2 Homometallic Alkoxides

188 Alkoxo and Aryloxo Derivatives of Metals
Zr⊲OPr i ⊳4.Pr i OH, 52 Nb⊲OPr i ⊳5 and Ta⊲OPr i ⊳5 75 with excess Al⊲OPr i ⊳3 yield 1:2
products only on volatilization, 52,74 irrespective of the excess of Al⊲OPr i ⊳3 taken
(Eqs 3.8 and 3.9).
Zr⊲OPr i ⊳4.Pr i OHC2Al⊲OPr i ⊳3
M⊲OPr i ⊳5C 2Al⊲OPr i ⊳3
Pr i OH
! ⊲Pr i O⊳2Al⊲ -OPr i ⊳2Zr⊲OPr i ⊳2⊲ -OPr i ⊳2Al⊲OPr i ⊳2
⊲3.8⊳
Pr i OH
! ⊲Pr i O⊳2Al⊲ -OPr i ⊳2M⊲OPr i ⊳3⊲ -OPr i ⊳2Al⊲OPr i ⊳2
⊲3.9⊳
where M D Nb or Ta.
The hafnium analogue of zirconium has been prepared76 in the 1:2 molar reaction
between Hf⊲OPri⊳4.PriOH and Al⊲OPri⊳3, with its structure recently elucidated by X-ray
crystallography. 77
The products, [⊲PriO⊳2ZrfAl⊲OPri⊳4g2] and[⊲PriO⊳3MfAl⊲PriO⊳4g2] are volatile and
monomeric in organic solvents. However, dimeric volatile products are obtained in
the 1:1 molar reactions of Al⊲OPri⊳3 with Zr⊲OPri⊳4.PriOH, Nb⊲OPri⊳5 and Ta⊲OPri⊳5 (Eqs 3.10 and 3.11):
2Zr⊲OPr i ⊳4.Pr i OH C 2Al⊲OPr i ⊳3
Pr i OH
!f⊲OPr i ⊳2Al⊲ -OPr i ⊳2Zr⊲OPr i ⊳2⊲ -OPr i ⊳g2
⊲3.10⊳
2M⊲OPr i ⊳5 C 2Al⊲OPr i ⊳3 !f⊲Pr i O⊳2Al⊲ -OPr i ⊳2M⊲OPr i ⊳3⊲ -OPr i ⊳g2
⊲3.11⊳
where M D Nb or Ta.
A few more illustrative examples of the synthesis of heterometal alkoxides by the
interactions of component alkoxides are represented by Eqs (3.12)–(3.23).
M⊲OBu t ⊳2 C M 0 ⊲OBu t ⊳ ! M⊲OBu t ⊳3M 0
where M D Ge(II), Sn(II), Pb(II); M 0 D In, Tl. 54
where M D Sr, Ba. 78
⊲3.12⊳
2Sn⊲OBu t ⊳2 C M⊲OBu t ⊳2 ! MfSn⊲OBu t ⊳3g2 ⊲3.13⊳
2Tl⊲OR⊳ C M⊲OR⊳4 ! Tl2M⊲OR⊳6 ⊲3.14⊳
M D Sn⊲IV⊳;RD Et. 55 M D Zr; R D CH⊲CF3⊳2. 79
Al⊲OPr i ⊳3 C 3Ga⊲OPr i ⊳3
Ga⊲OPr i ⊳3 C 3Al⊲OPr i ⊳3
Mg⊲OEt⊳2 C 2Sb⊲OEt⊳3
! AlfGa⊲OPr i ⊳4g3 73
! GafAl⊲OPr i ⊳4g3 73
! 1
80
2Mg2Sb4⊲OEt⊳16 ⊲3.15⊳
⊲3.16⊳
⊲3.17⊳