Paramagnetic point defects in silicon provide qubits that could open up pathways towards silicon-technology based, low-cost, room-temperature (RT) quantum sensing. The silicon dangling bond (db) is a natural candidate, given its sub-nanometer localization and direct involvement in spin-dependent charge-carrier recombination, allowing for electrical spin readout. However, in crystalline silicon, strong db spin-coherence loss is observed at RT due to rapid free-electron trapping, which strongly limits quantum applications. Combining density-functional theory and multifrequency (100 MHz–263 GHz) pulsed electrically detected magnetic resonance spectroscopy, we show that dbs in a hydrogenated amorphous silicon matrix form metastable spin pairs in a well-defined quasi two-dimensional (2D) configuration upon electron capture. Although highly localized, these entangled spin pairs exhibit nearly vanishing intrinsic dipolar and exchange coupling. The formation of this specific topological configuration involves a > 0.3 eV energy relaxation of a trapped electron, stabilizing the pair. This extends RT spin coherence times into the microsecond range required for spin-based quantum sensing.