Reactivity studies of phenylcalcium iodide towards THF yielding phenyl-free cage compounds - Crystal structures of [{(thf)Ca(O-CH=CH2)2}4 • CaO • CaI2] and [(CaO)4 • 4 (thf)3CaI2]

THF proved to be the favoured solvent for the direct synthesis of phenylcalcium iodide. However, ether degradation is the major side reaction in this solvent. Zinc-mediated degradation of THF leads to the formation of the cage compound [{(thf)Ca(O-CH=CH2)(2)}(4) center dot CaO center dot CaI2] (1) besides the zincate [(thf)(6)Ca] [ZnEt2Ph2]. The structure of 1 shows an oxygen-centered Ca-6 octahedron with iodine atoms bound to two opposite corners. Heating of phenylcalcium iodide in THF solution for several hours yields [(CaO)(4) center dot 4 (thf)(3)CaI2] (2) with a central Ca4O4 heterocubane unit. NMR monitoring of the reaction shows that the phenyl groups are converted to benzene due to alpha-deprotonation of THF. (C) 2009 Elsevier B. V. All rights reserved.