Synthesis and Characterization of Organoplatinum Dendrimers with 1,3,5-Triethynylbenzene Building Blocks

The multinuclear complexes 1,3,5-[trans-I(Et3P)2PtC≡C]3C6H3 (1) and 1,2,4,5-[trans-I(Et3P)2PtC≡C]4C6H2 (2) were prepared via σ-acetylide synthetic methodologies by reaction of tri- and tetraethynylbenzene with diiodobis(triethylphosphine)platinum. The combination of this synthetic coupling strategy with the divergent synthetic principle for the formation of dendrimers led to organometallic first- and second-generation dendrimers with ethynylplatinum units in the main chain. The outer spheres of the dendrimers consist of either terminal acetylenic groups or bis(triethylphosphine)platinum iodide groups. All compounds were fully characterized by elemental analysis, mass spectrometry, NMR, and vibrational spectroscopy. The single-crystal structure of a first generation dendrimer 3 with terminal acetylene groups was determined by X-ray analysis. It shows an out-of-plane twisting of all three terminal 1,3,5-triethynylbenzene groups as well as a twisting of one of the coordination planes around a platinum atom, relative to the central aromatic ring.