Metal complexes of amino acids and derivatives—XIII Some nickel(II) complexes of L-arginine zwitterions or L-argininate anions. A novel ionic → bidentate perchlorate rearrangement brought about by pressure[1–5

Abstract

Nickel(II) complexes have been isolated in which the ligand coordinates as an anion (Arg −) or a zwitterion (ArgH). These complexes, Ni(Arg) X· nH 2O ( X = Cl, Br, NO 3, ClO 4) and Ni(ArgH) x X 2· nH 2O ( X = Cl, NO 3, ClO 4, OH), are six-coordinate and contain a NiN 2O 4 coordination moiety. Only in the cases of Ni(ArgH) 2(NO 3) 2·H 2O and Ni(ArgH)(OH) 2·H 2O are X − groups coordinated. However, it has also been found that the complexes containing ionic perchlorate, when put under pressure, rearrange to form complexes containing bidentate perchlorato groups. The complexes have been characterised by magnetic measurements and by infrared and visible reflectance spectral methods.