A solution and solid state study of niobium complexes University of ...

Chapter 2
metal react spontaneously with alcohols, but other metals need an activation agent
or more complex reactions need to be applied. The general methods for synthesis
can be summarized as follows 72 :
Direct reactions of metals with alcohols: This method is the most used one in
laboratories. It is based on substitution of the hydroxyl hydrogen by a suitable
metal cation, accompanied by intense heat and H2 evolution
M + (1 + x) ROH → 1/y [MOR∙xROH]y + 1/2 H2 (2.4)
(y indicates the degree of polymerization)
Reactions of metal halides with alcohols: The reaction leads to the
substitution of a halide anion by a RO - group, forming the corresponding
alkoxide:
MClz + (x + y) ROH → MClz-x(OR)x(ROH)y + xHCl (2.5)
Reactions of metal oxides and hydroxides with alcohols: Metal oxides and
hydroxides react with alcohols to form the appropriate alkoxide and water:
MOx + 2x ROH → M(OR)2x + x H2O (2.6)
M(OH)x + x ROH → M(OR)x + x H2O (2.7)
Reactions of alcohols with organometallics: These reactions are useful for the
synthesis of mono- and mixed-metal alkoxides. The drawback of this reaction
is that most organometallics are air/moisture sensitive and complicates the
the reaction conditions:
MR2 + R’OH → 1/x [MOR’]x + RH (2.8)
MR3 + R’OH → 1/x [R2MOR’]x + RH (2.9)
R2MX + M’OR → 1/x [R2MOR’]x + M’X (2.10)
Alcohol interchange reactions: The activity of metal alkoxides in the
substitution reactions of alkoxo groups is one of their characteristic
properties:
M(OR)x + y R’OH → M(OR)x-y(OR’)y + y ROH (2.11)
72 L. John, Alkoxo Metal Complexes as Precursors for new Oxide Materials, Faculty of Chemistry, University of
Wroclaw, Poland, 72, 2008.
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