Synthesis and Crystal Structure of a Self-Assembled, Octanuclear Oxo-Tantalum(V) Derivative Containing the First Example of a Transition Metal M(8)(&mgr;-O)(12) Cage.

By reduction with CoCp(2) in THF or toluene, the tantalum(V) chlorocarbamato complex TaCl(2)(O(2)CNEt(2))(3), 1, gives high yields of the tantalum(III) N,N-diethylcarbamate, Ta(O(2)CNEt(2))(3), 2. On the other hand, good yields of the octanuclear &mgr;-oxo-N,N-diethylcarbamato cage compound Ta(8)(&mgr;-O)(12)(O(2)CNEt(2))(16), 3, were secured by reaction of 1 with sodium in THF. Compound 3 has been characterized by analytical and spectroscopic methods and by X-ray diffractometry.