Abstract
A bis-pyrrolide ligand containing a nonconjugated aromatic ring in the backbone was reacted with ThCl4(DME)(2), affording the corresponding mu(6)-{1,3-[2-C4H3N)(CH3)(2)C](2)C6H}ThCl3[Li(DME)(3)](1) complex. In this species, the pi-bonding interaction of the actinide with the ring is probably induced by steric constraint. The bonding mode of the pyrrolide rings was switched from sigma to pi upon treatment of complex 1 with Et3Al. This reaction was also accompanied by deprotonation of the aromatic ring and formation of two similar compounds with the ring sigma-bonded to the Th metal center. The two compounds {[{1,3-[(eta(5)-2-C4H3N)(CH3)(2)C](2)C6H4}Th(mu-Cl-AlEt2)(2)](mu-Cl)(2)[{1,3-[eta(5)-2-C4H3N)(CH3)(2)C]C6H4}Th] were isolated and fully characterized.,The common feature among these two species is that the switching of bonding mode of the pyrrolide rings, resulting from the coordination of the aluminum residues, is accompanied by deprotonation of the central ring. Attempts to reduce 1 yielded the paramagnetic [eta(5)-1,3-[(eta(5)-2-C4H3N)(CH3)(2)C](2)C6H4}ThK(mu-Cl)(3)][Li(DME)(3)](3), which on the basis of the connectivity might be regarded as a rare case of Th(III). However. DFT calculation have clucidated the electronic structure of this species, which should be regarded as containing tetravalent Th bonded to the ligand radical anion. The spin density is mainly localized at the ling C atom. which is deformed and deviates From the planarity. Similar reductions carried out Under slightly different reaction conditions afforded {mu(6)-1,3-[2-C4H3N)(CH3)(2)C](2)C6H4}Th{mu-eta(5)-1,3-[(eta(5)-2-C4H3N)(CH3)(2)C](2)C6H5}K(DME)(2) (4). In this complex the metal is surrounded by two ligands One of,which appears as having been partly hydrogenated at the central aromatic ring. Treatment of an hi situ generated transient low-valent Species with azobenzene as mild oxidizing agent resulted in reoxidation to a tetravalent thorium diphenylhydrazido species. [{eta(6)-1,3-[(eta(5)-2-C4H3N)(CH3)(2)C](2)C6H4}Th(mu-eta(2)-PhNNPh)(mu-Cl)(Cl)Li(DME)][Li(DME)(3)] (5).