Transition metal alkoxide complex
From Wikipedia, the free encyclopedia
A transition metal alkoxide complex is a kind of coordination complex containing one or more alkoxide ligands, written as RO−, where R is the organic substituent.[citation needed] Metal alkoxides are used for coatings and as catalysts.[1][2]
By metathesis reactions
Many alkoxides are prepared by salt-forming reactions from a metal chlorides and sodium alkoxide:
- MCln + n NaOR → M(OR)n + n NaCl
Such reactions are favored by the lattice energy of the NaCl, and purification of the product alkoxide is simplified by the fact that NaCl is insoluble in common organic solvents.
For electrophilic metal halides, conversion to the alkoxide requires no or mild base. Titanium tetrachloride reacts with alcohols to give the corresponding tetraalkoxides, concomitant with the evolution of hydrogen chloride:[3]
- TiCl4 + 4 (CH3)2CHOH → Ti(OCH(CH3)2)4 + 4 HCl
The reaction can be accelerated by the addition of a base, such as a tertiary amine. Other electrophilic metal halides can be used instead of titanium, for example NbCl5.[citation needed]
By electrochemical processes
Many alkoxides can be prepared by anodic dissolution of the corresponding metals in water-free alcohols in the presence of electroconductive additive. The metals may be Co, Ga, Ge, Hf, Fe, Ni, Nb, Mo, La, Re, Sc, Si, Ti, Ta, W, Y, Zr, etc. The conductive additive may be lithium chloride, quaternary ammonium halide, or other. Some examples of metal alkoxides obtained by this technique: Ti(OCH(CH3)2)4, Nb2(OCH3)10, Ta2(OCH3)10, [MoO(OCH3)4]2, Re2O3(OCH3)6, Re4O6(OCH3)12, and Re4O6(OCH(CH3)2)10.
