Facile syntheses of unsolvated Ul3 and tetramethylcyclopentadienyl uranium halides

In the course of comparing the reaction chemistry of (C5Me5)(3)U, 1, and its slightly less crowded analogue (C5Me4H)(3)U, 2, new syntheses of Ul(3), (C5Me4H)(3)U, (C5Me4H)(3)UCl, 3, and (C5Me5)(3)UCl, 4, have been developed. Additionally, (C5Me4H)(3)Ul, 5, and (C5Me4H)(2)UCl2, 6, have been identified for the first time. A facile synthesis of unsolvated Ul(3) is reported that proceeds in high yield with inexpensive equipment from iodine and hot uranium turnings. Both Ul(3) and Ul(3)(THF)(4) react with KC5Me4H in toluene to make unsolvated (C5Me4H)(3)U in higher yield than in previous reports that involve reduction of tetravalent (C5Me4H)(3)UCl, 3. A more atom-efficient synthesis of complex 3 is also reported that proceeds from reduction of t-BuCl, PhCl, or HgCl2 by 2. Similarly, (C5Me4H)(3)U reacts with Phl or Hgl(2) to generate (C5Me4H)(3)Ul. These studies also provided a basis to improve the synthesis of (C5Me5)(3)UCl from 1 by employing t-BuCl or HgCl2 as the halide source. Like (C5Me5)(3)UCl, the (C5Me4H)(3)UCl Complex reacts with HgCl2 to form (C5Me4H)(2) and (C5Me4H)(2)UCl2, 6, but unlike (C5Me5)(3)UX (X = Cl or l), the less substituted (C5Me4H)(3)UX complexes do not reduce t-BuCl or PhX. The synthesis of 6 from (C5Me4H)MgCl-THF and UCl4 is also included.