Metal aryloxides simple

There are a large number of synthetic routes to metal aryloxides. The synthetic strategy that is adopted depends largely on the available metal precursors as well as the nature of the ligand that is being used. Many of the synthetic methods used for simple aryloxide derivatives in nonprotic solvents are identical to those used for the corresponding metal alkoxides. 

The homoleptic metal dialkylamides are an important class of compounds in inorganic chemistry. They are typically synthesized by treatment of the corresponding halide with lithium or sodium dialkylamide. Although involving an extra synthetic step, there are numerous examples where metal dialkylamide intermediates are useful in the synthesis of metal aryloxide compounds. The reaction normally involves the simple addition of the parent phenol to the metal dialkylamide in a nonprotic, typically hydrocarbon, solvent (Eqs 6.36, 6.37, and 6.38 ). 

Table 1. Monomeric A1R1R2R3 complexes incorporating simple, monodeprotonated aryloxide ligands (Rl) and, where appropriate, Lewis base (L). R2, R3 = other ligands, C.N. = coordination number of the metal... 

In the context of bidentate ligands, and in a similar vein to the polyfunctional aryloxides discussed above [141, 142, 146, 147], the chelation of a metal centre by deprotonated j5-diketones is a recurrent feature of monomeric organooxide complexes of aluminium. The employment of such ligands results in the observation of simple hexa-coordinate complexes which incorporate three [RC(0)C(H)C(0)R ] moieties (R = R = Me [177,178], CF3 [179], Ph [180, 181] R = f-Bu, R = CF3 [182]). More recently, the cocrystallisation of M(acac)3 (M = Al, Cr) has allowed the crystallographic study of metal disorder in a series of solid solutions of stoichiometry Ali, cCi x(acac)3 (x = 0.02-0.91) [183, 184]. Chelation of the metal centre similar to that reported in monomeric ] -diketonates has also been noted in the presence of... 

The unsubstituted para-t-butyl calixarenes themselves complex metals via their aryloxide groups. Since aryloxide complexes are frequently oligomeric, the simple calixarenes do not give monomeric complexes. Aryloxides are hard ligands, therefore they readily form complexes with oxo-philic hard metal ions such as alkali metals, early transition metals, lanthanides, and actinides. Complexation is often inferred because the calixarene acts as a carrier for the metal ion from an aqueous to an organic phase. With the /wa-/-butylcalix[ ]arenes in alkaline solution, a value of n = 6 gives the best carrier for lithium(I), sodium(I), and potassium(I), with a value of n 8 giving the best carrier for rubidium(I) and caesium(I).15,16 Titanium(IV) complexes have been characterized,17-19 as well as those of niobium(V) and tantalum(V).20-22 These complexes are classified as... 

It has been concluded that the interaction of an analogous vanadium complex with hydrocarbons does not occur by a simple ct bond metathesis mechanism [35b], The alkylidene tantalum(V) complexes undergo intermolecular cyclo-metalation of the aryloxide hgand [35c] (Scheme VIII.5). 

The metal chlorides, bromides, and to a lesser extent iodides remain the single most important class of starting materials in inorganic chemistry. Many of them are conuner-ciaUy available in anhydrous form. The formation of aryloxide derivatives by simple addition of phenols to the corresponding anhydrous metal halide is sometimes a viable synthetic route that has been used for the formation of a variety of d-block metal compounds (Eq. 6.18) as well as some aryloxide complexes of the p-block metals. 

This method has been used to produce a variety of homoleptic aiyloxide complexes and has also been applied to the synthesis of mixed alkyl, aryloxide derivatives of metals. Partial substitution is typically achieved by simple control of the stoichiometry or by using sterically demanding aryloxides (Eqs 6.49, 6.50, and 6.51 ). 

The reaction of mixed alkyl, aryloxides of the group 4 metals with CO has not yielded simple insertion products. However, final products are clearly the result of subsequent reactivity of y/ -acyl intermediates. The compound [(ArO)2Ti(t/ -R NCR)(R)] undergoes reaction with CO to produce the non-planar oxa-aza-metallacycle [(ArO)2Ti OC(R)=C(R)N(R ) ]. Carbonylation of [(ArO)2MR2] in the presence of pyridine remarkably leads to pyridine-di-melhoxide complexes. The threo and erythro isomeric mixture can be rationahzed on the basis of nucleophilic attack of acyl groups on coordinated pyridine figands. ... 

For vanadium, the use of available lower valent hahdes has allowed the isolation of simple aryloxides with the metal in a variety of formal oxidation states (Table 6.24). Important mononuclear examples include [V(OC6H3Me2-2,6)3(py)2] and square planar [V(OC6H2Bu2-2,6-Me-4)2(py)2]. A variety of vanadium(v) aryloxides [(X)V(OAr>3] have also been isolated containing oxo (X = and imido (X = nr)388-390... 

Alkoxo and Aryloxo Derivatives of Metals Table 6.39 Simple aryloxides of nickel... 

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