30 mL) was stirred with MgClz (120 mg, 1.26 mmol) for 24 h at room temperature. The mixture was filtered and the solvent removed under reduced pressure, giving (v3-HB(3-Butpz)3)MgC1 (35 mg, 61%).Reaction of (q3-HB(3-Butpz)3)M&H3 with TlCl. A solution of (~~-HB(3-Butpz)~lMgCH~ (60 mg, 0.14 mmol) in EhO (30 mL) was stirred with TlCl (170 mg, 0.71 mmol) for 18 h at room temperature. The mixture was filtered and the solvent removed under reduced pressure, giving starting material (s3-HB(3-X-ray Structure Determinations. Details of the crystal data, data collection, and refinement parameters are available as supplementary material.Butpz)3JMgCH3.