Copper(I), Silver(I), and Palladium(II) Complexes of a Thiaoxamacrocycle Displaying Unusual Topologies

Coordination behavior of the 14-membered dibenzo-O2S2 macrocycle, L, with the soft metal ions such as Pd(II), Cu(I), and Ag(I) is reported. The X-ray structures of the complexes have been determined, and a range of less common structural types, including mono-, di-, and multinuclear species with discrete and continuous forms were obtained. A two-step approach via reaction of dichloro-palladium(II) complex of L as a metalloligand, with L through a treatment of silver(I) perchlorate, led to the formation of bis(ligand) monopalladium(II) complex, [Pd(L)2]·2ClO4·2CH3NO2 (1). In this case, the square-planar stereochemical demand of Pd(II) coupled with the coordination of the S2-donors of L to a metal center results in the formation of the bis(ligand)-type mononuclear complex. In 1, the ether oxygens of the ring are unbound. L reacts with CuBr to yield related 2:2:2 (metal/ligand/anion) complex of type [Cu2Br2(L)2] (2), in which two ligand molecules are linked by a rhomboid-type Cu−Br2−Cu cluster unit. However, the parallel reaction with CuI afforded the mixture of the isostructural 2:2:2 type complex [Cu2I2(L)2] (3a) and double-stranded 1D coordination polymer {[Cu2I2(L)2]·2CH3CN}n (3b). The framework of 3b contains four bridging L coordinated to a rhomboidal Cu−I2−Cu motif through the exomonodentate Cu−S bonds. Again, the ether oxygens do not coordinate in copper(I) halide complexes. The observed different reactivity between copper(I) bromide and copper(I) iodide was also confirm by an XRPD measurement. Unlike the Pd(II) and Cu(I) cases, L afforded an unusual tris(L)-disilver(I) (club-sandwich-type) complex [Ag2(L)3](PF6)2 (4) on its reaction with AgPF6. Each silver adopts a trigonal planar coordination environment with coordination sites occupied by two S atoms from one terminal ligand, and by one S atom from the bridging ligand; once again the ether oxygens are not coordinated. An NMR titration of the formation of complex 4 confirmed that the Ag/L stoichiometry of 2:3 found in the solid state is also maintained in solution.