Molecular Architecture <i>via</i> Coordination:  Self-Assembly, Characterization, and Host−Guest Chemistry of Mixed, Neutral-Charged, Pt−Pt and Pt−Pd Macrocyclic Tetranuclear Complexes. X-ray Crystal Structure of Cyclobis[[<i>cis</i>- Pt(dppp)(4-ethynylpyridine)₂][<i>cis</i>-Pd²⁺(PEt₃)₂2^-OSO₂CF₃]]

Abstract

Interaction of cis -Ptdppp( p -C 6 H 4 CN) 2 or cis -Ptdppp( p -C 2 C 6 H 4 N) 2 with cis -ML 2 (OSO 2 CF 3 ) 2 (M = Pt or Pd; L = PEt 3 or L 2 = dppp), in CH 2 Cl 2 or acetone, at room temperature, results in mixed, neutral-charged cyclic tetranuclear, Pt−Pt or Pt−Pd macrocyclic complexes in 90−99% yields via self-assembly. All tetramers are microcrystalline air- and water-stable solids with decomposition points > 170 °C. The benzonitrile based macrocycles can be disassembled in solution with 4,4‘-bipyridine, while the 4-ethynylpyridine systems are more stable toward a variety of guests. The 4-ethynylpyridine tetramers display host−guest chemistry with silver triflate via the “π -tweezer effect”. The X-ray crystal structure as well as FABMS, including isotope patterns, are reported for the tetranuclear macrocycle cyclobis[[ cis -Pt(dppp)(4-ethynylpyridine) 2 ][ cis -Pd 2+ (PEt 3 ) 2 2 - OSO 2 CF 3 ]] ( 14 ).