Aryloxides clusters

Sometimes, the formation of aryloxide clusters can be quite surprising. The reaction of K PR"(C6H4-2-OMe) (R" = CH(SiMe3)2) with Ybl2 under similar conditions yields the imexpected alkoxophosphide complex... 

Liddle TS, William C. Synthesis and structure of the novel octanuclear Utfaium aryloxide cluster [(hmqLi)g(THE)4](hmq = 2-hydroxy-4-methylquinoline monoanion) formation of a rare four-rung intercepted Li-O ladder. J Chem Soc Dalton Trans 2002 3923. ... 

The use of unsubstituted or 4-methyl phenols resulted in the formation of cluster compounds [58]. However, 2,6-di(fcrt-butyl) substituted aryloxide ligands allowed the isolation of mononuclear 3-coordinate homoleptie complexes of the lanthanide elements, the coordination mode of which was first demonstrated with the N(SiMe3)2 ligand [59], The 2,6-substitution pattern is very effective because the alkyl groups are directed towards the metal center and impose a steric coordination number onto the metal which is comparable to the Cp ligand (Cp 2.49 OC6H3rBu2-2,6 2.41) [60],... 

A combination of two square-pyramids of [Ln5((jt4-OH)( X3-OH)4] with one hollow octahedron of [Ln6([X3-OH)8] by vertex-sharing leads to the assembly of esthetically pleasing tetradecanuclear complexes with a rod-like cluster core (Figure 6.16). Complexes characterized by such a core have been successfully prepared using aryloxide [34, 35], P-diketonate [87], and amino acid ligands [104],... 

Clusters of lanthanide alkoxides, aryloxides, and macrocyclic polyaryloxides... 

It is clear from the chemistry of lanthanide clusters based on aryloxide ligands that lanthanide coordination chemistry can be further developed by having recourse to other fimctionalized aryloxide ligands. In this context, the use of constrained, macrocyclic polyaryloxide ligands such as calixarenes or their sulfur-containing analogues appears intriguing. 

The alkali metal is typically bound to the aryloxide oxygen atoms, although in a number of cases it has been shown that interactions between sodium and the phenoxy ring of aryloxide ligand are an important aspect of the bonding in the mixed metal cluster (Eq. 6.34 ). 

There has been an outburst of research interest in the structures, physical properties, and chemistry of the group 2 metal aryloxides. This is particularly true for the elements strontium and barium where work has been stimulated by the possible use of metal aryloxides as precursors (either via sol-gel or MOCVD processes) for the formation of binary and ternary oxides containing these metals.2 Synthetic procedures are based on either the halide (Be) alkyl derivatives (Mg, Grignard derivatives, etc.) or the actual metallic element (Ca, Sr, Ba). Structural studies (Tables 6.14-6.18) show for the smaller elements Be, Mg, and Ca that monomeric and dimeric structural motifs dominate, with rarer examples of trinuclear clusters, e.g. [Ca3(OPh)5(HMPA)6][OPh.2HOPh].2 2 in the case of strontium and barium a more extensive cluster chemistry has been developed for small aryloxide ligands, while monomeric units with terminal aryloxides can be formed with bulky ligands and sufficient additional Lewis bases, e.g. [Ba(OC6H2Bu2-2,6-Me-4)2(THF)3].2 ... 

It is also common that mixed metal derivatives of the lanthanides and group 1 metals are the products of synthesis. This can occur for small aryloxides leading to clusters, e.g. [La2Na3(/r4-OAr)3(/z2-OAr)6(dioxane)5] (OAr = OQH4Me-4), as well as in the generation of more discrete species with bulkier aryloxides, e.g. [(thf)Li(/i2-OAr)2La(OAr)2(THF)] (OAr = OC6H3Pr -2,6). In some situations the alkali metal interacts with the aryloxide jr-nucleus, e.g. [Cs( 7r-Ar-0)2La(OAr)2] (OAr = OC6H3P1I-... 

Ruthenium chemistry typically finds aryloxide ligands attached to the metal in low oxidation states. The extensive number of carbonyl aryloxide compounds reported for this metal exemplifies this (Table 6.34). The cluster compound [(H)2Ru6(CO)i6(M2-0-f -C6H4)] and derivatives contain the metallated phenoxide bridging two metal centres as well as -bound to another. 

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