The invention relates to a composition comprising a titanium or zirconium alkoxide or aryloxide, wherein the alkoxy group in the titanium or zirconium alkoxide is a group of formula R-0− wherein R is an alkyl group having 1 to 4 carbon atoms and the aryloxy group in the titanium or zirconium aryloxide is a group of formula Ar-0− wherein Ar is an aryl group having 6 to 12 carbon atoms, and wherein the composition additionally comprises 0.1 to 50 wt. % of an organic carbonate, based on the total weight of the composition. Further, the invention relates to a process for preparing such composition, comprising blending such titanium or zirconium alkoxide or aryloxide with an organic carbonate in such amounts that the resulting composition comprises 0.1 to 50 wt. % of the organic carbonate, based on the total weight of the composition. Still further, the invention relates to a process for preparing an aromatic carbonate, such as a diaryl carbonate, using said composition comprising a titanium or zirconium alkoxide or aryloxide; and to a process for making a polycarbonate from the diaryl carbonate thus prepared.