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 (Ar(R)OH, R = Me, tBu) with nBuLi in THF gave good yields of the lithiated derivatives (Ar(R)O)Li(THF)2. Addition of 2 equiv. of (ArRO)Li(THF)2 to ZrCl4(THF)2 in THF afforded the base-free dichloride complexes (Ar(R)O)ZrCl2 (R = Me 1a, tBu 1b). The dibenzyl derivative (Ar(Me)O)2Zr(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 [(Ar(R)O)2Zr]2(-6:6-C7H8) (R = Me 3a, tBu 3b). A similar reaction was carried out in benzene to produce the corresponding benzene-bridged analogue [(Ar(R)O)2Zr]2(mu-eta(6):eta(6)-C6H6) (R = Me 4a, tBu 4b). Treatment of 3a with 2 equiv. of 1-azidoadamantane (AdN3) in THF resulted in the release of toluene and N2, generating the monomeric imide complex (Ar(Me)O)2Zr(NAd)(thf) 5. When the analogous reaction was carried out in toluene, (Ar(Me)O)2Zr(AdNN=NNAd) 6 was obtained. Structures of (Ar(R)O)Li(THF)2, 1a, 2 and 5 were determined by X-ray crystallography.