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2 Homometallic Alkoxides

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196 Alkoxo and Aryloxo Derivatives of Metals<br />

fAl⊲OPr i ⊳4gMCl C KGa⊲OPr i ⊳4<br />

where M D Co(II), Ni(II).<br />

fZr2⊲OPr i ⊳9g2FeCl C KAl⊲OPr i ⊳4<br />

fZr2⊲OPr i ⊳9gFeCl2 C 2KAl⊲OPr i ⊳4<br />

fZr2⊲OPr i ⊳9gFeCl2 C KAl⊲OPr i ⊳4<br />

fZr2⊲OPr i ⊳9gFefAl⊲OPr i ⊳4gCl C KfTa⊲OPr i ⊳6g<br />

–KCl<br />

!fAl⊲OPr i ⊳4gMfGa⊲OPr i ⊳4g ⊲3.75⊳<br />

–KCl<br />

!fZr2⊲OPr i ⊳9g2FefAl⊲OPr i ⊳4g ⊲3.76⊳<br />

–KCl<br />

!fZr2⊲OPr i ⊳9gFefAl⊲OPr i ⊳4g2<br />

⊲3.77⊳<br />

–KCl<br />

!fZr2⊲OPr i ⊳9gFefAl⊲OPr i ⊳4gCl ⊲3.78⊳<br />

–KCl<br />

!fZr2⊲OPr i ⊳9gFefAl⊲OPr i ⊳4gfTa⊲OPr i ⊳6g<br />

⊲3.79⊳<br />

All the heterotri- and tetrametallic derivatives described above are moisture sensitive,<br />

hydrocarbon soluble, monomeric solids. Almost all these can be volatilized unchanged<br />

under reduced pressure, except some of the niobate and tantalate products, which tend<br />

to dissociate yielding Nb⊲OPr i ⊳5/Ta⊲OPr i ⊳5.<br />

The first crystallographically characterized heterotrimetallic isopropoxide was synthesized<br />

136,160 in 1996 by the reactions shown in Eqs (3.80) and (3.81):<br />

CdI2 C KM2⊲OPr i ⊳9<br />

toluene<br />

! ICdfM2⊲OPr i ⊳9gCKI # ⊲3.80⊳<br />

ICdfM2⊲OPr i ⊳9gCKBa⊲OPr i ⊳3 ! 1<br />

2 [fCd⊲OPri⊳3gBafM2⊲OPr i ⊳9g]2 C KI #<br />

⊲3.81⊳<br />

where M D Zr, Hf, Ti.<br />

A distinctive feature hitherto unnoticed in heterometallic alkoxide chemistry is the<br />

exchange of two chelating ligands around the central metal atom Ba; this rearrangement<br />

is probably favoured by greater oxophilicity of barium and its tendency to attain higher<br />

coordination states. Similar syntheses have been reported141,160–163 as illustrated by<br />

Eqs (3.82)–(3.86):<br />

SnCl2 C KMx ⊲OPr i ⊳y ! ClSnfMx ⊲OPr i ⊳ygCKCl # (3.82)<br />

⊲M D Al; x D 1; y D 4. M D Nb/Ta; x D 1, y D 6. M D Zr; x D 2; y D 9⊳<br />

MI2 C KfM 0 2⊲OPri⊳9g ! [IMfM 0 2⊲OPri⊳9g] C KI # (3.83)<br />

⊲M D Sn; M 0 D Zr, Ti. M D Pb; M 0 D Zr, Ti. M D Cd, M 0 D Sn⊲IV⊳⊳<br />

ClSnfZr2⊲OPr i ⊳9gCKAl⊲OPr i ⊳4 !fAl⊲OPr i ⊳4gSnfZr2⊲OPr i ⊳9gCKCl # ⊲3.84⊳<br />

CuCl2 C KHf2⊲OPr i ⊳9 ! ClCufHf2⊲OPr i ⊳9gCKCl # ⊲3.85⊳<br />

ClCufZr2⊲OPr i ⊳9gCKM⊲OPr i ⊳4 ! [fM⊲OPr i ⊳4gCufZr2⊲OPr i ⊳9g] C KCl # ⊲3.86⊳<br />

where M D Al, Ga. 8

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