SYNTHESIS, STRUCTURE, MAGNETISM, AND SPECTROSCOPIC PROPERTIES OF SOMEMONONUCLEAR AND DINUCLEAR NICKEL-COMPLEXES CONTAINING NONINNOCENT PENTANE-2,4-DIONE BIS(S-ALKYLISOTHIOSEMICARBAZONATE)-DERIVED LIGANDS

Deprotonation of [Ni(II)H(2)L(1))]I . 0.5CH(3)OH (1), where (H(2)L(1)) - represents the ligand pentane-2,4-dione bis(S-methylisothiosemicarba zonate(-), in an ethanol solution of aqueous ammonia under argon affor ds air-sensitive red-brown [Ni-II(HL(1))]. C2H5OH (2). Air oxidation o f 2 in ethanol/NH3 yields the paramagnetic green-black dinuclear speci es [Ni(L(1)-L(1))Ni] (3) where the ligand (L(1)-L(1))(6-) is formed by oxidative C-C coupling at the methine carbon atoms of (L(1))3-. I, th is formulation the nickel ions are trivalent. Reaction of 3 in ethanol with concentrated HCl affords red diamagnetic [Ni-II(H(2)L(1)-L(1)H(2 ))Ni1I(I)]Cl-2 . O.5C(2)H(5)OH (4). This reaction is a 2 electron redu ction of 3 with concomittant protonation at the ligand. Deprotonation of 4 in C2H5OH/ammonia under argon gives red-brown [Ni-II(HL(1)-L(1)H) Ni-II] C2H5OH (5). Replacement of the S-methyl groups in (H(2)L(1))(-) by two dodecyl groups, (CH2)(11)CH3, gives the ligand (H(2)L(2))(-); the complexes [Ni-II(H(2)L(2))I (6) and their dinuclear, oxidized form s [Ni(L(2)-L(2))Ni] (7) have been prepared analogously. The molecular structure of 3 (C18H28N12Ni2S4) has been determined by X-ray crystallo graphy. Crystal data for 3: space group P (1) over bar with a 11.475(2 ) Angstrom, b = 13.615(1) Angstrom, c = 18.207(6) Angstrom, alpha = 83 .87(1)degrees, beta = 88.36(1)degrees, gamma = 72.58(1)degrees, V=2698 .7(10) Angstrom(3), and Z = 2. The structure refinement converged to R = 0.066 for 8865 unique reflections. Electronic and NMR spectra, the magnetism, and electrochemistry of new compounds are reported. It is s hown that xanedione-tetrakis(S-alkylisothiosemicarbazonates) are nonin nocent ligands in 3 and 7.