Compared to well studied diatomic ligands (NO, CN-, CO), the axial bonds of carbene hemes is much The unusually large quadrupole splitting (Delta E-Q = +2.2 mm center dot s(-1)) and asymmetric parameter (eta = 0.9) of the five-coordinate heme carbene [Fe(TTP)(CCl2)], which is the investigations by means of Mossbauer effect Nuclear Resonance Vibrational Spectroscopy (NRVS). Three distinct measurements on one single crystal (two in-plane and one out-of-plane) have demonstrated comprehensive vibrational structures including stretch (429) and bending modes (472 cm(-1)) of the axial Fe-CCl2, and revealed iron vibrational anisotropy in three orthogonal directions for the first time. Frontier orbital analysis especially comparisons with diatomic analogues (NO, CN-, CO) suggest that CCl2, similar to NO, has led to strong but anisotropic it bonding in a ligand-based "4C"-coordinate which induced the vibrational anisotropies and very large Mossbauer parameters. This is contrasted to CN- and CO complexes which possess a porphyrin-based "4N"-coordinate electronic and vibrational structures due to inherent on-axis linear ligation.