Zn(II), Co(II) and Ni(II) complexes of a phosphorylthiourea derivative of 4-[(EtO)2P(O)CH2]-C6H4-NHC(S)NHP(O) (OiPr)2

Article abstract of DOI:10.1135/cccc2009074

The reaction of O,O'-diisopropyl phosphorisothiocyanatidate, (iPrO) ₂P(O)NCS, with diethyl-(4-aminobenzyl)phosphonate leads to the new N-phosphorylated thiourea derivative, 4-[(EtO)₂P(O)CH ₂]-C₆H₄NHC(

Full text of DOI:10.1135/cccc2009074

Zn(II), Co(II) and Ni(II) Complexes
507
Zn(II), Co(II) AND Ni(II) COMPLEXES OF A PHOSPHORYLTHIOUREA
DERIVATIVE OF 4-[(EtO)2P(O)CH2]-C6H4-NHC(S)NHP(O)(OiPr)2
1
2,
Maria G. BABASHKINA and Damir A. SAFIN *
A. M. Butlerov Chemistry Institute, Kazan State University, Kremlevskaya St. 18,
1
2
420008 Kazan, Russia; e-mail: maria.babashkina@ksu.ru, damir.safin@ksu.ru
Received May 27, 2009
Accepted January 13, 2010
Published online May 10, 2010
The reaction of O,O′-diisopropyl phosphorisothiocyanatidate, (iPrO)2P(O)NCS, with diethyl-
(4-aminobenzyl)phosphonate leads to the new N-phosphorylated thiourea derivative,
4-[(EtO)2P(O)CH2]-C6H4NHC(S)NHP(O)(OiPr)2 (HL). The reaction of its potassium salt KL
with Zn(II) or Co(II) in aqueous EtOH leads to the complexes of formulae M(L-O,S)2 (ZnL2,
CoL2). The metal cation in all complexes is coordinated by two deprotonated ligands
through the sulfur atoms of the thiocarbonyl groups and the oxygen atoms of the phospho-
ryl groups. The reaction of KL with Ni(II) leads to the formation of two types of complexes:
the blue Ni(L-N,S)2 complex, where the ligand is coordinated through the nitrogen atom
of the phosphorylamide group and the sulfur atom of the thiocarbonyl groups and light
red Ni(L-O,S)2 complex with the same coordination of L– anion as it was observed for ZnL2
and CoL2. According to UV/Vis spectral data, it was established that the metal cation of
Ni(L-N,S)2 is in a square-planar environment in CH2Cl2, whereas the Ni(L-O,S)2 complex
shows features of tetrahedral complexes.
Keywords: Coordination chemistry; Zinc complexes; Cobalt complexes; Nickel complexes;
N-Phosphorylthiourea; Chelates; N,S-Ligands; Phosphonates.
The coordination chemistry of polyfunctional ligands, capable of realizing
different coordination modes with metal cations1, is of interest for syn-
thesis of new selective complexing agents and analytical reagents. The rea-
sons that allow such ligands to bind metal ions in the various specific ways
are intimately connected with such fundamental problems of chemistry as
the nature of chemical bonding and the isomerism of coordination com-
pounds as well as the influence of the ligand structure on regio- and stereo-
selectivity of the bond formation.
Complexes of Zn(II), Co(II) and Ni(II) with N-(thio)phosphorylated
(thio)amides and (thio)ureas RC(X)NHP(Y)R′2 (X, Y = O, S) (HZ) are of inter-
est because of the diversity in composition of obtained complexes, versatil-
ity of the coordination modes around the central ion and different magnetic
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© 2010 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc2009074

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Babashkina, Safin:
properties2–9. An overwhelming majority of these complexes contain lig-
ands with the same donor chalcogen atoms (X = Y)5–9
.
Coordination compounds of Zn(II), Co(II) and Ni(II) cations with HZ
ligands, containing both sulfur and oxygen donor atoms (X ≠ Y), still re-
main poorly explored. The presence of the hard-donor carbonyl or phos-
phoryl oxygen atoms in the coordination sphere of the central ion makes it
coordinately unsaturated, which, in turn, might lead to the formation of
heteroligand and polynuclear complexes with the central atom having
the coordination number 5 or 6, or the formation of different isomers.
Hence, amidothiophosphates, containing different donor atoms X and Y,
show different coordination properties compared to their dithio analogues
RC(S)NHP(S)R′2.
The aim of the present work is to assess the effect of the structure of the
amidophosphate ligand 4-[(EtO)2P(O)CH2]C6H4NHC(S)NHP(O)(OiPr)2 (HL)
on the composition and structure of chelates containing Zn(II), Co(II) and
Ni(II) cations.
EXPERIMENTAL
Infrared spectra (Nujol; ν, cm–1) were recorded with a Specord M-80 spectrometer in the
range 400–3600 cm–1. NMR spectra (δ, ppm; J, Hz) were obtained on a Varian Unity-300 NMR
spectrometer at 25 °C. 1H and 31P{1H} spectra were recorded at 299.948 and 121.420 MHz,
respectively. Chemical shifts are referenced to SiMe4 (1H) and 85% H3PO4 31P{1H}). Elec-
(
tronic absorption spectra of 0.001 M CH2Cl2 solutions were measured on a Perkin–Elmer
Lambda-35 spectrometer in the range 200–1000 nm at 5–25 °C. Elemental analyses were per-
formed on a Perkin–Elmer 2400 CHN microanalyser.
4-[(EtO)2P(O)CH2]-C6H4NHC(S)NHP(O)(OiPr)2] (HL)
A solution of diethyl(4-aminobenzyl)phosphonate, (EtO)2P(O)CH2C6H4-4-NH2 (0.243 g, 1
mmol), in CH2Cl2 (15 ml) was added dropwise to
a solution of O,O′-diisopropyl
phosphorisothiocyanate, (iPrO)2P(O)NCS (0.245 g, 1.1 mmol), in the same solvent (15 ml)
(Scheme 1). The mixture was stirred at room temperature for 3 h. The solvent was then re-
SCHEME 1
Preparation of HL
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Zn(II), Co(II) and Ni(II) Complexes
509
moved in vacuum. The residue was recrystallized from a dichloromethane/n-hexane mixture
1:5 (v/v). The product was obtained as a colorless oil. Yield 0.331 g (71%). 1H NMR (CDCl3):
3
3
2
1.23 t, 6 H, JH,H = 7.0 (CH3, EtO); 1.38 d, 12 H, JH,3H = 6.1 (CH3, iPrO); 3.13 d, 2 H, JP,H
=
3
21.9 (CH2, P(O)CH2); 4.00 d. quart, 4 H, JH,H = 7.2, JPOCH = 10.9 (OCH2, EtO); 4.74 d. sept,
3
3
2
2 H, JH,H = 6.1, JPOCH = 7.0 (OCH, iPrO); 7.08 d, 1 H, JPNH = 8.3 (NH, P(O)NH); 7.21–7.59 m,
4 H (C6H4); 10.70 s, 1 H (NH). 31P{1H} NMR (CDCl3): –6.9, 1 P (P(O)NH); 25.5, 1 P
(P(O)CH2). IR: 997, 1013 (POC); 1204 (P=O, P(O)CH2); 1249 (P=O, P(O)NH); 1562 (SCN);
3139, 3286 (NH). For C18H32N2O6P2S (466.47) calculated: 46.35% C, 6.91% H, 6.01% N;
found: 46.42% C, 6.77% H, 6.11% N.
M[4-{(EtO)2P(O)CH2}C6H4NHC(S)NP(O)(OiPr)2]2 (M = Zn(II), Co(II)) (ML2)
A suspension of HL (0.233 g, 0.5 mmol) in aqueous ethanol (20 ml) was mixed with an
ethanolic solution of potassium hydroxide (0.031 g, 0.55 mmol). An aqueous solution of
ZnCl2 (20 ml) or Co(NO3)2·6H2O (0.041 or 0.087 g, 0.3 mmol) was added dropwise under
vigorous stirring to the resulting potassium salt solution (Scheme 2). The mixture was stirred
at room temperature for another 3 h and left standing overnight. The complex was ex-
tracted with dichloromethane, washed with water and dried with anhydrous MgSO4. The
solvent was then removed in vacuum. The residue was recrystallized from a dichloro-
methane/n-hexane mixture 1:3 (v/v).
3
ZnL2. A colorless oil. Yield 0.204 g (82%). 1H NMR (CDCl3): 1.21 t, 12 H, JH,H = 7.1
3
2
(CH3, EtO); 1.28 d, 24 H, JH,H = 6.0 (CH3, iPrO); 3.09 d, 4 H, JP,H = 21.7 (CH2, P(O)CH2);
3
3.89–4.11 m, 8 H (OCH2, EtO); 4.60 d. sept, 4 H, JH,H
≈
3JPOCH = 6.2 (OCH, iPrO);
7.15–7.23, 7.39–7.48 m, 8 H (C6H4); 7.79 s, 2 H (NH). 31P{1H} NMR (CDCl3): 5.7, 2 P
(P(O)N); 26.4, 2 P (P(O)CH2). IR: 1012, 1019 (POC); 1209 (P=O, P(O)CH2); 1167 (P=O,
P(O)NH); 1539 (SCN); 3299 (NH). For C36H62N4O12P4S2Zn (996.30) calculated: 43.40% C,
6.27% H, 5.62% N; found: 43.27% C, 6.35% H, 5.57% N.
CoL2. A dark blue oil. Yield 0.158 g (64%). IR: 1001, 1007 (POC); 1214 (P=O, P(O)CH2);
1159 (P=O, P(O)NH); 1564 (SCN); 3316 (NH). UV/Vis (λmax, nm (ε, mol–1 dm3 cm–1)): 564
(270); 600 (292); 663 (161). For C36H62CoN4O12P4S2 (989.86) calculated: 43.68% C, 6.31% H,
5.66% N; found: 43.81% C, 6.45% H, 5.72% N.
SCHEME 2
Preparation of ZnL2 and CoL2 (R = 4-[(EtO)2P(O)CH2]-C6H4)
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Ni[4-{(EtO)2P(O)CH2}C6H4NHC(S)NP(O)(OiPr)2]2 (NiL2)
A suspension of HL (0.233 g, 0.5 mmol) in aqueous ethanol (20 ml) was mixed with an eth-
anol solution of potassium hydroxide (0.031 g, 0.55 mmol). An aqueous solution (20 ml) of
NiCl2 (0.039 g, 0.3 mmol) was added dropwise under vigorous stirring to the potassium salt
solution (Scheme 3). The mixture was stirred at room temperature for another 3 h and left
standing overnight. The complex was obtained by extraction of the reaction mixture with
dichloromethane, washed with water and dried with anhydrous MgSO4. The solvent was
then removed in vacuum. The residue was extracted using n-hexane. The hexane-insoluble
residue was recrystallized from a dichloromethane/n-hexane mixture 1:3 (v/v), and the
Ni(L-N,S)2 complex was isolated as a blue precipitate. Yield 0.063 g (25%), m.p. 62.5–64 °C.
3
3
1H NMR (CDCl3): 1.19 t, 12 H, JH,H = 7.3 (CH3, EtO); 1.33 d, 24 H, JH,H = 6.2 (CH3, iPrO);
2
3.13 d, 4 H, JP,H = 22.0 (CH2, P(O)CH2); 3.94–4.17 m, 8 H (OCH2, EtO); 4.72 d. sept, 4 H,
3JH,H
≈
3JPOCH = 6.1 (OCH, iPrO); 7.19–7.39, 7.46–7.60 m, 8 H (C6H4); 10.59 s, 2 H (NH).
31P{1H} NMR (CDCl3): 2.0, 2 P (P(O)N); 26.7, 2 P (P(O)CH2). IR: 997, 1004 (POC); 1217 (P=O,
P(O)CH2); 1238 (P=O, P(O)NH); 1541 (SCN); 3171 (NH). UV/Vis, λmax, nm (ε, mol–1 dm3 cm–1
)
234 (~32960); 249 (~19080); 428 (1720); 535 (260); 653 (237). For C36H62N4NiO12P4S2
(989.61) calculated: 43.69% C, 6.31% H, 5.66% N; found: 43.78% C, 6.21% H, 5.79% N.
The hexane soluble Ni(L-O,S)2 complex was isolated as a light red oil. Yield 0.118 g (48%).
1H NMR (CDCl3): 1.28 br. s, 36 H (CH3, EtO + iPrO); 3.06 br. s, 4 H (CH2, P(O)CH2); 3.94 br. s,
8 H (OCH2, EtO); 4.56 br. s, 4 H (OCH, iPrO); 7.26 br. s, 8 H (C6H4); 6.48 br. s, 2 H (NH).
31P{1H} NMR (CDCl3): –361.7 br. s, 2 P (P(O)N); 34.0 br. s, 2 P (P(O)CH2). IR: 994, 1018
(POC); 1211 (P=O, P(O)CH2); 1162 (P=O, P(O)NH); 1571 (SCN); 3293 (NH). UV/Vis (λmax
,
nm (ε, mol–1 dm3 cm–1)): 693 (117); 719 (193); 784 (249). For C36H62N4NiO12P4S2 (989.61)
calculated: 43.69% C, 6.31% H, 5.66% N; found: 43.54% C, 6.29% H, 5.49% N.
SCHEME 3
Preparation of Ni(L-N,S)2 and Ni(L-O,S)2 (R = 4-[(EtO)2P(O)CH2]-C6H4)
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Zn(II), Co(II) and Ni(II) Complexes
511
RESULTS AND DISCUSSION
The IR spectrum of HL contains a band at 1249 cm–1 for vibration of the
P=O fragment of the P(O)NH group. It is shifted to low wavenumbers
(1159–1167 cm–1) in the spectra of ZnL2, CoL2 and Ni(L-O,S)2 due to the
coordination with the cations. The coordination shift (82–90 cm–1) is in the
region characteristic of the 1,5-O,S-coordination of the deprotonated
phosphorylated thioamides and thioureas towards Zn(II), Co(II) and Ni(II)
(refs2,8–11). The wavenumbers of the P=O group in the IR spectrum of
Ni(L-N,S)2 also decreases (11 cm–1) relative to that of the free ligand. The
absorption occurs in the region characteristic of the 1,3-N,S-coordination of
the Ni(II) cation to deprotonated phosphorylated thioamides and thioureas2.
The occurrence of the new broad and intense band at 1539–1571 cm–1, due
to the conjugated SCN group8, also proves the formation of complexes. The
presence of the substituted POC groups in HL and its complexes can be de-
duced from the IR spectra by their absorption bands at 994–1019 cm–1
(refs8,9).
Two bands for the arylNH and P(O)NH groups at 3139 and 3286 cm–1
are observed in the IR spectrum of HL, whereas a simple band at 3293–
3316 cm–1 corresponding to the arylNH group are present in the spectra of
ZnL2, CoL2 and Ni(L-O,S)2. It should be noted that the band of the arylNH
group in the IR spectra of ZnL2, CoL2 and Ni(L-O,S)2 is shifted to higher
wavenumbers relative to the band of the free ligand HL. This confirms the
absence of hydrogen bonding in the complexes8,9. The NH absorption band
in the spectrum of Ni(L-N,S)2 is observed at 3171 cm–1, in the characteristic
region of amide protons participating in hydrogen bonding8,9
.
It should be noted that in the IR spectra of all complexes, the band corre-
sponding to the P=O fragment of the P(O)CH2 group occurs between 1209
and 1217 cm–1, practically in the same region as in the free ligand (1204 cm–1),
or even shifted to higher wavenumbers. This confirms the absence of coor-
dination of the P=O group, in the P(O)CH2 fragment.
The 31P{1H} NMR spectrum of HL in a CDCl3 solution shows two singlet
at –6.9 and 25.5 ppm, corresponding to the P(O)NH and P(O)CH2 phospho-
rus atoms, respectively. In the 31P{1H} NMR spectrum of ZnL2, the reso-
nances for the phosphorylamide and phosphonic ester groups are observed
at 5.7 and 26.4 ppm, respectively. The signal corresponding to the P(O)N
group in ZnL2 is shifted downfield by 12.6 ppm. This fact also confirms
the 1,5-O,S-coordination of L– anion2,8–11. The phosphorylamide phospho-
rus signal in the spectrum of Ni(L-N,S)2 is also downfield shifted by 8.9
ppm. This confirms the 1,3-N,S-coordination of L– anion2. The singlet of
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Babashkina, Safin:
the P(O)CH2 groups in the spectra of ZnL2 and Ni(L-N,S)2 are practically in
the same region as in the free ligand.
The 31P{1H} NMR spectrum of Ni(L-O,S)2 also contains two singlets. The
signal of the P(O)N group is observed in an extremely high-field region, δ =
–361.7 ppm. The P(O)CH2 phosphorus is shifted to a lower field relative to
that in the spectrum of HL; the shift is 8.5 ppm. Thus, the Ni(L-O,S)2 com-
plex in CDCl3 is paramagnetic due to its tetrahedral geometry12–14
.
1
In the H NMR spectra of HL, ZnL2 and NiL2, the signals of the CH3 pro-
tons in the (iPrO)2P(O) and (EtO)2P(O) groups are observed as doublets,
triplets or broad singlets at 1.19–1.38 ppm and doublets of septets, doublets
of quartets, multiplets or broad singlets at 3.89–4.74 ppm, correspond to
the OCH and OCH2 protons of the groups. The signals of the C6H4 protons
in the spectra of HL, ZnL2 and NiL2 are multiplets or broad singlets at 7.15–
7.59 ppm. The CH2 proton signals appear at 3.06–3.16 ppm. A doublet and
singlet of the P(O)NH and arylNH protons at 7.08 and 10.70 ppm, respec-
tively, are in the spectrum of HL, whereas only singlets are observed for
the arylNH proton at 6.48–7.79 ppm in the 1H NMR spectra of ZnL2
and Ni(L-O,S)2. The signals are high-field shifted relative to that in the
spectrum of HL. This confirms the absence of hydrogen bonds in ZnL2
and Ni(L-O,S)2 (refs2,8–10). The arylNH proton resonance in the spectrum of
Ni(L-O,S)2 appears at 10.59 ppm and is slightly shifted relative to that in
the spectrum of HL. This confirms the preservation of hydrogen bonds in
Ni(L-N,S)2 (ref.2).
The investigation of CoL2 complex by 31P{1H} NMR spectrometry was not
successful due to the presence of paramagnetic Co(II). The signals in the
31P{1H} NMR spectrum of the CoL2 complex are absent because of strong
contact or pseudocontact interactions between the paramagnetic metal ion
and the phosphorus atoms5. These pseudocontact interactions are practi-
cally absent for the protons where the dipole–dipole interactions predomi-
nate.
1
The 1D H NMR spectrum of CoL2 in CDCl3 displays twelve well-resolved
isotropically shifted signals a–l (Fig. 1). The 1H NMR chemical shifts are
reported in Table I. All signals display broad signals (as measured at their
half-height). The ∆ν1/2 values are characteristic of a four-coordinated Co(II)
complex (S = 3/2)15–17. The assignment of signals was done on the basis of
1H-1H COSY spectra and chemical shifts.
Signal a, corresponding to the phenylene group, is partly overlapped with
the solvent signal. Signals b and c represent two protons each and corre-
spond to the P(O)CH2 groups. The signal of the NH protons (4.7 ppm) is
observed in the relatively high-field region. The signals e + f and g–l are due
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Zn(II), Co(II) and Ni(II) Complexes
513
to twelve and thirty six protons, respectively, of the isopropyl (iPrO) and
ethyl (EtO) groups (Table I). The COSY cross-peaks between signals e and
h–j, l, and f and g, k confirm their assignment to the iPrO and EtO groups.
1
It should be noted that all signals in the H NMR spectra of CoL2 and
Ni(L-O,S)2 are in the diamagnetic region (0–14 ppm); however the signals
are extremely broad.
In the UV spectrum of CoL2, there is an absorption band (corresponding to
4
the A2→4T1(P) transition)11 with peaks at 564 (εmax = 270 mol–1 dm3 cm–1),
TABLE I
1H NMR signals of paramagnetic CoL2 in CDCl3
Assignment protons
Signal (δ, ppm)
No. of protons
C6H4 + solvent
CH2(P(O)CH2)
NH
a (7.3)
b (6.5), c (5.9)
d (4.7)
2 (b) + 2 (c)
12 (e + f)
CH(iPrO)
CH2(EtO)
CH3(EtO)
e (4.0)
f (3.6)
g (2.5), k (1.2)
h (2.0), i (1.6)
j (1.4), l (0.8)
36 (g–l)
CH3(iPrO)
FIG. 1
1H NMR spectrum of CoL2 in CDCl3
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Babashkina, Safin:
600 (εmax = 292 mol–1 dm3 cm–1) and 663 (εmax = 161 mol–1 dm3 cm–1) nm.
The band shape is caused by spin–orbital interaction resulting (i) in a split-
4
ting of the state T1(P) state and (ii) in a resolved transitions in the next
4
doublet states with the same intensity. Other possible transitions, A2→4T2
4
and A2→4T1(F), are outside of the visible region. UV-spectral data support
the tetrahedral environment of the Co(II) cation in CoL2 (ref.11).
In the electronic absorption spectrum of Ni(L-N,S)2 in CH2Cl2 two bands
at 653 and 535 nm, two shoulders at 428 and 249 nm and a band at
234 nm are observed. The last high-energy intensive transitions (εsh
=
19 083 mol–1 dm3 cm–1 and εmax = 32 961 mol–1 dm3 cm–1) fall obviously into
ligand–ligand and ligand-to-metal transitions18–20. The long-wave spectral
region shows three bands with εmax = 237, 260 and 1717 mol–1 dm3 cm–1.
1
The bands at 653 and 535 nm of Ni(L-N,S)2 assigned to the A1g→1B1g
1
(d
→dxy ) and A1g→1B3g (dxz →dxy ) transitions, respectively, of square-
2 −y 2
plxanar isomers. The band at 428 nm can be assigned to the A1g→1B1g
(dz 2 →dxy ) transition with its high intensity derived from activation by the
1
ligand-to-metal transition18–20
.
In the electronic absorption spectrum of Ni(L-O,S)2, bands at 690–800 nm
3
are assigned to the T1(F)→3T1(P) transition. It supports the presence of the
tetrahedral chromophore in Ni(L-O,S)2 (refs12–14).
The UV/Vis spectra of Ni(L-N,S)2 and Ni(L-O,S)2 show no temperature
dependence in the range 5–25 °C. It shoud be also noted that the spectra
exhibit only bands typical of square-planar Ni(L-N,S)2 or tetrahedral
Ni(L-O,S)2 chromophores.
Unfortunately after numerous attempts, we were not successful to obtain
single crystals of the complexes suitable for X-ray diffraction study.
CONCLUSION
Novel Zn(II), Co(II) and Ni(II) complexes with HL have been synthesized.
NMR, UV/Vis and IR spectra showed that the thiourea is a 1,5-O,S-ligand in
ZnL2, CoL2 and Ni(L-O,S)2. The Ni(L-O,S)2 complex is the first example of
a Ni(II) complex with RNHC(S)NHP(O)(OiPr)2 ligands, containing the
–RNHC(S)– group having a 1,5-O,S-coordination. The central metal ion is
in a tetrahedral environment. The Ni(II) cation of Ni(L-N,S)2 is in a square-
planar environment and the deprotonated thiourea group shows a 1,3-N,S-
coordination mode.
Two isomers with different coordinations of HL to Ni(II) and with dif-
ferent polyhedral structures are a novel uniqueness in Ni(II) coordination
chemistry with RNHC(S)NHP(X)(OiPr)2 (X = O, S).
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Zn(II), Co(II) and Ni(II) Complexes
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This work was supported by the Russian Science Support Foundation.
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