Minimum energy structure of hydridotris(pyrazolyl)borato iridium(V) tetrahydride is not a C(3upsilon) capped octahedron

J Am Chem Soc. 2001 Oct 10;123(40):9822-9. doi: 10.1021/ja001233t.

Abstract

Recent synthesis and NMR spectroscopy of neutral Ir(V) complexes hydridotris(3,5-dimethylpyrazol-1-yl)borato tetrahydride (Tp*IrH(4)) and hydridotris(pyrazol-1-yl)borato tetrahydride (TpIrH(4)) have been interpreted as supporting face-capped octahedral structures (C(3upsilon)) with each of three Ir-H bonds trans to an Ir-N bond and the fourth hydride capping the IrH(3) 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) eta(2)-dihydrogen, dihydride structure are local minima and find that the C(3upsilon) 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*IrH(4) and the harmonic frequency calculations on the C(s), C(1), and C(3upsilon) structures also supports the assignment of the C(s)and C(1) structures as the observed ones.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Borates / chemistry*
  • Iridium / chemistry*
  • Magnetic Resonance Spectroscopy
  • Models, Chemical*
  • Models, Molecular
  • Molecular Conformation
  • Organometallic Compounds / chemistry*
  • Spectrophotometry, Infrared
  • Surface Properties
  • Thermodynamics

Substances

  • Borates
  • Organometallic Compounds
  • hydridotris(pyrazolyl)borato iridium(V) tetrahydride
  • Iridium