Lithium couple, metallic

Oxalamidinate anions represent the most simple type of bis(amidinate) ligands in which two amidinate units are directly connected via a central C-C bond. Oxalamidinate complexes of d-transition metals have recently received increasing attention for their efficient catalytic activity in olefin polymerization reactions. Almost all the oxalamidinate ligands have been synthesized by deprotonation of the corresponding oxalic amidines [pathway (a) in Scheme 190]. More recently, it was found that carbodiimides, RN = C=NR, can be reductively coupled with metallic lithium into the oxalamidinate dianions [(RN)2C-C(NR)2] [route (c)J which are clearly useful for the preparation of dinuclear oxalamidinate complexes. The lithium complex obtained this way from N,N -di(p-tolyl)carbodiimide was crystallized from pyridine/pentane and... 

The reduction of l,l-bis(diphenylphosphanyl) ethylene (248) with an excess of metallic lithium, activated by ultrasonic irradiation, leads to C—C coupling under the formation of a l,l,4,4-tetrakis(diphenylphosphanyl)butane (249) (Scheme 88)". Surprisingly, the lithium centres in the resulting dilithium compound do not form any lithium-carbon contacts, being coordinated by two diphenylphosphanyl groups and two TFIF molecules each. With this strucmral motif, the molecular structure is similar to the one of tris(phosphaneoxide) 20 (Section n. A), also obtained by Izod and coworkers upon deprotonation. ... 

Since some ILs have excellent electrochemical stability, as shown in Table 3.14, they are favorable for application as electrolyte materials. Recently, ionic liquids have been investigated as conductive and redox media for lithium ions. Stable electrochemical deposition and dissolution of Li metal (Li/Li+) was observed for the lithium salt solution of [Nni3][TFSI], [N 122,201][TFSI], and [PPi4][TFSI] [101-103]. In order to observe the redox couple of lithium metal, Ni should be used as working electrode because it does not form alloys with lithium metal. In addition to this, the atmosphere must be pure Ar, because Li metal reacts rapidly with N2 to form conductive LiN. 

The bifunctional cyclopropane 156 was also prepared by modified Simmons-Smith cyclopropanation 85) of 2-trimethylsilyl-2-propen-l-ol 157 84) followed by oxidation of the cyclopropylcarbinol 158 with activated manganese dioxide 88 >, in 72% overall yield, Eq. (50) 86,89). Coupling of the aldehyde 156 with 2,6-dimethylcyclohexenone 159 90) induced by the low valent titanium reagent from TiCl3 and zinc-copper couple (or lithium metal) provided the silylated cyclopropyldiene 160, in 50-60% yield, Eq. (51) 89 91>. 

Enolate Alkylations with Transition Metal Coordinated Electrophiles. Coordination of various transition metals to dienes and aromatic compounds sufficiently activates these compounds to nucleophilic addition, resulting in high asymmetric induction at the a-center. However, the manganese complexes of various benzene derivatives couple with lithium enolates in low selectivity at the nascent stereogenic center on the ring (eq 15). ... 

The reductive coupling of carbonyl compounds with formation of C-C double bonds was developed in the early seventies and is now known as McMurry reaction [38, 39]. The active metal in these reactions is titanium in a low-valent oxidation state. The reactive Ti species is usually generated from Ti(IV) or Ti(III) substrates by reduction with Zn, a Zn-Cu couple, or lithium aluminum hydride. A broad variety of dicarbonyl compounds can be cyclized by means of this reaction, unfunctionalized cycloalkenes can be synthesized from diketones, enolethers from ketone-ester substrates, enamines from ketone-amide substrates [40-42], Cycloalkanones can be synthesized from external keto esters (X = OR ) by subsequent hydrolysis of the primary formed enol ethers (Scheme 9). 

A remarkable reaction leading to polysilanes in which silicon atoms possess fourfold silicon coordination was pubhshed by Maxka et al. Tetrakis(chlorodi-methylsilyl)silane, which was obtained from SiCl4, Li, HMe2SiCl, and CCI4 was coupled using lithium metal in tetrahydrofuran (THF) solution. [(SiMe2)4Si] was obtained as a waxy orange solid with a yield of approximately 90%. 

It is possible to couple metalated alkyl compounds to aryl compounds. The lithium enolate anion of an ester was coupled to an aryl halide, for example, using a palladium catalyst. ... 

Further support for the proposed mechanism is provided by the results of experiments involving phenylbromide instead of ethylbromide (Jj6). The polarizable TT electrons of this aryl compound allow it to effectively compete with styrene for the sites on the lithium surface and thus the Wurtz coupling reaction becomes dominant. Similar results were obtained with ethyltosylate. Although the reaction of tosylate with living polystyrene is rapid and quantitative, yielding ethyl capped polymers, its reaction with the monomer and metallic lithium produces only 10% of the ethyl capped polymers, the remainder being evolved as butane. Again, the aromatic nature of tosylate allows it to compete with styrene for the lithium sites. 

The cell reaction for a bivalent metal sulfide and metallic lithium couple can be written as follows ... 

Batteries exposed to certain abusive conditions may experience thermal runaway - a series of coupled exothermic chemical reactions involving metallic lithium, lithium dithionite and possibly sulfur, resulting in the formation of sulfides. At the elevated temperatures resulting from these reactions, these products may further react with the carbon in the cathode to form carbon dioxide (CO2) and carbon disulfide (CS2). Carbon... 

Lithium insertion into titanium oxides plays on the redox couple Ti /TP at a potential of between 1.3 and 1.9 V versus Li/LL, depending on the polymorph. This potential window means that (1) safety risks linked to metallic lithium deposits can be avoided (intervening at 0 V) and (2) the copper collector can be replaced by less costly aluminum. 

Among all of the metal-air couples, the lithium-oxygen (Li-02) couple is especially attractive because it has the highest theoretical specific energy, as was shown in Table 22.1. Primary aqueous lithium-air batteries have been used for decades in applications such as life-vest beacons the battery is activated by sea water, and the... 

Fig. 7.5 Energy of the redox couples of iron (left) and vanadium (right) phosphate frameworks relative to the Fermi level of metallic lithium...

Ellis BL, Ramesh TN, Davis LJM, Govard GR, Nazar LE (2011) Structure and electrochemistry of two-electron redox couples in lithium metal fluorophosphates based on the tavorite structure. Chem Mater 23 5138-5148... 

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