MM quadruply bonded complexes supported by vinylbenzoate ligands: synthesis characterization photophysical properties and application as synthons

摘要

From the reactions between M2(TⁱPB)4 compounds and meta and para-vinylbenzoic acids (2 equiv.) in toluene at room temperature the compounds trans-M2(TⁱPB)2L2, where L = m-vinylbenzoate >1A (M = Mo) and >1B (M = W) and TⁱPB = 2,4,6-triisopropylbenzoate, and where L = p-vinylbenzoate >2A (M = Mo) and >2B (M = W) have been isolated. Compounds >1A and >2A have been shown to undergo Heck carbon–carbon coupling reactions with phenyliodide to produce trans-Mo2(TⁱPB)2(O2CC6H4-m-CHCH–C6H5)2, >3A and trans-Mo2(TⁱPB)2(O2CC₆H₄-p-CHCH–C₆H₅)₂, >4A. The molybdenum compounds >1A and >2A have been structurally characterized by single crystal X-ray crystallography. All the new compounds have been characterized by ¹H NMR, IR, UV-visible absorption and emission spectroscopy, high resolution MALDI-TOF MS, fs- and ns-transient absorption spectroscopy and fs-time-resolved IR spectroscopy. Electronic structure calculations employing density functional theory, DFT, and time-dependent DFT have been employed to aid in the interpretation of spectral data. All compounds show intense absorptions in the visible region corresponding to M₂δ to Lπ* charge transfer transitions. The lifetimes of the ¹MLCT state fall in the range of 1–10 ps and for the molybdenum complexes the T₁ states are ³δδ* with lifetimes ∼50 μs while for the tungsten complexes the T₁ are ³MLCT with lifetimes in the range of 3–10 ns.