Synthesis, Characterization, and Thermal Behavior of Polydentate Ligand Adducts of Barium Trifluoroacetate

The reaction of BaH2 with polydentate ligands and
CF3COOH in THF at −40 °C in 1:1:2 stoichiometries
leads
to compounds of general formula
[Ba(O2CCF3)2]mLn
(L = 12-crown-4 (1), triglyme (2),
2-(hydroxymethyl)-15-crown-5 (15-crown-5CH2OH) (3),
cryptand(222) (4),
18-crown-6·C5H5N (5),
2-(hydroxymethyl)-18-crown-6 (18-crown-6CH2OH) (6)). A sulfonate
compound,
Ba(O3SCF3)2(tetraglyme)
(7), was also prepared by a similar reaction.
The polydentate ligands of 1−6 are
coordinated to the barium atoms through all of their donating atoms,
and the
trifluoroacetate ligands are found in four distinct types of bonding
modes. The compounds were characterized
by spectroscopic and analytical methods, and
1−6 are among the first examples of group 2
trifluoroacetate
compounds with mononuclear or dinuclear structures in the solid state
as determined by single-crystal X-ray
diffraction.
Ba2(O2CCF3)4(12-crown-4)2
(1) crystallizes from ethanol in monoclinic space group
P21/n with a
=
11.014(1) Å, b = 12.016(1) Å, c =
15.269(1) Å, β = 104.47(1)°, and Z = 4.
Ba2(O2CCF3)4(triglyme)2
(2)
crystallizes from ethanol in monoclinic space group
P21/n with a =
11.203(1) Å, b = 12.220(1) Å, c =
15.451(1)
Å, β = 107.61(1)°, and Z = 4.
Ba2(O2CCF3)4(15-crown-5CH2OH)2
(3) crystallizes from ethanol in monoclinic
space group P21/c with a
= 12.445(2) Å, b = 12.499(3) Å, c
= 15.615(2) Å, β = 111.11 (1)°, and Z =
4.
Ba(O2CCF3)2(cryptand(222))
(4) crystallizes from toluene in the tetragonal space group
P43212 with a =
b =
9.263(2) Å, c = 35.897(7) Å, and Z
= 4.
Ba(O2CCF3)2(18-crown-6)(py)
(5) crystallizes from pyridine in
orthorhombic space group Pnma with a =
27.178(3) Å, b = 11.417(1) Å, c =
9.133(1) Å, and Z = 4.
Ba(O2CCF3)2(18-crown-6CH2OH)
(6) crystallizes from ethanol in monoclinic space group
Pn with a = 8.279(1) Å,
b
= 11.410(1) Å, c = 13.661(2) Å, β =
98.41(1)°, and Z = 2. Infrared spectroscopy on
1−6 supplied information
on the relationships among νasym(CO2),
bonding mode of the trifluoroacetate ligand, and donating ability of
the
polydentate ligand. Thermogravimetric analysis of
1−7 shows loss of the organic supporting
ligands in the
temperature range 250−600 °C with formation of
BaF2.