Metal rich metallaboranes of group 9 transition metals

Abstract

We report the synthesis and structural characterization of moderately air stable metal rich metallaboranes of iridium. Treatment of [Cp*IrCl₂]₂ with BH₃·thf at high temperature led to the isolation of a trimetallic [nido-5-(Cp*Ir)₃B₇H₁₁], 1. Compound 1 is isoelectronic and isostructural with decaborane-14 where three BH units in [B₁₀H₁₄] have been replaced by Cp*Ir fragments. As far as we are aware, 1 is the first example of a iridadecaborane having three metals. In addition to the formation of 1, a change in the reaction conditions enabled us to isolate a 7 sep [(Cp*Ir)₃B₄H₄], 2. The geometry of 2 can be viewed as a condensed polyhedron composed of Ir₃B₃ octahedron capped by a BH unit. All the compounds have been characterized by IR and ¹H, ¹¹B, and ¹³C NMR spectroscopy in solution, and the solid-state structures were established by X-ray crystallographic analysis. Quantum-chemical calculations by DFT methods for compounds 1 and 2 showed reasonable agreement with the experimentally observed structural parameters. The large HOMO–LUMO gaps are consistent with the high stabilities of the iridium clusters compared to their known Rh and Co analogues.