CHEMISTRY OF C-TRIMETHYLSILYL-SUBSTITUTED HETEROCARBORANES - 24 - SYNTHETIC, SPECTROSCOPIC, STRUCTURAL, AND REACTIVITY STUDIES ON HALF-SANDWICH AND FULL-SANDWICH YTTRACARBORANES OF 2,3-C2B4-CARBORANE AND 2,4-C2B4-CARBORANE LIGANDS

The reaction of YCl3 with i(THF)(2)]-1-Li(THF)(2)-2-(SiMe3)-3-(R)-2,3- C2B4H4 (R = SiMe3 and Me) or -H)(2)Na(THF)(2)]-1-Na(THF)(2)-2,4-(SiMe3 )(2)-2,4- C2B4H4 in 1:2 molar ratios in dry benzene produced the yttra carboranes 2)-4,4',5,5'-Li(THF)[1,1'-commo-Y(2,3-C2B4H4)(2)]} R = SiMe 3 (I) Me (II)) or ',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 foun d to react with excess NaH in dry THF to give a hydridoyttracarborane sandwich -[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-C2B4 H6 proved unsuccessful, instead, the reaction produced the mixed magne sa-/ yttracarborane ,3-C2B4H4]}-2,3-(SiMe3)(2)-2,3-C2B4H4(3.5C(6)H(6)) (IV). All compounds were characterized by their IR and H-1, B-11, and C-13 NMR spectra; V was also characterized by its Li-7 NMR spectrum. The structures of I, II, and IV were determined by single-crystal X-ra y 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 molecul e to give a very distorted tetrahedral arrangement around the metal. T he structure of III is a dimer in which each Y atom is bonded to two c arboranes and a THF, the fourth coordination site being occupied by a pair of Y-H-B bridges to two adjacent borons in a neighboring carboran e.