Bidentate Phosphine Ligand Impacts on Previously Inaccessible 5-Membered N-Heteroaryne Formation and Functionalization

5-Membered N-heteroarynes have long been considered synthetically inaccessible; however, we recently reported the use of a bisphosphine-ligated nickel center to stabilize and enable the formation of these otherwise unobtainable intermediates. Moti-vated by this success, we were compelled to study the role of the ancillary phosphine in aryne formation and reactivity. Here-in, a set four bidentate phosphine ligands with altered phosphine substituents and backbone length are interrogated for their competence as ancillary ligands for 5-membered N-heteroaryne formation. We determined that ligands with phenyl phosphine substituents or linker lengths longer than three carbons were unsuitable for this purpose, while ligands having alkyl phos-phine substituents and one, two, or three carbon linkers allowed for successful aryne formation. Reactivity studies using 2-PyZnBr as a nucleophilic coupling partner revealed intriguing regioselectivity enhancement (up to >20:1 r.r.) when utilizing ligands with altered linker lengths. We hypothesize that regioselectivity can be traced back to structural differences between these Ni-aryne complexes, as evidenced by crystallographic characterization.