Synthesis and characterization of four cubical molybdenum(V) tetramers and their catalytic properties for the epoxidation of cis-cyclooctene using H2O2

Molybdenum tetramers: Mo4(μ3-O)4[μ-O2P(CH2Cl)2]4O4 (1), Mo4(μ3-O)4(μ-O2P(CH2OH)2)4O4 (2), Mo4(μ3-O)4[μ-O2P(PhOMe)2]4O4 (3), and Mo4(μ3-O)4[μ-O2P(o-C6H4(CH2)2)]4O4 (4) have been synthesized and characterized by IR, UV–Vis, and 31P NMR spectroscopy. Molybdenum tetramers 1 and 4 along with the ligands L2A and L4 were structurally characterized by single crystal X-ray crystallography. An infinite 2D polymeric sheet was formed via inter and intra hydrogen bonds in the crystals of L2A. The crystals of L4 consist of infinite polymeric chains formed through hydrogen bonding. All molybdenum tetramers were tested as catalysts for the epoxidation of cis-cyclooctene in the presence of H2O2. Compounds 1 and 2 resulted in more than 80% epoxide after 24 hours at 70 °C, and displayed superior catalytic activities over compounds 3 and 4 under identical conditions. The superior catalytic activities of compounds 1 and 2 may be attributed to their better solubility in the ethanol/H2O2 system.

Molybdenum tetramers: Mo4(μ3-O)4[μ-O2P(CH2Cl)2]4O4 (1), Mo4(μ3-O)4(μ-O2P(CH2OH)2)4O4 (2), Mo4(μ3-O)4[μ-O2P(PhOMe)2]4O4 (3), and Mo4(μ3-O)4[μ-O2P(o-C6H4(CH2)2)]4O4 (4) have been synthesized and characterized by IR, UV–Vis, and 31P NMR spectroscopy. Molybdenum tetramers 1 and 4 along with the ligands L2A and L4 were structurally characterized by single crystal X-ray crystallography.Figure optionsDownload as PowerPoint slideHighlights
► Synthesis of tetramers with [Mo4O8]4+ cores stabilized by various phosphinates.
► Crystal structures of two of these ligands as well as two of the tetramers.
► Interesting H-bonding arrangements of the ligands.
► Epoxidation of cis-cyclooctene under H2O2/ethanol conditions.