Sustainable polymers from renewable resources

Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers

Bimetallic Fe–Au Carbonyl Clusters Derived from Collman’s Reagent: Synthesis, Structure and DFT Analysis of Fe(CO)4(AuNHC)2 and [Au3Fe2(CO)8(NHC)2]−

The reaction of the Collman's reagent Na2Fe(CO)(4) with two equivalents of Au(NHC)Cl (NHC = IMes, IPr, IBu) in thf results in the bimetallic Fe(CO)(4)(AuNHC)(2) (NHC = IMes, 2; IPr, 3; IBu, 4; IMes = C3N2H2(C6H2Me3)(2); IPr = C3N2H2(C6H (3) (i) Pr-2)(2); IBu = C3N2H2(CMe3)(2)) clusters in good yields. Heating 2 in dmf at 100 A degrees C results in the higher nuclearity cluster [Au3Fe2(CO)(8)(IMes)(2)](-) (5). 2-5 have been fully characterized via IR, H-1 and C-13 NMR spectroscopies and their structures determined by means of single crystal X-ray crystallography. Gas-phase DFT calculations were carried out on 2-5 and the model compound cis-Fe(CO)(4)(AuIDM)(2) (6) (IDM = C3N2H2Me2), in order to better understand the metal-metal and metal-ligand interactions in these compounds without the influence of packing forces

What Makes a Good (Computed) Energy Profile?

International audienceA good meal cannot be defined in an absolute manner since it depends strongly on where and how it is eaten and how many people participate. A picnic shared by hikers after a challenging climbing is very different from a birthday party among a family or a banquet for a large convention. All of them can be memorable and also good. The same perspective applies to computational studies. Required level of calculations for spectroscopic properties of small molecular systems and properties of medium or large organic or organometallic, polymetallic systems are different. To well-specified chemical questions and chemical systems, efficient computational strategies can be established. In this chapter, the focus is on the energy profile representation of stoichiometric or catalytic reactions assisted by organometallic molecular entities. The multiple factors that can influence the quality of the calculations of the Gibbs energy profile and thus the mechanistic interpretation of reactions with molecular organometallic complexes are presented and illustrated by examples issued from mostly personal studies. The usual suspects to be discussed are known: representation of molecular models of increasing size, conformational and chemical complexity, methods and levels of calculations, successes and limitations of the density functional methods, thermodynamics corrections, spectator or actor role of the solvent, and static vs dynamics approaches. These well-identified points of concern are illustrated by presentation of computational studies of chemical reactions which are in direct connection with experimental data. Even if problems persist, this chapter aims at illustrating that one can reach a representation of the chemical reality that can be useful to address questions of present chemical interest. Computational chemistry is already well armed to bring meaningful energy information to numerous well-defined questions