Syntheses and Structural Characterization of Ferrocene-Containing Double-Helicate and Mononuclear Copper(II) and Silver(I) Complexes

Abstract

The self-assembly and structural characterization of the new ferrocene-containing dicopper(II) double helicate [Cu 2 L 1 2 ] ( 1 ) and related copper(II) complex [CuL 2 (CH 3 CN)][ClO 4 ] 2 ( 2 ) and silver(I) complexes [AgL 2 (CH 3 CN)][BF 4 ] ( 3 ) and [AgL 2 ][BF 4 ] ( 4 ) have been achieved. These complexes are derived from inexpensive and easy-to-prepare ferrocene-containing bisbidentate Schiff-base ligands H 2 L 1, [(C 6 H 4 )(OH)CHNNC(CH 3 )(C 5 H 4 )] 2 Fe, and L 2, [(C 5 H 4 N)CHNNC(CH 3 )(C 5 H 4 )] 2 Fe. The neutral double-helical dicopper(II) complex 1 crystallizes in a polar space group. The two ferrocene-containing ligands strand interwined about each other and around the two tetrahedral copper ions in a double-helical fashion, with the Cu···Cu separation being 9.45 Å. The four metal centers are coplanar and form a slightly distorted rhombus with sides of ca. 5.8 Å. Reaction of the ligand L 2 and copper(II) constructed a mononuclear copper complex, 2 . X-ray structural analysis reveals that the copper(II) atom is coordinated in a distorted square pyramidal geometry, with four nitrogen atoms from the two bidentate bind sites forming the basal plane; the acetonitrile nitrogen atom occupies the apical position. The molecular structure of the silver(I) complex 3 is quite similar to that of copper complex 2, with the silver(I) surprisingly coordinated in a square pyramidal geometry. The silver(I) atom in mononuclear silver complex 4 is coordinated in a new square planar fashion. The result presented here shows that while the ligand ( L 1 ) 2 - can bridge two metal ions to give a double helicate with Cu(II), the ligand L 2 acts as a tetradentate ligand chelate to a single metal center in its structurally characterized complexes with Cu(II) and Ag(I). Crystal structures of the free ligand H 2 L 1 and L 2 are also reported for comparison.