Metal-pi interactions dominate in the solid-state structures of molecular heterobimetallic alkali-metal-europium(II) aryloxo complexes.

Treatment of Eu metal, 2,6-diphenylphenol (HOdpp), and MOdpp (M=Na, K) at elevated temperature in the presence of mercury afforded heterobimetallic complexes which were structurally characterized after crystallization from toluene. The structures of [MEu(Odpp)(3)]nPhMe (M=Na, n=1, 1; K, n=2.5, 2) consist solely of bridging aryloxide ligands and feature extensive pi-Ph-metal interactions. Rather than a heterobimetallic species, treatment of Eu metal and HOdpp with LiOdpp under similar conditions afforded a number of products, including a mixed-valent europium complex, [Eu(2)(Odpp)(3)][Eu(Odpp)(4)]4 PhMe (3). The structural framework of the [Eu(2)(Odpp)(3)](+) cation of 3 is similar to that of the molecular heterobimetallics 1 and 2, including the presence of pi-Ph-Eu interactions. The reluctance of the reaction to provide a Eu/Li heterobimetallic complex was exemplified by the simultaneous crystallization of [Eu(2)(Odpp)(4)]PhMe (6) and the homoleptic cubane [Li(4)(Odpp)(4)]2 C(6)H(14) (5) from toluene/hexane.