Group 13 elements alkyl halide compounds

Ziegler catalysis involves rapid polymerization of ethylene and a-ole-fins with the aid of catalysts based on transition-element compounds, normally formed by reaction of a transition-element halide or alkoxide or alkyl or aryl derivative with a main-group element alkyl or alkyl halide (1,2). Catalysts of this type operate at low pressures (up to 30 atm), but often at 8-10 atm, and, in special cases, even under reduced pressure, and at temperatures up to 120°C, but often as low as 20-50°C. Approximately 2,200,000 tons of polyethylene and 2,900,000 tons of polypropylene are produced per year with the aid of such catalysts. The polyeth-... 

Main-group elements X such as monovalent F, divalent O, and trivalent N are expected to form families of transition-metal compounds MX (M—F fluorides, M=0 oxides, M=N nitrides) that are analogous to the corresponding p-block compounds. In this section we wish to compare the geometries and NBO descriptors of transition-metal halides, oxides, and nitrides briefly with the isovalent hydrocarbon species (that is, we compare fluorides with hydrides or alkyls, oxides with alkylidenes, and nitrides with alkylidynes). However, these substitutions also bring in other important electronic variations whose effects will now be considered. 

The catalyst component consists of halides of IV-VIII group elements having transition valence and the cocatalysts are organometallic compounds like alkyls, aryls and hydrides of group I-IV metals. Although there are hundreds of such catalyst cocatalyst systems listed in table below. Systems based on the organoaluminium compounds such as triethyl aluminium (AlEt3) or diethyl aluminium chloride... 

Redistribution of substituents tends to be especially facile for halides, hydrides, and alkyls of Groups I—III nontransition elements because these compounds are electron-deficient. Bridging groups are present in many of these compounds. Even in the boron trihalides that are not bridged, a bridged transition state making use of the empty valence shell orbitals is possible, so that redistribution can occur with a relatively low activation energy (113) ... 

The best nucleophiles for the SrnI mechanism can make a relatively stable radical in the initiation part, either by resonance (enolates) or by placing the radical on a heavy element (second-row or heavier nucleophiles). The best electrophiles for the SrnI mechanism are able to delocalize the odd electron in the radical anion (aromatic leaving groups, carbonyl compounds), can make a stable radical (3° alkyl halides), and have a weak R-X (Br, I) bond. Tosylates and other pseudohalides are very poor SrnI electrophiles. If light is required for substitution to occur, the mechanism is almost certainly SrnI. 

The reaction of anionic species of group 14 elements with carbon electrophiles such as alkyl halides, acetates, and carbonyl compounds (eq (2))... 

Besides ethers, other compounds that form similar adducts accelerate the reaction of magnesium with an alkyl halide examples are dialkyl derivatives of elements of the Sixth Group (sulfur, selenium, and tellurium) and tertiary amines such as dimethylaniline, diethylaniline, pyridine, and quinoline. 

When alkyl halides react with metallic cadmium96,151 the primary product is probably the compound of type RCdX, as with the other elements of Group II, but so far such compounds have been obtained pure only by the action of anhydrous cadmium salts on dialkylcadmiums in anhydrous ether.152... 

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