Tiara-like Octanuclear Palladium(II) and Platinum(II) Thiolates and Their Inclusion Complexes with Dihalo- or Iodoalkanes

A tiara-like octanuclear palladium
thiolate complex, [Pd­(μ-SCH2CO2Me)2]8, that has a toroidal structure was synthesized
via reactions of either PdCl2 with methyl thioglycolate/N,N-diisopropylethylamine (DIEA) (conventional
method) or [PdCl2(MeCN)2] with m-C6H4(CMe2SCH2CO2Me)2 (alternative method). In the latter method,
the tiara-like complex formed via the corresponding SCS-pincer complex
and/or 1:1 PdCl2 and ligand complexes. With respect to
the platinum analogues, the alternative method efficiently produced
the tiara-like octanuclear complex [Pt­(μ-SCH2CO2Me)2]8 in high purity. Small molecules,
such as CH2Cl2, ClCH2CH2Cl, CH2Br2, and CH3I, were accommodated
in the inner voids of the tiara rings to form 1:1 inclusion complexes. These
complexes are stabilized not only by weak CH···X hydrogen
bonds (X = Cl or Br) between the methylene protons of four or eight
axially positioned methoxycarbonylmethyl groups on the tiara rings
and the halogen atoms of the guest molecules but also by weak coordination
of the halogen atoms to the transition-metal atoms.