Preparation of Mercury(II) Complexes of Tris[(2-pyridyl)methyl]amine and Characterization by X-ray Crystallography and NMR Spectroscopy

The complexation of Hg(II) by the tripodal ligand
tris[(2-pyridyl)methyl]amine (TMPA) was investigated
by
solution state NMR and X-ray crystallography. Mercury coordination
compounds exhibiting rarely observed
room-temperature solution state NMR
1H199Hg and
13C199Hg satellites were characterized.
Solvent, counterion,
temperature, and concentration effects on solution state NMR properties
were investigated. The solution state
NMR were correlated with two solid state structures. The
eight-coordinate complex
[Hg(TMPA)2](ClO4)2
(1)
crystallizes in the monoclinic space group
P21/n with a =
9.735(10) Å, b = 10.963(2) Å, c =
18.553(34) Å, β
= 103.81(12)°, and Z = 2. The mercury is at
the inversion center of a bicapped trigonal antiprism. The
Hg−Namine distance is 2.560(3) Å, and the average
Hg−Npyridyl distance is 2.58(2) Å. The
five-coordinate complex
[Hg(TMPA)Cl]2(HgCl4)
(2) crystallizes in the triclinic space group
P1̄ with a = 11.887(2) Å,
b = 13.260(2) Å,
c = 15.278(4) Å, α = 112.27(2)°, β =
109.39(2)°, γ = 90.670(10)°, and Z = 2.
The two crystallographically
unique cations are distorted trigonal bipyramids. The average
Hg−Cl distance is 2.355(12) Å, the average Hg−Namine distance is 2.43(2) Å, and the average
Hg−Npyridyl distance is 2.40(5) Å.