| prov:value
| - the radicals R3 are identical or different and are a hydrogen atom, a halogen atom, a C1 -C10 -alkyl group, which may be halogenated, a C6 -C10 -aryl group, an --NR16 2, --SR16, --OSiR16 3, --SiR16 3 or --PR16 2 radical, in which R16 is a halogen atom, a C1 -C10 -alkyl group or a C6 -C10 -aryl group,
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