2 Homometallic Alkoxides

Table 6.45 (Continued)
Metal Aryloxides 633
Bond Bond
length ( ˚A) angle ( Ž )
Compound Aryloxide M–O M–O–Ar Ref.
[Me3SiCH2Zn⊲ 2-
OAr⊳2ZnCH2SiMe3]
trigonal planar Zn
2-OC6H3Pri 2-2,6 1.98 (1), 1.93 (1)
1.94 (1), 1.94 (1)
[fMe3SiCH2Zn⊲ 2-OAr⊳2g2Zn] 2-OC6H3Pri trigonal planar and
tetrahedral Zn
2-2,6 1.950 (2)–1.985 (2) xii
[f⊲Me3Si⊳2NgZn⊲ 2-
OAr⊳2ZnfN⊲SiMe3⊳2g]
trigonal planar Zn
2-OC6H3Pri 2-2,6 1.951 (5), 1.944 (5)
1.951 (5), 1.962 (4)
xii
[(pz)Zn(OAr)]
pyrazolylborate, tetrahedral Zn
OC6H4NO2-4 1.860 (2) 132 xiv
[Zn(OAr) 2⊲BPh2⊳][BPh4] OC6H4⊲20 could be considered an
[⊲ArO⊳2BPh2] anion
-bipy⊳-2 2.125 (5), 2.136 (5) xv
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has been stimulated by the widespread use of these derivatives to carry out important
organic transformations. 13,536 This reactivity is a direct consequence of the Lewis
acidity of the aluminium aryloxides. Early work demonstrated that aluminium phenoxide
carried out the ortho-alkylation of phenols by olefins. 537,538 More recently the use
of bulky aryloxide ligands attached to aluminium to generate monomeric, “designer”
Lewis acid catalysts has been pioneered by Yamamoto and co-workers. 13 Important
examples include the compounds [Al(Me)(OC6H2Bu t 2 -2,6-X-4)2] (XD Me, acronym
“MAD” 539,540 and X D Br, “MABR” 541 ), [Al(Me)(OC6H3Ph2-2,6)2] (“MAPH” 542 )and
[Al(OC6H3Ph2-2,6)3] (“ATPH” 543 ). These compounds are all easily obtained by adding
xii