CP-ASTERISK-TACL2B4H8 - SYNTHESIS, CRYSTAL-STRUCTURE AND SPECTROSCOPIC CHARACTERIZATION OF AN AIR-STABLE, ELECTRONICALLY UNSATURATED, CHIRAL TANTALABORANE

Reaction between CpTaCl4(Cp* = eta(5)-C5H5) and BH3 . thf at 40 degre es C yields the pale red electronically unsaturated cluster CpTaCl2B4 H8 1 which despite having two electrons fewer than the seven pairs req uired for the observed square pyramidal geometry is stable in air; vie wed as a cluster, 1 is the first example of an unsaturated cluster con taining a single metal atom; viewed as a chiral 16-electron organometa llic complex it is isoelectronic with Cp(C2B9H11)TaCl2 and Cp[(Me3Si)( 2)C2B4H4] TaCl2.