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A newly developed and structurally characterized titanium complex [Ti(Phen)(OC2H5)2Cl2] (Phen = 1,10-phenanthroline) is reported as a homogeneous pre-catalyst for the selective oxidation of organic sulfides to sulfoxides with a stoichiometric amount of 30% aq. H2O2 in CH3OH at room temperature. This catalytic system showed high yield (95–100%) and good selectivity (92–100%) during the catalytic reaction in a short period of time.

Two 5-sulfosalicylic acid (H3ssal) and 1,10-phenanthroline (Phen) substituted titanium-oxo-clusters, [Ti6O8 (Hssal)2(Phen)6(H2O)4]·4OH·21H2O (TOC-1) and [Ti4O4(Hssal)4(Phen)4]·18H2O·4NH3 (TOC-2), have been synthesized and fully characterized by single crystal X-ray diffraction, FT-IR spectroscopy, elemental analysis, thermogravimetric analysis and fluorescence analysis. The structure of TOC-1 is a hexanuclear cluster containing a {Ti6(μ2-O)8} core, where all titanium ions can be described in a distorted octahedral geometry with both 1,10-phenanthroline and 5-sulfosalicylate serving as chelating ligands, while TOC-2 consists of a tetranuclear {Ti4(μ2-O)4} skeleton forming an approximate plane quadrilateral where both 5-sulfosalicylate and 1,10-phenanthroline ligands chelate to the titanium atom and the oxygen atom bridges two titanium atoms. Moreover, catalytic activity for the selective oxidation of sulfides, methyl phenyl sulfide (MPS) and phenyl sulfide (PPS), has also been explored. The results showed that TOCs 1 and 2 exhibit excellent catalytic performance in the oxidation of sulfides to sulfoxides with H2O2 as an oxidant. In particular, TOC-1 is an efficient homogeneous catalyst and very interestingly it can be recovered by filtration upon cooling and then reused at least four times without losing activity, which is very rare in the oxygenation of organic sulfides.

Two structurally diverse compounds, [Cu(Hbpdc)2(phen)] (1) and [Cu(bpdc)(phen)(H2O)]n (2) (H2bpdc=4,4′-biphenyldicarboxylic acid, phen=1,10-phenanthroline), were synthesized under hydrothermal conditions. Copper atom in 1 is four-coordinated to one bidentate phen ligand and two monodentate partly deprotonated 4,4′-biphenyldicarboxylates. As expected, the structure of 1 is a monomeric species and affords an extended two-dimensional hydrogen bonding architecture. Each copper atom in 2 is five-coordinated to one phen, one water molecule, and two bis-monodentate fully deprotonated 4,4′-biphenyldicarboxylates. Therefore, the structure of 2 is a one-dimensional chain.