Chemistry ofC-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

Abstract

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.

The N‐Lithiation of 2,4,6‐Triphenylborazine

“…[17] In this complex, one Li cation sits on top of an open C 2 B 3 face while the second is bonded sidewise to a B-B bond. This lithium carboranate on reaction with YCl 3 produces the complex [Li(thf) 4 ]{(1-Cl-1-H 6 )-2,2Ј,3,3Ј(Me 3 Si) 4 -4,4Ј,5,5Ј-Li(thf)[1,1Ј-commo-Y(2,3-C 2 B 4 H 4 ) 2 ]} [18] where the Li cation of the yttriate coordinates to four B atoms (2 each per carborane unit) with Li-B distances of 2.31(4), 2.27(4), and 2.49(4) Å. In the starting material the Li-B distances are Li1-B3 2.291(9), Li1-B4 2.371(9), and Li1-B5 2.237(10) Å.…”

exo-nido- versus closo-Lanthanacarboranes. Synthesis and Structure of exo-nido-[(C6H5CH2)2C2B10H10]Ln(DME)3, [exo-nido-{(C6H5CH2)2C2B9H9}Ln(THF)3]2 (Ln = Sm, Yb), and closo-exo-[(C6H5CH2)2C2B10H<

“…These measured values compare with the 2.823(4) Å in [η 5 :η 6 -Me 2 Si(C 9 H 6 )(C 2 B 10 H 11 )]Sm III (THF) 2 , 2.764(3) and 2.841(3) Å in [η 5 :η 6 -Me 2 Si(C 5 H 4 )(C 2 B 10 H 11 )]Sm III (THF) 2 , 3d, 2.983(11) Å in [( η 6 -C 2 B 10 H 12 )Eu II (MeCN) 3 ] ∞ ,3b and 3.03(1) Å in [( η 6 -C 2 B 10 H 12 ) 2 Eu II (THF) 2 ] 2- 3b. The average Sm(1)···B (B 3 face) distance of 3.013(5) Å is very close to the average Sm(2)···B (B 3 face) distance of 3.037(5) Å, which can be compared with the 3.037(3) Å in 1 , 3.042(8) Å in [ exo-nido- {(C 6 H 5 CH 2 ) 2 C 2 B 9 H 9 }Sm II (DME) 2 ] 2 ,2c and 2.800(14) Å in {[( η 5 -(Me 3 Si) 2 C 2 B 4 H 4 )Sm III ] 3 [( μ 2 -(Me 3 Si) 2 C 2 B 4 H 4 Li) 3 ( μ 3 -OMe)][ μ 2 -Li(THF) 3 ] 3 ( μ 2 -O)} 4c. The closest approach of the benzyl substituents to Sm(1) and Sm(2) is through C(20) and C(4) at distances of 2.939(5) and 3.079(5) Å, respectively, and the smaller Sm(1)···C(20) distance corresponds to the smaller C(11)−C(19)−C(20) angle of 108.6(4)°.…”

Synthesis, structure and reactivity of rare-earth metallacarborane alkyls [η1:η5-O(CH2)2C2B9H9]Ln(σ:η1-CH2C6H4-o-NMe2)(THF)2

“…The Y-C(13)/ Y-N(1) distances of 2.415(4)/2.657(3) Å ( The average Y-cage atom distance of 2.751(5) Å is significantly Scheme 1 Synthesis of rare-earth metallacarborane alkyls. longer than that of 2.670(5) Å in [η 1 :η 17…”