Uranium(V) and uranium(IV/V) mixed valence complexes with p- tert-butylhomocalix[ n]arenes ( n = 4, 6)

Abstract

The homocalixarenes p- tert-butyltetrahydroxy[3.1.3.1]metacyclophane (H 4L 1) and p- tert-butylhexahydroxy[2.1.2.1.2.1]metacyclophane (H 6L 2) react with UCl 4 to give new polyphenoxide uranium complexes which have been characterized by X-ray diffraction. In the mononuclear compound [Hpy][UCl 2(L 1)] · 2.5py ( 2), the U V centre is bound to the four phenoxide groups and two chlorine atoms. Further inclusion of hydrogen bonded counter-ions and solvent molecules in the macrocycle cavity results in dimerization through weak interactions. The tetranuclear complex [U 4Cl 2O 2(L 2) 2(H 2O)(thf)] · 3thf ( 3) is a mixed valence compound comprising two U IV and two U V centres bound to three or four phenoxide groups each and bridged by two μ 3-oxo, two chlorine and two phenoxide groups. The localization of the U IV and U V ions is indicated by the differing bond lengths. The crystal structure of the uncomplexed macrocycle H 6L 2 · 5py ( 1) is also reported.