Organobarium compounds

The barium phosphonium dibenzylide 18, first organobarium compound not belonging to the cyclopentadienyl series, was isolated at the same time (Scheme 12) [58]. In the latter, the Ba + ion is encapsulated by two C2-symmet-ric phosphonium ligands of opposite chirality. 

Alkyl derivatives of the alkaline-earth metals have also been used to initiate anionic polymerization. Organomagnesium compounds are considerably less active than organolithiums, as a result of the much less polarized metal-carbon bond. They can only initiate polymerization of monomers more reactive than styrene and 1,3-dienes, such as 2- and 4-vinylpyridines, and acrylic and methacrylic esters. Organostrontium and organobarium compounds, possessing more polar metal-carbon bonds, are able to polymerize styrene and 1,3-dienes as well as the more reactive monomers. 

The first organobarium compound not containing a cyclopentadienyl group has been obtained 57 (Ar = Cf,H4Me-4) <970M225>. 

Barium oxide, barium salicylate and/or other organobarium salts 2) Organometallic salts of lanthanum, hafnium and tantalum and their oxides Replacements for lead and copper compounds currently employed for ballistic modification. Particularly attractive due to production of considerably less smoke during combustion of propellants [245]. 

Furthermore, organobarium reagents, prepared from anhydrous Bal2 and (sily-loxy)allyllithium, react with carbonyl compounds at the least sterically hindered terminus (i.e. the y position)14. The ratio of y- to a-products depends upon the size of the silyl... 

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