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

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 (C 3 v ) with each of three Ir−H bonds t...

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Veröffentlicht in:Journal of the American Chemical Society 2001-10, Vol.123 (40), p.9822-9829
Hauptverfasser: Webster, Charles Edwin, Singleton, Daniel A, Szymanski, Michael J, Hall, Michael B, Zhao, Cunyuan, Jia, Guochen, Lin, Zhenyang
Format: Artikel
Sprache:eng
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Zusammenfassung: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 (C 3 v ) 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 C s edge-bridged octahedral tetrahydride structure and a C 1 η2-dihydrogen, dihydride structure are local minima and find that the C 3 v 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 C s , C 1, and C 3 v structures also supports the assignment of the C s and C 1 structures as the observed ones.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja001233t