synthesis of end-functionalized polymers (EFP) by using olefin metathesis polymerization have been introduced including basic characteristics in ring-opening metathesis polymerization (ROMP) of cyclic olefins and acyclic diene metathesis (ADMET) polymerization for synthesis of conjugated polymers.
Organometallic Reaction Mechanisms: Olefin Polymerization Catalysis and C-H Bond Activation by The mechanism of an intramolecular C-H activation process was found to involve two competing pathways. as Olefin Polymerization Catalysts.
Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds.   Because of the relative simplicity of olefin metathesis, it often creates fewer undesired by-products and hazardous wastes than alternative organic plombier-nemours.com ontology ID: RXNO Advantages over traditional polymerization method.
Traditionally, polymerization of α-olefins was done by radical polymerization (Figure 4). Problem with this technique was that the formation of undesired allylic radicals leaded to branched polymers. 3 For example, radical polymerization of propene gived branched polymers with large molecular weight distribution.
The effects of linear low-density polyethylene (LLDPE) on the mechanical properties of high-density polyethylene (HDPE) film blends 86 amounts of co-monomers such as butene, hexene, or octene. The details of the mechanism of olefin polymerization by the Kaminsky catalyst depend, inter alia, on the structure of the olefin.
Ethylene is singular and has been studied in most detail. Results for the substituted ethylenes, propylene and 1-hexene, will be given later.