Diverse structures, weak interactions, and catalytic properties of three palladium 2-sulfobenzoate complexes with 1,10-phenanthroline

<div><p>Three complexes with same components, Pd^II, 2-sulfobenzoate and 1,10-phenanthroline, [Pd(phen)₂]⋅2(2-Hsb) (<b>1</b>), [Pd(phen)₂](2-Hsb)⋅(2-Hsb)⋅2H₂O (<b>2</b>), and [Pd(phen)₂]⋅[Pd(phen)(2-sb)₂]⋅6H₂O (<b>3</b>), where 2-H₂sb is 2-sulfobenzoic acid and phen is 1,10-phenanthroline, were synthesized and characterized by IR spectra, elemental analyses, thermogravimetric analyses, UV–vis absorption spectra and powder X-ray analysis. Single X-ray crystal structural analyses showed that <b>1</b> and <b>2</b> are ionic species, while <b>3</b> is a dimer through weak bonding interactions. In <b>1</b> and <b>2</b>, 2-Hsb⁻ ligands are partly deprotonated and it is fully deprotonated in <b>3</b>. In <b>2</b> and <b>3</b> there are hydrogen bonds and <i>π–π</i> interactions. Extended hydrogen bonding structures for <b>2</b> and <b>3</b> are 1-D and 3-D architectures, respectively. The oxidation of methyl phenyl sulfide by <b>1</b>-<b>3</b> as homogeneous catalysts gave high conversion and selectivity in methanol. The addition of 2-sulfobenzoic acid in the catalytic reaction further promotes the conversion.</p>