Assembly of Soft Metal Complexes of an O₄S₂-Macrocycle Displaying Endocyclic Monomer, Dumbbell-Like Dimer, and Endo-/Exocyclic Polymer Structures

A comparative investigation of the coordination behavior of an O 4 S 2 -donor macrocycle L with the thiaphilic soft metal ions Ag +, Cu +, Hg 2+, and Pd 2+ is reported. The X-ray structures of seven complexes ( 1 – 7 ) have been determined, and a range of structural types and coordination modes, including discrete to continuous forms, mono- to multinuclear, and endo- to exocyclic structures involving M–S bonds, are presented. First, reactions of L with AgClO 4, Hg(NO 3 ) 2, and K 2 PdCl 4 afforded the typical endocyclic 1:1 complexes [Ag L ]ClO 4 ( 1 ) without anion binding, as well as [Hg L (NO 3 ) 2 ] ( 2 ), and [Pd L Cl 2 ] ( 3 ), with anion binding. Further reaction of the anion-free complex 1 with different spacer ligands ( L′: dabco = 1,4-diazabicyclo[2.2.2]octane and bpp = 1,4-bis(4-pyridyl)piperazine) resulted in the formation of the interesting “dumbbell”-like complexes [Ag 2 L 2 (dabco)](ClO 4 ) 2 ( 4 ) and [Ag 2 L 2 (bpp)](ClO 4 ) 2 ( 5 ), exhibiting a [( L Ag)- L′ -(Ag L )] arrangement, respectively. Furthermore, the straightforward one-pot reactions of L with AgClO 4 in the presence of L′ also resulted in the isolation of the corresponding “dumbbell” complexes. Comparative NMR studies suggest the existence of corresponding structures of this type in solution. Contrasting with the discrete structures of 1 – 5, reactions of L with CuBr and AgSCN afforded a double-stranded 1D network {[(Cu 2 Br 2 ) L 2 ]·2CH 2 Cl 2 } n ( 6 ) linked with a rhomboidal Cu 2 Br 2 cluster and an endo-/exocyclic 1D network [Ag 4 L 2 (SCN) 4 ] n ( 7 ), respectively. The latter complex features an unusual fishbone-like structure in which endocyclic silver(I) complexes are attached to a “looped” exocyclic backbone of type {Ag-(1,3-μ 2 -SCN) 2 -Ag-(1,1,3-μ 3 -SCN)-Ag} n via Ag-SCN bonds.