Synthesis and Structure of a New Bulky Hybrid Scorpionate/Cyclopentadienyl Ligand and its Lithium Complex

The reaction of 5-(1-adamantyl)-3-methyl-1H-pyrazole with dibromomethane yields a product mixture bis(3-adamantyl-5-methylpyrazolyl)methane (H2C(PzAd,Me)2, 2 a), (3-adamantyl-5-methylpyrazolyl)-(3-methyl-5-adamantylpyrazolyl)methane ((H2C(PzAd,Me)(PzMe,Ad), b) and bis(3-methyl-5-adamantylpyrazolyl)methane (H2C(PzMe,Ad)2, c). Lithiation sterically congested H2C(PzAd,Me)2 (2 a) subsequent addition diphenylfulvene lithium 1,1-bis(3-adamantyl-5-methylpyrazolyl)-2,2-diphenyl-2-ethyl-cyclopentadienide, [(thf)Li{Cp−CPh2−CHPzAd,Me}] (3) which is unable to form thf adduct but can be hydrolyzed H5C5−CPh2−CHPzAd,Me (4). Adamantyl groups in 5-position bis(pyrazolyl)methane, i. e. b c, prohibit formation fulvene adduct. For comparison reasons, [{H5C5−CPh2−CHPzMe2}LiI] (1 has been prepared via protolysis (thf)lithium 1,1-bis(3,5-dimethylpyrazolyl)-2,2-diphenyl-2-ethyl-cyclopentadienide, [(thf)Li{Cp−CPh2−CHPzMe2}] the presence calcium iodide.