Computational Details

All the calculations in this paper were carried out using Gaussian09 program package \cite{2016} revision D.01. Several Density Functional Theory (DFT) based methods were used: the range separated functional wB97X-D \cite{Chai_2008} was used as the primary method. All the geometry optimizations, harmonic vibrational frequencies, and energies were calculated using the 6-311G** basis set\cite{Schuchardt_2007} for C, H, B, O, F and N atoms; for Ni and Cs atoms we used the LANL2DZ basis set \cite{Schuchardt_2007}, which includes the corresponding effective core potentials. The SMD \cite{Marenich_2009} solvent model was chosen to include THF solvent effects implicitly. Gibbs free energy calculations included entropy corrections as introduced by Martin.\cite{Martin_1998} A model ligand, trimethylphosphine (PMe3), was considered instead of the bulkier tricyclohexylphosphine (PCy3) used in the experiments.  A data set collection of all computational results is available in the ioChem- BD repository \cite{_lvarez_Moreno_2014} and can be accessed by following this link.  

Results and Discussion

The optimal geometries and relative energies of all possible intermediates and transition states (TSs) were evaluated by means of DFT based methods. In Martin’s reaction, the Ni(PCy3)2 complex plays the role of catalyst and the two reactants that exchange fragments are aryl fluoride and the diboron 5,5-dimethyl-1,3,2-dioxaborolane (B2nep2). Therefore, there is any reason preventing this reaction to follow a classical cross-coupling mechanism. Also, the oxidative addition and the reductive elimination as the first and last steps, respectively, seem to be well accepted. However, as mention above, the recipe contains sodium phenolate, which its role is unraveled yet. In order to understand the basics of the reaction mechanism, we outlined three possible scenarios for the transmetalation step: (a) absence of base, (b) presence of the phenolate ion, (c) participation of both the phenolate ion together with its Na+ counter-ion. Also, considering the labile character of the metal-phosphine bonds,\cite{Taube_1952} we examined the reactivity of both mono- and bis-phosphine complexes in each reaction step.