Ring Opening and C−O and C−N Bond Cleavage by Transient Reduced Thorium Species

Reduction of the tetravalent complex [{2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}ThCl2 (THF)]·THF (2) of
the tripyrrolide dianion 2,5-[(C4H3N)CPh2]2C4H2N(Me) afforded different products depending on the
reaction conditions. In every case, the reaction proceeded via the initial formation of a reduced species,
as indicated by the very rapid formation of a dark red color followed by slow and complete discoloration.
In the case of the reduction in toluene, the complexes ({2,5-[(C4H3N)CPh2]2[C4H2N]}2Th[K(toluene)]2)·1.5(toluene) (3a) and {2,5-[(C4H3N)CPh2]2[C4H2N]}2Th[K(DME)]2 (3b) were obtained, depending on
the crystallization solvent (toluene versus DME). In both cases, the products arose from a loss of the
methyl group attached to the central pyrrole ring N atom. When the reduction was carried out in DME
as a solvent, the complex {[{2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}Th(OMe)]2(m-OC2H4OMe)2}· 0.75(hexane)
(5) was isolated. This species is derived from two different pathways of C−O cleavage of the DME
solvent. Reduction of {2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}ThCl{(C4H3N)CPh2[C4H3N(Me)]} (6), containing
both the monoalkylated tripyrrolide and dipyrrolide ligands, afforded instead pyrrolide ring opening and
formation of [({2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}Th[(C4H3N)CPh2(CCHCHCHNMe)])2(m-K)][K(DME)4]·2(hexane) (7).