Several six-coordinate iron(II) carbene tetra-(pentafluorophenyl)porphyrin (TFPP) complexes, [Fe(TFPP)(CPh2)(1-EtIm)] (1-EtIm = 1-ethylimidazole) and [Fe(TFPP)(CPh2)(1,2-Me(2)Im)] (1,2-Me(2)Im = 1,2-dimethylimidazole), are isolated and studied by UV-vis, single-crystal X-ray, and Mossbauer spectroscopies. The single-crystal structural studies revealed noteworthy features including strong and "hard" axial carbene bonds (Fe-C) but "flexible" trans ligand bonds (Fe-N-Im). The Mossbauer spectra of [Fe(TFPP)(CPh2)(1-EtIm)] and [Fe(TFPP)(CPh2)-(1,2-Me(2)Im)] are obtained on solid-state samples between 25 and 295 K, which give very large Delta E-Q values (1.8-1.9 mm/s), suggesting a weak effect of the trans imidazole ligands. Comparisons with diatomic carbon-donor ligands (CO, CS, and CN-) demonstrate considerably stronger pi bonding of the :CPh2 carbene.