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

Abstract

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.