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L. M. Martínez-Prieto and P. W. N. M. van Leeuwen
sites [2]. As these different catalytically active sites can transform the reactants in
different ways, the manner to control MNP selectivity is always a challenge.
An efficient strategy to control the activity and selectivity of an MNP is the use
of ancillary ligands that can transform the NP surface. As in organometallic complexes, surface ligands are able to modify the electronic and steric properties of
MNPs, and therefore modify their catalytic properties [3]. In fact, there are many
similarities between a ligand coordinated to an MNP and in a molecular complex
[4]. For example, the coordination modes of the ancillary ligands at the NP surface
are very similar to the ones found in organometallic chemistry. Indeed, the chemical adsorptions between the ligand and the MNP surface are normally due to the
donation of a lone pair of electrons of the ancillary ligand to the metal, in the same
way as in coordination chemistry. In general, efficient ligands for molecular complex
stabilization are also good as MNP stabilizer. In addition to all of the above, the interaction between the reactants and the surface ligands can also influence the catalytic
activity of the catalysts; depending on the ligand coordinated at the MNP surface,
it can boost or inhibit the reactivity of a certain functional group [5]. Therefore, the
use of ancillary ligands in MNP catalysis opens the door of a new way to improve
the selectivity and activity of a catalyst, until now mainly exploited by homogeneous
catalysis.
Ruthenium nanoparticles (Ru NPs) are nanostructures of interest in catalysis as
they are active in a great number of catalytic processes, such as hydrogenations,
oxidations, C-H activation reactions, and Fischer–Tropsch synthesis [6]. Ru NPs
are also very convenient for studying ligand effects in MNP catalysis since they
easily accommodate ligands on their surface [7]. Moreover, surface studies by FTIR or solid-state NMR (ruthenium presents a negligible Knight shift) can be easily
performed on Ru NPs by using CO as a probe molecule. For all of this, this chapter
will focus on Ru NP catalysis but with some discussion toward other metals when
required.
The key to control the potential of ancillary ligands on Ru NP catalysis is to
comprehend the synergy between the ligands and the ruthenium and the way that both
interact with the substrate, which ultimately enables the enhancement of the catalyst
activity/selectivity. Therefore, the aim of this chapter is to give an overview of the
recent advances on the influence of nitrogen-, oxygen-, phosphorus-, and carbonligands in Ru NP catalysis. In principle, the Ru NP catalysts will be divided into: (i)
Ligand-stabilized Ru NPs, where the ligands do not only stabilize Ru NPs but also
are able to modify their catalytic properties and (ii) supported ligand-functionalized
Ru NPs, where the catalytic properties of supported Ru NPs are modified through
the coordination of the ligands on the metal surface.
L. M. Martínez-Prieto and P. W. N. M. van Leeuwen
sites [2]. As these different catalytically active sites can transform the reactants in
different ways, the manner to control MNP selectivity is always a challenge.
An efficient strategy to control the activity and selectivity of an MNP is the use
of ancillary ligands that can transform the NP surface. As in organometallic complexes, surface ligands are able to modify the electronic and steric properties of
MNPs, and therefore modify their catalytic properties [3]. In fact, there are many
similarities between a ligand coordinated to an MNP and in a molecular complex
[4]. For example, the coordination modes of the ancillary ligands at the NP surface
are very similar to the ones found in organometallic chemistry. Indeed, the chemical adsorptions between the ligand and the MNP surface are normally due to the
donation of a lone pair of electrons of the ancillary ligand to the metal, in the same
way as in coordination chemistry. In general, efficient ligands for molecular complex
stabilization are also good as MNP stabilizer. In addition to all of the above, the interaction between the reactants and the surface ligands can also influence the catalytic
activity of the catalysts; depending on the ligand coordinated at the MNP surface,
it can boost or inhibit the reactivity of a certain functional group [5]. Therefore, the
use of ancillary ligands in MNP catalysis opens the door of a new way to improve
the selectivity and activity of a catalyst, until now mainly exploited by homogeneous
catalysis.
Ruthenium nanoparticles (Ru NPs) are nanostructures of interest in catalysis as
they are active in a great number of catalytic processes, such as hydrogenations,
oxidations, C-H activation reactions, and Fischer–Tropsch synthesis [6]. Ru NPs
are also very convenient for studying ligand effects in MNP catalysis since they
easily accommodate ligands on their surface [7]. Moreover, surface studies by FTIR or solid-state NMR (ruthenium presents a negligible Knight shift) can be easily
performed on Ru NPs by using CO as a probe molecule. For all of this, this chapter
will focus on Ru NP catalysis but with some discussion toward other metals when
required.
The key to control the potential of ancillary ligands on Ru NP catalysis is to
comprehend the synergy between the ligands and the ruthenium and the way that both
interact with the substrate, which ultimately enables the enhancement of the catalyst
activity/selectivity. Therefore, the aim of this chapter is to give an overview of the
recent advances on the influence of nitrogen-, oxygen-, phosphorus-, and carbonligands in Ru NP catalysis. In principle, the Ru NP catalysts will be divided into: (i)
Ligand-stabilized Ru NPs, where the ligands do not only stabilize Ru NPs but also
are able to modify their catalytic properties and (ii) supported ligand-functionalized
Ru NPs, where the catalytic properties of supported Ru NPs are modified through
the coordination of the ligands on the metal surface.