prov:value
| - R3 and R4 are identical or different and are a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C1 -C10 -, preferably C1 -C4 -alkyl group, which may be halogenated, a C6 -C10 -, preferably C6 -C8 -aryl group, an --NR2 10, --SR10, --OSiR3 10, --SiR3 10, or PR2 10 radical in whcih R10 is a halogen atom, preferably a chlorine atom, or a C1 -C10 -, preferably C1 -C3 -a
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