One-dimensional chain structures constructed from tetra(acetamidato)dirhodium(II,III) complexes and square planar platinum and palladium complexes

The reaction of [Rh2(acam)4(H2O)2]ClO4 (1) (Hacam = acetamide) with K2PtCl4 in aqueous solution gave crystals of [Rh2(acam)4(H2O)2][Rh2(acam)4{(μ-Cl)2PtCl2}] · 2H2O (2). The reaction of 1 with K2PdCl4 produced the palladium analog [Rh2(acam)4(H2O)2][Rh2(acam)4{(μ-Cl)2PdCl2}] · 2H2O (3) and a small amount of an aquated palladium complex [Rh2(acam)4{(μ-Cl)2PdCl(H2O)}] · H2O (4). Complexes 2 and 3 have anionic chains of [Rh2(acam)4{(μ-Cl)2MCl2}]− (M = Pt, Pd), while 4 includes neutral chains of [Rh2(acam)4{(μ-Cl)2PdCl(H2O)}]. Although all of the structures include infinite chains of (–Rh–Rh–Cl–M–Cl–)n (M = Pt, Pd), the chain structures are different; zigzag for 2 and 3 and helical for 4. In the structures of 2 and 3, the counter cation [Rh2(acam)4(H2O)2]+ made a hydrogen-bonded chain with the crystallization water molecules. The cationic chains and the anionic chains are connected with hydrogen bonds. In the structure of 4, the chains are also linked together by direct hydrogen bonds between the chains and those with the crystallization water molecules. ESR spectra of the powdered samples of 2 and 3 at 77 K were consistent with a rhombic structure: for 2, g1 = 2.111, g2 = 2.054, g3 = 2.004; for 3, g1 = 2.115, g2 = 2.057, g3 = 2.007. These results indicate that there is a spin flip-flop exchange between the cations, [Rh2(acam)4(H2O)2]+, and the Rh25+ units in the anionic chains. The electrical conductivities of 2 and 3 were in the order of 10−7 S cm−1 at room temperature.

The reaction of [Rh2(acam)4(H2O)2]ClO4 (Hacam = acetamide) with K2MCl4 (M = Pt, Pd) in aqueous solution gave crystals of [Rh2(acam)4(H2O)2][Rh2(acam)4{(μ-Cl)2MCl2}] · 2H2O that include an anionic zigzag chain structure of [Rh2(acam)4{(μ-Cl)2MCl2}]−. A small amount of [Rh2(acam)4{(μ-Cl)2PdCl(H2O)}] · H2O that includes neutral helical chains of [Rh2(acam)4{(μ-Cl)2PdCl(H2O)}] was crystallized from the reaction solution with K2PdCl4.Figure optionsDownload as PowerPoint slide