Synthesis, structure and properties of some 3d-element complexes with 2-[2-(hydroxybenzylidene)-amino]-2-hydoxymethylpropane-1,3-diol

Article abstract of DOI:10.1023/B:RUCO.0000022802.31132.6c

2-[2-(Hydroxybenzylidene)-amino]-2-hydoxymethylpropane-1,3-diol (HL) reacts with cobalt, nickel, copper and zinc chlorides, bromides and acetates in water-ethanol solutions and gives MLX·nH₂O and ML ₂·nH₂O complexes (M = Co, Ni, Cu, Zn; X = Cl, Br; n = 0-5). Single crystals of CuLBr were grown, and its crystal structure was determined by X-ray diffraction analysis. The crystals are tetragonal, a = 17.024(2), c = 8.720(2) A, space group P42₁c, Z = 8, R ₁ = 0.0349. In the structure of this complex, the copper atom coordinates the deprotonated HL molecule. The coordination polyhedron of the central atom is an elongated tetragonal pyramid. Its base is built of the imine nitrogen atom, phenolic and alcoholic oxygen atoms, and bromine atom. The apex of the pyramid is occupied by the bromine atom of the adjacent complex connected with the initial complex by the plane of sliding reflection. Thus, the crystal contains infinite chains of complexes running along the c axis, the complexes being united by both bridging bromine atoms and O-H...O hydrogen bonds. The conclusions on the compositions and structures of the remaining compounds were made on the basis of elemental and combined thermal analyses, IR spectroscopy, and magnetic chemistry data. The copper halide complexes were found to have dimeric, and the other metal complexes monomeric, structures. In the synthesized complexes, the azomethine HL can function as a bidentate or tridentate ligand. The thermolysis of the coordination compounds proceeds through the stages of elimination of crystal water molecules (75-90°C) or inner-sphere water molecules (145-155°C) and complete thermal destruction (485-550°C).

Full text of DOI:10.1023/B:RUCO.0000022802.31132.6c

Russian Journal of Coordination Chemistry, Vol. 30, No. 4, 2004, pp. 269–274. Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 4, 2004, pp. 288–294.
Original Russian Text Copyright © 2004 by Tsapkov, Chumakov, Antosyak, Bocelli, Samus’, Gulya.
Synthesis, Structure and Properties of Some 3d-Element
Complexes with 2-[2-(Hydroxybenzylidene)-amino]-2-
hydoxymethylpropane-1,3-diol
V. I. Tsapkov*, Yu. M. Chumakov**, B. Ya. Antosyak**, G. Bocelli***,
N. M. Samus’*, and A. P. Gulya*
* Moldova State University, ul. Matteevicha 60, Chisinau, 277009 Moldova
** Institute of Applied Physics, Academy of Sciences of Moldova, Academiei 5, Chisinau, Moldova
*** Center of Structural Diffractometry, Parma, Italy
Received September 30, 2003
Abstract—2-[2-(Hydroxybenzylidene)-amino]-2-hydoxymethylpropane-1,3-diol (HL) reacts with cobalt,
nickel, copper and zinc chlorides, bromides and acetates in water–ethanol solutions and gives MLX · nH2O and
ML2 · nH2O complexes (M = Co, Ni, Cu, Zn; X = Cl, Br; n = 0–5). Single crystals of CuLBr were grown, and
its crystal structure was determined by X-ray diffraction analysis. The crystals are tetragonal, a = 17.024(2), c =
8.720(2) Å, space group P421Ò, Z = 8, R1 = 0.0349. In the structure of this complex, the copper atom coordinates
the deprotonated HL molecule. The coordination polyhedron of the central atom is an elongated tetragonal pyr-
amid. Its base is built of the imine nitrogen atom, phenolic and alcoholic oxygen atoms, and bromine atom. The
apex of the pyramid is occupied by the bromine atom of the adjacent complex connected with the initial com-
plex by the plane of sliding reflection. Thus, the crystal contains infinite chains of complexes running along the
c axis, the complexes being united by both bridging bromine atoms and O–ç···O hydrogen bonds. The conclu-
sions on the compositions and structures of the remaining compounds were made on the basis of elemental and
combined thermal analyses, IR spectroscopy, and magnetic chemistry data. The copper halide complexes were
found to have dimeric, and the other metal complexes monomeric, structures. In the synthesized complexes, the
azomethine HL can function as a bidentate or tridentate ligand. The thermolysis of the coordination compounds
proceeds through the stages of elimination of crystal water molecules (75–90°C) or inner-sphere water mole-
cules (145–155°C) and complete thermal destruction (485–550°C).
2-Amino-2-hydroxymethylpropane-1,3-diol
from a solution, determine the composition and struc-
[H2NC(CH2OH)3] containing a number of donor atoms ture, and to study their physicochemical properties.
is known to form coordination compounds with transi-
The reaction of aqueous solutions of chlorides, bro-
tion-metal ions, where it can act as a mono-, bi-, and tri-
mides, and acetates of the indicated metals with HL
dentate or bridging ligand [1–3]. The amino group of
(taken at the 1 : 1 and 1 : 2 molar ratios) results in fine-
the ligand favors its condensation with aldehydes and
lycrystalline compounds MLX · nH2O (I, II, IV, VI,
ketones thus increasing the number of functional
VII, IX) and ML2 · nH2O (III, V, VIII, X), where M =
groups and dentate number. Complexation of transition
Co (I–III), Ni (IV, V), Cu (VI–VIII), Zn (IX, X); X =
metals with such ligands in solution was studied earlier
Cl (I, IV, VI, IX), Br (II, VII); n = 0 (VI, VII, IX), 2
in [4–7].
(X), 3 (V, VIII), 4 (II), 5 (I, III, IV).
The purpose of this work was to find optimal condi-
tions of isolation of cobalt, nickel, copper, and zinc
complexes with the product of condensation of 2-
EXPERIMENTAL
amino-2-hydroxymethylpropane-1,3-diol with sali-
cylic aldehyde, 2-[2-(hydroxybenzylidene)-amino]-2-
hydoxymethylpropane-1,3-diol (HL)
The initial HL was prepared as described elsewhere [8].
Synthesis of I. To 30 ml of hot aqueous solution
(50–55°C) containing 10 mmol of cobalt(II) chloride
hexahydrate, 20 ml of C2H5OH containing 10 mmol of
HL was added. The resulting reaction mixture was
heated to 50–55°C with continuous stirring for 25–
30 min. After cooling the solution, dark brown fine
crystals precipitated; they were filtered on a glass filter,
washed with small quantities of alcohol and ether, and
dried in air.
HO
OH
OH
N
HO
(HL)
1070-3284/04/3004-0269 © 2004 åÄIä “Nauka /Interperiodica”

270
TSAPKOV et al.
Table 1. Results of elemental analysis and magnetochemical study of complexes I–X
Content (found/calculated), %
µeff, µB
(294 K)
Com-
pound
Empirical formula
Yield, %
Hal
M
N
I
C11H24ClCoNO9
C11H22BrCoNO8
C22H38CoN2O13
C11H24ClNNiO9
C22H34N2NiO11
C11H14ClCuNO4
C11H14BrCuNO4
C22H34CuN2O11
C11H14ClNO4Zn
C22H32N2O10Zn
69
73
75
71
74
65
68
72
70
75
8.42/8.69
14.19/14.44
13.31/13.56
9.59/9.88
3.30/3.43
2.94/3.22
4.35/4.69
3.18/3.43
5.16/4.99
4.18/4.33
3.64/3.80
4.68/4.95
4.03/4.31
4.86/5.10
4.96
5.06
4.90
2.98
3.18
1.65
1.60
2.06
II
18.15/18.39
III
IV
V
8.51/8.69
14.15/14.44
10.35/10.52
19.54/19.78
17.28/17.39
11.07/11.31
19.75/20.03
11.60/11.84
VI
VII
VIII
IX
X
10.79/10.97
21.45/21.74
10.69/10.94
Similarly, compounds II, IV, VI, VII, and IX were elemental analysis and selected physicochemical
prepared using corresponding cobalt, nickel, copper, parameters of complexes I–X are given in Table 1.
and zinc chlorides or bromides and HL (1 : 1 molar
ratio) as initial reagents.
Single crystals of complex VII suitable for the
X-ray diffraction analysis were obtained by recrystalli-
zation of the compound from the water–ethanol (1 : 1)
solution.
Complexes III, V, VIII, and X were synthesized by
the reaction of the indicated metal acetate hydrates with
HL (1 : 2 molar ratio) using a similar procedure.
Molar conductivity of the solutions of complexes I–
X in DMF (20°C, cå = 0.01 mol/l) was measured with
a R-38 slide-wire bridge.
Complexes I–X are readily soluble in water, alco-
hols, dimethylformamide (DMF), and dimethyl sulfox-
ide (DMSO) and insoluble in ether. The results of the
IR spectra of the complexes were recorded on an
Specord M80 spectrophotometer with mineral and flu-
orinated oil mulls.
Br(1)
Magnetic susceptibility was measured at room tem-
perature by the Gouy method with Co[Hg(NCS)4] as a
standard.
Thermal curves for I–X were recorded on an OD-
102 derivatograph at the rate of 5 K/min in the 20–
1000°C temperature range in air.
O(2)
Cu(1)
O(1)
X-ray diffraction study of complex VII was car-
ried out on a Bruker AXS Smart diffractometer with a
CCD detector (MoKα radiation, room temperature).
Absorption was corrected with the SHELXTL-NT
V5.1 programs [9]. Structure VII was solved by the
direct method and refined by the least-squares method
in anisotropic approximation for non-hydrogen atoms
and isotropic approximation for hydrogen atoms with
the use of the SHELX97 programs [10]. Hydrogen
atoms were located from Fourier difference syntheses.
C(7)
C(6)
C(9)
N(1)
C(8)
C(5)
C(4)
C(11)
O(3)
C(2)
C(1)
C(10)
C(3)
O(4)
The details of the experiment are given in Table 2.
Coordinates and thermal parameters of basis atoms are
Fig. 1. Structure of complex VII.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 30 No. 4 2004

SYNTHESIS, STRUCTURE AND PROPERTIES OF SOME 3d-ELEMENT COMPLEXES
271
Table 2. Crystallographic data and details of experiment Table 3. Atomic coordinates (×104) and equivalent isotro-
and refinement of structure VII
pic thermal parameters Ueq (×103) in structure VII
Atom
x
y
z
Ueq, Å2
M
364.66
0.71073
Wave length, Å
Crystal system
Cu(1)
Br(1)
O(1)
O(2)
O(3)
O(4)
N(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
8161(1) 7455(1)
9030(1)
30(1)
37(1)
33(1)
35(1)
34(1)
33(1)
24(1)
27(2)
27(1)
37(2)
41(2)
42(2)
38(2)
28(2)
21(1)
32(1)
30(2)
28(2)
Tetragonal
7086(1) 7715(1) 10723(1)
Space group
P421/c
Unit cell parameters
a, Å
7839(2) 6413(2)
8658(3) 8455(3)
10855(3) 8700(3)
9242(3) 8452(3)
9073(3) 7425(3)
9234(3) 6836(4)
8820(3) 6103(3)
9103(3) 5536(3)
8774(4) 4797(4)
8150(4) 4617(4)
7848(4) 5158(4)
8159(4) 5920(3)
9549(3) 8156(3)
9472(3) 8515(3)
10421(3) 8000(4)
9192(4) 8729(3)
8630(5)
9687(5)
7653(5)
4940(5)
7672(5)
6786(7)
6720(8)
5684(9)
5557(8)
6522(7)
7533(8)
7656(6)
7633(6)
9240(7)
7302(7)
6465(6)
17.024(2)
8.720(2)
2527.2(7)
8
c, Å
V, Å3
Z
ρ (calcd), g/m3
µ, mm–1
F(000)
1.917
4.895
1440.0
Crystal size, mm
θ, deg
0.2 × 0.3 × 0.4
1.69–25.01
Index range
–20 ≤ h ≤ 20, –20 ≤ k ≤ 20,
–10 ≤ l ≤ 10
Number of measured
reflections
24415
Number of unique reflections
2232 (Rint = 0.084)
Number of reflections
with I > 2σ(I)
1769
Number of refined parameters
GOOF
178
0.967
Final R factor (I > 2σ(I))
R factor for total array
∆ρ(max) and ∆ρ(min), e Å–3
R1 = 0.0349, wR2 = 0.0624
R1 = 0.0586, wR2 = 0.0667
0.334 and –0.261
listed in Table 3; interatomic distances and bond angles
are presented in Table 4.
Cu(1)–O(2) 1.981(4), Cu(1)–N(1) 1.953(5), Cu(1)–
Br(1) 2.392(1) Å. The Br(1) atom occupies the apex of
the Cu(1)' coordination polyhedron of the adjacent
RESULTS AND DISCUSSION
1
complex (Cu(1)'–Br(1) 3.340 Å). The angles between
The copper atom in structure VII coordinates the
deprotonated HL molecule (Fig. 1). The coordination
polyhedron of the central atom is an elongated tetrago-
nal pyramid. Its base is built of the imine N(1) atom,
phenolic and alcoholic O(1) and O(2) atoms, and Br(1)
atom. Deviations of these atoms from the mean plane
they determine fall within the 0.091–0.119 Å range; the
copper atom extends from this plane by 0.064 Å. The
bond lengths are as follows: Cu(1)–O(1) 1.888(4),
this bond and the coordination bonds of the atoms in the
base of pyramid vary in the range of 80.4°–103.3°.
Thus, the crystal contains infinite chains of complexes
running along the c axis, the complexes being united by
both bridging bromine atoms and hydrogen bonds
(O(1)···O(4)' 2.72(8), O(1)···ç(11)' 1.8(6) Å, angle
1
Coordinates of the atoms labeled with primes are ' y + 1.5, x +
1.5, z – 0.5; '' y, x + 2, –z + 2; ''' –y + 2, x, –z + 1.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 30 No. 4 2004

272
TSAPKOV et al.
Table 4. Interatomic distances and bond angles in structure VII
Bond
d, Å
Bond
d, Å
Cu(1)–O(1)
Cu(1)–N(1)
Cu(1)–O(2)
Cu(1)–Br(1)
O(1)–C(7)
O(2)–C(9)
O(3)–C(10)
O(4)–C(11)
N(1)–C(1)
N(1)–C(8)
1.888(4)
1.953(5)
1.981(4)
2.3923(9)
1.314(6)
1.438(7)
1.434(7)
1.413(7)
1.296(7)
1.485(7)
C(1)–C(2)
C(2)–C(3)
C(2)–C(7)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(8)–C(9)
C(8)–C(10)
C(8)–C(11)
1.435(8)
1.408(8)
1.424(8)
1.382(8)
1.389(9)
1.389(9)
1.405(8)
1.534(8)
1.536(8)
1.405(8)
Angle
ω, deg
Angle
ω, deg
O(1)Cu(1)N(1)
O(1)Cu(1)O(2)
N(1)Cu(1)O(2)
O(1)Cu(1)Br(1)
N(1)Cu(1)Br(1)
O(2)Cu(1)Br(1)
C(7)O(1)Cu(1)
C(9)O(2)Cu(1)
C(1)N(1)C(8)
C(1)N(1)Cu(1)
C(8)N(1)Cu(1)
N(1)C(1)C(2)
C(3)C(2)C(7)
C(3)C(2)C(1)
C(7)C(2)C(1)
C(4)C(3)C(2)
95.5(2)
169.4(2)
81.5(2)
C(3)C(4)C(5)
C(6)C(5)C(4)
C(5)C(6)C(7)
O(1)C(7)C(6)
O(1)C(7)C(2)
C(6)C(7)C(2)
N(1)C(8)C(9)
N(1)C(8)C(10)
N(1)C(8)C(11)
C(9)C(8)C(10)
C(11)C(8)C(10)
C(9)C(8)C(11)
O(2)C(9)C(8)
O(3)C(10)C(8)
O(4)C(11)C(8)
117.5(6)
121.8(6)
121.8(6)
118.8(6)
124.0(5)
117.1(6)
105.4(4)
112.7(4)
109.4(4)
108.9(4)
111.6(5)
108.7(5)
106.8(5)
106.8(5)
112.9(5)
93.7(1)
170.7(1)
89.7(1)
126.7(4)
113.6(3)
121.3(5)
123.3(4)
115.2(4)
126.4(6)
119.2(6)
117.0(6)
123.8(6)
122.5(7)
O(1)H(11)'O(4)' 157(5)°) (Fig. 2). The chains are also and O(1)N(1)C(1)C(2)C(7) planes is 4.1°. In
linked by hydrogen bonds: O(2)···O(3)'' 2.62(1),
O(3)''···ç(2) 1.8(1) Å, angle O(2)H(2)O(3)'' 178(4)°;
O(3)'''···O(4) 2.71(8), O(4)···ç(10)''' 1.8(9) Å, angle
O(3)'''H(10)'''O(4) 169(5)°.
di(µ−Ophenoxy)-bis{nitrato-2-[2-hydroxyethylimino)-
methyl]-phenolo-imidazolecopper [11], nitrato-2-oxy-
ethylimino-2-oxy-1-benzaldehyde-3-picolinecopper [12],
and 3-hydroxypropylsalicylaldiminatocopper [13], it is
equal to 20.6°, 14.9°, and 22.7°, respectively. At the
same time, nitrato-2-[2-(hydroxyethylimino)-methyl]-
In compound VII, the six-membered metal cycle
Cu(1)O(1)N(1)C(1)C(2)C(7) is slightly bent along the
O(1)···N(1) line. The angle between the Cu(1)O(1)N(1) phenolocopper [14], nitrato-2-[2-(hydroxyethylimino)-
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 30 No. 4 2004

SYNTHESIS, STRUCTURE AND PROPERTIES OF SOME 3d-ELEMENT COMPLEXES
273
b
0
Cu(1)'
O(3)''
H(2)
a
Br(1)
O(2)
Cu(1)
H(11)'
c
O(4)'
O(1)
O(4)
H(10)'''
O(3)'''
Fig. 2. Fragment of packing of complexes in crystals of VII.
methyl]-phenolo-4-picolinecopper [15], and 2-[2- planes is 2.9°. The five-membered metal cycle
(hydroxoethylimino)-methyl]-phenolocopper [16] do not Cu(1)O(2)N(1)C(8)C(9) has a gauche conformation;
exhibit such a bend. The benzene ring (A) lies nearly in the deviations of the C(8) and C(9) atoms from the
plane of the O(1)N(1)C(1)C(2)C(7) fragment (B) of the Cu(1)O(2)N(1) plane are –0.209(8) and 0.312(9) Å,
six-membered metal cycle; the angle between the A and B respectively.
Table 5. Thermal analysis of complexes I–X
Mass loss
Kinetic parameters of process
Number
Com- of effect
pound in thermal
curve
Temperature
of complete
decomposition, °C
T, °C
corresponds
Eac,
found/calculated, % to the elimina-
tion of
logZ**
kJ/mol*
I
1
2
1
2
1
1
2
1
1
75
175
80
13.0/13.2
8.5/8.8
3H2O
2H2O
2H2O
2H2O
5H2O
3H2O
2H2O
3H2O
H2O
40.1
89.9
49.9
68.9
37.6
36.9
75.1
45.4
35.1
3.7
8.7
5.0
6.8
3.4
3.5
7.0
4.2
3.4
515
500
II
8.0/8.3
165
90
8.2/8.3
III
IV
15.0/15.1
13.5/13.2
9.0/8.8
540
500
80
165
90
V
9.5/9.6
525
485
470
500
520
550
VI
VII
VIII
IX
X
75
5.5/5.3
1
1
85
90
9.5/9.5
3H2O
2H2O
42.6
37.3
4.0
3.6
6.5/6.6
* E is the activation energy of the solid-phase reaction.
ac
** Z is the preexponential factor.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 30 No. 4 2004

274
TSAPKOV et al.
The visual microscopic study of powdered com- thermic effects at 75–90°C; the weight loss corresponds
plexes I–VI and VIII–X revealed their homogeneity. to elimination of crystal water molecules. Compounds
Because single crystals of the complexes were not I, II, and IV show the second endothermic effect at
available, we used IR spectroscopy, magnetic chemis- 165–175°C corresponding to elimination of two inner-
try, and combined thermal analysis (TA) methods in sphere water molecules. On the last stage of thermoly-
order to identify them and study their structures.
sis (470–550°C), thermal oxidative destruction of the
coordinated azomethine occurs (accompanied by exo-
thermic effect). As follows from Table 5, the tempera-
ture of complete decomposition (T) of the complexes
depends on the nature of the central atom and its ligand
surrounding; for the compounds with the same compo-
sition, it decreases in the series TZn > TCo > TNi > TCu.
The nature of the acido ligand and the number of
azomethine molecules also affect the T value. Introduc-
tion of the second L– ligand into the complex increases
the temperature by 15–40°C; with the same central
atom, TCl > TBr.
The absorption bands in the IR spectrum of com-
pound VII were assigned with account of its structural
data. The tridentate chelating function of monodeproto-
nated ligand L– was confirmed by (a) disappearance of
the absorption band δ(OH)phenol that was observed for a
free azomethine in the 1237–1230 cm–1 range; (b) shift
of the band ν(C=N) by 20–18 cm–1 toward lower fre-
quencies as compared to the band in the initial HL
(1635 cm–1); (c) split and low-frequency shift (by 15–
10 cm–1) of the absorption bands due to the alcoholic
OH groups at 3290–3270 (ν(OH)alcohol) and 1055–
1050 cm–1 (v(C–O)alcohol) and broadening of the band
ν(C–O)phenol at 1540 cm–1; (d) appearance of new bands
corresponding to ν(Cu–N) (510 and 405 cm–1) and
ν(Cu–O) (470 cm–1).
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Comparison of the IR spectra of complex VII and of
the remaining nine compounds revealed identical posi-
tions of the main characteristic absorption bands. This
indicates the same mode of coordination of L– to the
central ions. Negligible difference is found only for
compound VIII in the region of the absorption bands of
the alcoholic OH groups; they have almost the same
position as the bands in the initial HL. Probably, in
complex VIII, L– functions as a bidentate ligand that is
coordinated to the central atom through the deproto-
nated phenol O atom and azomethine N atom, while in
the remaining complexes, it acts as a tridentate ligand
(as in complex VII).
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The determination of the molar conductivity of the
dimethylformamide solutions of the complexes
obtained suggests that all of them, like compound VII,
20
are nonelectrolytes (µ
= 3–7 Ω–1 cm2 mol–1).
1000
10. Sheldrick, G.M., SHELX97. Program for the Refinement
of Crystal Structure, Göttingen (Germany): Univ. of
Göttingen, 1997.
The data of the magnetochemical study show
(Table 1) that the cobalt compounds I–III have effec-
tive magnetic moments (µeff) corresponding to three
unpaired electrons and an oxidation number of the cen-
tral ion equal to +2. Complexes IV and V are paramag-
netic; judging from their µeff, the Ni2+ ion has a pseudo-
octahedral ligand surrounding. Compound VIII is
monomeric, since its magnetochemical data at room
temperature correspond to the spin value for one
unpaired electron. Complex VI with the lowered value
of µef is a polynuclear compound like complex VII.
11. Chumakov, Yu.M., Biyushkin, V.N., Malinovskii, T.N.,
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14. Chumakov, Yu.M., Biyushkin, V.N., Malinovskii, T.N.,
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15. Chumakov, Yu.M., Biyushkin, V.N., Malinovskii, T.N.,
TA of the synthesized complexes shows that their
thermolysis proceeds in several stages (Table 5). Ther-
mal curves of complexes I–V, VIII, and X have endo-
et al., Koord. Khim., 1990, vol. 16, no. 7, p. 945.
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