Spin-crossover phenomena of four iron complexes, [Fe(amp)(3)](2+) (amp = 2-(aminomethyl)pyridine), [Fe(acac(2)trien)](+) (H(2)acac(2)trien = N,N’-bis(1-methyl-3-oxobutylidene)triethylenetetramine), [Fe(sal(2)trien)](+) (H(2)sal(2)trien = N,N’-disalicylidenetriethylenetetramine), and [Fe(acpa)(2)](+) (Hacpa = N-(1-acetyl-2-propylidene)-2-pyridylmethylamine), intercalating into the montmorillonite interlayer space were examined by the magnetic susceptibility measurement and Fe-57 Mossbauer spectroscopy. Confinement of the complexes in the 2D space brings some dispersion and drop of the spin-crossover temperature in comparison with those for their spin equilibria in solution. Twisting deformation of the complexes was proposed to be responsible for the observed variation of the relative stability between high-spin and low-spin species.