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2 Homometallic Alkoxides

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462 Alkoxo and Aryloxo Derivatives of Metals<br />

In many cases only partial substitution occurs, yielding mixed aryloxide, alkoxide<br />

compounds (Eq. 6.44 128 ).<br />

SiMe 2Bu t<br />

OH<br />

OH<br />

SiMe2Bu t<br />

SiMe 2Bu t<br />

O<br />

[Ti(OPr Ti<br />

O<br />

i )4] 2HOPri + +<br />

SiMe2Bu t<br />

(6.44)<br />

Recent mechanistic work on the formation of rhenium aryloxides by treatment of<br />

the corresponding methoxide, ethoxide, or isopropoxide with phenolic reagents, shows<br />

the intermediacy of a hydrogen-bonded adduct as well as the exchange pathway shown<br />

in Eq. 6.45. 129<br />

OC<br />

CO<br />

L<br />

Re<br />

OC<br />

O<br />

L<br />

CH 3<br />

OC<br />

CO<br />

L<br />

Re<br />

OC<br />

O<br />

L<br />

Ar<br />

+HOAr<br />

−HOCH3<br />

OC<br />

CO<br />

L<br />

Re<br />

OC<br />

O<br />

L<br />

ArOH<br />

OC<br />

CO<br />

L<br />

Re<br />

OC<br />

O<br />

L<br />

Ar<br />

CH3<br />

HOCH3<br />

OPr i<br />

OPr i<br />

OC<br />

CO<br />

L<br />

Re<br />

OC L<br />

Ar<br />

O O<br />

H<br />

CH 3<br />

(6.45)<br />

AsMe2<br />

where X = H, CH3, OCH3, CF3, Cl, NMe2;L2 = ; ArO = O X.<br />

3.6 From Metal Alkyls and Aryls<br />

3.6.1 By Protonolysis Reactions<br />

AsMe2<br />

Metal–alkyl bonds that contain a high degree of carbanion character will react with<br />

phenols to produce the corresponding phenoxide and alkane as a readily removed<br />

by-product (Eqs 6.46, 130 6.47, 131 and 6.48 132 ).<br />

Me 3C CMe 3<br />

Me 3C<br />

OH<br />

OH<br />

CMe3<br />

Me 3C CMe 3<br />

OK<br />

+ 2KCH2Ph + 2CH3Ph (6.46)<br />

OK<br />

Me 3C<br />

CMe3

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