Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors

Abstract

The preparation and characterization of the macrocyclic diamido-diarsine ligand [As₂N₂]Li₂(1,4-dioxane) (1) (where As₂N₂ = PhAs(CH₂SiMe₂NSiMe₂CH₂)₂AsPh) and a series of early transition metal complexes are presented. The complexes [As₂N₂]MCl₂ (M = Zr, 2; Ti, 4) and the complex ([As₂N₂]Y)₂(µ-Cl)₂ (5) can be prepared by reaction of 1 with the corresponding THF adduct of the metal halide. The iodide derivative of 2, [As₂N₂]ZrI₂ (3) can be prepared by reaction with iodotrimethylsilane. The lithium complex 1 displays a very long lithium–arsenic bond distance of 3.162(10) Å, and the yttrium complex 5 is the first known complex containing a yttrium–arsenic bond. Reduction of 2, 3 or 4 using C₈K or activated magnesium decomposed the complexes in such a manner that the ligand was separated from the metal centre. Indirect evidence suggests this may be due to reduction of arsenic in the ligand in preference to the metal.