Synthesis and Reactivity of Lewis-Base-Supported Terminal Thorium Imido Metallocene, (η⁵-C₅Me₅)₂Th═N(p-tolyl)(dmap)₂

Treatment of (η⁵-C₅Me₅)₂ThMe₂ (1) with p-tolylNH₂ in toluene, in the presence of 4-dimethylaminopyridine (dmap), affords a Lewis base-supported terminal thorium imido metallocene, (η⁵-C₅Me₅)₂Th═N(p-tolyl)(dmap)₂ (5), alongside the release of methane. In toluene solution, an equilibrium is established among complex 5, dmap, and the amido pyridyl complex (η⁵-C₅Me₅)₂Th[NH(p-tolyl)][κ²-C,N-4-(Me₂N)C₅H₃N] (5'), setting the stage for diverse reactivity. Complex 5 may initiate [2 + 2], [2 + 4], [2 + 1], or [2 + 3] cycloadditions with elemental sulfur and selenium, alkynes, carbodiimides, ketones, thio-ketones, isothiocyanates, CS₂, organic nitriles and isonitriles, as well as organic azides. Moreover, imido moiety can act as a nucleophile toward metal halides, esters, and azidosilanes; and it may promote deprotonation reactions with 1-methylimidazole, 2,6-Me₂C₅H₃NO, Me₃PO, silanes, amidate PhCONH(p-tolyl), and nitriles (PhCH₂CN and Ph₂CHCN). Notably, reaction of 5 with Me₃SiCHN₂ forms the bimetallic complex [(η⁵-C₅Me₅)₂Th]₂(μ-N═NN═CSiMe₃)₂ (44) with toluene elimination. In contrast, complex 5' undergoes reactions with elemental selenium and tellurium, PhSiH₂Cl, organic isonitriles (2,6-Me₂C₆H₃NC, Me₃CNC, and C₆H₁₁NC), and organic azides (p-tolylN₃ and Ph₃CN₃) to afford amido selenido, amido tellurido, chloro pyridyl, amido pyridyl, amido alkenyl, and bis-amido complexes, respectively. Furthermore, a comparison with related terminal imido thorium metallocenes illustrates how substituent effects on the cyclopentadienyl and imido ligands influence the reactivity of these molecules.