prov:value
| - ast one of R2 to R5 is a group containing a heteroatom, the rest of R2 to R5 are independently hydrogen or a C1 to C100 group, preferably a C4 to C20 alkyl group (preferably butyl, isobutyl, pentyl hexyl, heptyl, isohexyl, octyl, isooctyl, decyl, nonyl, dodecyl) and any of R2 to R5 also may or may not be bound to M, provided that in the first formula if M is a group 4 metal then the R4 and R5 grou
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