A new class of biomimetically relevant ''scorpionate'' ligands .2. The (2-hydroxyphenyl)bis(pyrazolyl)methanes: Structural characterization of a series of mono-, di-, and trinuclear nickel(II) complexes

The preparation of a new class of mixed functionality biomimetic ligand, (2-hydroxyphenyl)bis(pyrazolyl)methane, L1, (2-hydroxyphenyl)bis(3,5-dimethylpyrazolyl)methane, L2, and (2-hydroxyphenyl)bis(3-isopropylpyrazolyl)methane, L3, is described. These ligands were used to synthesize the nickel(II) complexes, [Ni(L1)(2)], 1 . MeCN; [Ni(L2)(2)], 2 . 0.5MeOH and 2 . 2H(2)O; [Ni(mu-L2)(2)NiCl2], 3 . 2H(2)O and 3 . 2CH(2)Cl(2); [Ni-3(mu(3)-Cl)(2)(mu-L3)(2)(L3)(MeOH)]Cl, 4 . MeOH . 4H(2)O and 4 . MeOH . 1.42(i)Pr(2)O; and [Ni-3(mu(3)-OH)(2)(mu-L3)(3)][BF4], 5 and 5 . 2Me(2)CO. X-ray crystal analysis of 1-5 gave the following structural parameters: 1 . MeCN, C28H25N9NiO2, triclinic, a = 10.600(3) Angstrom, b = 11.371(3) Angstrom, c = 12.194(3) Angstrom, alpha = 71.17(2)degrees, beta = 94.69(2)degrees, gamma = 83.04(2)degrees, space group <P(1)over bar>, Z = 2; 2 . 2H(2)O, C34H42N8NiO4, monoclinic, a = 9.037(2) Angstrom, b = 19.272(3) Angstrom, c = 19.643(3) Angstrom, beta = 94.69(2)degrees, space group C2/c, Z = 4; 3 . 2CH(2)Cl(2), C36H42N8Cl6Ni2O2, monoclinic, a = 13.891(4) Angstrom, b = 18.188(7) Angstrom, c = 15.012(4) Angstrom, beta = 92.70(2)degrees, space group C2/c, Z = 4; 4 . MeOH . 1.42(i)Pr(2)O, C67.52H96.88Cl3N12Ni3O6.42, monoclinic, a = 12.400(2) Angstrom, b = 13.520(1) Angstrom, c = 24.616(3) Angstrom, beta = 102.04(1)degrees, space group Pn, Z = 2; 5 . 2Me(2)CO, C63H83N12BF4Ni3O7, monoclinic, a = 14.521(3) Angstrom, b = 18.827(3) Angstrom, c = 26.283(4) Angstrom, beta = 105.85(2)degrees, space group: P2(1)/c, Z = 4. The effects on the type of complex formed with varying steric hindrance on the pyrazole rings is discussed.