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)CPh 2 ] 2 C 4 H 2 N(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)CPh 2 ] 2 [C 4 H 2 N]} 2 Th[K(toluene)]2)· 1.5(toluene) (3a) and {2,5-[(C4H3N)CPh2]2[C4H2N]} 2 Th[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-OC 2 H 4 OMe) 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).