2 Homometallic Alkoxides

460 Alkoxo and Aryloxo Derivatives of Metals
This process can also lead to the formation of metal–aryloxide bonds
via activation of pendant methoxy-aryl groups. For example the treatment of
[Cp⊲ 5 -C5H4CEt2C6H4OMe-2⊳TiCl2] with LiBr was found to lead to the chelating
phenoxide [Cp⊲ 5 -C5H4CEt2C6H4O-2⊳TiCl]. 114 The use of 2,6-dimethoxyphenyl
substituents can lead to bulky phosphine ligands. Early work by Shaw et al. showed
that ligands such as PBu t 2 fC6H3⊲OMe⊳2-2,6g can generate aryloxy-phosphines with
elimination of MeCl at iridium metal centres. 115 This type of reaction is now been
extended to a variety of metal systems. 116,117 In some situations the activation by
metal centres of the stronger aryl-O bond can occur within aryl-ethers. 118
3.4 From Metal Dialkylamides
The homoleptic metal dialkylamides are an important class of compounds in inorganic
chemistry. 119 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, 120 6.37, 121 and 6.38 122 ).
Ce[N⊲SiMe3⊳2]3 C 3HOAr ! Ce⊲OAr⊳3 C 3HN⊲SiMe3⊳2 ⊲6.36⊳
Me3C
where HOAr = HO X; X = H, Me, CMe3 .
Me 3C
Me2N
Mo
Me2N NMe2 NMe2
Mo
NMe2
NMe2
H3C
where ArOH = HO .
H 3C
6ArOH
ArO
Mo
ArO
ArO
Mo
OAr
OAr
OAr
+ 6HNMe2 (6.37)
[fYb⊲NR2⊳⊲ -NR2⊳g2] C4HOAr
! [fYb⊲OAr⊳⊲ -OAr⊳g2] ⊲6.38⊳
4HNR2
Bu t
where R = SiMe3; OAr = O Me.
Bu t
The dialkylamine that is produced can be readily removed, leaving the desired
product. In some instances, either incomplete substitution can occur (bulky aryloxides,