868592-59-0Relevant academic research and scientific papers
Uranium(III)/(IV) nitrile adducts including UI4(N≡CPh) 4, a synthetically useful uranium(IV) complex
Enriquez, Alejandro E.,Scott, Brian L.,Neu, Mary P.
, p. 7403 - 7413 (2005)
The synthesis of complexes used to elucidate an understanding of fundamental An(III) and An(IV) coordination chemistry requires the development of suitable organic-soluble precursors. The reaction of oxide-free uranium metal turnings with 1.3 equivalents of elemental iodine in acetonitrile provided the U(III)/U(IV) complex salt, [U(N≡CMe)9][UI6][I] (1), in which the U(III) cation is surrounded by nine acetonitrile molecules in a tricapped trigonal prismatic arrangement, a [UI6]2- counterion, and a noncoordinating iodide. The U-N distances for the prismatic and capping nitrogens are 2.55(3) and 2.71(5) A, respectively. The same reaction performed in benzonitrile afforded crystalline UI4(N≡ CPh)4 (3) in 78% isolated yield. In the solid state, 3 shows an eight-coordinate U(IV) atom in a puckered square antiprismatic geometry with U-N and U-I distances of 2.56(1) and 3.027(1) A, respectively. This benzonitrile UI4 adduct is a versatile U(IV) synthon that is soluble in methylene chloride, benzonitrile, and tetrahydrofuran, and moderately soluble in toluene and benzene, but decomposes in benzonitrile at 198°C to [UI(N≡CPh)8][UI]6 (4), a U(III)/U(IV) salt analogous to 1. A toluene slurry of 3 treated with 2.2 equiv of Cp*MgCl· THF (Cp* = pentamethylcyclopentadienide) provided Cp*2UI2(N≡CPh) (5) in low yields. Single-crystal X-ray structure determination shows that the iodide ligands in 5 are in a rare cis configuration with an acute I-U-I angle of 83.16(7)°. Treatment of a methylene chloride solution of 3 with KTp* (Tp* = hydridotris(3,5-dimethylpyrazolylborate)) formed green Tp*UI3 (6) which was converted to yellow Tp*UI3(N≡CMe) (7) by rinsing with acetonitrile. Addition of 2.2 equiv of KTp* to a toluene solution of 3 followed by heating at 95°C, filtration, and crystallization led to the isolation of the dinuclear species [Tp*UI(dmpz)] 2[μ-O] (9) (dmpz = 3,5-dimethylpyrazolide), presumably formed by hydrolytic cleavage of excess KTp* by adventitious water. The Tp* complexes 6, 7, and 9 were characterized by single-crystal X-ray diffraction, NMR, FT-IR, and optical absorbance spectroscopies.
