Activation of a Si=Si Bond by eta1-coordination to a transition metal.

Reaction of the disilenide 1 with Cp2ZrCl2 yields 2, the first transition metal complex with an eta1-sigma-bonded disilene moiety. The compound 2 exhibits a strongly red-shifted UV-vis absorption, resulting in an intensely green color. The Si=Si bond in 2 is considerably activated as shown by the rearrangement to a silyl-substituted zirconocene 3. X-ray diffraction studies on 2 reveal that the Si=Si bond is significantly longer than that in the precursor 1. Conversely, the Zr-Si distance is considerably smaller than the corresponding distance in 3, suggesting a certain degree of electron donation toward the 16e- zirconium center.