145290-13-7Relevant academic research and scientific papers
Early actiniae alkoxide chemistry. Synthesis, characterization, and molecular structures of Th(IV) and U(IV) aryloxide complexes
Berg, John M.,Clark, David L.,Huffman, John C.,Morris, David E.,Sattelberger, Alfred P.,Streib, William E.,Van Der Stays, William G.,Watkin, John G.
, p. 10811 - 10821 (2007/10/02)
Several synthetic procedures have been developed for the preparation of early actinide aryloxide complexes. Simple alcoholysis of the actiniae metallacycle ([(Me3Si)2N]2An(CH2SiMe 2NSiMe3)] [An = Th (1), U (2)] using 1 equiv of 2,6-disubstituted phenol results in the protonation of the An-C bond to form mono(aryloxide) complexes An(O-2,6-R2C6H3)[N(SiMe3) 2]3 [An = U; R = t-Bu (3). i-Pr (4). An = Th; R = t-Bu (5), Me (6)] in essentially quantitative yield. For An = Th, further stepwise substitution products, the bis(aryloxide) or tris(aryloxide) complexes Th(O-2,6-t-Bu2C6H3)2[N(SiMe 3)2]2 (7) and Th(O-2,6-t-Bu2C6H3)3[N(SiMe 3)2] (8), are readily isolated depending on the stoichiometry of added phenol. Prolonged (36 h) reflux with excess 2,6-di-tert-butylphenol fails to provide the homoleptic Th(O-2,6-t-Bu2C6H3)4 via this simple protonolysis reaction. Thorium metallacycle 1 reacts with 4 equiv of HO-4-t-BuC6H4 to produce polymeric [Th(O-4-t-Bu2C6H4)4] x, addition of pyridine to which yields the monomeric adduct Th(O-4-t-BuC6H4)4(py)3 (10). For alcoholysis reactions employing the uranium metallacycle (2), addition of slightly greater than 4 equiv of HO-2,6-t-Bu2C6H3 in refluxing toluene for 6 h provides U(O-2,6-R2C6H3)4 [R = t-Bu (11), i-Pr (12)]. While alcoholysis fails to provide the homoleptic Th(O-2,6-t-Bu2C6H3)4 (9), we can prepare this complex via a metathetical procedure. Reaction of ThI4(THF)4 with 4 equiv of KO-2,6-t-Bu2C6H3 in THF provides 9 in high yield. For less sterically-demanding aryloxide ligands, metathesis of ThI4(THF)4 with 4 equiv of KO-2,6-R2C6H3 in THF results in formation of bis(THF) adducts Th(O-2,6-R2C6H3)4(THF)2 [R = Me (13), i-Pr (14)]. The THF adducts readily exchange with pyridine to give Th(O-2,6-Me2C6H3)4(py)2 (15). These new aryloxide compounds have been characterized by elemental analysis, 1H NMR, infrared spectroscopy, and, for U(O-2,6-t-Bu2C6H3)[N(SiMe3) 2]3 (5), An(O-2,6-t-Bu2C6H3)4, [An = Th (9), U (11)], and Th(O-2,6-Me2C6H3)4(py)2 (15), single-crystal X-ray diffraction. In 5, the U metal center is coordinated to the O atom of the aryloxide ligand and the N atoms of the three silylamide ligands, in a pseudotetrahedral fashion with U-O and U-N distances of 2.145 (8) and 2.285 (11) ?, respectively. An(O-2,6-t-Bu2C6H3)4 complexes (An = Th, U) are isostructural and possess crystallographic 54 symmetry. Each set of four An-O bond lengths is identical [2.189 (6) ?, Th; and 2.135 (4) ?, U], and the O-An-O angles are of two types, four of 110.46 (15)° for An = Th [110.2 (1)°, An = U] and two of 107.5 (3)° for An = Th [108.0 (2), An = U], and correspond to a slight flattening of the central AnO4 core. 15 has a pseudo-octahedral geometry about the central Th atom with the two pyridine ligands occupying cis positions. The average Th-N and Th-O distances are respectively 2.679 and 2.198 ?. Crystal data for 5 (-155°C): orthorhombic space group P212121; a = 11.257 (3), b = 19.761 (6), c = 19.589 (7) ?; K= 4357.46 A°3; dcalc = 1.409 g cm-3; Z = 4. 9 (-171°C): tetragonal space group 14; a = b = 14.082 (5), c = 13.468 (5) ?; V= 2670.75 ?3; dcalc = 1.317 g cm-3 Z = 2. 11 (-145°C): tetragonal space group 14; a = b = 14.066 (2), c = 13.404 (2) ?; V = 2652.10 ?3; d = 1.327 g cm-3; Z = 2.15 (-171°C): monoclinic space group P21/n; a = 14.724 (3), b = 19.724 (3), c = 15.456 (2) ?; β= 100.95 (1)°; V = 4407.01 ?3; dcalc = 1.458 g cm-3; Z = 4.
