Synthesis of Organouranium(IV) Triflates from U(OTf)4 or from Alkyl or Amide Precursors

The uranium(IV) triflate [U(OTf)4] (1) (OTf = OSO2CF3) gives stable adducts with Lewis bases, such as [U(OTf)4(py)] (2) (py = pyridine). The crystal structure of a solvate of [U(OTf)4(OPPh3)3] (3), which exhibits a bidentate OTf group, has been determined. Substitution of the triflate ligands of 1 with LiNEt2, Kacac (acac = MeCOCHCOMe), KCp (Cp = η-C5H5), and K2COT (COT = η-C8H8) has led to the formation of [U(NEt2)4], [U(acac)4], [U(Cp)3(OTf)] (4), and [U(COT)(OTf)2(py)] (5), respectively. However, the bis(cyclopentadienyl) compounds [U(Cp*)2(OTf)2] (6) (Cp* = η-C5Me5) and [U(Cp)2(OTf)2(py)] (7) could not be prepared from 1. Complexes 4−7 have been isolated in good yields from the protonolysis reactions of the corresponding alkyl or amide precursors by means of pyridinium triflate. Compound 5 has also been prepared by treating [U(COT)2] with either [pyH][OTf] or 1 in pyridine. The crystal structures of [U(Cp)2(OTf)2(py)2] (8) and [U(COT)(OTf)2(OPPh3)2]·0.5py (9) have been determined.