2 Homometallic Alkoxides

30 Alkoxo and Aryloxo Derivatives of Metals
Homoleptic derivatives
MClx ⊲thf⊳ C xLiOR Et2O orTHF⊲L⊳
! 1
m [M⊲OR⊳x ⊲L⊳y]m C xLiCl # (2.70)
(M D Cr, 226 R D CHBut 2 , x D 3, L D THF, n D 3, y D 1, m D 1; M D Cr,226 R D
CHBut 2 , x D 3, L D Et2O, n D 0, y D 0, m D 1; M D Y, Nd, 227 R D CBu t 2CH2PMe2, x D 3, L D THF, n D 0, y D 0, m D 1; M D U, 228 R D CHBu t 2 , x D 4, L D THF,
n D 0, y D 0, m D 1).
The above reactions when carried out in 1:4 molar ratio with CrCl3(thf)3 and FeCl3 226
result in heterobimetallic alkoxide complexes, respectively of the types [(thf)Li( -
OCHBut 2 )2Cr(OCHBut 2 )2] and [(HOCBut 2 )Li( -OCHBut2 )2Fe(OCHBut 2 )2].
Heteroleptic derivatives
MClx C nLiOR Et2O orTHF/hexane
! M⊲OR⊳nClx n⊲L⊳y C LiCl # (2.71)
(M D Ti, 228 R D CBu t 2 CH2PMe2, 227a CBu t 3 ,228 x D 3, n D 2, y D 0; M D Ti, Zr, 228
R D CBu t 2 , x D 4, n D 1or2,y D 0; M D U,229 x D 4, n D 2, y D 2 ⊲L D Et2O⊳).
The same reaction (Eq. 2.71) carried out with chromium trichloride or cobalt
dichloride with two equivalents of the lithium reagent yields the heterobimetallic
species [(thf)2Li( -OCBu t 3 )Cr(OCBut 3 )]230 or [(thf)3Li( -Cl)Co(OCBu t 3 )2], 231 respectively.
The reaction represented by Eq. (2.71) has also been used in the preparation
of alkoxide derivatives of vanadium(III), chromium(VI), and molybdenum(III)
(Eqs 2.72–2.74):
VCl3 C xLiOCH2CF3
where x D 1or2, 232
benzene
! VCl3 x ⊲OCH2CF3⊳x C xLiCl # ⊲2.72⊳
CrO2Cl2 C xLiOR ! CrO2⊲OR⊳x Cl2 x C xLiCl # ⊲2.73⊳
where R D CH2CF3, CH2CCl3, CH2CH2Cl when x D 1or2 233 and R D CH⊲CF3⊳2,
x D 2. 234
Mo2Cl6⊲dme⊳ C 6LiOR DME
! Mo2⊲OR⊳6 C 6LiCl #CDME ⊲2.74⊳
where R D Bu t ,CMe2Et. 170
2.6 Preparation of Alkoxide Derivatives from Metal(loid) Hydroxides and
Oxides (Method F)
Hydroxides and oxides of non-metals behave as oxyacids or acid anhydrides and therefore
react with alcohols to form esters (alkoxides of these non-metallic elements) and
water:
M⊲OH⊳x C xROH ↽ ⇀ M⊲OR⊳x C xH2O " ⊲2.75⊳
MOx C 2xROH ⇀
↽ M⊲OR⊳2x C xH2O " ⊲2.76⊳