Synthesis, Characterization, and X‑ray Molecular Structure of Tantalum CCC-N-Heterocyclic Carbene (CCC-NHC) Pincer Complexes with Imidazole- and Triazole-Based Ligands

Abstract

Unprecedented Ta bis­(NHC) pincer complexes have been synthesized and characterized by extension of the early-transition-metal amido methodology. The reaction of 1,3-bis­(3-butylimidazol-1-yl)­benzene diiodide (<b>1</b>) with stoichiometric and substoichiometric amounts of (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V) yielded (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­diiodotantalum­(V) (<b>2</b>) and (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>3</b>). Use of excess (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V) to metalate 1,3-bis­(3-butylimidazol-1-yl)­benzene diiodide (<b>1</b>) yielded (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>3</b>) exclusively. Furthermore, the first early-transition-metal (group 3–5) triazole-based NHC complex, (1,3-bis­(3-butyltriazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>5</b>), has been synthesized via amine elimination of 1,3-bis­(3-butyltriazol-1-yl)­benzene diiodide (<b>4</b>) with (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V)