The 1-N amides 1 ∞[Eu2(Pyr)4(PyrH)2(NH3)] · PyrH and [Yb2(Cbz)4(NH2)2(NH3)4] · 3CbzH: Distinctions in the crystal structures, thermal properties and ammonolysis tendency

Abstract

Abstract The low-temperature oxidation of the rare earth metals europium and ytterbium with the 1-N amines pyrrole and carbazole in liquid ammonia gave the pyrrolate 1 ∞[Eu2(Pyr)4(PyrH)2(NH3)] · PyrH (1) (Pyr – = C4H4N–, pyrrolate anion; PyrH = C4H4NH, pyrrole) and the carbazolate [Yb2(Cbz)4(NH2)2(NH3)4] · 3CbzH (2) (Cbz – = C12H8N–, carbazolate; CbzH = C12H8NH), respectively. Though both compounds are ammine complexes, the course through the redox potentials ELn(II/III) as well as the growing steric demand of the ligand result in various differences in the properties of the products. 1 shows a 1-dimensional structure of pyrrolate, pyrrole groups and one equivalent of ammonia coordinating and bridging divalent europium centers. This includes η 5 – π-interactions between the metal centers and pyrrolate and pyrrole rings. The resulting polymer shows a rather high thermal stability and melts at 445 °C prior to decomposition under release of ammonia at 475 °C. Contrary to this, 2 contains dimeric units around trivalent ytterbium consisting of carbazolate, ammonia and NH– 2 amide groups. No π-interactions are observed. Instead ammonolysis of liquid ammonia results in formation of an amide that contains two different amide groups. The thermal stability of 2 is lower than of 1. The building units of complex 2 decompose at 310 °C without melting. Both compounds were investigated by low-temperature single crystal X-ray analysis, Mid IR, Far IR and Raman spectroscopy as well as simultaneous DTA/TG.