David Watson

Dr David Watson


Undergraduate Admissions Tutor and Lecturer in Physical and Materials Chemistry

Biography

Areas of specialism

Physical Chemistry; Heterogeneous Catalysis; Surface Science; Electrochemistry; Photocatalysis

University roles and responsibilities

  • Undergraduate Admissions Tutor

My teaching

My publications

Highlights

“Critical Role of Oxygen in Silver-Catalyzed Glaser−Hay Coupling on Ag(100) under Vacuum and in Solution on Ag Particles.” Noé Orozco, Georgios Kyriakou, Simon K. Beaumont, Javier Fernandez Sanz, Juan P. Holgado, Martin J. Taylor, Juan P. Espinoś, Antonio M. Maŕquez, David J. Watson, 
Agustin R. Gonzalez-Elipe, Richard M. Lambert, Acs Catal., 2017, 7, 3113. DOI: 10.1021/acscatal.7b00431

 

ABSTRACT: The essential role of oxygen in enabling heterogeneously catalyzed Glaser−Hay coupling of phenylacetylene on Ag(100) was elucidated by STM, laboratory and synchrotron photoemission, and DFT calculations. In the absence of coadsorbed oxygen, phenylacetylene formed well-ordered dense overlayers which, with increasing temperature, desorbed without reaction. In striking contrast, even at 120 K, the presence of oxygen led to immediate and complete disruption of the organic layer due to abstraction of acetylenic hydrogen with formation of a disordered mixed layer containing immobile adsorbed phenyl-acetylide. At higher temperatures phenylacetylide underwent Glaser−Hay coupling to form highly ordered domains of diphenyldiacetylene that eventually desorbed without decomposition, leaving the bare metal surface. DFT calculations showed that, while acetylenic H abstraction was otherwise an endothermic process, oxygen adatoms triggered a reaction-initiating exothermic pathway leading to OH(a) + phenylacetylide, consistent with the experimental observations. Moreover, it was found that, with a solution of phenylacetylene in nonane and in the presence of O2, Ag particles catalyzed Glaser−Hay coupling with high selectivity. Rigorous exclusion of oxygen from the reactor strongly suppressed the catalytic reaction. Interestingly, too much oxygen lowers the selectivity toward diphenyldiacetylene. Thus, vacuum studies and theoretical calculations revealed the key role of oxygen in the reaction mechanism, subsequently borne out by catalytic studies with Ag particles that confirmed the presence of oxygen as a necessary and sufficient condition for the coupling reaction to occur. The direct relevance of model studies to a mechanistic understanding of coupling reactions under conditions of practical catalysis was reaffirmed.

KEYWORDS: Glaser−Hay coupling, silver surface, catalysis, C−C bond formation, XPS, STM, DFT

Sonogashira Cross-Coupling and Homocoupling on a Silver Surface: Chlorobenzene and Phenylacetylene on Ag(100).” Carlos Sanchez-Sanchez, Noe Orozco, Juan P. Holgado, Simon K. Beaumont, Georgios Kyriakou, David J. Watson, Agustin R. Gonzalez-Elipe, Leticia Feria, Javier Fernández Sanz, Richard M. Lambert, J. Am. Chem. Soc., 2015, 137 (2), 940–947. DOI: 10.1021/ja5115584

 

ABSTRACT: Scanning tunneling microscopy, temperature-programmed reaction, near-edge X-ray absorption fine structure spectroscopy, and density functional theory calculations were used to study the adsorption and reactions of phenylacetylene and chlorobenzene on Ag(100). In the absence of solvent molecules and additives, these molecules underwent homocoupling and Sonogashira cross-coupling in an unambiguously heterogeneous mode. Of particular interest is the use of silver, previously unexplored, and chlorobenzenenormally regarded as relatively inert in such reactions. Both molecules adopt an essentially flat-lying conformation for which the observed and calculated adsorption energies are in reasonable agreement. Their magnitudes indicate that in both cases adsorption is predominantly due to dispersion forces for which interaction nevertheless leads to chemical activation and reaction. Both adsorbates exhibited pronounced island formation, thought to limit chemical activity under the conditions used and posited to occur at island boundaries, as was indeed observed in the case of phenylacetylene. The implications of these findings for the development of practical catalytic systems are considered.

 

 

 

 

 

 

Observing the in situ chiral modification of Ni nanoparticles using scanning transmission X-ray microspectroscopy.” David J. Watson,* Sushma Acharya, Richard E.J. Nicklin, Georg Held, Surf. Sci., 2014, 629, 108-113. DOI: http://dx.doi.org/10.1016/j.susc.2014.03.018

 

ABSTRACT: Enantioselective heterogeneous hydrogenation of C=O bonds is of great potential importance in the synthesis of chirally pure products for the pharmaceutical and fine chemical industries. One of the most widely studied examples of such a reaction is the hydrogenation of β-ketoesters and β-diketoesters over Ni-based catalysts in the presence of a chiral modifier. Here we use scanning transmission X-ray microscopy combined with near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) to investigate the adsorption of the chiral modifier, namely (R,R)-tartaric acid, onto individual nickel nanoparticles. The C K-edge spectra strongly suggest that tartaric acid deposited onto the nanoparticle surfaces from aqueous solutions undergoes a keto-enol tautomerisation. Furthermore, we are able to interrogate the Ni L2,3-edge resonances of individual metal nanoparticles which, combined with X-ray diffraction (XRD) patterns showed them to consist of a pure nickel phase rather than the more thermo- dynamically stable bulk nickel oxide. Importantly, there appears to be no “particle size effect” on the adsorption mode of the tartaric acid in the particle size range ~90–~300 nm.

Publications

“Influence of Adsorption Geometry in the Heterogeneous Enantioselective Catalytic Hydrogenation of a Prototypical Enone.” Simon K. Beaumont, Georgios Kyriakou, David J. Watson, Owain P.H. Vaughan, Anthoula C. Papageorgiou, and Richard M. Lambert, J. Phys. Chem. C, 2010, 114. 15075.

“Sonogashira Coupling on an Extended Gold Surface in Vacuo: Reaction of Phenylacetylene with Iodobenzene on Au(111).” Vijay K. Kanuru, Georgios Kyriakou, Simon K. Beaumont, Anthoula C. Papageorgiou, David J. Watson, and Richard M. Lambert, J. Am. Chem. Soc., 2010, 132, 8081.

“Review of 'Handbook of Asymmetric Heterogeneous Catalysis materials' Edited by Kuiling Ding And Yasuhiro Uozumi.” D.J. Watson, Appl. Organometal. Chem., 2010, 24, 147.

“Chemoselective catalytic hydrogenation of acrolein on Ag(111): effect of molecular orientation on reaction selectivity.” K. Brandt, M. Chiu, D. Watson, M. Tikhov, R. Lambert, J. Am. Chem. Soc., 2009, 131, 17286.

“Deprotection, tethering, and activation of a one-legged metalloporphyrin on a chemically active metal surface: [SAc]P-Mn(III)Cl on Ag(100).” M. Turner, O.P.H. Vaughan, G. Kyriakou, D.J. Watson, L.J. Scherer, A.C. Papageorgiou, J.K.M. Sanders, R.M. Lambert, J. Am. Chem. Soc., 2009, 131, 14913.

“Heterogeneously catalyzed asymmetric hydrogenation of C=C bonds directed by surface-tethered chiral modifiers.” D.J. Watson, R.J.B.R. John-Jesudason, S.K. Beaumont, G. Kyriakou, J.W. Burton and R.M. Lambert, J. Am. Chem. Soc., 2009, 131,14584.

“Deprotection, tethering, and activation of a catalytically active metalloporphyrin to a chemically active metal surface: [SAc]4P-Mn(III)Cl on Ag(100).” M. Turner, O.P.H. Vaughan, G. Kyriakou, D.J. Watson, L.J. Scherer, G.J.E. Davidson, J.K.M. Sanders and R.M. Lambert, J. Am. Chem. Soc., 2009, 131, 1910.

“Mechanistic insights into the proline-directed enantioselective heterogeneous hydrogenation of isophorone.” A.I. McIntosh, D.J. Watson and R.M. Lambert, Langmuir, 2007, 23, 6113.

“Electron impact-assisted carbon film growth on Ru(0001): Implications for next-generation EUV lithography.” G. Kyriakou, D.J. Davis, R.B. Grant, D.J. Watson, A. Keen, M. Tikhov and R.M. Lambert, J. Phys. Chem. C., 2007, 111, 4491.

“Interactions of 4-chlorophenol with TiO2 polycrystalline surfaces: A study of environmental interfaces by NEXAFS, XPS, and UPS.” A. Orlov, D.J. Watson, F.J. Williams, M. Tikhov and R.M. Lambert, Langmuir, 2007, 23, 9551.

“Electrochemical characterization of PtPd alloy single crystal surfaces prepared using Pt basal planes as templates.” F.J. Vidal-Iglesias, A. Al-Akl, D. Watson and G.A. Attard, J. Electroanal. Chem., 2007, 611, 117.

“Sulphur, normally a poison, strongly promotes chemoselective catalytic hydrogenation: stereochemistry and reactivity of crotonaldehyde on clean and S-modified Cu(111).” M.E. Chui, G. Kyriakou, F.J. Williams, D.J. Watson, M.S. Tikhov and R.M. Lambert, Chem. Commun., 2006, 12, 1283.

“Heterogeneously-catalyzed asymmetric C=C hydrogenation: Origin of enantioselectivity in the proline-directed Pd/isophorone system.” A.I. McIntosh, D.J. Watson, J.W. Burton and R.M. Lambert, J. Am. Chem. Soc., 2006, 128, 7329.

“A new method for the preparation of PtPd alloy single crystal surfaces.” F.J. Vidal-Iglesias, A. Al-Akl, D.J. Watson and G.A. Attard, Electrochem. Commun., 2006, 8, 1147.

“Tilt the molecule and change the chemistry: Mechanism of sulfur promoted chemoselective catalytic hydrogenation of crotonaldehyde on Cu(111).” M.E. Chui, D.J. Watson, G. Kyriakou, M.S. Tikhov and R.M. Lambert, Angew. Chem. Int. Ed., 2006, 45, 7530.

“Surface segregation and reconstructive behaviour of the (100) and (110) surfaces of platinum-palladium bulk alloy single crystals: A Voltammetric and LEED/AES Study.” D.J. Watson and G.A. Attard, Surf. Sci., 2006, 515, 87.

“Surface characterisation and electrochemical behaviour of well-defined Pt-Pd(111) single crystal surfaces: A comparative study using Pt(111) and palladium-modified Pt(111) electrodes.” T.J. Schmidt, N.M. Markovic, V. Stamenkovic, P.N. Ross Jr., G.A. Attard and D.J. Watson, Langmuir, 2002, 18, 6969.

“Photoemission studies of chiral metal surfaces using circularly polarized synchrotron radiation.” G.A. Attard, D.J. Watson, E.A. Seddon, S.M. Cornelius, E. Herrero and J. Feliu, Phys. Rev. B: Condens. Matter, 2001, 64, 115408.

“Electrochemical evaluation of the morphology and enantioselectivity of Pt/Graphite.” G.A. Attard, J.E. Gillies, C.A. Harris, D.J. Jenkins, P. Johnston, M.A. Price, D.J. Watson and P.B. Wells, Appl. Catal., A, 2001, 222, 393.

“The electro-oxidation of glucose using platinum-palladium bulk alloy single crystals.” D.J. Watson and G.A. Attard, Electrochim. Acta, 2001, 46, 3157.