A ladder polysilane as a template for folding palladium nanosheets

Although discrete nano-sized compounds consisting of a monolayer sheet of multiple atoms have attracted much attention, monolayer transition metal nanosheets are difficult to access. Here we report a template synthesis of the folding metal nanosheet (2) consisting of 11 palladium atoms by treatment of a ladder polysilane, decaisopropylbicyclo[2.2.0] hexasilane (1), with Pd((CNBu)-Bu-t)(2). Crystallographic analysis reveals that the compound is composed of two monolayer Pd-7 sheets sharing three palladium atoms at the junction. Each Pd atom is stabilized by Pd-Si sigma-bonds, Pd-Pd bonds and coordination of isocyanides. Ligand exchange of 2 from (CNBu)-Bu-t to CN(2,4,6-Me-3-C6H2) is accompanied by structural rearrangement, leading to the formation of another folding Pd-11 nanosheet (3) consisting of two edge-sharing Pd7 sheets. The shapes of the Pd-7 sheets as well as the dihedral angle between the two Pd7 sheets are dependent on the substituent of the isocyanide ligand.