Alkoxides aryloxide compounds

In THF, monomeric RMgX (I) and R2Mg (II) co-exist over a wide concentration range for the chlorides, bromides and iodides. The fluorides are present as the F-bridged dimers across the whole concentration range. Similarly, the alkoxide and aryloxide compounds, RMgOR, are present as the R2Mg(/r-OR )2Mg species in THF. 

TABLE 8. Selected H and NMR data for magnesium alkoxide and aryloxide compounds... 

Many polymeric chromium(III) complexes in this general class exist. For the general formula [Cr(L)(0PRR 0)2] , compounds have been prepared involving hydroxide, perfluorocarboxy-late, alkoxide, aryloxide and carboxylates.849,850... 

Boyle, T.J. and Ottley, L.A.M. (2008) Advances in structurally characterized lanthanide alkoxide aryloxide and silyloxide compounds. Chemical Reviews, 108, 1896-1917. 

The general formula for boric acid esters is B(OR)2. The lower molecular weight esters such as methyl, ethyl, and phenyl are most commonly referred to as methyl borate [121 -43-7] ethyl borate [130-46-9J, and phenyl borate [1095-03-0] respectively. Some of the most common boric acid esters used in industrial appHcations are Hsted in Table 1. The nomenclature in the boric acid ester series can be confusing. The lUPAC committee on boron chemistry has suggested using trialkoxy- and triaryloxyboranes (5) for compounds usually referred to as boric acid esters, trialkyl (or aryl) borates, trialkyl (or aryl) orthoborates, alkyl (or aryl) borates, alkyl (or aryl) orthoborates, and in the older Hterature as boron alkoxides and aryloxides. CycHc boric acid esters, which are trimeric derivatives of metaboric acid (HBO2), are known as boroxines (1). 

Compounds 134, 135 and 136 (Figure 71) are aUcylzinc alkoxides and aryloxides that exist as discrete monomeric molecules in the solid state. These compounds have in common that in addition to the covalently bonded alkoxy or aryloxy group, two... 

The nature of these products is unknown, but they may be mixed oxidation state UV/UVI species. Dioxouranium(VI) alkoxides, U02(0R)2, and some alcohol solvates are also known, (c) Aryloxides. The only aryloxides known are the dioxouranium(VI) compounds... 

Alkoxides and aryloxides demonstrate similar chemistry to that of hydroxides in that it is possible to prepare mixed metal or double metal derivatives similar to hydroxo salts such as Na2[Sn(OH)6]. The formation of mixed metal alkoxides, e.g. Na2[Zr(OEt)6] and Ln[Al(OPri)4]3, is typically a result of the electron deficiency (Lewis acidity) of the metal centers in units of the type M(OR)x or M(OAr)JC (x < 5). This then leads either to oligomerization via alkoxide bridges or, in the presence of other alkoxides, to the formation of mixed metal compounds. 

Of the vast array of physical techniques available to the modern chemist, many have been applied to the study of metal alkoxides and aryloxides. We have decided to summarize the physical and spectroscopic properties of alkoxides and aryloxides according to stoichiometry and include techniques only where they highlight a particularly interesting characteristic of these compounds. The mass of more routine data that has been accumulated cannot be covered in detail here. 

Chart 3 Alkoxide and aryloxide ligands used in lanthanide diene polymerization catalysts and model compounds... 

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