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Bis(cyclopentadienyl) Titanium Dinitrogen Chemistry: Synthesis and Characterization of a Side-on Bound Haptomer

Supporting Info

Tamara E. Hanna, Wesley H. Bernskoetter, Marco W. Bouwkamp, Emil Lobkovsky, and Paul J. Chirik*

Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853

Organometallics, 2007, 26 (9), pp 2431–2438

DOI: 10.1021/om0611913

Publication Date (Web): March 27, 2007

Corresponding author. E-mail: pc92@cornell.edu.

Abstract

The titanocene dinitrogen complex [(η⁵-C₅H₂-1,2,4-Me₃)₂Ti]₂(μ₂,η²,η²-N₂) (1-N₂) has been prepared both by dihydrogen reductive elimination from the in situ generated monohydride derivative and by alkali metal reduction of the corresponding monoiodide. In the solid state, 1-N₂ contains a side-on bound N₂ ligand with an N−N bond length of 1.216(3) Å, consistent with a significant contribution from a two-electron-reduced diazenido ([N₂]^2-) fragment. Attempts to maintain side-on coordination of the N₂ ligand but increase the wedge dihedral by introducing isopropyl or tert-butyl substituents induced a change in hapticity to end-on and a less activated bridging dinitrogen ligand. The ansa-titanocene dinitrogen complexes rac-[Me₂Si(η⁵-C₅H₂-2-SiMe₃-4-^tBu)₂Ti]₂(μ₂,η¹,η¹-N₂) (4-N₂) and [Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃-3-^tBu)Ti]₂(μ₂,η¹,η¹-N₂) (5-N₂) have also been prepared and crystallographically characterized and shown to have weakly activated, end-on dinitrogen ligands. The latter example coordinates two additional equivalents of N₂ upon cooling under a dinitrogen atmosphere in pentane solution.

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Published In Issue April 23, 2007
Received December 30, 2006

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Article

Bis(cyclopentadienyl) Titanium Dinitrogen Chemistry: Synthesis and Characterization of a Side-on Bound Haptomer