Equatorial ligand substitution by hydroxide in uranyl Pacman complexes of a Schiff-base pyrrole macrocycle.

The synthesis of the mono-uranyl complex [UO(2)(THF)(H(2)L(Me))] of a ditopic Schiff-base pyrrole macrocycle is described and is shown to adopt a Pacman wedge-shaped structure in which the uranyl dication is desymmetrised and sits solely in one N(4)-donor compartment to leave the other vacant. While investigating the mechanism of the previously reported, base-initiated, reductive silylation chemistry of [UO(2)(THF)(H(2)L(Me))], we found that uranyl hydroxide complexes could be isolated. As such, the reaction between [UO(2)(THF)(H(2)L(Me))] and KH in THF generated the dimeric cation-cation hydroxide [{UO(2)(OH)K(C(6)H(6))(H(2)L(Me))}(2)] when crystallised from C(6)H(6), or alternatively, when crystallised from THF, the monomeric THF-adducted cation-cation complex [UO(2)(OH)K(THF)(2)(H(2)L(Me))] was isolated. These compounds result formally from the substitution of the equatorial THF molecule by hydroxide, and it was also shown that the reaction between dry KOH and [UO(2)(THF)(H(2)L(Me))] generated [{UO(2)(OH)K(C(6)H(6))(H(2)L(Me))}(2)].