2 Homometallic Alkoxides

16 Alkoxo and Aryloxo Derivatives of Metals
according to the following reaction:
Ca C 4HOC2H4OMe n-hexane
! 1
9 [Ca9⊲OC2H4OMe⊳18].2⊲HOC2H4OMe⊳ C H2 " ⊲2.4⊳
By contrast, a similar reaction with barium granules followed a different course 51
to yield [H4Ba6O⊲OCH2CH2OMe⊳14] which has been characterized by single-crystal
X-ray diffraction studies.
Recently, it has been reported that monomeric Ba[O⊲CH2CH2O⊳nCH3]2 (n D 2or3)
products are obtained in the reactions of barium granules with an oligoether alcohol 52
in tetrahydrofuran (Eq. 2.5):
Ba C 2HO⊲CH2CH2O⊳nCH3
THF
! Ba[O⊲CH2CH2O⊳nCH3]2 C H2 " ⊲2.5⊳
where n D 2or3.
The factor(s) determining the variation in the nature of products in the reaction of
Ca/Ba with chelating alcohols obviously require further investigations.
Interestingly, the reaction of barium with a sterically demanding alcohol having
donor functionality yields a volatile derivative 53 with excellent solubility (even in
n-pentane) (Eq. 2.6):
Ba C 2HOCBu t ⊲CH2OPr i ⊳2
2.1.2 Group 3 and the f-block Metals
THF/NH3
! Ba[OCBu
⊲ H2⊳
t ⊲CH2OPr i ⊳2]2
⊲2.6⊳
The method involving direct reaction of a metal with alcohol was extended by Mazdiyasni
et al. 54 for the formation of scandium, yttrium, and lanthanide alkoxides using
mercuric chloride (10 3 –10 4 mol per mol of metal) as a catalyst:
Ln C 3Pr i OH
(excess)
Ln D Sc,Y,Dy,andYb.
HgCl2⊲cat.⊳ 1
!
heat n [Ln⊲OPri⊳3]n C 3
2 H2 " ⊲2.7⊳
Mercuric chloride appears to form an amalgam with the metal which reacts with
isopropyl alcohol to yield the triisopropoxide. Mazdiyasni et al. 54 also noticed that the
use of HgCl 2 in stoichiometric ratio resulted in the formation of alkenoxide contaminated
with chloride. For example, the reaction of yttrium metal, isopropyl alcohol, and
mercuric chloride in 1:3:4 molar ratio yielded yttrium isopropeneoxide 55 and hydrogen
chloride:
Y C 3HOCH⊲CH3⊳2 C 4HgCl 2
! Y[OC⊲CH3⊳DCH2]3 C 4Hg C 8HCl C 1
2 H2
⊲2.8⊳
The above route has also been utilized for the synthesis of neodymium 56 and
yttrium 57 alkoxides as shown by Eqs (2.9) and (2.10):
4Nd C 16Pr i OH ! [Nd⊲OPr i ⊳3.Pr i OH]4 C 6H2 " ⊲2.9⊳
10Y C 30HOC2H4OMe ! [Y⊲OC2H4OMe⊳3]10 C 15H2 " ⊲2.10⊳