Coordination chemistry of a chelating amidoximato ligand

A potentially general strategy for accessing the rarely encountered coordination of amidoximates through both oximato O and amido N atoms was developed. The new amidoxime (Z)-(RC)-C-1(=NOH)(NRH)-H-2 (R-1 = mesityl, R-2 = 2-[{dimethylamino}methyl]phenyl), H2L, was prepared by reaction of equimolar amounts of the appropriate nitrile oxide and primary amine. Treatment of H2L with 1 equiv of AlMe3 produced the dimeric species (MeAlL)(2) (1) possessing the formally dianionic ligand L2- bound to the aluminum via the oximato oxygen and the amido and amino nitrogens. The oximato oxygen atoms serve to link the two monomeric organoaluminum units together. Reaction of (ON)Cr((NPr2)-Pr-i)(3) with H2L provided the diamagnetic complex (ON)Cr((NPr2)-Pr-i)(eta (3)-L) (2). Interaction of 2 with excess methanol led, in particular, to the oxidative loss of NO and yielded the paramagnetic dimer [Cr(LH)(OMe)(mu -OMe)](2) (3) containing the eta (3)-bound amidoximato ligand protonated at its oximato nitrogen. In addition to spectroscopic characterizations of the new substances, single-crystal X-ray structures of H2L, 1 .4/3C(6)H(6), and 3 . MeOH were obtained.