Enforced η¹-Fluorenyl and Indenyl Coordination to Zirconium: Geometrically Constrained and Sterically Expanded Complexes Derived from the Bifunctional (FluPPh₂NAr)⁻ and (IndPPh₂NAr)⁻ Ligands

Abstract

The (FluPPh2NAr) and (IndPPh2NAr) ligands 2a–c and 4a–c (a, Ar = Ph; b, R = DIPP; c, = Mes) were readily prepared by Staudinger reactions between aryl azides and Flu/Ind diphenylphosphines, and they were coordinated to zirconium via toluene elimination. The propensity of the pendent phosphazene group to enforce low hapticity of the Flu and Ind rings in the ensuing complexes has been demonstrated experimentally and theoretically. Of particular interest, geometrically constrained and sterically expanded structures have been evidenced spectroscopically and structurally for both complexes [(FluPPh2NPh)ZrBn3] 5a and [(IndPPh2NPh)ZrBn3] 7a. In addition, the ability of the aryl substituent at nitrogen to modulate the hapticity of the Ind ring (from η1, to η2, and η3) has been substantiated, and intramolecular CH-activation reactions leading to doubly cyclometalated complexes 6c and 8c have been observed when R = Mes.