prov:value
| - In addition, Ra and Rb can be a boron-containing group, such as, for example, ???X???BR1 2, in which X is an element from group VIa of the Periodic Table of the Elements or an NR group, where R is hydrogen or a C1-C20-hydrocarbon radical, such as C1-C20-alkyl or C1-C20-aryl, and R1 are identical or different and are a hydrogen atom, a halogen atom, a boron-free C1-C40-hydrocarbon-containing group,
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