Synthesis and structural characterization of one- and two-dimensional coordination polymers based on platinum–silver metallic backbones

Abstract

Seven Pt–Ag coordination polymers [Pt(NH₃)₂(NHCO^tBu)₂Ag(H₂O)](ClO₄) (1), [Pt₂(dap)₂(NHCO^tBu)₄Ag₂(NO₃)(ClO₄)] (dap = 1,2-diaminopropane, 2), [Pt₂(en)₂(NHCO^tBu)₄Ag₂(m-C₆H₄(CO₂)₂)]·3H₂O (en = ethylenediamine, 3), [Pt₂(NH₃)₂(NHCO^tBu)₂Ag₂(p-C₆H₄(CO₂)₂)]·2H₂O (4), [Pt₃(en)₃(NHCO^tBu)₆Ag₂(p-C₆H₄(CO₂)₂)_1.5]·6H₂O (5), [Pt(NH₃)₂(NHCO^tBu)₄Ag(4-C₅H₄NCO₂)₂]·10H₂O (6), and [Pt₂(en)₂(NHCO^tBu)₄Ag₂(4-C₅H₄NCO₂)](ClO₄) (7) were synthesized from the corresponding [Pt(RNH₂)₂(NHCO^tBu)₂] and Ag salts, respectively, and their structures were determined by X-ray crystallography. The Pt and Ag units aggregate into one-dimensional chains based on Pt–Ag backbones. Compounds 1, 2, and 6 possess an extended zigzag Pt–Ag chain motif, and the metallic chains arrange in a parallel fashion into layered structures. Compounds 3–5, and 7 form 2-D brick wall sheets due to the coordination of the bifunctional anions to the Ag⁺ ions of the neighboring chains. These polymers are constructed based on the Pt–Ag interactions and the coordination of amidate oxygen atoms to Ag ions. There are three kinds of short Pt–Ag bonds observed in the structures of these compounds. The Pt–Ag metallic backbone is formed by the stacking unsupported Pt–Ag bonds, the amidate doubly bridged Pt–Ag bonds, and the amidate singly bridged Pt–Ag bonds. In the chains, the Pt–Ag bond distances are quite short, and appear in the range of 2.78–2.97 Å, which are comparable to known Pt–Ag dative bonds.