The invention relates to a curable composition comprising a) at least one polymer having at least one silicon-containing group of formula (1) —Si(R1)k(Y)3-k  (1), wherein each R1 is independently selected from a hydrocarbon radical containing 1 to 20 C atoms or a triorganosiloxane group of formula —O—Si(R2)3, wherein each R2 is independently selected from a hydrocarbon radical containing 1 to 20 C atoms; each Y is independently selected from a hydroxy group or a hydrolysable group; and k is 0, 1, or 2; b) at least one mixture of paramagnetic titanium complexes, characterized by a Landé g-factor of less than 2 detected by Electron Paramagnetic Resonance Spectroscopy; c) optionally, at least one compound which has a hydrolysable silicon-containing group and a molecular weight in the range of 100 to 1000 g/mol, an aminosilane preparations containing these compositions thereof.