We have explored the structural and energetic properties of a series of RMX₃–NH₃ (M=Si, Ge; X=F, Cl; R=CH₃, C₆H₅) complexes using density functional theory and low-temperature infrared spectroscopy. In the minimum-energy structures, the NH₃ binds axially to a halogen, while the organic group resides in equatorial site about the metal. Remarkably, the primary mode of interaction in several of these systems seems to be hydrogen bonding (C-H–N), rather than a tetrel N-M interaction. This is particularly clear for the RMCl₃–NH₃ complexes, and analyses of the charge distributions of the acid fragment corroborate this assessment. We also identified a set of metastable geometries in which the ammonia binds axial to the organic substituent. Acid fragment charge analysis also provide a clear rationale as to why these configurations are less stable than their R-equatorial counterparts. In matrix-IR experiments, we see clear evidence of the minimum-energy form of CH₃SiCl₃–NH₃, but analogous results for CH₃GeCl₃–NH3 are less conclusive. Computational scans of the M-N distance potentials for CH₃SiCl₃–NH₃ and CH₃GeCl₃–NH₃, both in the gas phase and bulk dielectric media reveal a great deal of anharmonicity, and a propensity for condensed-phase structural change.