prov:value
| - The process as claimed in claim 17, wherein R6 are identical and R3 is OR8, SR8, and PR8 2 where R8 is a hydrogen atom, a halogen atom, C1-C40-group which may be halogenated, ???SiR9 3, ???NR9 2, ???Si(OR9)3, ???Si(SR9)3 or ???PR9 2, where R9 are identical or different and are each a halogen atom, a C1-C8-alkyl group or a C6-C10-aryl group.
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