starting materials merely hydrolyze to teo 2 and an organic moiety then it should follow that since the organic moieties are not biologically active in the present context the biological activity of teo 2 and the formed aqueous solution should be identical under comparable conditions the fact that this is not the case see e g examples 13 14 and 16 infra support the existence of the present complexes and contradict the possibility that the aqueous solutions contain merely teo 2 and an organic moiety the existence of the complexes is further illustrated by the differing solubilities in phosphate buffer solution pbs at ph7 of the starting materials for the present process compared with tecl 4 and teo 2 stated in mg te 100 ml pbs see below for identity of starting materials moreover the product of preparation 3 cannot be formed by merely mixing the components teo2 and ethane 1 2 diol which must be refluxed together for reaction to take place while the present invention is not to be regarded as limited by any theory nevertheless unpublished studies by the present inventors demonstrate that e g teo2 and ethane 1 2 diol from the hydrolysis in aqueous solution of the product of preparation 1 can form a thermodynamically stable complex which is a well defined species in aqueous solution see the illustrative model depicted in fig1 and that the.