Synthesis, Structures, and Reactivity of Diazabutadiene-Ligated Rare-Earth Radical Complexes Bearing Adaptable Auxiliary Ligands

Abstract

Bis(diazabutadiene) rare-earth diradical complexes [( Mes DAD) 2 REL] (1−4) were synthesized, of which the auxiliary ligand L could be borohydride, alkyl, alkoxide, or aminoxide ligands. The synthetic approach was utilized by a one-pot reaction, including reduction of DAD and salt metathesis of ligands. Singlecrystal X-ray diffraction results showed that complexes 1−4 maintained similar distorted square-pyramidal coordination spheres, and the DAD ligands were all traditional DAD radical anions. When the auxiliary ligand was changed to a less bulky Npyrrolyl ligand, a partial ligand redistribution product [( Mes DAD) Lu(NC 4 H 4 ) 2 ] 2 (5) was found. The redox reactivity of DAD ligands in rare-earth diradical complexes was also studied. The singleelectron reduction of 1 yielded [Lu( Mes DAD •− )( Mes DAD 2− )-(THF)]( 6), and the disproportionation reaction of [( Mes DAD) 2 ScCl(THF)] in tetramethylethylenediamine (TMEDA) gave a 1:1 product of Mes DAD and [( Mes DAD)ScCl(TMEDA)] (7). Furthermore, the reaction of Mes DAD with SmI 2 resulted in an unexpected C−C coupling product 8, which is a new reaction mode for DAD radicals.