COORDINATION MODES OF A SERIES OF XYLYLENE-BRIDGED BIS(1,4,7-TRIAZACYCLONON-1-YL) LIGANDS - SYNTHESIS, STRUCTURE, AND PROPERTIES OF NICKEL(II) AND COPPER(II) COMPLEXES

Three bis(1,4,7-triazacyclonon-1-yl) ligands, 1,2-bis(1,4,7-triazacycl onon-1-ylmethyl) (L-1), 1,3-bis(1,4,7- triazacyclonon-1-ylmethyl)benze ne (L-2), and 1,4-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene (L-3), h ave been synthesized and their nickel(II) and copper(II) coordination chemistry investigated. Reaction of L-1 with excess Ni2+ ions affords a mixture of mononuclear and binuclear complexes, which are readily se parated by cation exchange chromatography and crystallized as their pe rchlorate salts, [NiL1](ClO4)(2) (1) and [Ni2L1(H2O)(6)](ClO4)(4) . 4H (2)O (2). Similar treatment of L-2 and L-3 With excess Ni2+ ions affor ds exclusively the binuclear complexes [Ni2L2(H2O)(6)](ClO4)(4) (3) an d [Ni3L3(H2O)(6)](ClO4)(4) . 3H(2)O (4), respectively. Reaction of all three ligands with excess Cu2+ ions also yields binuclear complexes, which may be isolated as neutral species, [Cu2LBr4]. xDMF (5, L = L-1, x = 1; 6, L = L-2, x = 0; 7, L = L-3, x = 0), Or as perchlorate salts , [Cu3L(H2O)(4)](ClO4)(4) . xH(2)O (8, L = L-1, x = 5; 9, L = L-2, x = 4; 10, L = L-3, x = 5). The mononuclear copper(II) complex of L-1 is prepared by reaction of L-1 with Cu2+ ions in a 1:1 mole ratio and iso lated as its perchlorate salt, [CuL1](ClO4)(2) . 2H(2)O (11). The X-ra y structures of complexes 1.H2O, 4, 5, and 11 have been determined. Co mpound 1.H2O crystallizes in the monoclinic space group P2(1)/c (No. 1 4) with a = 9.212(3) Angstrom, b = 17.805(8) Angstrom, 16.501(6) Angst rom, beta = 103.36(3)degrees, V = 2633(1) Angstrom(3), and Z = 4; 4, i n the monoclinic space group P2(1)/c (No. 14) with a = 9.108(4) Angstr om, b = 25.857(5) Angstrom, c = 17.524(2) Angstrom, beta = 92.73(2)deg rees, V = 4122(2) Angstrom(3), and Z = 4; 5, in the trigonal space gro up P3(1)21 (No. 152) with a = 10.889(5) Angstrom, c = 22.220(9) Angstr om, V = 2281(1) Angstrom(3), and Z = 3; and 11, in the monoclinic spac e group P2(1)/c (No. 14) with a = 9.45(1) Angstrom, b = 19.51(2) Angst rom, c = 15.10(1) Angstrom, beta = 96.93(8)degrees, V = 2763(4) Angstr om(3), and Z = 4. The nickel(II) and copper(ll) centers in the mononuc lear complexes, 1.H2O and 11, lie in distorted octahedral environments , sandwiched by the two facially coordinating triamine rings of L-1 In complex 4, the two triamine rings of L-3 coordinate to separate nicke l(II) centers, with the distorted octahedral coordination sphere about each of the metal centers being completed by water molecules. Similar ly, in complex 5, the two triamine rings of L-1 bind separate copper(I I) centers, with the distorted square pyramidal coordination sphere ab out each of the metal centers being completed by bromide anions.