The Continuum Between Hexagonal Planar and Trigonal Planar Geometries**

Garçon, Martí; Phanopoulos, Andreas; Sackman, George; Richardson, Christopher J. K.; White, Andrew J. P.; Cooper, Richard I.; Edwards, Alison J.; Crimmin, Mark R.

doi:10.1002/anie.202211948

“…of 2 from 1 is calculated to form Int‐1 with a small energy cost (Δ G ° 298K =10.3 kcal mol −1 ). This process occurs with a shift in the bonding of 1 along the continuum from hexagonal planar toward trigonal planar, [35] strengthening the Mg‐H interactions in the equatorial plane, and pre‐organising the complex for dissociation of an equivalent of 2 . Similar coordinatively unsaturated intermediates were recently described in related systems for the zincation of C−H bonds [24] .…”

Section: Methodsmentioning

confidence: 99%

Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes**

Garçon

¹

,

Phanopoulos

²

,

White

³

et al. 2022

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Reaction of a hexagonal planar palladium complex featuring a [PdMg 3 H 3 ] core with H 2 is reversible and leads to the formation of a new [PdMg 2 H 4 ] tetrahydride species alongside an equivalent of a magnesium hydride co-product [MgH]. While the reversibility of this process prevented isolation of [PdMg 2 H 4 ], analogous [PtMg 2 H 4 ] and [PtZn 2 H 4 ] complexes could be isolated and characterised through independent syntheses. Computational analysis (DFT, AIM, NCIPlot) of the bonding in a series of heterometallic tetrahydride compounds (Ni-Pt; Mg and Zn) suggests that these complexes are best described as square planar with marginal metal-metal interactions; the strength of which increases slightly as group 10 is descended and increases from Mg to Zn. DFT calculations support a mechanism for H 2 activation involving a ligand-assisted oxidative addition to Pd. These findings were exploited to develop a catalytic protocol for H/D exchange into magnesium hydride and zinc hydride bonds.

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“…of 2 from 1 is calculated to form Int‐1 with a small energy cost (Δ G ° 298K =10.3 kcal mol −1 ). This process occurs with a shift in the bonding of 1 along the continuum from hexagonal planar toward trigonal planar, [35] strengthening the Mg‐H interactions in the equatorial plane, and pre‐organising the complex for dissociation of an equivalent of 2 . Similar coordinatively unsaturated intermediates were recently described in related systems for the zincation of C−H bonds [24] .…”

Section: Methodsmentioning

confidence: 99%

Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes**

Garçon

¹

,

Phanopoulos

²

,

White

³

et al. 2022

Self Cite

View full text Add to dashboard Cite

Reaction of a hexagonal planar palladium complex featuring a [PdMg 3 H 3 ] core with H 2 is reversible and leads to the formation of a new [PdMg 2 H 4 ] tetrahydride species alongside an equivalent of a magnesium hydride co-product [MgH]. While the reversibility of this process prevented isolation of [PdMg 2 H 4 ], analogous [PtMg 2 H 4 ] and [PtZn 2 H 4 ] complexes could be isolated and characterised through independent syntheses. Computational analysis (DFT, AIM, NCIPlot) of the bonding in a series of heterometallic tetrahydride compounds (Ni-Pt; Mg and Zn) suggests that these complexes are best described as square planar with marginal metal-metal interactions; the strength of which increases slightly as group 10 is descended and increases from Mg to Zn. DFT calculations support a mechanism for H 2 activation involving a ligand-assisted oxidative addition to Pd. These findings were exploited to develop a catalytic protocol for H/D exchange into magnesium hydride and zinc hydride bonds.

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“…Shortly thereafter, the Crimmin group expanded on their study of the gap between the hexagonal planar MH Mg{ Ar nacnac}). 425 X-ray and neutron diffraction studies in combination with computational studies revealed that the zincbased donors tend to form C 3h geometries, while the magnesium analogues prefer to adopt a D 3h symmetry (Scheme 84b). The evidence from this work indicates that the hexagonal planar bonding extreme is favored in systems with large ionic contributions to the M−Mg interaction, implying a formal description of the system as a metalate(0) fragment [MH 3 ] 481 This compound formed by formal Cp − transfer with release of a phosphine ligand from 715, as observed upon reaction with either MgCp 2 or TlCp.…”

Section: Transition-metal Magnesium Compounds and Related Heavier Alk...mentioning

confidence: 99%

“…Ion-pairing interactions can occur in the absence of a cation sequestering agent. While studies by Fürstner, Hevia, − Mountford, ,,, Crimmin, − Wolf, Peters, − ,− and Lu, ,− among other contributions, illustrate that ion-pairing is a frequent phenomenon, only a handful of the investigations explicitly address the influence of such interactions on their reactivity. However, from these investigations it has become clear that the countercation may have profound influence on the reaction patterns, stoichiometric or catalytic, of metalates.…”

Section: Synthesis and Basic Reactivity Patterns Of D-block Metalatesmentioning

confidence: 99%

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

Landaeta,

Horsley Downie,

Wolf

2024

Chem. Rev.

10

0

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This review surveys the synthesis and reactivity of low-oxidation state metalate anions of the d-block elements, with an emphasis on contributions reported between 2006 and 2022. Although the field has a long and rich history, the chemistry of transition metalate anions has been greatly enhanced in the last 15 years by the application of advanced concepts in complex synthesis and ligand design. In recent years, the potential of highly reactive metalate complexes in the fields of small molecule activation and homogeneous catalysis has become increasingly evident. Consequently, exciting applications in small molecule activation have been developed, including in catalytic transformations. This article intends to guide the reader through the fascinating world of low-valent transition metalates. The first part of the review describes the synthesis and reactivity of d-block metalates stabilized by an assortment of ligand frameworks, including carbonyls, isocyanides, alkenes and polyarenes, phosphines and phosphorus heterocycles, amides, and redox-active nitrogen-based ligands. Thereby, the reader will be familiarized with the impact of different ligand types on the physical and chemical properties of metalates. In addition, ion-pairing interactions and metal−metal bonding may have a dramatic influence on metalate structures and reactivities. The complex ramifications of these effects are examined in a separate section. The second part of the review is devoted to the reactivity of the metalates toward small inorganic molecules such as H 2 , N 2 , CO, CO 2 , P 4 and related species. It is shown that the use of highly electron-rich and reactive metalates in small molecule activation translates into impressive catalytic properties in the hydrogenation of organic molecules and the reduction of N 2 , CO, and CO 2 . The results discussed in this review illustrate that the potential of transition metalate anions is increasingly being tapped for challenging catalytic processes with relevance to organic synthesis and energy conversion. Therefore, it is hoped that this review will serve as a useful resource to inspire further developments in this dynamic research field.

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The Continuum Between Hexagonal Planar and Trigonal Planar Geometries**

Cited by 11 publications

References 43 publications

Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes**

Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes**

Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes**

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

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