Synthesis, Characterization, and Magnetic Behaviour of Dinuclear Nickel(II) Complexes of N,N′‐Substituted Dithiooxamides derived from α‐Amino Acids

New dinuclear complexes of the types [Ni2(L)-(H2O)2] and [Ni2(L)(H2O)6] [H4L = N,N′-bis(carboxymethyl) dithiooxamide (H4GLYDTO), N,N′-bis(1-carboxyethyl) dithiooxamide (H4ALADTO), N,N′-bis(1-carboxy-2-methylpropyl) dithiooxamide (H4VALDTO) and N,N′-bis-(1-carboxy-3-methylbutyl) dithiooxamide (H4LEUDTO)] have been prepared and characterized by IR and electronic absorption spectroscopy, and the structure of [Ni2(ALADTO)-(H2O)6] crystals has been determined by single crystal X-ray analysis. This compound is composed of discrete dinuclear units in which two NiII atoms with NO4S kernels are linked by a single [ALADTO]4- group that coordinates through its carboxylato oxygen, amino nitrogen and thiolato sulphur atoms. In each dimer unit the two nickel(II) ions in distorted octahedral coordination are separated by 5.863(2) A The temperature dependence of the magnetic susceptibility of the new compounds was measured over the range 2 to 300 K. In the complexes of [GLYDTO]4- and [ALADTO]4- the two Ni atoms are antiferromagnetically coupled, with J = -23.51(4) and -20.95(8) cm-1, respectively. By constrast, [Ni2(VALDTO)(H2O)2], [Ni2(VALDTO)(H2O)6] and [Ni2-(LEUDTO)(H2O)2] remain paramagnetic down to 2 K, with magnetic moment values between 2.8 and 3.3 M.B. © WILEY-VCH Verlag GmbH, 2001.