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The accurate and efficient assignment of atomic partial charges is crucial for many applications in theoretical and computational chemistry, including polarizable force fields, dispersion corrections, and charge-dependent basis sets. Classical charge models struggle to distinguish between neutral and zwitterionic fragments because, unlike quantum mechanical methods, there are no discrete electronic states. This limitation can lead to either reduced or additional artificial charge transfer (CT) at different interfragment distances. To address this issue, we propose a new version of a bond capacity electronegativity equilibration (EEQBC) model, which limits artificial CT between distant fragments in the simple EEQ framework. EEQBC offers excellent agreement with DFT-based reference charges for elements up to lawrencium (Z = 103) with mean absolute errors as low as 0.02 and 0.07 e− for random PubChem molecules and "mindless" molecules (MLMs), respectively. Thanks to its computational efficiency for both atomic charges and their analytical nuclear gradients, EEQBC is highly suitable as an initial charge guess for next-generation tight-binding methods. For seamless accessibility, EEQBC is implemented in the freely available multicharge program at: github.com/thfroitzheim/multicharge/tree/eeq-bc.

We report an enantiodivergent Pd-catalyzed cross-coupling reaction between unactivated enantioenriched alkylcarbastannatrane nucleophiles and aryl electrophiles in which the stereochemical course of the reaction is dictated by the inclusion or omission of a Cu(I) co-transmetalating agent. Use of a new electron-deficient biarylphosphine ligand (MaPhos) is required to promote the previously unreported stereoinvertive transmetalation pathway for unactivated secondary alkylstannanes. When a Cu(I) salt is included as a co-transmetalating agent, the stereochemical course of the reaction changes from stereoinvertive to stereoretentive. Thus, both enantiomers of the cross-coupling product can be accessed in high enantiopurity using a single achiral ligand. Mechanistic investigations suggest that net-stereoretentive alkyl transfer, in the presence of Cu(I), results from consecutive stereoretentive transmetalations from tin to copper and copper to palladium. In contrast, direct alkyl transmetalation from tin to palladium proceeds primarily via a stereoinvertive pathway that is facilitated by the presence of electron-deficient ligands.