The coordination modes of the [Au(PPh3)]+ cation to metal alkynyl complexes have been investigated. On addition to ruthenium, a vinylidene complex, [Ru(η5-C5H5)(PPh3)2(CCPh{AuPPh3})]+, is obtained while addition to a gold(III) compound gives di- and trinuclear gold complexes depending on the conditions employed. In the trinuclear species, a gold(I) cation is sandwiched between two gold(III) alkynyl complexes, suggesting that coordination of multiple C–C triple bonds to gold is facile.

The manifold of reaction pathways for the oxidative addition of phenyl bromide and phenyl chloride substrates to phosphine-modified palladium(0) complexes has been investigated with dispersion-corrected density functional theory (B3LYP-D2) for a range of synthetically relevant ligands, permitting the evaluation of ligand, substrate and method effects on calculated predictions. Bulky and electron-rich ligands PtBu3 and SPhos can access low-coordinate complexes more easily, facilitating formation of the catalytically active species throughout the cycle. While the bisphosphine oxidative addition step is reasonably facile for the smaller PCy3 and PPh3 ligands, the dissociation of these ligands to generate reactive palladium complexes becomes more important and the catalyst is more likely to become trapped in unreactive intermediates. This study demonstrates the feasibility of exploring the catalytic manifold for synthetically relevant ligands with computational chemistry, but also highlights the remaining challenges.

Experimental results have long suggested that catalyst optimization is an inherently multivariate process, requiring the screening of reaction conditions (temperature, pressure, solvents, precursors, etc.), catalyst structure (metal and ligands), and substrate scope. With a view to demonstrating the feasibility and utility of multivariate computational screening of organometallic catalysts, we have investigated the structural and electronic properties of a library of transition-metal-coordinated alkyne and vinylidene tautomers in different coordination environments. By varying the substituents on the organic moiety of 60 alkyne/vinylidene pairs we were able to capture and quantify the key structural and electronic effects on tautomer preference. For a carefully selected subset of substituents, the effects of metal and ancillary ligands were then explored. We have been able to formulate a protocol for assessing the stabilization of vinylidenes in transition-metal complexes, suggesting that the d6 square-based-pyramidal metal fragment [RuCl2(PR23)(═C═CHR1)], combined with electron-withdrawing substituents R1 and electron-rich groups R2, would provide the ideal conditions favoring the vinylidene form thermodynamically.

We present a computational exploration of the effect of systematic variation of backbones and substituents on the properties of bidentate, cis-chelating P,P donor ligands as captured by calculated parameters. The parameters used are the same as reported for our ligand knowledge base for bidentate P,P donor ligands, LKB-PP (Organometallics 2008, 27, 1372–1383; Organometallics 2012 31, 5302–5306), but calculation protocols have been streamlined, suitable for an extensive evaluation of ligand structures. Analysis of the resulting LKB-PPscreen database with principal component analysis (PCA) captures the effects of changing backbones and substituents on ligand properties and illustrates how these are complementary variables for these ligands. While backbone variation is routinely employed in ligand synthesis to modify catalyst properties, only a limited subset of substituents is commonly accessed and here we highlight substituents which are likely to generate new ligand properties, of interest for the design and improved sampling of bidentate ligands in homogeneous organometallic catalysis.

We have expanded the ligand knowledge base for bidentate P,P- and P,N-donor ligands (LKB-PP, Organometallics 2008, 27, 1372–1383) by 208 ligands and introduced an additional steric descriptor (nHe8). This expanded knowledge base now captures information on 334 bidentate ligands and has been processed with principal component analysis (PCA) of the descriptors to produce a detailed map of bidentate ligand space, which better captures ligand variation and has been used for the analysis of ligand properties.

The association and dissociation of ligands plays a vital role in determining the reactivity of organometallic catalysts. Computational studies with density functional theory often fail to reproduce experimental metal–ligand bond energies, but recently functionals which better capture dispersion effects have been developed. Here we explore their application and discuss future challenges for computational studies of organometallic catalysis.

We have used dispersion-corrected DFT (DFT-D) together with solvation to examine possible mechanisms for reaction of PhX (X = Cl, Br, I) with Pd(PtBu3)2 and compare our results to recently published kinetic data (F. Barrios-Landeros, B. P. Carrow and J. F. Hartwig, J. Am. Chem. Soc., 2009, 131, 8141–8154).1 The calculated activation free energies agree near-quantitatively with experimentally observed rate constants.

We have expanded the ligand knowledge base for monodentate P-donor ligands (LKB-P, Chem. Eur. J. 2006, 12, 291−302) by 287 ligands and added descriptors derived from computational results on a gold complex [AuClL]. This expansion to 348 ligands captures known ligand space for this class of monodentate two-electron donor ligands well, and we have used principal component analysis (PCA) of the descriptors to derive an improved map of ligand space. Potential applications of this map, including the visualization of ligand similarities/differences and trends in experimental data, as well as the design of ligand test sets for high-throughput screening and the identification of ligands for reaction optimization, are discussed. Descriptors of ligand properties can also be used in regression models for the interpretation and prediction of available response data, and here we explore such models for both experimental and calculated data, highlighting the advantages of large training sets that sample ligand space well.

Changing the coordinated ligands is a powerful and synthetically convenient way of modifying and fine-tuning the properties of transition metal complexes, especially those active in homogeneous catalysis. Parameters capturing such changes in the steric and electronic characteristics of complexes have played a key role in improving our understanding of ligand effects on the kinetic, thermodynamic, spectroscopic and structural behaviour of such species. Such ligand parameters can be useful for interpreting experiments, but they can also guide the discovery of novel ligands from ligand maps and allow the prediction of ligand effects before further experimentation. The latter aims especially are best served if such parameters can be determined before ligands and complexes have been synthesised, and here we review calculated descriptors for phosphorus(III) ligands as widely used in organometallic and coordination chemistry. We also discuss the application of such ligand descriptors in models, maps and predictions of ligand effects, describe related computational studies of the metal–phosphorus bond, and provide an overview of the statistical methods used.

We describe the development of a ligand knowledge base designed to capture the properties of C-donor ligands coordinating to transition metal centres, LKB-C. This knowledge base has been developed to describe both singlet (Arduengo and Fischer) and triplet (Schrock) carbenes, as well as related neutral monodentate C-donor ligands. The descriptors evaluated and used have been derived from a range of coordination environments to maximise their transferability and hence utility for the investigation of such ligands. These descriptors have been analysed with different statistical approaches, both individually to determine their chemical context, and collectively by principal component analysis thereby allowing the derivation of maps of ligand space for different ligand sets. The utility of such maps for investigating ligand similarity and identification of target areas for future ligand designs has been discussed. In addition, linear regression models have been fitted for the prediction of a calculated response variable, highlighting further potential applications of such a knowledge base.

The ligand knowledge base approach has been extended to capture the properties of 108 bidentate P,P- and P,N-donor ligands. This contribution describes the design of the ligand set and a range of DFT-calculated descriptors, capturing ligand properties in a variety of chemical environments. New challenges arising from ligand conformational flexibility and donor asymmetry are discussed, and descriptors are related to other parameters, such as the ligand bite angle. A novel map of bidentate ligand space, potentially useful in catalyst design and discovery, has been derived from principal component analysis of the resulting LKB-PP descriptors. In addition, a range of multiple linear regression models have been derived for both experimental and calculated data, considering ligand bite angles in square-planar palladium complexes and ligand dissociation energies from octahedral chromium complexes, respectively. These data sets were fitted with models based on LKB descriptors to explore the transferability of descriptors to different coordination environments and to illustrate potential applications of such models in catalyst design, allowing predictions about novel or untested ligands.

We have used dispersion-corrected DFT (DFT-D) together with solvation to examine possible mechanisms for reaction of PhX (X = Cl, Br, I) with Pd(PtBu3)2 and compare our results to recently published kinetic data (F. Barrios-Landeros, B. P. Carrow and J. F. Hartwig, J. Am. Chem. Soc., 2009, 131, 8141–8154).1 The calculated activation free energies agree near-quantitatively with experimentally observed rate constants.

The association and dissociation of ligands plays a vital role in determining the reactivity of organometallic catalysts. Computational studies with density functional theory often fail to reproduce experimental metal–ligand bond energies, but recently functionals which better capture dispersion effects have been developed. Here we explore their application and discuss future challenges for computational studies of organometallic catalysis.

We present a computational exploration of the effect of systematic variation of backbones and substituents on the properties of bidentate, cis-chelating P,P donor ligands as captured by calculated parameters. The parameters used are the same as reported for our ligand knowledge base for bidentate P,P donor ligands, LKB-PP (Organometallics 2008, 27, 1372–1383; Organometallics 2012 31, 5302–5306), but calculation protocols have been streamlined, suitable for an extensive evaluation of ligand structures. Analysis of the resulting LKB-PPscreen database with principal component analysis (PCA) captures the effects of changing backbones and substituents on ligand properties and illustrates how these are complementary variables for these ligands. While backbone variation is routinely employed in ligand synthesis to modify catalyst properties, only a limited subset of substituents is commonly accessed and here we highlight substituents which are likely to generate new ligand properties, of interest for the design and improved sampling of bidentate ligands in homogeneous organometallic catalysis.

The manifold of reaction pathways for the oxidative addition of phenyl bromide and phenyl chloride substrates to phosphine-modified palladium(0) complexes has been investigated with dispersion-corrected density functional theory (B3LYP-D2) for a range of synthetically relevant ligands, permitting the evaluation of ligand, substrate and method effects on calculated predictions. Bulky and electron-rich ligands PtBu3 and SPhos can access low-coordinate complexes more easily, facilitating formation of the catalytically active species throughout the cycle. While the bisphosphine oxidative addition step is reasonably facile for the smaller PCy3 and PPh3 ligands, the dissociation of these ligands to generate reactive palladium complexes becomes more important and the catalyst is more likely to become trapped in unreactive intermediates. This study demonstrates the feasibility of exploring the catalytic manifold for synthetically relevant ligands with computational chemistry, but also highlights the remaining challenges.

We describe the development of a ligand knowledge base designed to capture the properties of C-donor ligands coordinating to transition metal centres, LKB-C. This knowledge base has been developed to describe both singlet (Arduengo and Fischer) and triplet (Schrock) carbenes, as well as related neutral monodentate C-donor ligands. The descriptors evaluated and used have been derived from a range of coordination environments to maximise their transferability and hence utility for the investigation of such ligands. These descriptors have been analysed with different statistical approaches, both individually to determine their chemical context, and collectively by principal component analysis thereby allowing the derivation of maps of ligand space for different ligand sets. The utility of such maps for investigating ligand similarity and identification of target areas for future ligand designs has been discussed. In addition, linear regression models have been fitted for the prediction of a calculated response variable, highlighting further potential applications of such a knowledge base.

The coordination modes of the [Au(PPh3)]+ cation to metal alkynyl complexes have been investigated. On addition to ruthenium, a vinylidene complex, [Ru(η5-C5H5)(PPh3)2(CCPh{AuPPh3})]+, is obtained while addition to a gold(III) compound gives di- and trinuclear gold complexes depending on the conditions employed. In the trinuclear species, a gold(I) cation is sandwiched between two gold(III) alkynyl complexes, suggesting that coordination of multiple C–C triple bonds to gold is facile.