Quaternary carbon centers are desirable targets for drug discovery and complex molecule synthesis, yet the synthesis of these motifs within traditional cross-coupling paradigms remains a significant challenge due to competing β-hydride elimination pathways. In contrast, the bimolecular homolytic substitution (SH2) mechanism offers a unique and attractive alternative pathway. Metal porphyrin complexes have emerged as privileged catalysts owing to their ability to selectively form primary metal-alkyl complexes, thereby eliminating the challenges associated with tertiary alkyl complexation with a metal center. Herein, we report an iron-catalyzed cross-electrophile coupling of tertiary bromides and primary alkyl electrophiles for the formation of all-carbon quaternary centers through a biomimetic SH2 mechanism.