title: Minimum energy structure of hydridotris(pyrazolyl)borato iridium(V) tetrahydride is not a C(3upsilon) capped octahedron.
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.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Webster
authors.forename: D A
authors.initials: DA
authors.lastname: Singleton
authors.forename: M J
authors.initials: MJ
authors.lastname: Szymanski
authors.forename: M B
authors.initials: MB
authors.lastname: Hall
authors.forename: C
authors.initials: C
authors.lastname: Zhao
authors.forename: G
authors.initials: G
authors.lastname: Jia
authors.forename: Z
authors.initials: Z
authors.lastname: Lin
mesh_terms: D001881:Borates / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D001881:Borates; D009942:Organometallic Compounds; C439086:hydridotris(pyrazolyl)borato iridium(V) tetrahydride; D007495:Iridium