C₂ - Symmetric Chelating Silyl Amides as Ancillary Ligands for d⁰ Early Transition Metals

Early transition-metal chemistry has received increased attention in recent years, particularly as new applications in catalysis and polymer chemistry have been developed. Much of this new chemistry involves complexes which possess cyclopentadienyl ligand sets. Research efforts have also been devoted to the development of alternative ligand sets that may provide better control of the electronic and steric properties of the metal center. One approach involves use of ancillary multidentate amido ligands to support reactive and highly electrophilic metal centers. We have been exploring use of C₂ - symmetric bis(silylamido) ligands, derived from biphenyl and binaphthyl backbones. Poor pi-donors, and sterically hindered, such ligands are expected to support electrophilic metal centers and enforce coordinative unsaturation. The C₂ - symmetric binding sites these systems provide can be expected to promote stereoselectivity in their reactions.

The lithiated silylamine 1, used as a starting material for synthesis of metal complexes, was obtained according to the scheme below:

References:
Diamine synthesis: Kanoh, S. et al Polymer Journal 1987, 19, 1047.
Related ligand systems: Drost, C.; Hitchcock, P. B.; Lappert, M. F. J. Chem. Soc. Dalton Trans 1996, 3595; Cloke, F. G. N.; Geldbach, T. J.; Hitchcock, P. B.; Love, J. B. J. Organomet. Chem. 1996, 506, 343

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