Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 24. Synthetic, Spectroscopic, Structural, and Reactivity Studies on Half- and Full-Sandwich Yttracarboranes of 2,3-C2B4- and 2,4-C2B4-Carborane Ligands

• Published in: Organometallics 1998-07, Vol.17 (15), p.3196-3203
• Main Authors: Hosmane, Narayan S, Zhu, Dunming, Zhang, Hongming, Oki, Aderemi R, Maguire, John A
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om980096u

The reaction of YCl3 with closo-exo-5,6-[(μ-H)2Li(THF)2]-1-Li(THF)2-2-(SiMe3)-3-(R)-2,3-C2B4H4 (R = SiMe3 and Me) or closo-exo-5,6-[(μ-H)2Na(THF)2]-1-Na(THF)2-2,4-(SiMe3)2-2,4-C2B4H4 in 1:2 molar ratios in dry benzene produced the yttracarboranes [Li(THF)4]{1-Cl-1-(THF)-2,2‘-(SiMe3)2-3,3‘-(R)2-4,4‘,5,5‘-Li(THF)[1,1‘-commo-Y(2,3-C2B4H4)2]} (R = SiMe3 (I), Me (II)) or {Na(THF)3}2{[1-(THF)-1-(μ-H)2-2,2‘,4,4‘-(SiMe3)4-1,1‘-commo-Y(2,4-C2B4H4)2]2} (III) in yields of 83%, 80%, and 74%, respectively. Compound I was found to react with excess NaH in dry THF to give a hydridoyttracarborane sandwich 1-H-2,2‘,3,3‘-(SiMe3)4-[4,4‘,5-Li(THF)]2-[1,1‘-commo-Y(2,3-C2B4H4)2] (V) in 80% yield. Attempts to prepare the half-sandwich yttracarboranes directly from the reaction of YCl3, Me3SiCH2MgCl, and 2,3-(SiMe3)2-2,3-C2B4H6 proved unsuccessful, instead, the reaction produced the mixed magnesa-/yttracarborane closo-1-Y-{1,1‘-(μ-Cl)2-exo-[5,6-(μ-H)2-Mg(THF)2]-1,1‘-(μ-Cl)2-[closo-1-Mg(THF)-2,3-(SiMe3)2-2,3-C2B4H4]}-2,3-(SiMe3)2-2,3-C2B4H4(3.5C6H6) (IV). All compounds were characterized by their IR and 1H, 11B, and 13C NMR spectra; V was also characterized by its 7Li NMR spectrum. The structures of I, III, and IV were determined by single-crystal X-ray crystallography. Compound I is a bent-sandwich complex in which the Y atom is bonded to two carborane units, a Cl anion, and a THF molecule to give a very distorted tetrahedral arrangement around the metal. The structure of III is a dimer in which each Y atom is bonded to two carboranes and a THF, the fourth coordination site being occupied by a pair of Y−H−B bridges to two adjacent borons in a neighboring carborane.