Metallosupramolecular chemistry with bis(benzene-o-dithiolato) ligands

The bis(benzene-o-dithiol) ligands H(4)-1, H(4)-2, and H(4)-3 react with Ti(OC(2)H(5))(4)] to give dinuclear triple-stranded helicates Ti(2)L(3)](4)(-) (L = 1(4)(-), 2(4)(-), 3(4)(-)). NMR spectroscopic investigations revealed that the complex anions possess C(3) symmetry in solution. A crystal structure analysis for (PNP)(4)Ti(2)(2)(3)] ((PNP)(4)14]) confirmed the C(3) symmetry for the complex anion in the solid state. The complex anion in Li(PNP)(3)Ti(2)(1)(3)] (Li(PNP)(3)13]) does not exhibit C(3) symmetry in the solid state due to the formation of polymeric chains of lithium bridged complex anions. Complexes 13](4)(-) and 14](4)(-) were obtained as racemic mixtures of the Delta,Delta and Lambda,Lambda isomers. In contrast to that, complex (PNP)(4)Ti(2)(3)(3)] ((PNP)(4)15]) with the enantiomerically pure chiral ligand 3(4)(-) shows a strong Cotton effect in the CD spectrum, indicating that the chirality of the ligands leads to the formation of chiral metal centers. The o-phenylene diamine bridged bis(benzene-o-dithiol) ligand H(4)-4 reacts with Ti(4+) to give the dinuclear double-stranded complex Li(2)Ti(2)(4)(2)(mu-OCH(3))(2)] containing two bridging methoxy ligands between the metal centers. The crystal structure analysis and the (1)H NMR spectrum of (Ph(4)As)(2)Ti(2)(4)(2)(mu-OCH(3))(2)] ((Ph(4)As)(2)(16]) reveal C(2) symmetry for the anion Ti(2)(4)(2)(mu-OCH(3))(2)](2)(-). For a comparative study the dicatechol ligand H(4)-5, containing the same o-phenylene diamine bridging group as the bis(benzene-o-dithiol) ligands H(4)-4, was prepared and reacted with TiO(acac)(2)] to give the dinuclear complex anion Ti(2)(5)(2)(mu-OCH(3))(2)](2)(-). The molecular structure of (PNP)(2)Ti(2)(5)(2)(mu-OCH(3))(2)] ((PNP)(2)17]) contains a complex anion which is similar to 16](2)(-), with the exception that strong N-H...O hydrogen bonds are formed in complex anion 17](2)(-), while N-H...S hydrogen bonds are absent in complex anion 16](2)(-).