Low-viscosity concentrated solutions of alkaline earth metal alkoxides in aprotic solvents and processes for preparation thereof

A solution comprising a mixed alkaline earth alkoxide compound of formula M(OCH2R6)2-a-b(OR7)a[(CHR8)nOR9]b in a mixture with an aluminum compound of formula Al(OCH2R6)3-c-d(OR7)c[O(CHR8)—OR9]d in an aprotic solvent, wherein

• M is an alkaline earth metal selected from Mg, Ca, Ba, and Sr;
• OCH2R6 is an alkoxide radical composed of at least 3 and a maximum of 40 C atoms having a branch in the 2-position, relative to O;
• R7 is an alkyl radical containing 2-15 C atoms which is either linear or has a branch at the 3- or higher position relative to O;
• O(CHR8)nOR9 is an alkoxide radical in which
• R8 is an alkyl radical containing 1-6 C atoms which is either linear or has a branch at the 3- or higher position relative to O;
• R9 is an alkyl radical containing 2-15 C atoms which is either linear or has a branch;
• n is an integer between 1 and 4;
• a+b≦2;
• c+d≦3;
• a and c are from 0.01 to 0.8;
• and
• b and d each range from 0.1 to 1.99;
• and
• wherein the solution has a content of aluminum relative to the alkaline earth metal in the range between 0.2 and about 20 mol %.