The base-assisted cyclometallation of 2-phenylpyridine (2-phpyH) by Cp*Co(III) was holistically addressed both theoretically and experimentally. Combined DFT and DLPNO-CCSD(T) methods assisted by QTAIM-based noncovalent interactions plots (NCI plots), interacting quantum atoms (IQA), and local energy decomposition (LED) analyses have been used for a comparative study of the CMD-promoted cyclocobaltation and the parent cycloiridation of the 2-phpyH. Results suggest a remarkable contribution of noncovalent interactions, especially local electrostatic interactions, in the evolution of the reactive site giving a rational for the optimization of cyclocobaltation. The theoretically predicted benefits of using the acetamidate anion as a base is rationalized and verified experimentally. Cobaltacycle [Cp*Co(2-phpy-C,N)I] was efficiently synthesized from the air-stable [Cp*CoI2]2 and 2-phpyH, in the presence of LiNHAc as base in 83% yield whereas with anhydrous NaOAc as base only 12% yield were achieved under similar conditions. By applying the [NHAc] -promoted cyclometallation various cobaltacycles were synthesized, analytically characterized and their structures resolved by X-ray crystallization analysis, confirming the importance of the acetamidate in the base-assisted cyclometallation. Experimental kinetic isotope effect (KIE) studies validated by Bigeleisen equation-based KIE computations confirm that the formation of the agostic transient is indeed the kinetic determining step of the CMD mechanism in dichloromethane. Application of the [Cp*CoI2]2/LiNHAc mixture to the catalysis of the condensation of 1,2-diphenyacetylene to various aromatics reveals the coexistence of two mechanisms, i.e. CMD and electrophilic C-H activation. PhD stipend. YC thanks the Centre de Calcul de l'Université de Strasbourg for providing access to the HPC facilities (project g2019a126c).

The performance of six newly synthesized benzo[h]quinoline-derived acetonitrilo pentamethylcyclopentadienyl iridium(III) tetrakis(3,5-bis-trifluoromethylphenyl)borate salts bearing different substituents À X (À OMe, À H, À Cl, À Br, À NO 2 and À (NO 2 ) 2 ) on the heterochelating ligand were evaluated in the dehydro-O-silylation of benzyl alcohol and the monohydrosilylation of 4-methoxybenzonitrile by Et 3 SiH, two reactions involving the electrophilic activation of the SiÀ H bond. The benchmark shows a direct dependence of the catalytic efficiency with the electronic effect of À X, which is confirmed by theoretical assessment of the intrinsic silylicities Π of hydridoiridium(III)-silylium adducts and by the theoretical evaluation of the propensity of hydridospecies to transfer the hydrido ligand to the activated substrate. The revisited analysis of the IrÀ SiÀ H interactions shows that the most cohesive bond in hydridoiridium(III)-silylium adducts is the IrÀ H one, while the IrÀ Si is a weak donor-acceptor dative bond. The Si…H interaction in all the cases is noncovalent in nature and dominated by electrostatics confirming the heterolytic cleavage of the hydrosilane's SiÀ H bond in this key catalytically relevant species.

In an effort to determine the thermochemistry of established organometallic transformation, the well documented reaction of alkynes with a palladacycle was investigated by isothermal titration calorimetry (ITC). Although the mechanism of the insertion of unsaturated substrates into the PdÀ C bond of cyclopalladated compounds is known, no information is available so far about their thermochemistry. The enthalpies of the reactions of PhÀ C�CÀ Ph and MeOC(O)À C�C(O)COMe with the bisacetonitrilo salt of the N,N-benzylamine palladacycle were determined by ITC in chlorobenzene after having optimized the conditions to ensure that only the double and a single insertion of alkynes were occurring respectively. The reaction energy profile established by DFT for the double insertion process involving PhÀ C�CÀ Ph confirmed earlier conclusions on the rate determining character of the first insertion. Further computations of reaction enthalpies reveal significant discrepancies between ITC and DFT-D/continuum solvation enthalpies, that are suspected to arise from an unexpected explicit noncovalent interaction of PhCl with the components of the reaction.