Insertion-deinsertion reactions

Insertion-Deinsertion Reactions. An example of a facile reversible insertion-deinsertion reaction is seen in the reactions between M2(OR)g compounds and CC which give M2(OR)... 

It has been established that the above cathode reaction is actually a proton transfer (or proton insertion/ deinsertion) reaction between Ni(OH)2 and NiOOH lattices. Eq. (1) can thus be rewritten as ... 

It has been suggested that intermolecular incorporation, i.e. oxidative addition and complexation of a substrate by a metal should be favored, intramolecular reactions, i.e. insertion, migration and deinsertion reactions should be invariant, and extmsion reactions such as reductive elimination or decomplexation should be disfavored by pressure [13], However, decomplexation reactions are in most cases ligand exchange reactions, which can proceed by associative mechanisms, and indeed, there is ample evidence that ligand exchange reactions can be accelerated by pressure [2]. 

Behind the interest manifested in binuclear complexes stands the expectation that they will display fundamentally new modes of reactivity. Naturally, we also expect that they can show the patterns of reactivity known for mononuclear complexes. These include Lewis base associ-ation/dissociation, Lewis acid association/dissociation, ligand migration (insertion/deinsertion), oxidative addition/reductive elimination, and oxidative ligand coupling/reductive ligand uncoupling, as well as electron-transfer. While these reaction patterns do occur with binuclear... 

The main reaction involved with all these electrode materials is a proton insertion/deinsertion which supplies protons to the electrolyte when electrodes are anodically polarized and catches protons from the electrolyte when they are cathodically polarized. This protonic cathode-anode exchange can be pointed out in the following reactions. 

Insertion-Deinsertion. An unsaturated ligand such as an alkene can undergo insertion into a bond between the metal of a complex and a hydrogen or a carbon. These reactions are reversible, and the reverse reaction is called deinsertion. 

The SEI is an inhomogeneous film which is composed of various reduction products and results from the chemical reaction between lithium and an electrolyte solution. The SEI plays the key role in lithium ion insertion-deinsertion and the electrochemical processes at the interface. However, Raman spectroscopy is rarely employed to investigate SEI layers... 

Migratory insertion and its microscopic reversal, that is, migratory deinsertion, are two of the 20 or so fundamental processes discussed in Sect. 1.2 in which Pd participates. In principle, they should be observed with a wide variety of substrates. In reality, however, the current scope of these processes observable with organopalladiums is almost totally limited to those that involve CO and related compounds, such as isonitriles. Conse-qnently, the migratory insertion-deinsertion chemistry of organopalladium compounds at present is essentially synonymous with their carbonylation-decarbonylation reactions. 

Platina-/3-diketone 6 reacts with 2 equiv. of phosphine ligand to give a 50% yield of acyl complex 7, with half the starting 6 remaining over time this reaction mixture evolves to give a mixture of f/s- and /r< //.f-isomers of methyl carbonyl complexes 8 (Scheme 2). One of the isomers of 8 exhibits a reversible CO insertion/deinsertion, which may be brought about by the simple expedient of solvent removal or addition. 

In this chapter the elementary reaction of CO2 with a discrete M-C bond is discussed. The coupling of CO2 with unsaturated hydrocarbons, which may also imply insertion of CO2 into an M-C bond, is discussed in Chap. 5. The insertion-deinsertion of CO2 into M-R bonds (R alkyl or aryl moiety) is relevant to carboxylation-decarboxylation processes which are very important in biological systems [38]. In this case, as seen for the insertion into M-H bonds, two mechanisms are possible, as depicted in Scheme 4.11. 

The reaction of the carbonato complex with C02 has allowed the demonstration of a facile insertion-deinsertion equilibrium. The study of the deinsertion reaction has allowed estimation of the activation parameters as being = 130 4.0 kJ mor and AS = 121.6 11.9 J moP K . From the above values the authors have calculated an approximate value of the equiUbrium cmistant for the carboxylation reaction equal to 3 x 10 M at 195 K (or a AG value for the same reaction of < 50 kJ moP ), showing that the insertion of CO2 into the M-O-alkyl bond is both kineticaUy and thermodynamically very favored. This trend has also been confirmed for the insertion of CO2 into the Nb-OR bond in [Nb(OR)5]2 (R = methyl, ethyl, aUyl) (see Sect. 6.2.2.1), a catalyst for the synthesis of dialkyl carbonates [67]. Very recently, the facile insertion of CO2 into metal-phenoxide bonds has been reported [68] for cobalt and zinc complexes (Fig. 4.2). It should be noted that such metal systems are used as catalysts in the copolymerization of CO2 with epoxides. 

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