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

Abstract

Rare-earth metallacarborane alkyls can be stabilized by the incorporation of a functional sidearm into both π and σ ligands. Reaction of [Me₃NH][7,8-O(CH₂)₂-7,8-C₂B₉H₁₀] with one equiv. of Ln(CH₂C₆H₄-o-NMe₂)₃ gave metallacarborane alkyls [η¹:η⁵-O(CH₂)₂C₂B₉H₉]Ln(σ:η¹-CH₂C₆H₄-o-NMe₂)(THF)₂ (Ln = Y (3a), Gd (3b), Er (3c)) via alkane elimination. They represent the first examples of rare-earth metallacarborane alkyls. Treatment of 3a with RNCNR (R = Cy, ⁱPr) or 2-benzoylpyridine afforded the corresponding mono-insertion products [η¹:η⁵-O(CH₂)₂C₂B₉H₉]Y[η²-(RN)₂C(CH₂C₆H₄-o-NMe₂)](DME) (R = Cy (4a), ⁱPr (5a)) or [η¹:η⁵-O(CH₂)₂C₂B₉H₉]Y[C₅H₄NC(Ph)(CH₂C₆H₄-o-NMe₂)O](THF)₂ (6a), respectively. Complex 3a also reacted with ArNCO or ArNC (Ar = 2,6-diisopropylphenyl, 2,6-dimethylphenyl) to give di-insertion products [η¹:η⁵-O(CH₂)₂C₂B₉H₉]Y[OC(NC₆H₃Me₂)N(C₆H₃Me₂)C(CH₂C₆H₄-o-NMe₂)O](THF)₂ (7a) or [η¹:η⁵-O(CH₂)₂C₂B₉H₉]Y[C(NC₆H₃ⁱPr₂)C(NC₆H₃ⁱPr₂)(CH₂C₆H₄-o-NMe₂)](DME) (8a). These results showed that the reactivity pattern of the Ln–C σ bond in rare-earth metallacarborane alkyls was dependent on the nature of the unsaturated organic molecules. New complexes were characterized by various spectroscopic techniques and elemental analysis. Some were further confirmed by single-crystal X-ray analysis.