Synthesis, chemistry, and electronic structures of group 9 metallaboranes

Abstract

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 [M₂B₆H_10+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.