Thorium(iv) alkyl and allyl complexes of a rigid NON-donor pincer ligand with flanking 1-adamantyl substituents.

Palladium-catalyzed coupling of 1-adamantylamine (2 equiv.) with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylxanthene afforded the proligand 4,5-bis(1-adamantylamino)-2,7-di-tert-butyl-9,9-dimethylxanthene, H-2[XAd] (1), which upon deprotonation with excess KH or KCH2Ph in THF or dme generated [{K(THF)(3)}(2)(XAd)] (2a) and [K-2(XAd)(dme)] (2b). Subsequent reaction of in situ generated 2a or 2b with [ThCl4(dme)(2)] yielded [(XAd)ThCl4K2]x(dme) (3; x = 0.5-2), which reacted with 2 equiv. of LiCH2SiMe3 or K[allyl(TMS)] to afford the bis(hydrocarbyl) complexes [(XAd)Th(CH2SiMe3)(2)(THF)] (4) and [(XAd)Th((3)-allyl(TMS))(2)] {5; allyl(TMS) = 1-(SiMe3)C3H4}. Dialkyl complex 4 was stable at 80 degrees C for at least 2.5 hours, but decomposed over 4.5 hours at 110 degrees C. Diallyl complex 5 was stable for hours at 85 degrees C, and suffered less than 5% decomposition after 10 minutes at 155 degrees C. At room temperature, averaging of the syn and anti protons of the allyl CH2 groups of 5 occurred on the NMR timescale, as a consequence of rapid -sigma- hapticity changes. Additionally, low temperature H-1 and C-13 NMR spectroscopy indicates that 5 exists as a rapidly exchanging mixture of two isomers with C-1 and C-2 symmetry. Compounds 2a, 4 and 5 were crystallographically characterized.