Platinum group metal thiacrown complexes as precursors for self-assembly reactions

Abstract

We report that our previously published molecular square, [{Pt([9]aneS3)(bipy)}4](OTf)8, although quite stable in nitromethane, slowly establishes an equilibrium with another coordination polymer, most likely a triangle, in acetonitrile. Multinuclear measurements on the square precursor complex, [Pt([9]aneS3)Cl2], show acetonitrile coordination upon dechlorination in that solvent, and acetonitrile coordination is additionally confirmed by the solid-state structure of [Pt([9]aneS3)(MeCN)2]2+. We form the complex through the reaction of [Pt([9]aneS3)Cl2] with excess AgPF6 in refluxing MeCN to produce a solid-state solution containing two complex cations with exclusive hexafluorophosphate counterions. Besides [Pt([9]aneS3)(MeCN)2]2+, a second cation is obtained, [Pt([9]aneS3)2]2+, which shows disorder between a double endo and a rare double exo conformation for the two [9]aneS3 ligands. We also report the structures of two Rh(III) thiacrown complexes, cis-[Rh([12]aneS4)Cl2](PF6), which involves cis chloro ligands and an asymmetric binding of the two equatorial sulphur donors, as well as trans-[Rh([16]aneS4)(H2O)(Cl)](OTf)2 with adjacent rather than alternating chair and twist-boat conformations. Lastly, the crystal structure of [{Pd([9]aneS3)(Cl)}2(pyrazine)](OTf)2 displays a pyrazine ligand bridging two [Pd([9]aneS3)Cl]+ moieties with cis stereochemistry of the two chloro ligands. Distortion of the pyrazine ligand is observed, which alleviates strain from bridging the two Pd centres. The extended structure of the complex consists of chains of dimers running parallel to the b-axis of the crystal.