An Early–Late Transition Metal Hybrid Analogue of Hexaborane(12)

Metal assisted borane condensation
method has been employed for
the preparation of novel metallaborane cluster containing group 4
metal. Pyrolysis of [Cp*IrB3H9], 1, with in situ generated zirconium bisborohydrate [Cp2Zr­(BH4)2], produced from the fast metathesis
reaction of [Cp2ZrCl2] and LiBH4,
and excess of BH3·THF yielded arachno-[(Cp2Zr)­(Cp*Ir)­B4H10], 2, in 56% yield. Compound 2 constitutes the first crystallographic
structure determination of hexaborane(12) metal analogue containing
zirconium. The observed geometry of 2 can be generated
from a dodecahedron by removing two vertices and an edge. Anticipating
a straight metal fragment substitution/addition reaction, mild thermolysis
of 2 with [Fe2(CO)9] was carried
out. However, the reaction led to the formation of known trimetallic
[Cp*IrFe2(CO)9] cluster via cluster degradation.
In addition, density functional theory (DFT) calculations have been
carried out for 2 and other hypothetical early–late
combinations of hexaborane(12) metal analogues to reveal the electronic
structures.