Computational Evidence of the Importance of Substituent Bulk on Agostic Interactions in Ir(H)2(PtBu2Ph)2+

Ujaque, Gregori; Cooper, Alan C.; Maseras, Feliu; Eisenstein, Odile; Caulton, Kenneth G.

doi:10.1021/ja9729894

Cited by 114 publications

(103 citation statements)

References 69 publications

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“…The sawhorse as a reference shape: Even if the sawhorse geometry 1 is not a very common one, it bears wide interest because of 1) the possibility of carrying out association reactions on the open side of the metal atom, 2) the ability of some such structures to form agostic interactions with pending groups of coordinated ligands, [16] and 3) the possibility of fluxional behavior through an intermediate square-planar geometry. [17] Geometrically, a sawhorse is characterized by a large bond angle (maybe close to 1808) between the two transoid ligands and a small angle (of around 908) between the two cisoid ligands.…”

Section: Resultsmentioning

confidence: 99%

Mapping the Stereochemistry and Symmetry of Tetracoordinate Transition‐Metal Complexes

Cirera

Alemany

Álvarez

2003

Chemistry A European J

193

203

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A continuous shape and symmetry study of tetracoordinate transition-metal complexes is presented, in an attempt to provide a systematic description of the stereochemistry of the metal coordination sphere in this important family of compounds. A tetrahedron/square-planar symmetry map has been developed, the main distortion paths of the ideal geometries are presented, and the applicability of a sawhorse shape measure is discussed. More than 13,000 structural data sets have been analyzed and the corresponding stereochemistries assigned from the values of their tetrahedral and square-planar symmetry measures. A good number of structures that are quite distant from the two ideal geometries can be adequately described as snapshots along the spread pathway for their interconversion, making use of the corresponding path deviation function. Further analysis of the structural data by metal electron configuration or by the denticity and conformation of the ligands provide general rules to describe the stereochemical preferences of tetracoordinate transition metal centers.

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Section: Resultsmentioning

confidence: 99%

Mapping the Stereochemistry and Symmetry of Tetracoordinate Transition‐Metal Complexes

Cirera

Alemany

Álvarez

2003

Chemistry A European J

193

203

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“…[7] Since agostic bond energies in the 10-15 kcal mol À1 range have been determined for the Group 6 complexes, [6] our slightly longer agostic bond in [H 2 C=ZrH 2 ] is probably almost as strong.…”

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confidence: 96%

[H₂CZrH₂]: The Simplest Carbene Hydride Complex, Agostic Bonding, and CH Activation of CH₄ to Form [(CH₃)₂ZrH₂]

2004

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High oxidation state transition-metal complexes with a carbon-metal double bond have proven important for understanding the nature of metal coordination and for catalysts in alkene-metathesis and alkane-activation reactions. [1][2][3] Several early transition-metal alkylidenes are agostic, [1] and these compounds provide the opportunity to characterize the agostic interaction of hydrogen to a transition-metal center in a simple carbene complex (most agostic interactions involve much more complicated systems) and to help understand the important alkane CÀH bond-activation process (a key step in many transition-metal catalyzed reactions). [4][5][6][7][8] The simplest compound of this type is the methylidene complex, [H 2 C = MH 2 ], which is an ideal model system to examine substituent effects and the agostic interaction. Such Group 4 compounds have been investigated by electronicstructure calculations using small basis sets and shown to have symmetrical structures without agostic interactions. [9][10][11] Recently we have treated laser-ablated Ti, Zr, and Hf atoms with CH 3 F and prepared the fluorine substituted [H 2 C = MHF] derivatives. [12][13][14] These methylidene species result from ahydrogen migration in the initial [CH 3 MF] intermediate. Our electronic-structure calculations using basis sets with polarization functions reveal a tilted CH 2 group and provide evidence for agostic interaction in the [H 2 C=MHF] molecules.The simple [H 2 C = MH 2 ] analogues contain two intense infrared chromophores, namely the CH 2 and MH 2 groups, which are sensitive to the distortion associated with intramolecular agostic bonding. Hence the IR spectrum of [H 2 C= ZrH 2 ] can provide evidence for agostic interaction through symmetry lowering in the molecule, as can computations using large basis sets. In particular, a simple count of [CHD = ZrHD] isotopomers provides a ready method to confirm agostic interactions in this simplest possible carbene complex, as only two isotopomers (cis and trans) will be formed if there is no agostic interaction (C 2v or C s symmetry), but four isotopomers (cis and trans for H and for D in the agostic position) if there is agostic interaction (C 1 symmetry). We report herein the first experimental characterization of [H 2 C = ZrH 2 ] and demonstrate the agostic CÀH···Zr interaction from the IR spectrum in solid neon and from density functional structure and frequency calculations.The laser-ablation matrix-IR experiment has been described elsewhere. [15,16] Briefly, laser-ablated zirconium atoms (Johnson-Matthey) reacted with CH 4 (Matheson), 13 CH 4 , CD 4 , CH 2 D 2 (Cambridge Isotopic Laboratories) in excess neon (Spectra Gases) during condensation on a CsI window at 5 K. IR spectra were recorded at 0.5 cm À1 resolution on a Nicolet 750 spectrometer with HgCdTe detector. Samples were irradiated by a mercury arc lamp (175 W, globe removed), were annealed, and more spectra were recorded.Complementary density functional theory (DFT) calculations were performed using the Gaussian 98 package, [...

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“…The steric bulk of the tBu substituents or the planarization of the ligand backbone possibly contribute to the stabilization of squareplanar instead of saw-horse coordination, which is generally observed for four-coordinate iridium(III). [23] However, DFT calculations predict a square-planar structure for the less sterically encumbered model complex [IrCl(L 4 )] + (R = Me; 2 Me ), as well (see below). The structural parameters of 2 and 1 in the crystalline state are very similar.…”

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Square‐Planar Iridium(II) and Iridium(III) Amido Complexes Stabilized by a PNP Pincer Ligand

et al. 2011

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Computational Evidence of the Importance of Substituent Bulk on Agostic Interactions in Ir(H)₂(P^tBu₂Ph)₂⁺

Cited by 114 publications

References 69 publications

Mapping the Stereochemistry and Symmetry of Tetracoordinate Transition‐Metal Complexes

Mapping the Stereochemistry and Symmetry of Tetracoordinate Transition‐Metal Complexes

[H₂CZrH₂]: The Simplest Carbene Hydride Complex, Agostic Bonding, and CH Activation of CH₄ to Form [(CH₃)₂ZrH₂]

Square‐Planar Iridium(II) and Iridium(III) Amido Complexes Stabilized by a PNP Pincer Ligand

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Computational Evidence of the Importance of Substituent Bulk on Agostic Interactions in Ir(H)2(PtBu2Ph)2+

Cited by 114 publications

References 69 publications

Mapping the Stereochemistry and Symmetry of Tetracoordinate Transition‐Metal Complexes

Mapping the Stereochemistry and Symmetry of Tetracoordinate Transition‐Metal Complexes

[H2CZrH2]: The Simplest Carbene Hydride Complex, Agostic Bonding, and CH Activation of CH4 to Form [(CH3)2ZrH2]

Square‐Planar Iridium(II) and Iridium(III) Amido Complexes Stabilized by a PNP Pincer Ligand

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Computational Evidence of the Importance of Substituent Bulk on Agostic Interactions in Ir(H)₂(P^tBu₂Ph)₂⁺

[H₂CZrH₂]: The Simplest Carbene Hydride Complex, Agostic Bonding, and CH Activation of CH₄ to Form [(CH₃)₂ZrH₂]