Lithium tetrakis aluminate

Lithium aluminum hydride dissolves in pyridine and forms lithium tetrakis-(A -dihydropyridyl)aluminate which itself is a reducing agent for purely aromatic ketones [440, 441]. 

Heteroaromatics are subdivided, according to the electron influence of the heteroatom, into w-electron-deficient compounds and compounds with an excess of it electrons on the ring carbon atoms. The typical ff-electron-delicient compound pyridine has so far been made to react only in one case the reaction of lithium tetrakis(A-dihydropyridyl)-aluminate (LDPA) [112-114), obtainable from pyridine and lithium aluminum hydride, with trifluoromethanesulfenyl chloride in an excess of pyridine affords 3-trifluoromethylmercaptopyridine in low yield (13%) (60). This reaction probably occurs through sulfenylation of the l,2-dihydrop5T idyl moiety of the LDPA with the formation of a 2,5-... 

The lithium tetrakis (dihydrogenphosphido) aluminate, which is soluble in diglyme, shows typical organic and inorganic substitution reactions and can be used to introduce PH2 groups into molecules. The compound is quantitatively hydrolysed thus ... 

Lithium aluminum hydride reacts readily with pyridine to yield lithium tetrakis-(A/-dihydropyridyI)aluminate, LiAI(NR2)4 (structures 108 and 109).152 The NR2 groups represent 1,4-dihydro- and/or, 1,2-dihydropyridyl residues. The two diverse N-ligands may be part of the same molecule in association with the A1 metal. The structure of the adduct has been investigated by IR and NMR spectroscopy and by deuterium-labeling experiments. The latter approach has been used to determine the 1,2 to 1,4 ratio, which is found to be close to 1 2 when the reaction is carried out at room temperature. The N—A1 bond is assumed to be covalent, though of a markedly more ionic character as compared to the N—H bond in dihydropyridines.152... 

Dialkylamido complexes54 are generally more tractable than those containing NH2 groups. Lithium tetrakis(dimethylamido)aluminate is obtained by the reaction shown in equation (4).55... 

Reaction of methanetellurol with lithium aluminum hydride in diethyl ether caused liberation of hydrogen and formation of lithium tetrakis[methyltelluro]aluminate. This compound was not isolated but reacted with silyl or germyl halides to give silyl or germyl methyl tellurium derivatives4. 

Lithium tetrakis[methyltelluro]aluminate, prepared from methanetellurol and lithium aluminum hydride, reacted with silyl, germyl, and stannyl halides at low temperatures to produce, for instance, methyl silyl tellurium derivatives1. 

The results were interpreted in terms of steric requirements of the actual reducing species. It was suggested that attack of BH4" proceeds exclusively along the 1,4-reduction mode, whereas alkoxyborohy-drides (formed as reaction products) prefer the 1,2-reduction mode. The pyridine borine itself does not reduce enones under the reaction conditions, but it inhibits formation of alkoxyborohydrides. - The same trend was observed with aluminum hydride reductions. When LiAlH4 was first reacted with pyridine to form lithium tetrakis(dihydro-N-pyridyl)aluminate, 1,4-reduction predominated. ... 

Lithium aluminum hydride (LAH) reductions are carried out in aprotic solvents and give rise to the dihydro- and tetrahydropyridine derivatives. LAH reacts with both pyridines and pyridinium salts. It has been known for some time that aged ( 24 h) pyridine and LAH solutions form complexes of lithium tetrakis(A -dihydropyridinyl)aluminate (40, LDPA), - which is believed to consist of a mixture of the 1,2- and 1,4-dihydropyridines (by NMR). Indeed, LDPA itself has been used as a selective reducing agent for ketones and affords 3-substituted pyridines (41) on reaction with alkyl halides. 2,5-Dihydropyridines have been identified as intermediates in similar reactions. Kuthan and co-workers have shown that for 3,5-dicyan-... 

Lithium aluminum hydride-Pyridme [Lithium tetrakis(N-dihydropyridyl)aluminate, LDPA], 1, 599-600. 

Treatment of cyclopropanecarbonyl chloride with excess of lithium tetrakis(trimethyl-silyl)aluminate in the presence of a catalytic amount of copper(I) cyanide gave cyclopropyl-carbonyltrimethylsilane in 89% yield. 

Lithium tetrakis(methylselenato)aluminate reacts with bromotrimethylsilane to form methylselenotrimethylsilane in 70-95% yield [350] (Eq. 3.170) ... 

The zinc and cadmium organosilyl compounds are about equally unstable, in sharp contrast to the mercury compounds. The reaction of lithium tetrakis(trimethylsilyl) aluminate with zinc acetate in diethyl ether yields (25 %) bis(trimethylsilyl) zinc [435]. This compound can be kept for about three weeks under an inert gas at — 20 °C. The reaction of lithium tetrakis(trimethylsilyl) aluminate with cadmium acetate forms bis(trimethylsilyl) cadmium [435] (27%, very unstable, sensitive to light). Bis(tri-t-butylsilyl) cadmium [436] (m. p. 140 °C, slightly yellowish crystals which turn greenish black on exposure to air) can be obtained from tri-r-butylsilane and diethylcadmium (Eq. 3.230) ... 

Lithium tetrakis(trimethylsilyl) aluminate [445] LiAl[(H3C)3Si]4-2DME (m.p. 93 °C), which is relatively stable, has been prepared in 44 % yield from Al, Si, Hg and chlorotrimethylsilane in DME/TMF. Non-solvated NaAl[(H3C)3Si]4 was obtained in similar fashion. This compound reacts with aluminium chloride in pentane at 25 °C to form solvent-free tris(trimethylsilyl)aluminium [446] (47% m.p. 60°C (dec.)) (Eq. 3.239) ... 

The difficultly accessible 3-substituted pyridines have been synthesized in one step by alkylation (or bromlnatlon) of lithium tetrakis(N-dihydropyridyl)aluminate, which is readily prepared by the reduction of pyridine with L1A1H4. ... 

In the course of the study of use of pyridine as solvent, Lansbury discovered that on dissolving powdered lithium aluminum hydride (0.5 g.) in pyridine (50 ml.) and letting the orange solution stand in a stoppered bottle for at least 24 hrs. one obtains a solution of anew, milder reducing agent NMR and IR data show that the substance lacks Al-H bonds and contains both 1,2- and 1,4-dihydropyridine groups bound to aluminum. It is regarded as tetrakis-(N-dihydropyridyl)-aluminate ... 

---