Comprehensive Thermochemical Benchmark Set of Realistic Closed-Shell Metal Organic Reactions.

We introduce the new MOR41 benchmark set consisting of 41 closed-shell organometallic reactions resembling many important chemical transformations commonly used in transition metal chemistry and catalysis. It includes significantly larger molecules than presented in other transition metal test sets and covers a broad range of bonding motifs. Recent progress in linear-scaling coupled cluster theory allowed for the calculation of accurate DLPNO-CCSD(T)/CBS(def2-TZVPP/def2-QZVPP) reference energies for 3d,4d,5d-transition metal compounds with up to 120 atoms.

A computationally efficient double hybrid density functional based on the random phase approximation.

We present a revised form of a double hybrid density functional (DHDF) dubbed PWRB95. It contains semi-local Perdew-Wang exchange and Becke95 correlation with a fixed amount of 50% non-local Fock exchange. New features are that the robust random phase approximation (RPA) is used to calculate the non-local correlation part instead of a second-order perturbative treatment as in standard DHDF, and the non-self-consistent evaluation of the Fock exchange with KS-orbitals at the GGA level which leads to a significant reduction of the computational effort.

Spin crossover in Fe(II) and Co(II) complexes with the same click-derived tripodal ligand.

The complexes [Fe(tbta)2](BF4)2·2EtOH (1), [Fe(tbta)2](BF4)2·2CH3CN (2), [Fe(tbta)2](BF4)2·2CHCl3 (3), and [Fe(tbta)2](BF4)2 (4) were synthesized from the respective metal salts and the click-derived tripodal ligand tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (tbta). Structural characterization of these complexes (at 100 or 133 K) revealed Fe-N bond lengths for the solvent containing compounds 1-3 that are typical of a high spin (HS) Fe(II) complex. In contrast, the solvent-free compound 4 show Fe-N bond lengths that are characteristic of a low spin (LS) Fe(II) state.

Implementation of nuclear gradients of range-separated hybrid density functionals and benchmarking on rotational constants for organic molecules.

We have implemented the nuclear gradient for several range-separated hybrid density functionals in the general quantum chemistry code ORCA. To benchmark the performance, we have used a recently published set of back-corrected gas phase rotational constants, which we extended by three molecules. In our evaluation, CAM-B3LYP-D3 and ωB97X-D3 show great accuracy, and are surpassed by B2PLYP-D3 only.

Benchmark study of the performance of density functional theory for bond activations with (ni,pd)-based transition-metal catalysts.

The performance of 23 density functionals, including one LDA, four GGAs, three meta-GGAs, three hybrid GGAs, eight hybrid meta-GGAs, and ten double-hybrid functionals, was investigated for the computation of activation energies of various covalent main-group single bonds by four catalysts: Pd, PdCl(-), PdCl2, and Ni (all in the singlet state). A reactant complex, the barrier, and reaction energy were considered, leading to 164 energy data points for statistical analysis. Extended Gaussian AO basis sets were used in all calculations.

Effects of London dispersion correction in density functional theory on the structures of organic molecules in the gas phase.

A benchmark set of 25 rotational constants measured in the gas phase for nine molecules (termed ROT25) was compiled from available experimental data. The medium-sized molecules with 18-35 atoms cover common (bio)organic structure motifs including hydrogen bonding and flexible side chains. They were each considered in a single conformation.

Modeling Transition Metal Reactions with Range-Separated Functionals.

The performance of range-separated functionals for the calculation of reaction profiles of organometallic compounds is considered. Sets of high-level computational results are used as reference data for the most part. The benchmark data include a number of reactions involving small molecules reacting with the Pd atom, PdCl(-), PdCl2, and a Ni atom, the reaction of a model Grubbs catalyst, and the ligand binding in a real Grubbs catalyst.

Mechanistic studies on the Pd-catalyzed direct C-H arylation of 2-substituted thiophene derivatives with arylpalladium bipyridyl complexes.

Direct C-H phenylation of 2-ethylthiophene and 2-chlorothiophene with PhPdI(bipy) complex to form either the corresponding 4-phenyl or 5-phenylthiophene derivative is studied under stoichiometric conditions using various Lewis acids as additives. It is shown that reactions occur via the corresponding cationic Pd complex (PhPdbipy(+)) and that the counteranion determines the regioselectivity. High-level DFT calculations reveal that C-C bond formation occurs via a carbopalladation pathway and not via electrophilic palladation.

How to compute isomerization energies of organic molecules with quantum chemical methods.

The reaction energies for 34 typical organic isomerizations including oxygen and nitrogen heteroatoms are investigated with modern quantum chemical methods that have the perspective of also being applicable to large systems. The experimental reaction enthalpies are corrected for vibrational and thermal effects, and the thus derived "experimental" reaction energies are compared to corresponding theoretical data. A series of standard AO basis sets in combination with second-order perturbation theory (MP2, SCS-MP2), conventional density functionals (e.