Synthesis, Structure, and Bonding of d⁰/f<i>ⁿ</i> Metallacarboranes\nIncorporating the η⁷-Carboranyl Ligand

Abstract

Treatment of 1,2-(C₆H₅CH₂)₂-1,2-C₂B₁₀H₁₀ with excess Na or Li metal in THF followed by reaction\nwith MCl₃ in the presence of excess alkali metal gave novel 13-vertex <i>closo-</i>metallacarboranes {[(C₆H₅CH₂)₂C₂B₁₀H₁₀]M(THF)}₂{Na(THF)₃}₂·2THF (M = Dy (<b>1</b>), Y (<b>2</b>), Er (<b>3</b>)) or [{(C₆H₅CH₂)₂C₂B₁₀H₁₀}M(THF)]₂[Li(THF)₄]₂<b></b>(M = Y (<b>5</b>), Er (<b>6</b>)) in moderate to good yield, respectively. Recrystallization of <b>3</b> from a DME\nsolution afforded DME-coordinated metallacarborane {[(C₆H₅CH₂)₂C₂B₁₀H₁₀]Er(DME)}₂{Na(DME)₂}₂ (<b>4</b>).\n<b>2</b> and <b>5</b> are the first examples of d⁰ metallacarboranes incorporating a η⁷-carboranyl ligand. All of these\ncomplexes have been fully characterized by various spectroscopic date, elemental analyses, and X-ray diffraction\nstudies. Molecular orbital calculations indicate that the metal−carborane bonding is well delocalized and can\nbe described as the orbital interactions between the metal's five d orbitals and the cage's five symmetry-adapted frontier orbitals. It is anticipated that only the d⁰/f<i>ⁿ</i> transition metal ion with the proper size is capable\nof being η⁷-bound to an <i>arachno</i>-carboranyl ligand.