The effects of steric hindrance on the complexation of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) by chelators based on cis,cis-1,3,5-triaminocyclohexane (tach) have been studied. The chelators studied are the 2-methylpyridyl pendant-arm derivatives of tach, ‘tachpyr’ (N,N′,N″-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane), and the N-alkylated analogs ‘(N–Me)3tachpyr’ (N,N′,N″-trimethyl-N,N′,N″-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane) and ‘(N–Et)3tachpyr’ (N,N′,N″-triethyl-N,N′,N″-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane). Hexacoordinate complexes, [MIIL]X2 resulted from reaction of the appropriate metal ion salts with L in alcoholic medium (M = Mn, Co, Ni, Cu, Zn; L = tachpyr, (N–Me)3tachpyr, (N–Et)3tachpyr; X = ClO4−, NO3−, Cl−). The Mn(II) and Co(II) complexes have high-spin electron configurations, based on solution magnetic susceptibility, electronic spectral and/or X-ray crystallographic studies. However, solution visible-near IR electronic spectra and single-crystal X-ray crystallography demonstrate weakened bonding in the complexes of (N–R)3tachpyr relative to tachpyr, due to steric effects of methyl or ethyl groups on coordinated tach amines. Structures of [Zn(tachpyr)]2+ and [Ni(tachpyr)]2+ indicate a clear preference of tachpyr and derivatives for octahedral geometry, while [Cu((N–Me)3tachpyr)]2+ exhibits a classic Jahn–Teller tetragonal distortion. The complex [Mn(tachpyr)](ClO4)2 demonstrates a striking influence of the metal ion on the coordination geometry, with a trigonal-prismatic coordination of Mn(II) and considerable distortion of the tach-amino donor groups. The coordination geometry and distortions are attributed to the large size of high-spin d5 Mn(II) and the absence of ligand-field stabilization energy, coupled with the observed preference of tachpyr derivatives for octahedral geometry. The [MII(tachpyr)]2+ complexes (M = Co, Ni, Cu and Zn) are inert in aqueous pH 5.5 media. However, all metal complexes of N-alkylated tachpyr, as well as [Mn(tachpyr)](ClO4)2, dissociate metal ion in aqueous pH 5.5 medium, consistent with their steric hindrance and distortions respectively.