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A Carbon-Free Sandwich Complex [(P5)2Ti]2-

Urnezius, E.; Brennessel, W. W.; Cramer, C. J.; Ellis, J. E.; Schleyer, P. v. R.
Science 2002, 295, 832.

Reactions of highly reduced titanium complexes with white phosphorus, P4, at or below 25o C yielded brown to deep red-brown salts of the first entirely inorganic metallocene, [(h5-P5)2Ti]2- (1). Like ferrocene and other carbon-based sandwich complexes, the structure of 1 has parallel and planar five-membered rings symmetrically positioned about the central metal atom. Despite its electron deficient (16 electron) and formally zerovalent titanium character, salts of 1 are remarkably stable toward heat and air, both in solution and in the solid state. Computational studies show that the pentaphosphacyclopentadienyl unit, P5, functions as an unusually effective acceptor ligand and this results in substantial stabilization of 1.

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