David O. Marler

The structure of U3(O)(OCMe3)10, and unusual trinuclear U(IV) oxo-alkoxide

Abstract In an attempt to prepared tetrakis(tert-butoxy)uranium(IV) a trinuclear oxo-alkoxide of uranium(IV) was obtained instead. The compound has the formula U 3 O[(CH 3 ) 3 CO] 10 and it crystallizes in the hexagonal space group P6 3 mc with a = b = 18.256(4) A, c = 10.013(2) A, Z = 2. The trinuclear unit is strikingly reminiscent of that in Mo 3 O(OCH 2 CMe 3 ) 10 . In contrast to the molybdenum compound where there is metal-metal bonding, the U⋯U distance of 3.574(1) A indicates a non-bonded interaction.

Structural and vibrational characteristics of the tetrasulfatodimolybdenum ions with MoMo bond orders of 3.5 and 4.0

Abstract The compound K 4 [Mo 2 (SO 4 ) 4 ]Br·4H 2 O has been made and its crystal structure determined. Space group P 4/ mnc ; unit cell dimensions, a = 11.903(2), c = 8.021(1) A, V = 1136(1) A 3 . The compound is isomorphous with the analogous chloride whose structure has been reported. The MoMo and MoBr distances are 2.169(2) and 2.926(1) A, respectively and the [Mo 2 (SO 4 ) 4 ] 3− ions reside on crystallographic special positions with 4/ m symmetry. The Raman spectra of both the bromo and chloro compounds have been measured and the MoMo stretching frequency is 370 ± 1.5 cm −1 in each, for the compounds containing the natural isotopic distribution of molybdenum. The chloro compound has been prepared containing the pure isotope 92 Mo as well, and the Raman spectra recorded. The v (MoMo) band is shifted by 6.8 ± 0.5 cm −1 . The compound K 4 [Mo 2 (SO 4 ) 4 ]·2H 2 O has also been prepared with Mo at natural abundance and with the pure isotope 100 Mo, whereby a shift of 8.5 ± 0.5 cm −1 was found. These and other results will be discussed with regard to the similarity of the Raman spectra of the Mo 2 (S0 4 ) 4 3− and M0 2 (S0 4 ) 4 4− species.