Process for the preparation of partial and ortho esters of vanadium, niobium or tantalum

The present invention relates to a novel process for the preparation of metal acid esters, in which vanadium, niobium or tantalum are present as metal atoms. The process is characterised in that the chlorides or oxychlorides of these metals are reacted with organosilane esters. Partial esters of the said metal acids, in which one or more chlorine atoms of the metal chlorides or oxychlorides are replaced by ester groups, are formed in this reaction. The metal acid partial esters prepared according to the process are obtained in very concentrated form and can be selectively removed from the resulting mixture in a simple manner. The resulting metal acid partial esters can be very easily further esterified to the corresponding metal acid ortho esters in a manner known per se, very pure ortho esters likewise being obtained.