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

The preparation and characterization of the macrocyclic diamido-diarsine ligand [As2N2] Li-2(1,4-dioxane) ( 1) ( where As2N2 = PhAs(CH2SiMe2NSiMe2CH2)(2)AsPh) 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)( mu-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) Angstrom, 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.