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 [{κ 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 [{κ 3 ‐N‐HC(3‐Ad‐5‐Mepz) 3 }MgMe]I, which was readily deprotonated to afford the neutral compound [{κ 3 ‐N‐C(3‐Ad‐5‐Mepz) 3 }MgMe]. The related magnesium butyl compound [{κ 3 ‐N‐C(3‐Ad‐5‐Mepz) 3 }MgBu] was prepared from the reaction of 1 and MgBu 2 . Treating this with LiAlH 4 or LiAlD 4 led to rare examples of terminal magnesium hydride/deuteride complexes, [{κ 3 ‐N‐C(3‐Ad‐5‐Mepz) 3 }MgH/D]. All neutral magnesium alkyl and hydride compounds were crystallographically authenticated. Reaction of [{κ 3 κN‐C(3‐Ad‐5‐Mepz) 3 }Li(thf)] with [YbI 2 (thf) 2 ] yielded the first structurally characterized f‐block tris(pyrazolyl)methanide complex, [{κ 3 ‐N‐C(3‐Ad‐5‐Mepz) 3 }YbI(thf)].