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).

对含三吡咯二阴离子2,5-[(C4H3N)CPh2]2C4H2N(Me)的四价配合物[{2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}ThCl₂(四氢呋喃(THF))]·THF（2）进行还原反应时，产物随反应条件不同而有所差异。
所有反应均通过先生成还原中间体的路径进行：反应体系会迅速显现深红色，随后缓慢且完全褪色，这一现象印证了还原中间体的初始形成。
当以甲苯为溶剂进行还原反应时，根据结晶溶剂的不同（甲苯 vs 二甲氧基乙烷(DME)），可分别得到配合物({2,5-[(C4H3N)CPh2]2[C4H2N]}₂Th[K(甲苯)]₂)·1.5(甲苯)（3a）与{2,5-[(C4H3N)CPh2]2[C4H2N]}₂Th[K(DME)]₂（3b）。两类产物均由连接于中心吡咯环氮原子上的甲基脱除所生成。
当以二甲氧基乙烷(DME)为溶剂进行还原反应时，可分离得到配合物{[{2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}Th(OMe)]₂(μ-OC₂H₄OMe)₂}·0.75(己烷)（5）。该物种由DME溶剂发生两种不同路径的C-O键断裂后生成。
还原同时含有单烷基化三吡咯配体与二吡咯配体的配合物{2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}ThCl{(C4H3N)CPh2[C4H3N(Me)]}（6）时，反而会发生吡咯环开环反应，生成[({2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}Th[(C4H3N)CPh2(C=CHCH=CHNMe)])₂(μ-K)][K(DME)₄]·2(己烷)（7）。