Structural versatility of anion-pi interactions in halide salts with pentafluorophenyl substituted cations.

A series of pentafluorophenyl substituted ammonium, iminium, amidinium, and phosphonium halides are presented which show extensive anion-pi interactions. Hereby, the well-known anion-donor-pi-acceptor as well as "eta6" anion-pi-complex type interactions are observed. The latter is supported by fixation of the anion on top of the aromatic system through hydrogen bonding.

Hierarchical assembly of helicate-type dinuclear titanium(IV) complexes.

The ligands 4-7-H(2) were used in coordination studies with titanium(IV) and gallium(III) ions to obtain dimeric complexes Li(4)[(4-7)(6)Ti(2)] and Li(6)[(4/5a)(6)Ga(2)]. The X-ray crystal structures of Li(4)[(4)(6)Ti(2)], Li(4)[(5b)(6)Ti(2)], and Li(4)[(7a)(6)Ti(2)] could be obtained. While these complexes are triply lithium-bridged dimers in the solid state, a monomer/dimer equilibrium is observed in solution by NMR spectroscopy and ESI FT-ICR MS.

Self-assembly of an unpolar enantiomerically pure helicate-type metalla-cryptand.

Chiral tetraketone ligands are obtained by Claisen-type condensation of 4-bromoacetophenone with the acetone ketal of L-tartraic acid diethylester and lead with gallium(III) or iron(III) ions in self-assembly processes to dinuclear helicate-type cryptands which are able to bind lithium cations.