Synthesis of Cyclical Diamine Templated Uranium Sulfates

Abstract

The hydrothermal synthesis of uranium sulfates in the presence of a series of structurally related organic templating agents has been investigated. Piperazine, 2-methylpiperazine, and 1,4-diazabicyclo[2.2.2]octane, each of which is based upon the same six-membered cyclical diamine, exhibit different point symmetries and hydrogen-bonding characteristics. Small changes in the template structure result in marked differences in the reaction product. Three new compounds were synthesized and structurally characterized, [N 2 C 4 H 12 ][UO 2 (H 2 O)(SO 4 ) 2 ], [N 2 C 5 H 14 ][UO 2 (H 2 O)(SO 4 ) 2 ], and [N 2 C 6 H 14 ][UO 2 (H 2 O)(SO 4 ) 2 ]. The inorganic framework of each compound was found to be dependent on the template structure. [N 2 C 4 H 12 ][UO 2 (H 2 O)(SO 4 ) 2 ] consists of one-dimensional [UO 2 (H 2 O)(SO 4 ) 4/2 ] ∞ 2 - chains, which hydrogen bond to one another to form quasi two-dimensional layers. One-dimensional chains are observed in [N 2 C 5 H 14 ][UO 2 (H 2 O)(SO 4 ) 2 ]. These chains, which have the formula [UO 2 (H 2 O)(SO 4 ) 4/2 (UO 2 (H 2 O)(SO 4 ) 2 )] ∞ 4- are unprecedented in uranium chemistry. Two-dimensional layers are observed in [N 2 C 4 H 12 ][UO 2 (H 2 O)(SO 4 ) 2 ]. Each uranyl [UO 2 ] 2+ unit is bound to one water molecule and four bridging sulfate tetrahedra.