Aryloxide analogue

Although metal alkoxides were successfully used as a synthon for the synthesis (see Scheme 9) of more interesting homo- and heteroleptic metal alkyls, they have not attained the same importance as their sterically hindered aryloxide analogues. This finding might be due to the general solubility of both the products [i.e., desired metal alkyls and alkali metal (generally lithium) alkoxides] in hydrocarbon solvents. This limitation has made a cleaner separation of the products more difficult. 

A hither facet of research has involved the structural characterisation of aluminium complexes which incorporate polydentate salen-type ligands. These have been noted in both neutral and monocationic (ion-separated) contexts (the latter requiring that the metal centre be stabilised by an external Lewis base) [35]. While such charged systems are invariably mononuclear the same is only usually true of their neutral analogues by virtue of the sterically demanding bis(aryloxide), chelating ligand. In the context of these latter complexes, dimerisation has been noted [251] while, more recently, the employment of flexible alkyl chains between two salen-coordinated aluminium ions has enabled the observation of dinuclear compounds [160, 161]. 

Although so far utilized (64a) only for the preparation of aryloxide derivatives, ether adducts of the lanthanide nitrates, such as [Ln(N03)3-Me0(CH2CH20)4Me], may also prove to be convenient starting materials for their alkoxide analogues by reactions with alkali alkoxides. 

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. 

Introduction.—Few reviews have appeared dealing with more or less general aspects of cyclophosphazene chemistry. The role of cyclophosphazenes as model compounds for reactions of their polymeric analogues has been discussed some fundamental subjects in the area of phosphorus-nitrogen chemistry such as aminolysis, alcoholysis, hydrolysis, and tautomerization phenomena have also been discussed. An extensive review has appeared dealing with reactions of phosphazenes with alkoxides and aryloxides. ... 

The 4-methylphenoxide complexes / c-[Re(OAr)(CO)3L2] 0 = PMc3, L2 = diars) show much less tendency to insert electrophiles compared to the methoxide analogues. Neither phenoxide reacts with CO2 whereas only the PMe3 derivative will insert CS2. In contrast both methoxides insert both CO2 and CS2. " Again mechanistic data pointed to a direct attack of metal-bound alkoxide(aryloxide) on the electrophilic carbon atom. 

Hexakis(6-deoxy-6-iodo-2,3-di-0-methyl) a-cyclodextrin, on treatment with alkoxides and aryloxides, gave products derived by nucleophilic displacements of the iodide at five residues and elimination of hydrogen iodide to give the 6-deoxy-5-ene function at the sixth residue. P-Cyclodextrin was converted to the per-3-thio-D-altro analogue and then treated with the tetra-substituted benzene 37 to give the compound 38 which contains four cyclodextrin units and forms a 1 1 complex with tetraarylporphyrins. Disulfides, produced by linking monothio-cyclodextrin, have been described and include the 6,6-dimer, which is known, and the new 3,3- and 3,6-linked dimers. ... 

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