Barium organometallic compounds

The new silazane 5 may be reacted with activated metals, organometallic compounds or simple metal amides, or may first be transformed to its lithium salt and then reacted with metal(II) chlorides [11]. In all these cases, metal derivatives of 5 are obtained with the general formula j [Mc (/BuO)Si 9N(9M, which have no further base coordinated to the metal. So far we have synthesized amides with M = Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba, all elements in oxidation state +2. X-ray structure determinations have been performed on the calcium, manganese, iron, zinc, and barium derivatives. 

Although the first report of an organometallic compound of the heavier alkaline earth metals appeared near the beginning of the twentieth century,291 the RMX Grignard analogs of Ca, Sr, and Ba never fulfilled their promise as general-purpose synthetic reagents. More difficult to form, less thermally stable, and less selective in their reactions than their Mg counterparts, the literature data of the compounds was often contradictory, and many syntheses were irreproducible (see Calcium, Strontium, and Barium in COMC (1982)). 

Of the organometallic compounds of Group II elements, undoubtedly the chemistry of the magnesium compounds is best known. By contrast, the remaining elements in this group have received less attention and it is only recently that more information on organo derivatives of beryllium and, to lesser extent, of calcium, strontium, and barium has become available. Therefore, most of the observations regarding redistribution equilibria have been of more or less qualitative nature. 

Recently some papers have appeared which deal with the related structures of the heavier alkali earth metal organometallic compounds. Cyclopentadienyl derivatives of calcium, strontium, and barium proved to possess sufficient stability to permit their synthesis and subsequent crystallization. These results are briefly included in this review (see Table 111). 

T.P. Hanusa (2000) Coordination Chemistry Reviews, vol. 210, p. 329 - Non-cyclopentadienyl organometallic compounds of calcium, strontium and barium . 

This reaction was clarified with hexenyl stearate (I) at 60°C during the reaction between zinc stearate and 4-chloro-2-hexene in tetrahydro-furan. During this reaction, zinc stearate reacts immediately with 2 mol of model compound, and kinetic laws do not suggest the presence of CIZnOCOR as an intermediate product in the substitution reaction. Nevertheless, such an organometallic compound was suggested by Frye and Horst (9) and also by Anderson and McKenzie (10) who assumed that such compounds accounted for the ligand exchange between cadmium chloride and barium carboxylate. 

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. 

In 1958, poly(ethylene oxide)s of very high molecular weight became available. These products range in molecular weight from about 100 000 to 5 x 10 and above. Details of the techniques used to manufacture these polymers have not been disclosed, but the essential feature is the use of (generally) heterogeneous initiator systems. Effective initiators are mainly of two types, namely alkaline earth compounds (e.g., carbonates and oxides of calcium, barium and strontium) and organometallic compounds (e.g., aluminium and zinc alkyls and alkoxides, commonly with added co-catalysts). 

Barrett AGM, Crimmin MR, Hill MS, Procopiou PA (2010) Heterofunctionalization Catalysis with Organometallic Compounds of Calcium, Strontium and Barium. Proc R Soc 466 927-963... 

With some remarkable exceptions, the organometallic compounds of group 2 are redox-inactive species that demonstrate a +2 oxidation state [1-6]. The cation achieves a noble gas configuration, while complexes of calcium, strontium and barium possess d° electron configurations. The ionic radii of the dications increase as the group is descended (Mg " < < Sr < Ba ), whereas the Pauling... 

W. E. Lindsell in Structure oj Magnesium, Calcium, Strontium, and Barium Compounds in Comprehensive Organometallic Chemistry, G. Wilkinson. F. G. A. Stone, E. W. Abel. Eds., Vol. 1. pp 155-252. Pergamon, Oxford 1982. 

The use of sterically bulky ligands to provide kinetic stability to compounds of the heavier group 2 elements has become widely practiced, and has facilitated the synthesis of diorganyl complexes of various types. Advances in the organometallic chemistry of bonded compounds of calcium, strontium, and barium have been reviewed. 

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]. 

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