Research Guides

Department of Chemistry University of Oxford

Professor John E. McGrady

Research Interests     Updated 30/06/2020

My group's research interests lie in the electronic structure of inorganic systems. We have interests in a wide range of problems drawn from molecular and solid-state transition-metal chemistry as well as main-group reactivity, and as a result we apply a similarly diverse range of methodologies, from empirical theory (Extended Huckel) at one extreme to multi-configurational SCF techniques (CASSCF) at the other. Much of our work is done with DFT, both in molecular and solid-state contexts. We work closely with experimental groups around the world with shared interests in structure, magnetochemistry, electrochemistry and reactivity. The brief summary below highlights some of the areas that we are involved in at the moment.

 

Electronic structure of Zintl-ion clusters

In collaboration with Professor Zhong-Ming Sun at Nankai University, China, we are working on models of Zintl-ion cluster growth and bonding. These typically highly anionic clusters crystallise from mixtures of low-valent transition metal ions and clusters of tetrel elements ([Sn9]4-, for example). They form elegant and often large clusters, where the final dispersion of elements is dictated by the balance between tetrel-tetrel and transition metal-transition metal bonding vs tetrel-transition metal bonding. The mechanisms of cluster growth are a particular interest to us, as is the relationship between these molecular species and the extended Zintl phases.

[Cu4@E18]4- (E = Sn, Pb): Fused Derivatives of Endohedral Stannaspherene and Plumbaspherene,  L. Qiao, C. Zhang, C.-C. Shu, H. W. T. Morgan, J. E. McGrady and Z.-M. Sun, J. Am. Chem. Soc., 2020, accepted. http://dx.doi.org/10.1021/jacs.0c04815

 

                                              CuSn DOS

 

A family of lead clusters with precious metal cores, C.C. Shu, H.W.T. Morgan, L. Qiao, J. E. McGrady and Z.-M. Sun, Nature Comm., 2020, 11, 3477.

Featured as an editor's highlight.

Au/Pb clusters: Nature Comm, 2020.

Structure and Bonding in [Sb@In8Sb12]3- and [Sb@In8Sb12]5-, C. Liu, N. V. Tkachenko, I. A. Popov, N. Fedik, X. Min, C.Q. Xu, L.-J. Li, J. E. McGrady, A. J. Boldyrev and Z. -M. Sun, Angew. Chem. Int. Ed., Engl., 2019, 58, 8367.

Cover art for [Sb@In8Sb12]3-/5-: Angew. Chem, 2019.

Synthesis and structure of a family of rhodium polystannide clusters [Rh@Sn10]3-, [Rh@Sn12]3-, [Rh2@Sn17]6- and the first triply-fused stannide, [Rh3@Sn24]5- C. Liu, X. Jin, L. -J. Li, J. Xu, J. E. McGrady and Z. -M. Sun, Chem. Sci., 2019, 10, 4394.

 

Artists impression of formation of [Rh3Sn24]5-: Chem. Sci, 2019.

Synthesis and Characterization of [Ru@Ge12]​3-​: An Endohedral 3-​Connected Cluster, G. Espinoza-Quintero, J. C. A. Duckworth, W. K. Myers, J. E. McGrady and J. M. Goicoechea, J. Am. Chem. Soc., 2014, 136, 1210.

 

The electronic structure of cluster compounds

Metal cluster compounds present a significant challenge to models of structure and bonding - the work of Wade and Mingos in the 1970's, for example, revolutionised our understanding of electron-deficient boranes and their transition metal analogues. More recently, endohedrally encapsulated clusters, where a transition metal sits inside a cluster cage, have provoked interest, in part because they represent the smallest models for transition metal impurities in bulk semiconductors like silicon or germanium. In many cases the metal and cage are essentially independent units: 60-electron [Ni@Pb12]2-, for example, can be thought of as a closed-shell d10 metal inside a 'closo' [Pb12]2- icosahedron (4n + 2 = 50 valence electrons). In work with Prof José Goicoechea's group, we have explored a relatively new class of cluster where the vertices of the cluster are 3-connected rather than 4- or 5-connected, as is typical of deltahedral structures. 3-connected vertices are generally associated with electron precise (5n) electron counts, but if 5n electrons are assigned to the cage in e.g. [Ru@Ge12]3-, the metal is left in an unreasonably high oxidation state. The key to understanding these systems is to note that pairs of electrons can play a dual role, satisfying the valence requirements of the metal and the cluster simultaneously. This 'jigsaw' model emphasises the importance of interpenetration of the electron density at the metal and on the cluster. In cases where the endohedral transition metal ion lies in the middle of d-block, the ground-state wavefunction is typically strongly multi-configurational. In such cases, the CASSCF methodology offers an alternative perspective to DFT.

                          

 

 

 

Metal-Metal Bonds

The interactions between transition metal ions themselves are notoriously difficult to model theoretically, and the ground-state wavefunctions are typically poorly described by a single-determinant wavefunction. This problem is particularly pressing in the first-row transition metals, where the absence of a radial node in the 3d orbital means that electron-electron repulsions are large. We use CAS/GASSCF and CASPT2 methodologies to explore the evolution of metal-metal bonding in these systems, both as a function of composition and of oxidation state.           

Redox‐Dependent Metal−Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling, M. Obies, N. R. Perkins, V. Arcisauskaite, G. A. Heath, A. J. Edwards and J. E. McGrady, Chem. Eur. J., 2018, 24, 5309.  HOT PAPER

Metal-metal Interactions in Trinuclear Chains, Chemistry Views, 2018.

MC-SCF description of the electronic states in trimetallic chains: Chem. Eur. J. 2018.

 

Spectroscopic properties

In collaboration with Prof. Raphael Raptis (Florida International University), we have also investigated the nature of the mixed valency (localised or delocalised) in reduced ferric/ferrous clusters.

A Redox-Induced Spin-State Cascade in a Mixed-Valent Fe33-O) Triangle, E. Govor, Evgen, K. Al-Ameed, I. Chakraborty, C. S. Coste, O. Govor, Y. Sanakis, J. E. McGrady and R. G. Raptis, Angew. Chem., 2017, 56, 582-586.

Spin-state equilibria in mixed-valence Fe3 clusters: Angew. Chem. 2017

Experimental and Theoretical Mossbauer Study of an Extended Family of Fe8(μ-O)4(μ-4-R-px)12X4 Clusters. E. M. Zueva, W. M. C. Sameera, D. M. Pinero, I Chakraborty, E. Devlin, P. Baran, K. Lubruskova, Y. Sanakis, J. E. McGrady and R. G. Raptis, Inorg. Chem., 2011, 50, 1021.

 

Electronic structure of low-dimensional metal oxides

Oxide lattices typically stable the highest accessible oxidation states of transition metal ions, but the reduction of perovskite and Ruddlesden-Popper phases by sources of hydride, developed by Hayward and co-workers, has provided access to a wide range of new compounds with the transition metal in unprecedented low oxidation states. This includes cases where the hydride replaces the oxide in the lattice and other where the hydride removes layers of oxide ions as H2O. These compounds are kinetically but not thermodynamically stable, but nevertheless they offer the opportunity to study transition metal ions in previously unprecedented electronic environments.

The role of π-blocking hydride ligands in a pressure-induced insulator-to-metal phase transition in SrVO2H, T. Yamamoto, D. Zeng, T. Kawakami, V. Arcisauskaite, K. Yata, M. Amano Patino, N. Izumo, J. E. McGrady, M. A. Hayward and H. Kageyama, Nature Comm.2017, 8, 1217.

LaSr3NiRuO4H4: A 4d Transition-Metal Oxide-Hydride Containing Metal Hydride Sheets, L. Jin, M. Lane, D. Zeng, F.K.K. Kirschner, F. Lang, P. Manual, S. J. Blundell, J. E. McGrady and M. A. Hayward, Angewandte Chemie2018, 57, 5025.

Density of states in 2-dimensional Ni/Ru oxide hydrides: Angew. Chem. 2018

Pressure-Induced Transitions in the 1-Dimensional Vanadium Oxyhydrides Sr2VO3H and Sr3V2O5H2, and Comparison to 2-Dimensional SrVO2H, T. Yamamoto, H.W.T. Morgan, D. Zeng, T. Kawakami, M. Amano-Patino, M.A. Hayward, H. Kageyama and J.E. McGrady, Inorg. Chem., 2019, 58, 15393.

 

Mechanism in Organometallic and Main group chemistry

Our group has a long-standing interest in mechanism in its broadest sense. The work on cluster growth mechgansism has been mentioned above, but we are also active in more conventional studies of reaction mechanism in both main-group and organometallic chemistry. In collaboration with Dr. Chris Russell at Bristol University, we have been exploring mechanism of bond activation by main group compounds (phosphabenzenes), and also the role of Au as a catalytsi metal.

Oxidative Addition, Transmetalation, and Reductive Elimination at a 2,2 '-Bipyridyl-Ligated Gold Center, M. J. Harper, C. J. Arthur, J. Crosby, E. J. Emmett, R. L. Falconer, A. J. Fensham-Smith, P. J. Gates, T. Leman, J. E. McGrady, J. F. Bower and C. A. Russell, J. Am. Chem. Soc., 2018, 140, 4440.

Au-catalysed C-I bond activation: J. Am. Chem. Soc. 2018

Hydrofunctionalisation of an Aromatic Triphosphabenzene, R. L. Falconer, D. Zeng, M. Green, D. W. Stephan, J. E. McGrady and C. A. Russell, Chem. Eur. J., 2019, 25, 13686.

Hydrogen Activation by an Aromatic Triphosphabenzene, L. E. Longobardi, C. A. Russell, M. Green, N. S. Townsend, K. Wang, A. J. Holmes, S. B. Duckett, J. E. McGrady and D. W. Stephan, J. Am. Chem. Soc., 2014, 136, 13453.

Potential energy surface for Si-H activation: Chem. Eur. J. 2019

 

With Professor Jose Goicoechea in Oxford, we have focussed on aspects of main-group chemistry, and in partocular on rearrangement pathways that are accessible to multiply-bonded compounds of the heavier main-group elements. In this work we make extensive use of isolobal analogies to identify parallels with organic reactions, and explore how the different electronic properties of e.g. a CH fragment vs P influence their reactivity.

Base induced isomerisation of a phosphaethynolato-borane: mechanistic insights into boryl migration and decarbonylation to afford a triplet phosphinidene, D. W. N. Wilson, M. P. Franco, W. K. Myers, J. E. McGrady and J. M. Goicoechea, Chem. Sci., 2020, 11, 862.

 

Coherent transport through metal-metal bonded molecular wires

Another main interest of the group is to understand the link between electronic structure and electron transport properties of extended metal atom chain (EMAC) complexes, where hlical array of oligo-α-pyridyl ligands is used to support a chain of metal centres. These systems have been the subject of a protracted debate in the inorganic chemistry community due to their polymorphism – they exist is symmetric and unsymmetic forms. Our current objective is to relate the fundamental electronic structure of these EMAC complexes to their conductance as measured, for example, by STM. Ultimately, an understanding of these phenomena will be essential to the development of new computer architectures based on molecular-scale components.

 

In search of structure-​function relationships in transition-​metal based rectifiers, T. Weng, D. DeBrincat, V. Arcisauskaite and J. E. McGrady, Inorganic Chemistry Frontiers2014, 1, 468.

Low-symmetry distortions in extended metal atom chains: origins and consequences for electron transport, V. P. Georgiev, P. J. Mohan, D. DeBrincat and J. E. McGrady, Coord. Chem. Rev., 2013, 290.

Attenuation of conductance in cobalt extended metal atom chains, V. P. Georgiev. W.M.C. Sameera and J. E. McGrady, J. Phys. Chem. C, 2012, 20163.

Influence of Low-Symmetry Distortions on Electron Transport through Metal Atom Chains: When Is a Molecular Wire Really "Broken"?, V. P. Georgiev and J. E. McGrady, J. Am. Chem. Soc., 2011, 132, 12590.

 

Redox-active ligands

                                                                               

We also have a strong interest in exploring the ways in which electrons are transferred between transition metals (and metal clusters) and redox-active coordinated ligands. Recent highlights include the study of redox-noninnocent complexes of bipyridyl (with Dr Jose Goicoechea, Oxford and Prof Sreebrata Goswami, IACS, Kolkata) . Our studies have illustrated that the open-shell character plays a defining role in controlling the direction of electron transfer processes.

A Homologous Series of First-Row Transition-Metal Complexes of 2,2 '-Bipyridine and their Ligand Radical Derivatives: Trends in Structure, Magnetism, and Bonding, M. Irwin, L.R. Doyle, T. Kramer, R. Herchel, J.E. McGrady and J.M. Goicoechea, Inorg. Chem., 2012, 51, 12301.

On the Mechanism of Water Oxidation by a Bimetallic Manganese Catalyst: A Density Functional Study. W. M. C. Sameera, C. J. McKenzie and J. E. McGrady, Dalton Trans., 2011, 40, 3859.

 

 

 

Endohedral clusters

1. Structure and bonding in endohedral transition metal clusters

X. Jin and J. E. McGrady, Adv. Inorg. Chem.2019, 73, 265.

2. Quantum chemical models for the absorption of endohedral clusters on Si(111)-(7 x 7): a subtle balance between W-Si and Si-Si bonding

X. Jin, V. Arcisauskaite and J. E. McGrady, Phys. Chem. Chem. Phys.2019, 21, 1368.

3. The structural landscape in 14-vertex clusters of silicon, M@Si14: when two bonding paradigms collide

X. Jin, V. Arcisauskaite and J. E. McGrady, Dalton Trans.2017, 46, 11366.

4. Biradical character in the ground state of [Mn@Si12]+: a DFT and CASPT2 study

V. Arcisauskaite, D. Fijan, M. Spivak, C. deGraaf and J. E. McGrady, Physical Chemistry Chemical Physics, 2016, 18, 24006-24014

5. The structural landscape in 14-vertex clusters of silicon, M@Si14: when two bonding paradigms collide

X. Jin, V. Arcisauskaite and J. E. McGrady Dalton Trans., 2017, 46, 11636-11644.

6. On the structural landscape in endohedral silicon and germanium clusters, M@Si12 and M@Ge12

J. M. Goicoechea and J. E. McGrady, Dalton Trans., 2015, 44, 6755-6766.

7. Structural trends in ten-vertex endohedral clusters, M@E10 and the synthesis of a new member of the family, [FeSn10]3-

T. Kraemer, J. C. A. Duckworth, M. D. Ingram, B. Zhou, J. E. McGrady and J. M. Goicoechea, Jose M., Dalton Trans., 2013, 42, 12120-12129.
 

Zintl Ions

8. A family of lead clusters with precious metal cores

C.C. Shu, H.W.T. Morgan, L. Qiao, J. E. McGrady and Z.-M. Sun, Nature Comm., 2020, in press. DOI : 10.1038/s41467-020-17187-4

9. Structure and Bonding in [Sb@In8Sb12]3- and [Sb@In8Sb12]5-

C. Liu, N. V. Tkachenko, I. A. Popov, N. Fedik, X. Min, C.Q. Xu, L.-J. Li, J. E. McGrady, A. J. Boldyrev and Z. -M. Sun, Angew. Chem. Int. Ed., Engl., 2019, 58, 8367.

10. Synthesis and structure of a family of rhodium polystannide clusters [Rh@Sn10]3-, [Rh@Sn12]3-, [Rh2@Sn17]6- and the first triply-fused stannide, [Rh3@Sn24]5-

C. Liu, X. Jin, L. -J. Li, J. Xu, J. E. McGrady and Z. -M. Sun, Chem. Sci., 2019, 10, 4394.

11. Synthesis and Characterization of [Ru@Ge12]3-: An Endohedral 3-Connected Cluster

G. Espinoza-Quintero, J. C. A. Duckworth, W. K. Myers, J. E. McGrady, and J. M. Goicoechea, J. Am. Chem. Soc., 2014, 136, 1210-1213.

 

Low-valent oxides

12. Pressure-Induced Transitions in the 1-Dimensional Vanadium Oxyhydrides Sr2VO3H and Sr3V2O5H2, and Comparison to 2-Dimensional SrVO2H, T. Yamamoto, H.W.T. Morgan, D. Zeng, T. Kawakami, M. Amano-Patino, M.A. Hayward, H. Kageyama and J.E. McGrady, Inorg. Chem., 2019, 58, 15393.

13. LaSr3NiRuO4H4: A 4d Transition-Metal Oxide-Hydride Containing Metal Hydride Sheets

L. Jin, M. Lane, D. Zeng, Dihao; F. K. K. Kirschner, F. Lang, P. Manuel, S. J. Blundell, J. E. McGrady and M. A. Hayward, Angew. Chem., Int. Ed., 2018, 57, 5025-5028.

14. The role of π-blocking hydride ligands in a pressure-induced insulator-to-metal phase transition in SrVO2H

T. Yamamoto, D. Zeng, Kawakami, V. Arcisauskaite, K. Yata, M. A. Patino, N. Izumo, J. E. McGrady, H. Kageyama, and M. A. Hayward, Nature Comm., 2017, 8, 1-7

15. SrFe0.5Ru0.5O2: Square-Planar Ru2+ in an Extended Oxide

F. Denis Romero, S. J. Burr, J. E. McGrady, D. Gianolio, G. Cibin and M.A. Hayward, J. Am. Chem. Soc., 2013, 135, 1838-1844.

 

Metal-metal bonds

16. Introduction and general survey of metal-metal bonds

 McGrady, John E., Molecular Metal-Metal Bonds (2015), 1-22.

17. Redox-Dependent Metal-Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling

M. Obies, N. R. Perkins, V. Arcisauskaite, G. A. Heath, A. J. Edwards and J. E. McGrady,  Chem. Eur. J., 2018, 24, 5309-5318.

18. A multiconfigurational approach to the electronic structure of trichromium extended metal atom chains

M. Spivak, V. Arcisauskaite, X. Lopez, J. E. McGrady and C. de Graaf, C., Dalton Trans., 2017, 46, 6202-6211.

19. A Redox-Induced Spin-State Cascade in a Mixed-Valent Fe33-O) Triangle

E. V. Govor, K. Al-Ameed, I. Chakraborty, C. S. Coste, O. Govor, Y. Sanakis, J. E. McGrady and R. G. Raptis,  Angew. Chem., Int. Ed., 2017, 56, 582-586

 

Mechanistic Organometallic and Main-group Chemistry

20. Oxidative Addition, Transmetalation, and Reductive Elimination at a 2,2'-Bipyridyl-Ligated Gold Center

M. J. Harper, C. J. Arthur, J. Crosby, E. J. Emmett, R. L. Falconer, A. J. Fensham-Smith, P. J. Gates, T. Leman,  J. E. McGrady, J. F. Bower and C. A. Russell, J. Am. Chem. Soc., 2018, 140, 4440-4445.

21. Hydrofunctionalisation of an Aromatic Triphosphabenzene

R. L. Falconer, D. Zeng, M. Green, D. W. Stephan, J. E. McGrady and C. A. Russell, Chem. Eur. J., 2019, 25, 13686.

22. Hydrogen Activation by an Aromatic Triphosphabenzene

L. E. Longobardi, C. A. Russell, M. Green, N. S. Townsend, K. Wang, A. J. Holmes, S. B. Duckett, J.E. McGrady, D. W. Stephan, J. Am. Chem. Soc., 2014, 136, 13453.

23. Base induced isomerisation of a phosphaethynolato-borane: mechanistic insights into boryl migration and decarbonylation to afford a triplet phosphinidene,

D. W. N. Wilson, M. P. Franco, W. K. Myers, J. E. McGrady and J. M. Goicoechea, Chem. Sci., 2020, 11, 862.

24. How formaldehyde inhibits hydrogen evolution by [FeFe]-hydrogenases: Determination by 13C ENDOR of direct Fe-C coordination and order of electron and proton transfers

A. Bachmeier, J. Esselborn, S. Hexter, Suzannah, T. Kramer, K. Klein, T. Happe, J. E. McGrady, W.K. Myers and F. A. Armstrong, J. Am. Chem. Soc., 2015, 137, 5381-5389

 

Electron transport

25. Can heterometallic 1-dimensional chains support current rectification?

D. DeBrincat, O. Keers and J. E. McGrady, Chem. Comm., 2013, 49, 9116-9118.

26. Low-symmetry distortions in Extended Metal Atom Chains (EMACs): Origins and consequences for electron transport

V. P. Georgiev, P. J. Mohan, D. DeBrincat and J. E. McGrady, Coord. Chem. Rev, 2013, 257, 290-298.

 

Redox non-innocent ligands

27. Redox Noninnocence in Coordinated 2-(Arylazo)pyridines: Steric Control of Ligand-Based Redox Processes in Cobalt Complexes P. Ghosh, S. Samanta, S. K. Roy, S. Joy, T. Kramer, J. E. McGrady and S. Goswami, Inorg. Chem. 2013, 52, 14040-14049.

28. A Homologous Series of First-Row Transition-Metal Complexes of 2,2'-Bipyridine and their Ligand Radical Derivatives: Trends in Structure, Magnetism, and Bonding

M. Irwin, L. R. Doyle, T. Kramer, Tobias; R. Herchel, J. E. McGrady and J. M. Goicoechea, Inorg. Chem., 2012, 51, 12301-12312.