| Abstract
| - Recent synthesis and NMR spectroscopy of neutral Ir(V) complexes hydridotris(3,5-dimethylpyrazol-1-yl)borato tetrahydride (Tp*IrH4) and hydridotris(pyrazol-1-yl)borato tetrahydride (TpIrH4) have been interpretedas supporting face-capped octahedral structures (C3v) with each of three Ir−H bonds trans to an Ir−N bondand the fourth hydride capping the IrH3 face. Here, density functional geometry optimizations and coupledcluster calculations on hydridotris(pyrazol-1-yl)borato iridium tetrahydrogen find that a Cs edge-bridgedoctahedral tetrahydride structure and a C1 η2-dihydrogen, dihydride structure are local minima and find thatthe C3v structure is a local maximum (second-order saddle point). Several low energy transition states connectingthe local minima have been located, and these minima can be used to simulate the experimental NMR spectra.A comparison of the experimental infrared spectrum of Tp*IrH4 and the harmonic frequency calculations onthe Cs, C1, and C3v structures also supports the assignment of the Cs and C1 structures as the observed ones.
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