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Minimum Energy Structure of Hydridotris(pyrazolyl)borato Iridium(V) Tetrahydride Is Not a C 3 v Capped Octahedron

2001; American Chemical Society; Volume: 123; Issue: 40 Linguagem: Inglês

10.1021/ja001233t

1943-2984

Charles Edwin Webster, Daniel A. Singleton, Michael J. Szymanski, Michael B. Hall, Cunyuan Zhao, Guochen Jia, Zhenyang Lin,

Lanthanide and Transition Metal Complexes

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 interpreted as supporting face-capped octahedral structures (C3v) with each of three Ir−H bonds trans to an Ir−N bond and the fourth hydride capping the IrH3 face. Here, density functional geometry optimizations and coupled cluster calculations on hydridotris(pyrazol-1-yl)borato iridium tetrahydrogen find that a Cs edge-bridged octahedral tetrahydride structure and a C1 η2-dihydrogen, dihydride structure are local minima and find that the C3v structure is a local maximum (second-order saddle point). Several low energy transition states connecting the 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 on the Cs, C1, and C3v structures also supports the assignment of the Cs and C1 structures as the observed ones.