Organometallic compounds of aluminum

Other organometallic compounds of aluminum include the alkyl hydrides, R2A1H. Molecular association of these compounds leads to cyclic tetramers. When the dimeric and trimeric compounds are dissolved in a basic aprotic solvent, the aggregates separate as a result of formation of bonds between A1 and the unshared pair of electrons on the solvent molecule. Toward Lewis bases such as trimeth-ylamine, aluminum alkyls are strong Lewis acids (as are aluminum halides). 

Aluminum is the most abundant metal and the third most abundant element in the Earth s crust, behind only oxygen and silicon. Its low weight and useful properties make aluminum and its alloys valuable materials for manufacturing and electrical applications. Inorganic compounds of aluminum are plentiful and used as absorbents, catalysts, ionic conductors, ceramics, and electrical materials. Organometallic compounds of aluminum are also of great industrial importance and fundamental discoveries continue to be made regarding the variety of coordination numbers, structures, oxidation states, and reactivity exhibited by aluminum. ... 

A. McKillop.J. D. Smith,andl.J. Worralleds, Organometallic Compounds of Aluminum, Gallium, Indium and Thallium , Chapman and Hall, New York, 1985. 

A) Ziegler method Catalyst systems can be prepared by reacting a nickel(II) salt with an organometallic compound of the main group metals but aluminum is preferred. 

The low-pressure polymerization of olefins using Ziegler-Natta catalysts, i.e., mixtures of compounds of transition groups IV to VI of the periodic table of the elements together with organometallic compounds of groups I to III is widely applied. Such catalysts, consist of titanium alkyl compounds and aluminum alkyl compounds or alkylaluminum halides. 

Pentamethylantimony was the first It6Sb species to be obtained by Wittig and Torssell in 1955 (104) Various other derivatives of this type have since been synthesized, and a range of preparative methods has been described. Among these are the alkylation of RiSbX, R3SbX2, and SbX species with organometallic compounds of lithium, magnesium, aluminum,... 

Ziegler-Natta Catalysts (Heterogeneous). These systems consist of a combination of a transition metal compound from groups IV to VIII and an organometallic compound of a group I—III metal.23 The transition metal compound is called the catalyst and the organometallic compound the cocatalyst. Typically the catalyst is a halide or oxyhalide of titanium, chromium, vanadium, zirconium, or molybdenum. The cocatalyst is often an alkyl, aryl, or halide of aluminum, lithium, zinc, tin, cadmium, magnesium, or beryllium.24 One of the most important catalyst systems is the titanium trihalides or tetra-halides combined with a trialkylaluminum compound. 

The organometallic chemistry of aluminum is dominated by the chemistry of aluminum(lll), but lower oxidation state compounds are now accessible. The first examples of this class of compounds are carbonyl complexes such as Al(CO), A1(C0)2, and Al3(CO), which were generated upon exposure of aluminum atoms to CO in matrix-isolation experiments near 20 K. The number, relative intensities, and frequency of the carbonyl stretches in the IR spectra, along with isotopic labeling and EPR studies were used to verify these compositions. These complexes exhibit vco values of 1868, 1985 and 1904, and 1715 cm , respectively, indicative of Al- CO 7t backbonding. The carbonyl species are unstable at higher temperatures and no stable carbonyl complex of aluminum, in any oxidation state, has been reported. The monomeric aluminum-alkene adducts A1( -C2H4) and k rf-CeHe) were similarly identified in inert matrices at low temperature. No room-stable alkene complexes of aluminum have been reported. 

The less reactive organometallic compounds of silicon and lead also convert aluminum chloride into organoaluminum chlorides.243... 

This is the most commonly utilized method for synthesis of transition metal complexes with M —C a bonds. The following substrates are utilized halides, acetylacetonates, acetates, /-electron element alcoholates, as well as organometallic compounds of lithium, magnesium, aluminum, sodium, zinc, mercury, elements of group 14, etc. Ethers and hydrocarbons are used as solvents. In general, the synthesis should be carried out at lower temperatures and under inert atmosphere. 

In a series of studies over an extended period we found that this reaction is of uncommon synthetic and structural importance. Although it is best effected generally by the use of -butyllithium in ether, we showed that this exchange reaction proceeds with organometallic compounds of such metals as sodium, magnesium, barium, and aluminum. -In an examination of different solvents, we observed that low-boiling petroleum ether appears to be especially useful for reactions involving secondary and tertiary alkyl-lithium compounds which could not be prepared readily or used conveniently in ether solution. 

Recently, we have studied the addition of organometallic compounds to aluminum-imines and silylimines which are easily prepared from nitriles and aldehydes ly treatment with diisobutyl aluminum hydride (DIBAH) and lithium hexamethyl disilyl... 

There is a dearth of structural information about the mixed organometallic compounds. Lithium aluminum tetraethyl is isostructural with dimethyl-beryllium (42), as one might expect after noting that the ratio of metal atoms to alkyl groups is the same in the two compounds. The structure of LlA1(C2H5)4 is shown in Fig. 7 the relevant bond distances and angles are... 

---