Lead(II) complexes with Kemp’s tricarboxylate: Can lone pair activity be discerned?

Abstract

Kemp’s triacid (H3kta; cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid) has been used to synthesize three lead(II) complexes under solvo-hydrothermal conditions. [Pb3(kta)Cl3] (1) and [Pb3(H3kta)(kta)2] (2) are both diperiodic coordination polymers displaying hydrophobic surfaces with protruding methyl groups, complex 2 being isomorphous with an SrII complex previously reported. In contrast, [Pb(Hkta)(phen)] (3), where phen is 1,10-phenanthroline, is a monoperiodic, helical coordination polymer. In all cases, PbII cations are in seven- or eight-coordinate environments of predominantly hemidirected nature. The possible effects of the PbII valence shell lone pair are discussed in terms of coordination geometry and Pb⋅⋅⋅H weak interactions as revealed on Hirshfeld surfaces. Only in complex 1 is a short Pb⋅⋅⋅H contact at 2.84 Å possibly indicative of appreciable basicity of the metal ion. All three complexes show similar weak luminescence, apparently independent of the nature of the ligands.