Methylmagnesium bromide has been used as a probe to determine the active oxidation state(s) of iron responsible for the cross-coupling of alkyl Grignard reagents with aryl chlorides.  Methylmagnesium bromide is incapable of reducing the iron to an active state so it will only couple if a discrete iron compound having the correct reduced state is used.  We have purchased or synthesized iron complexes having oxidation states ranging from �II to I and attempted to use each in the catalytic cross-coupling of chlorobenzene with both methylmagnesium bromide and isobutylmagnesium bromide.  The complex(s) that catalyzed the cross-coupling of both reagents were in an active oxidation state while those that only coupled isobutylmagnesium bromide had to be reduced further.  We have used the information gained to attempt the cross-coupling of several Grignard reagents without �-hydrogens or others incapable of reducing iron , including isopropymagnesium bromide.

Methylmagnesium bromide as a probe for the active oxidation state of iron in Kumada couplings of alkyl Grignard reagents

245th National Meeting (2013)

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