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

Abstract

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).

Ring opening of aromatic heterocycles by uranium complexes

“…Thorium complexes that ring-opened pyridine N-oxide [18] and uranium complexes that cleaved pyrazole [19] are also known. Our group has been investigating the reactivity of group 3 metal [20e24] and uranium alkyls [25,26] supported by a 1,1 0 -ferrocenylene-diamide ligand [27e29] toward aromatic N-heterocycles [22,30e35].…”

Reductive Coupling of Acetonitrile by Uranium and Thorium Hydride Complexes To Give Cyanopentadienyl Dianion (C6N3H7)2−

“…Normally, it would not be possible to obtain reductive thorium chemistry analogous to that accessible from U III complexes, as few Th III compounds are known 24–27. For example, there is no thorium analogue of 1 .…”

Titanium‐Promoted Dinitrogen Cleavage, Partial Hydrogenation, and Silylation

“…For 1 to be formed, it must be assumed that a simple one‐electron attack on such an intermediate may cleave the residual NN single bond to generate one nitride (hence the necessity for the Na counteraction) and one nitrogen radical. As ethers are known to be attacked by radicals or by species with radical‐type behavior affording a variety of fragmentation patterns,21 it is conceivable that simple hydrogen‐atom abstraction may readily form the final compound. However, it is also possible that the hydrogen atom has been provided by the ligand system of another molecule at the expense of the reaction yield.…”