Solution-state NMR and X-ray crystallography were used to investigate the complexation of Hg(IT) by the tridentate ligand bis[(2-pyridyl)methyl] amine (BMPA). Mercury coordination compounds exhibiting rarely observed solution-state NMR (HHg)-H-1-Hg-199 satellites were characterized. Temperature and concentration effects on solution-state NMR properties were investigated. The solution-state NMR were correlated with two solid-state structures. The distorted trigonal prismatic complex [Hg(BMPA)(2)](ClO4)(2 .)0.5 toluene (1) crystallizes in the triclinic space group P (1) over bar with 10.953(5) Angstrom, b = 12.812(5) Angstrom, c = 13.006(5) Angstrom, alpha = 67.50(3)degrees, beta = 82.74(3)degrees, gamma = 67.88(3)degrees, and Z = 2. The Hg-N-amine bonds are 2.404(4) and 2.350(4) Angstrom and the Hg-N-pyridyl bond lengths are similar, ranging from 2.352(4) to 2.557(5) Angstrom. Solution NMR studies are consistent with rapid equilibrium between isomeric trigonal prismatic and facial octahedral forms of this complex. A twisting mechanism is proposed to mediate interconversion. The distorted square planar complex [Hg(BMPA)NCCH3](ClO4)(2) (7) crystallizes in the monoclinic space group P2(1)/c with a = 12.987(2) Angstrom, b = 17.469(4) Angstrom, c = 8.886(2) Angstrom, beta = 95.200(12)degrees, and Z = 4. The Hg-N-amine distance is 2.403 Angstrom, the average Hg-N-pyridyl distance is 2.23 Angstrom, and the Hg-N-nitrile distance is 2.229 Angstrom. The BMPA ligand is bound to Hg(II) in a meridional fashion with a solvent molecule in the same plane and close associations to two axial perchlorates with Hg-O distances of 2.707(7) and 2.90(2) Angstrom. Solution NMR studies support limited dynamics for a cation with similar interactions between BMPA and Hg(II).