Uncovering alternate reaction pathways to access uranium(IV) mixed-ligand aryloxide-chloride and alkoxide-chloride metallocene complexes: Synthesis and molecular structures of (C5Me5)2U(O-2,6-iPr2C6H3)(Cl) and (C5Me5)2U(O-tBu)(Cl)

Reaction of the trivalent uranium complex (C5Me5)(2)U(O-2,6-(Pr2C6H3)-Pr-i)(THF) (1) with copper(I) chloride affords the corresponding tetravalent mixed-ligand aryloxide-chloride complex (C5Me5)(2)U(O-2,6-(Pr2C6H3)-Pr-i)(Cl) (2). The oxidative functionalization protocol cannot be extended to the synthesis of (C5Me5)(2)U(O-Bu-t)(Cl) (3) since the corresponding trivalent precursor is not stable. Salt metathesis between (C5Me5)(2)UCl2 and (KOBu)-Bu-t is the method of choice for the preparation of the tetravalent alkoxide-chloride derivative (C5Me5)(2)U(O-Bu-t)(Cl) (3). The X-ray crystal structures of (C5Me5)(2)U (O-2,6-(Pr2C6H3)-Pr-i)(Cl) (2) and (C5Me5)(2)U(O-Bu-t)(Cl) (3) are reported and represent the first structurally characterized uranium(IV) metallocene aryloxide-chloride and alkoxide-chloride complexes, respectively. Both complexes adopt a pseudo-tetrahedral geometry, with a chloride and aryloxide/alkoxide ligand occupying the plane bisecting the metallocene unit. (C) 2011 Elsevier B. V. All rights reserved.