Synthesis, Chemistry, and Electronic Structures of Group 9 Metallaboranes

Dimetallaoctaborane­(12)
of Ru, Co, and Rh have been well-characterized by a range of spectroscopic
techniques and X-ray diffraction studies. Thus, reinvestigation of
the Ir-system became of interest. As a result, a slight modification
in the reaction conditions enabled us to isolate the missing Ir analogue
of octaborane(12), [(Cp*Ir)2B6H10], 1. Compound 1 adapts a geometry similar
to that of its parent octaborane(12) and Ru, Co, and Rh analogues.
In [M2B6H10+x]­(M
= Ru, x = 2; M = Co and Rh, x =
0), there exist two M–H–B protons. However, a significant
difference observed in [(Cp*Ir)2B6H10] is the presence of two Ir–H instead of Ir–H–B
protons that eventually controls the reactivity of this molecule.
For example, unlike [M2B6H10]­(M =
Co or Rh), the Ir-analogue does not react with metal carbonyl compounds
or [Au­(PPh3)­Cl]. Along with 1, a closo trimetallic 8-vertex iridaborane [(Cp*Ir)3B5H4Cl], 2 was also isolated. Additionally,
from another reaction, 12-vertex closo iridaboranes
[(Cp*Ir)2B10Hy(OH)z], 3a and 3b (3a: y = 12, z = 0; 3b: y = 8, z = 2), have
also been isolated. Further, density functional theory calculations
were performed to gain useful insight into the structure and stability
of these compounds.