Lithium salts molecular structures

Addition of anhydrous LiX (X = OH, Cl, Br, 1) to Li[Bu"C(NBu%] in THF afforded laddered aggregates in which two neutral lithium amidinates chelate one LiX unit. When the added salt is Lil, the monomeric laddered aggregate is isolated as a bis-THF adduct. In the case of LiOH, LiCl, and LiBr, the ladders dimerize about their external LiX edges. This process is highlighted in Scheme 10 for LiOH. The molecular structure of the resulting dimeric ladder complex is depicted in Figure 2. °... 

A first structural characterization of a cyclobutadiene dianion was performed by Boche and coworkers, who generated the dilithium salt of the 1,2-diphenylbenzocyclobutadiene dianion (143) (by deprotonation with n-butyllithium in the presence of TMEDA) (Figure 17) . Nevertheless, the molecular structure of 143 resembles more the structures of dilithiated alkenes, synthesized by reaction of the corresponding alkynes with metallic lithium. In that class of compounds, carbon-carbon bonds, capped by two lithium centres, are the structural motif (see Section II. E). 

The physical and chemical properties of the tetrahydroborates show more contrasts than the salts of nearly any other anion. The alkali metal salts are the most stable. In dry air, NaBH4 is stable at 300°C and in vacuo to 400°C with only partial decomposition. In contrast, several tetrahydroborates, including the titanium, thallium, gallium, copper, and silver salts, are unstable at or slightly above ambient temperatures. The chemical and physical properties of the tetrahydroborates are closely related to molecular structure. Sodium tetrahydroborate, which is typical of the alkali metal tetrahydroborates except for the lithium salt, has a face-centered cubic (fee) crystal lattice which is essentially ionic and contains the tetrahedral [BHJ- anion. The tetrahydroborates of the polyvalent metals are in many cases the most volatile derivatives of these metals known. Aluminum tris(tetrahydroborate)... 

For the preparation of MIPM, the above phenol, 2,5-dimethoxyphenol was isopropylated with isopropyl bromide in methanolic KOH giving 2,5-dimethoxy-l-(i)-propoxybenzene as an oil. This formed the benzaldehyde with the standard Vilsmeier conditions, which melted at 77-78 °C from hexane and which gave a yellow malononitrile derivative melting at 171.5-173 °C. The nitrostyrene, from nitroethane in acetic acid was orange colored and melted at 100-101 °C from either methanol or hexane. This was reduced with lithium aluminum hydride in ether to give 2,5-dimethoxy-4-(i)-propoxyamphetamine hydrochloride (MIPM). The properties of the isolated salt were strange (soluble in acetone but not in water) and the microanalysis was low in the carbon value. The molecular structure had a pleasant appeal to it, with a complete reflection symmetry shown by the atoms of the amphetamine side chain and the isopropoxy side chain. But the nature of the actual product in hand had no appeal at all, and no assay was ever started. 

In further studies of ion-pairing, a variety of sec-a-silyl benzylic lithium compounds 39, 40, 41 and 42, were prepared, both externally and internally solvated, the latter by means of a potential ligand attached to the carbanionic moiety. Ion-paired carbanide salts tend to assemble into several arrangements which differ in aggregation, solvation and in the proximity of anion to cation. Many of these species interconvert rapidly relative to the NMR time scale even at quite low temperatures. An internally solvated ion-pair carbanide salt is more likely to assume a single molecular structure, to undergo the latter exchange processes more slowly and thus be more amenable to NMR spectroscopic studies of structure and dynamic behavior. 

The complexes Me2E(C5H4)(C5Me4)TiCl2 (E = Si, Ge) have been prepared by the reaction of the corresponding lithium salt of the cyclopentadiene with TiCl4(THF)2 and the molecular structure of the silyl derivative has been determined by X-ray diffraction. In combination with MAO, the silyl derivative catalyzes the polymerization of ethylene.1693... 

Six-coordinate mono-Cp chloride complex 355 containing two mono-anionic, o/7/w-substituted phenoxy-imine [0, . ]-r pc ligands was obtained by salt metathesis involving the reaction of CpZrCI (DME) and the lithium salt of the ligand in THF (Scheme 77).269 If the centroid of the Cp ring is considered as a single coordination site, the molecular structure of this complex can be described as octahedral, with a tram (O-O), as (N-N), and as (Cl-Cp)... 

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