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2 Homometallic Alkoxides

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114 Alkoxo and Aryloxo Derivatives of Metals<br />

4.4.1 Monoalkanolamines<br />

A comparative study of the reactivity of metal alkoxides towards ethanolamine,<br />

HOCH2CH2NH2, indicated distinct differences between the reactivity of the hydroxyl<br />

and amino groups. For example, reactions of a large number of metal (Sm, Gd, Er,<br />

Yb, Y, Ti, V, Nb, U, Fe, Ni, B, Si, Sb) alkoxides with ethanolamines proceed with the<br />

metallation of the hydroxyl proton only as shown by Eq. (2.204):<br />

benzene<br />

M⊲OR⊳x C yHO⊲CH2⊳mNH2 ! M⊲OR⊳x y[O⊲CH2⊳mNH2]y C yROH "<br />

⊲2.204⊳<br />

⊲M D Sm, 689 Gd, Er, Yb, Y; 148,156 x D 3; y D 1, 2or3;mD 2; R D Pr i .<br />

M D Ti, 623,624 x D 4, y D 1, 2, 3or4;mD 2; R D Et, Bu n , Pr i . M D OV; 691<br />

x D 3; y D 1, 2, 3; m D 2, R D Et. M D Nb, 625 Ta; 626 x D 5; y D 1; m D 2;<br />

R D Et. M D U; 627 x D 5; y D 1, 2, 3, 4or5;mD 2; R D Et. M D Fe; 283<br />

x D 3; y D 1, 2or3;mD 2, R D Pr i . M D Ni; 692 x D 2; y D 1or2;mD 2;<br />

R D Me, Pr i . M D B, 693 Al, 694 Ga; 185 x D 3, y D 1, 2or3;mD 2; R D Pr i .<br />

M D B, 695 x D 3; y D 3; m D 2or3;RDMe. M D Si ⊲in the presence of Na⊳; 696<br />

x D 4; y D 4; m D 2; R D Et. M D Sb; 627 x D 3; y D 1, 2, or 3; m D 2; R D Et⊳<br />

Similar reactions with different types of N-alkyl- and N,N-dialkyl-aminoalcohols<br />

(R 0 OH) have yielded derivatives which are generally soluble (in organic solvents) and<br />

volatile. Some typical reactions are illustrated by Eqs (2.205):<br />

M⊲OR⊳x C yR 0 OH benzene<br />

! M⊲OR⊳x y⊲OR 0 ⊳y C yROH " ⊲2.205⊳<br />

⊲M D Ti, 623,624 Zr; 697 x D 4; y D 1, 2, 3, or 4; R 0 D CH2CH2NHMe, CH2CH2NHEt,<br />

CH2CH2NMe2, CH2CH2NEt2, CHMeNMe2;RD Pr i . M D Cu; 698 x D 2; y D 2;<br />

R 0 D CH2CH2NMe2, CHMeCH2NMe2, 698,699 CH2CH2NMeCH2CH2NMe2; 698<br />

R D Me. M D B; 695 x D 3; y D 3; R 0 D CH2CH2NHMe, CH2CH2NMe2,<br />

CH2CH2NEt2,⊲CH2⊳3NMe2,⊲CH2⊳3NEt2;RD Me. M D Al; 700 x D 3; y D 1, 2, or 3;<br />

R 0 D ⊲CH2⊳2NHMe,⊲CH2⊳2NHEt,⊲CH2⊳2NEt2,⊲CH2⊳2NMe2, CHMeCH2NEt2;<br />

R D Pr i ⊳<br />

By contrast, with alkoxides of niobium, 625 tantalum, 626 germanium, 701 tin, 621 and<br />

antimony 627 both the hydroxylic and the amino group protons of ethanolamine undergo<br />

replacement reactions to form cyclic derivatives (Eq. 2.206):<br />

M(OR) x + yHOCH 2CH 2NH 2<br />

benzene<br />

(RO) x−2y M<br />

O CH 2<br />

N<br />

CH2<br />

H y<br />

+ 2yROH<br />

⊲M D Nb, Ta; x D 5; y D 2; R D Et ⊲soluble⊳. M D Ge; x D 4; y D 1;<br />

⊲2.206⊳

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