The complex Ni(?2-TEMPO)2, 1  , was obtained from the reaction of Ni(COD)2 with two equivalents of the TEMPO radical. Compound 1   contains exclusively ?2-TEMPO ligands in a �bow-tie� structural configuration. Compound 1   reacts with two electron donor ligands tert-butyl isocyanide and pyridine at room temperature to yield the distorted square planar nickel complexes Ni(?2-TEMPO)(?1-TEMPO)(CNtBu), 2  , and Ni(?2-TEMPO)(?1-TEMPO)(NC5H5), 3  . The reaction of phenylacetylene with 1   at room temperature furnishes the phenyl acetylide complex Ni(?2-TEMPO)(?1-TEMPOH)(?1-CCPh), 4  which also has a distorted square planar structure.   The reaction of alkynes with 1  at room temperature is general and similar reactivity is observed with acetylene, trimethylsilyl acetylene, and 1, 4-diacetylenebenzene to afford the respective acetylide products, Ni(?2-TEMPO)(?1-TEMPOH)(?1-CCH), 5  , Ni(?2-TEMPO)(?1-TEMPOH)(?1-CCSiMe3), 6  , and Ni(?2-TEMPO)(?1-TEMPOH)[?1-CC(C6H4)CCH], 7  . In addition, the reaction of compound 1   with 1, 4-diacetylenebenzene also gives the complex Ni(?2-TEMPO)(?1-TEMPOH)[?1-CC(C6H4)CC]Ni(?2-TEMPO)(?1-TEMPOH), 8  , where the alkyne ligand is now linked by two Ni(?2-TEMPO)(?1-TEMPOH) groupings. The formation of these acetylide complexes are unusual examples of hydrogen atom transfer from the substrate alkynyl group to a coordinated TEMPO ligand. The facile reactivity of 1  is aided by the ability of the TEMPO ligand to convert between ?2 and ?1 binding modes. Computational studies of this interconversion will also be addressed.

Small molecule activation by the nitroxide containing complex Ni(?2-TEMPO)2

246th National Meeting (2013)

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