Activation of Triphenylphosphine Oxide Mediated by Trivalent Organouranium Species
Treating a family of uranium benzyl compounds, Tp*2U(CH2Ph) (1-Bn), Tp*2U(CH2-para-iPrPh) (1-iPr), Tp*2U(CH2-para-tBuPh) (1-tBu), or Tp*2U(CH2-meta-OMePh) (1-OMe), which are supported by two hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) ligands, with a single equivalent of triphenylphosphine oxide (OPPh3) causes a unique carbon–carbon coupling to occur. The products of this reaction, Tp*2U[OP(C6H5)2(C6H5CH2C6H5)] (2-Ph), Tp*2U[OP(C6H5)2(C6H5CH2-p-iPrC6H4)] (2-iPr), Tp*2U[OP(C6H5)2(C6H5CH2-p-tBuC6H4)] (2-tBu), and Tp*2U[OP(C6H5)2(C6H5CH2-m-OCH3C6H4)] (2-OMe), are characterized by coupling between the benzyl substituent and the para-carbon of one of the phenyl groups of OPPh3. To probe the scope of this unusual reactivity, 1-Bn was treated with different tris(aryl)phosphine oxides, including tris(p-tolyl)phosphine oxide, which yields Tp*2U[OP(p-tolyl)2(C6H4(CH3)CH2C6H5)] (3-tolyl). All compounds were characterized by multinuclear NMR, vibrational, and electronic absorption spectroscopies. When possible, X-ra...