In a number of cases the activity of hydroxide and oxide catalysts received from coprecipitation method is not equal to the total activity of mixed hydroxides or oxides. Assumption that heteronuclear hydroxides could be formed by coprecipitation of metal hydroxides was stated. In the case of rare-earth and two charged 3d-metal ions it was shown that heteronuclear hydroxo complexes can be formed by interaction of these metal ions at initial stages of their cohydrolysis under certain conditions. In some cases these complexes are destroyed with time. Such heteronuclear hydroxo complexes are new compounds and can show high catalytic activity owing to features of their structure. Highly effective oxide catalysts can be produced by thermal decomposition on the basis of these heteronuclear hydroxides.