Synthesis, Structure, and Reactivity of a Dimeric Zinc(I) Compound Stabilized by a Sterically Demanding Diiminophosphinate Ligand

Abstract

The new sterically demanding aminoiminophosphorane Ph₂P(NDip)(NHDip) (Dip=C₆H₃-2,6-iPr₂; LH, 1) has been prepared as a precursor to the potassium complex [LK] (2) and a series of heteroleptic zinc(II) complexes, namely [(LZnBr)₂] (3), [LZnMe] (4), [LZnEt] (5), and [(LZnI)₂] (6). The products have been obtained either through a salt metathesis route by using complex 2 and ZnBr₂ to give compound 3, through a direct reaction of ligand precursor 1 and ZnR₂ (R=Me or Et) yielding complexes 4 or 5, respectively, or through iodination of complexes 4 or 5 by using I₂ to afford compound 6. Reduction of the heteroleptic zinc(II) halide complexes 3 or 6 by using a dimeric magnesium(I) compound as a selective, stoichiometric, and soluble reducing agent afforded the new zinc(I) dimer [(LZn)₂] (7) in good yield. Compounds 1–7 were crystallographically and spectroscopically characterized and the coordination behavior of the diiminophosphinate ligand has been investigated and compared with related CN-based ligands. An initial reactivity study has been carried out on [(LZn)₂] (7) by using small-scale reactions and the oxidative addition of small alkyl halides across the ZnZn bond has been found to generate equimolar amounts of the alkyl complexes 4 or 5 and the halide complexes 3 or 6, respectively.