Self-assembly of 2∶2 and 3∶3 metallamacrocyclic complexes of platinum(II) with symmetrical, bipodal N′,N′,N‴N‴-tetraalkyl-N,N″-phenylenedicarbonylbis(thiourea)

Abstract

Bipodal N′,N′,N‴N‴-tetraalkyl-N,N″-phenylenedicarbonylbis(thiourea) readily ‘self-assemble into’ Pt₂L₂ and Pt₃L₃ metallamacrocyclic complexes depending on whether the S,O chelating moieties are meta or para relative to each other in the ligand. Thus treatment of PtCl₄^2– with one equivalent of 3,3,3′,3′-tetra(n-butyl)-1,1′-terephthaloylbis(thiourea), {H₂L¹}₂, leads to the exclusive formation of the cis-[Pt(L¹-S,O)]₃ complex, while 3,3,3′,3′-tetraethyl-1,1′-isophthaloylbis(thiourea), {H₂L²}₂, yields only the cis-[Pt(L²-S,O)]₂ complex. The cis-[Pt(L¹-S,O)]₃ complex forms extremely friable crystals, necessitating X-ray data collection in mother-liquor, the lattice of which was found to contain chloroform, water and ethanol molecules as ‘guests’. By contrast, the sparingly soluble diethyl-substituted Pt₂L₂ complex does not include solvent molecules in the crystal lattice.