Cp*TaCl2B4H8: synthesis, crystal structure and spectroscopic characterization of an air-stable, electronically unsaturated, chiral tantalaborane

Abstract

Reaction between Cp*TaCl₄ (Cp* = η⁵-C₅H₅) and BH₃·thf at 40 °C yields the pale red electronically unsaturated cluster Cp*TaCl₂B₄H₈ 1 which despite having two electrons fewer than the seven pairs required for the observed square pyramidal geometry is stable in air; viewed as a cluster, 1 is the first example of an unsaturated cluster containing a single metal atom; viewed as a chiral 16-electron organometallic complex it is isoelectronic with Cp(C₂B₉H₁₁)TaCl₂ and Cp[(Me₃Si)₂C₂B₄H₄]TaCl₂.