Lithium coordination chemistry

In recent years this simple picture has been completely transformed and it is now recognized that the alkali metals have a rich and extremely varied coordination chemistry which frequently transcends even that of the transition metals. The efflorescence is due to several factors such as the emerging molecular chemistry of lithium in particular, the imaginative use of bulky ligands, the burgeoning numbers of metal amides, alkoxides, enolates and organometallic compounds, and the exploitation of multidentate... 

The lithium phosphonium diyiides 1, first described by Wittig and Rieber (R=H) [45] were until recently mainly used as ligands in coordination chemistry [46]. These species also constitute excellent tools in organic synthesis [47], still recently attested by works described below (Scheme 9). 

Lithium halides disrupt the dimeric structures of 59a or 59c to give distorted cubes of the type 60, in which a molecule of the lithium halide is entrapped by a Li2[E(NtBu)3] monomer.164,165 Similar structures are found for the MeLi, LiN3 and LiOCH=CH2 adducts of 59a.166 168 The pyramidal dianion [Te(N Bu)3]2 has a rich coordination chemistry,169 171 although redox processes are sometimes observed in metathetical reactions with metal halides. For example, reaction with PhPCl2 gives a spirocyclic Te(IV) complex of the [PhP(NtBu)3]2 dianion,163 while treatment with Sn(II) salts generates a complex with a four-coordinate Sn(IV) = Te functionality.172... 

Oi T, Odagiri T, Nomura M (1997) Extraction of lithium from GSJ rock reference samples and determination of their lithium isotopic compositions. Anal Chim Acta 340 221-225 Oi T, Shimizu K, Tayama S, Matsuno Y, Hosoe M (1999) Cubic antimonic acid as column-packing material for chromatographic lithium isotope separation. Sep Sci Tech 34 805-816 Olsher U, Izatt RM, Bradshaw JS, Dailey NK (1991) Coordination chemistry of lithium ion a crystal and molecular structure review. Chem Rev 91 137-164... 

To uncover new reaction pathways towards unprecedented target materials, the understanding of structure formation principles is important. One of the lead structural principles in lithium organic chemistry is the /X3-capping of the metalated carbon atom Ca to a lithium triangle. This motif can further aggregate to form deltahedra. The tetrahedra and octahedra can either be free of solvent or be coordinated by Lewis-basic donor molecules... 

Dimeric and higher aggregate lithium amides can generally be classified into the coordination motifs illustrated in Scheme 2.2. The four-membered (LiN)2 ring is ubiquitous in lithium amide chemistry and is observed both in discrete dimeric structures in either planar (Scheme 2.2, A) or non-planar (Scheme 2.2, B) geometries as well as in oligomeric and polymeric (ladder) frameworks (Scheme 2.2, C). Trimeric six-membered (LiN), ring... 

The chemistry of the alkali metals has in the past attracted little attention as the metals have a fairly restricted coordination chemistry. However, interesting and systematic study has blossomed over the past 25 years, largely prompted by two major developments the growing importance of lithium in organic synthesis and materials science, and the exploitation of macrocyclic ligands in the formation of complexed cations. Section 12.4 deals with the use of complexed cations in the generation of alkalides and electrides. 

In the lithium and cesium enolates of o-methoxyacetophenone, the methoxy oxygen coordinates with the smaller lithium cation but not with the cesium cation . Other examples of lithium enolate chemistry include a thermochemical analysis of the aldol reaction of lithiopinacolonate with pivalaldehyde and a comparison of the proton affinities and aggregation states of lithium alkoxides, phenolates, enolates, -dicarbonyl enolates, carboxylates and amidates. Although the lithium enolate of cyclopropanone itself remains unknown, derivatives (accompanied by their aUenoxide isomer) have been implicated in the reaction of a-(trimethylsilyl) vinyl lithium with CO. That both species are seemingly formed is surprising because cyclopropanone enolate is expected to be much less stable than its acyclic isomer cyclopropene is less stable than allene by almost 90 kJmol-. ... 

It has long been known that thiolate ligands (RS ), which are formally derived from thiols (RSH) by deprotonation, are well suited to form metal complexes (1). Specific reviews of this area have covered the structural chemistry of metal thiolates (la), the coordination chemistry of metal thiolates from a bioinorganic perspective (lb), transition metal thiolates (lc), and, most recently, early transition metal thiolates (Id). Because of potential thione-thiol tautomerism, a review dealing with complexes of heterocylic thione donors (le) is also relevant. This chapter concentrates on thiolate complexes of copper , lithium, and magnesium, but we also mention, for comparison or contrast, many related species of silver and gold and of some complexes that contain selenolate and tellurolate ligands. However, it should be emphasized that we have not attempted a comprehensive literature search outside the primary field of interest. 

One further insight into the coordination chemistry of these lithium enolates is obtained from the stereoselectivity observed in the reactions of chiral a-alkoxyketone enolates. For example, the... 

Ciampolini, M., Nardi, N., Valtancoli, B. and Micheloni, M. (1992) Small aza cages as fast proton sponges and strong lithium hinders. Coordination Chemistry Reviews, 120, 223-236. 

He has carried out researches in various fields of inorganic chemistry (coordination chemistry of 3d-metals, high-temperature chemistry of molten fluorides), physical chemistry (phase equilibria in molten salt systems), electrochemistry (thermodynamics of metal-electrolyte interface, electrodeposition of refractory and other metals from molten salts, lithium batteries and active materials for them) and, more recently, nanochemistry of inorganic oxide materials. 

---