Syntheses and structures of zirconium(IV) complexes supported by 2,6-di-adamantylaryloxide ligands and formation of arene-bridged dizirconium complexes with an inverse sandwich structure

The reaction of 2,6-di-adamantyl-4-R-phenol ((ArOH)-O-R, R = Me, Bu-t) with (BuLi)-Bu-n in THF gave good yields of the lithiated derivatives ((ArO)-O-R)Li(THF)(2). Addition of 2 equiv. of ((ArO)-O-R)Li(THF)(2) to ZrCl4(THF)(2) in THF afforded the base-free dichloride complexes ((ArO)-O-R)ZrCl2 (R = Me 1a, Bu-t 1b). The dibenzyl derivative ((ArO)-O-Me)(2)Zr(CH2Ph)(2) 2 was synthesized by addition of 2 equiv. of PhCH2MgCl to 1a in toluene. Reduction of the dichloride complexes 1a and 1b with KC8 in toluene led to the formation of the toluene-bridged dizirconium complexes [((ArO)-O-R)(2)Zr](2)(mu-eta(6):eta(6)-C7H8) (R= Me 3a, Bu-t 3b). A similar reaction was carried out in benzene to produce the corresponding benzene-bridged analogue [((ArO)-O-R)(2)Zr](2)(mu-eta(6):eta(6)-C6H6) (R= Me 4a, Bu-t 4b). Treatment of 3a with 2 equiv. of 1-azidoadamantane (AdN(3)) in THF resulted in the release of toluene and N-2, generating the monomeric imide complex ((ArO)-O-Me)(2)Zr(NAd)(thf) 5. When the analogous reaction was carried out in toluene, ((ArO)-O-Me)(2)Zr(AdNN = NNAd) 6 was obtained. Structures of ((ArO)-O-R)Li(THF)(2), 1a, 2 and 5 were determined by X-ray crystallography.