An Extremely Bulky Tris(pyrazolyl)methanide: A Tridentate Ligand for the Synthesis of Heteroleptic Magnesium(II) and Ytterbium(II) Alkyl, Hydride, and Iodide Complexes

The tris(pyrazolyl) methane compound HC(3-Ad-5-Mepz)(3) [1, 3-Ad-5-Mepz = 3-(1-adamantyl)-5-methylpyrazolyl] and its regioisomer, HC(3-Ad-5-Mepz)(2)(3-Me-5-Adpz), were synthesized and crystallographically characterized. Deprotonation of 1 with MeLi afforded the lithium complex [{kappa(3)-N-C(3-Ad-5-Mepz)(3)}Li(thf)], which incorporates a tris(pyrazolyl)methanide ligand of unprecedented bulk. Reaction of 1 with MeMgI gave the ionic coordination complex [{kappa(3)-N-HC(3-Ad-5-Mepz)(3)}MgMe] I, which was readily deprotonated to afford the neutral compound [{kappa(3)-N-C(3-Ad-5-Mepz)(3)}MgMe]. The related magnesium butyl compound [{kappa(3)-N-C(3-Ad-5-Mepz) (3)}MgBu] was prepared from the reaction of 1 and MgBu2. Treating this with LiAlH4 or LiAlD4 led to rare examples of terminal magnesium hydride/deuteride complexes, [{kappa(3)-N-C(3-Ad-5-Mepz)(3)}MgH/D]. All neutral magnesium alkyl and hydride compounds were crystallographically authenticated. Reaction of [{kappa(3)kappa N-C(3-Ad-5-Mepz)(3)}Li(thf)] with [YbI2(thf)(2)] yielded the first structurally characterized f-block tris(pyrazolyl) methanide complex, [{kappa(3)-N-C(3-Ad-5-Mepz)(3)}YbI(thf)].