Ligand Scavenging and Catalytic Utilization of the Phototransient ReH5(PMe2Ph)2

Green, Mark; Huffman, John C.; Caulton, Kenneth G.; Rybak, Witold K.; Ziółkowski, Józef J.

doi:10.1016/s0022-328x(00)86115-x

Cited by 41 publications

(7 citation statements)

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“…)-Ir-P(40) angle of 150°and the P(2)-Ir-P(21) and P(2)-Ir-P(40) angles of 105°clearly reflect the large bulk of the PCy 2 Ph groups. The calculated Ir-P(21) and Ir-P(40) bond distances are longer than the experimental values by 0.065 Å, while the discrepancy is even larger (0.13 Å) for Ir-P(2), which is trans to a hydride. The best agreement is obtained for MP2/II.…”

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confidence: 53%

“…Synthesis and Characterization of [IrH( η 2 -C 6 H 4 P t Bu 2 )(P t Bu 2 Ph)][BAr ‘ 4 ]. Ortho-metalation of a phenyl group on a phosphine ligand is a common reaction for low-valent unsaturated metal complexes, and is promoted by the presence of large (i.e., t Bu) pendant groups on the phosphine, in contrast to the rarity of ortho-metalation involving PMe 2 Ph . The metalation of a phosphine can have a profound influence on the reactivity of the complex and radically change the steric profile of the phosphine ligand.…”

Section: Resultsmentioning

confidence: 99%

“…Ortho-metalation of a phenyl group on a phosphine ligand is a common reaction for low-valent unsaturated metal complexes, and is promoted by the presence of large (i.e., t Bu) pendant groups on the phosphine, 8 in contrast to the rarity of ortho-metalation involving PMe 2 Ph. 40 The metalation of a phosphine can have a profound influence on the reactivity of the complex and radically change the steric profile of the phosphine ligand. The effective cone angle of the metalated phosphine increases and can promote the dissociation of other ligands via increased steric repulsions (i.e., labilizing effect).…”

Section: Synthesis and Characterization Of [Irh(η 2 -C 6 H 4 P T Bu 2...mentioning

confidence: 99%

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Computational and Experimental Test of Steric Influence on Agostic Interactions: A Homologous Series for Ir(III)

et al. 1998

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Chloride abstraction (using NaBAr‘4, Ar‘ = 3,5-(CF3)2C6H3) from Ir(H)2Cl(PtBu2Ph)2 gives cis,trans-Ir(H)2(PtBu2Ph)2 +, which has two agostic interactions with methyl C−H groups on different tBu groups. The molecule exists as diastereomers, due to stereochemistry at P. Chloride can be similarly abstracted from ortho-metalated IrH(η2-C6H4PtBu2)Cl(PtBu2Ph) to give square-pyramidal IrH(η2-C6H4PtBu2)(PtBu2Ph)+, which has only one agostic interaction, involving a tBuC−H bond; steric constraints on each phosphine leave no more C−H bonds available to donate to the remaining empty Ir(III) orbital. The smaller ligand PCy2Ph yields only the tris-phosphine complex Ir(H)2(PCy2Ph)3 +, and this is shown to have a square-pyramidal structure with one agostic cyclohexyl group and large Pax−Ir−P angles (104−106°). The analogous Ir(H)2(PiPr2Ph)3 + has similar inter-phosphorus angles, but no agostic interaction. Geometrical optimization of IrH2L3 + (PCy2Ph, PiPr2Ph) with the hybrid quantum mechanics/molecular mechanics (QM/MM) method (IMOMM) at the IMOMM (B3LYP:MM3) and IMOMM (MP2:MM3) levels permits a more detailed understanding of the influence of steric factors on the occurrence of an agostic bond. The MP2/MM3 method gives the results in closer agreement with experiment. Steric factors place the agostic bond in the vicinity of the metal center but at a distance that is too long to be considered as bonding. The electron-donating ability of the C−H bond and the electron accepting capacity of the metal center, which are introduced only at the QM level, bring the two partners in a bonding situation.

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Section: Resultsmentioning

confidence: 99%

Section: Synthesis and Characterization Of [Irh(η 2 -C 6 H 4 P T Bu 2...mentioning

confidence: 99%

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Computational and Experimental Test of Steric Influence on Agostic Interactions: A Homologous Series for Ir(III)

et al. 1998

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“…We have reported the phosphine substituent dependence of enthalpies for addition of small ligands to such species, in an attempt to establish differences among phosphines which might otherwise all be categorized as “bulky”. We have also reported the ease of ortho- metalation of P t Bu 2 Ph to Ir I , in contrast to the rarity of ortho -metalation involving the smaller phosphine PMe 2 Ph . It is therefore important to recognize that using, among others, the bulky phosphines listed above can have the consequence of metal attack on normally inert C−H bonds (C−C or P−C bond scission might also be anticipated), to give either new products or products of MD/C−H isotopic scrambling.…”

Section: Discussionmentioning

confidence: 90%

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

et al. 1998

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While Ir(H)2(PtBu2Ph)2 + has been shown experimentally to have two agostic tBu groups, ab initio B3LYP calculations on IrH2[P(Et)H2]2 + show that the CH3 group of the phosphine ligand does not form any agostic bond with the strongly electron-deficient (14-valence electron) metal. In contrast, integrated molecular mechanics/molecular orbital (IMOMM) calculations on the full complex Ir(H)2(PtBu2Ph)2 + duplicate the experimentally observed agostic interaction. Thus, at least in this case, the agostic interaction is due in part to the trapping of a C−H bond in the vicinity of the metal by the steric effects of the other groups of the bulky phosphine. This necessity of steric “constraint” identifies an additional influential factor for the agostic interaction.

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“…As an analogue to the known complexes of Ir and Rh, (C 5 Me 5 )Re(PMe 3 )H 2 undergoes oxidative addition of alkane after losing H 2 upon irradiation. However, contrary to the behavior of Rh and Ir complexes, the CpRe(PPh 3 ) 2 H 2 loses PPh 3 upon irradiation, 36,37 perhaps due to the trans disposition of the hydride ligands. However, the intermediate species that is responsible for alkane oxidative addition in this case must contain at least one H ligand, making it different from the one that Bergman et al 27 reported.…”

Section: ■ Introductionmentioning

confidence: 99%

Effect of Ancillary Ligands (A) on Oxidative Addition of CH₄ to Rhenium(III) Complexes: A = B, Al, CH, SiH, N, and P Using MP2, CCSD(T), and MCSCF Methods

Parveen

Cundari

2017

J. Phys. Chem. A

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A computational study of oxidative addition (OA) of methane to Re(OCH)A (A = ancillary ligand, which thus may interact with the metal) was carried out. The choice of ancillary ligands has been made based on their electronic properties: A = B or Al (Lewis acid), CH or SiH (electron precise), N (σ-donor), and P (σ-donor/π-acid). The main objective of this study was to understand how variation in A affects the structural and electronic properties of the reactant d-Re(III) complex, which can ultimately tune the kinetics and thermodynamics of OA. Results obtained from MP2 calculations revealed that, for OA of CH to Re(OCH)A, the order of ΔG for a choice of ancillary ligand is B > Al > SiH > CH > N > P. Single point calculations for ΔG obtained with CCSD(T) showed excellent agreement with those computed with MP2 methods. MCSCF calculations indicated that oxidative addition transition states are well described by a single electronic configuration, giving further confidence in the MP2 approach used for geometry optimization and ΔG determination, and that the transition states are more electronically similar to the d-Re(III) reactant than the d-Re(V) product.

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Ligand Scavenging and Catalytic Utilization of the Phototransient ReH5(PMe2Ph)2

Cited by 41 publications

References 5 publications

Computational and Experimental Test of Steric Influence on Agostic Interactions: A Homologous Series for Ir(III)

Computational and Experimental Test of Steric Influence on Agostic Interactions: A Homologous Series for Ir(III)

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

Effect of Ancillary Ligands (A) on Oxidative Addition of CH₄ to Rhenium(III) Complexes: A = B, Al, CH, SiH, N, and P Using MP2, CCSD(T), and MCSCF Methods

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Ligand Scavenging and Catalytic Utilization of the Phototransient ReH5(PMe2Ph)2

Cited by 41 publications

References 5 publications

Computational and Experimental Test of Steric Influence on Agostic Interactions: A Homologous Series for Ir(III)

Computational and Experimental Test of Steric Influence on Agostic Interactions: A Homologous Series for Ir(III)

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

Effect of Ancillary Ligands (A) on Oxidative Addition of CH4 to Rhenium(III) Complexes: A = B, Al, CH, SiH, N, and P Using MP2, CCSD(T), and MCSCF Methods

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

Effect of Ancillary Ligands (A) on Oxidative Addition of CH₄ to Rhenium(III) Complexes: A = B, Al, CH, SiH, N, and P Using MP2, CCSD(T), and MCSCF Methods