Synthesis of some nickel(II) diphosphine complexes having coordinated carboxylates

Article abstract of DOI:10.1080/15533170802293238

Treatment of aminobis(methylphosphine) complexes of nickel(II) with carboxylic acids in the presence of silver(I) salts in dichloromethane gives the corresponding nickel(II) complexes of the type [NiA(P-P] where A = CO ₃- (carbonate), (2), 2 - OC₆H₄CO₂- (salicylate, Sal), (3), -O₂CCH₂CH₂CH(NH ₂)CO₂- (glutamate, Glu), (4), -O₂CCH ₂CH₂CO₂- (succinicate, Suc), (5); P-P = (Cy₂PCH₂)2NMe (dcpam), (Ph₂PCH₂)2NMe (dppam). The complexes have been characterized by spectroscopic techniques such as 31P-[1H] NMR, FT-IR, UV-Vis, and mass spectrometry.

Full text of DOI:10.1080/15533170802293238

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Synthesis of Some Nickel(II) Diphosphine Complexes
Having Coordinated Carboxylates
Osman Serindag a & Mustafa Keles a
a Department of Chemistry, Faculty of Science and Letters , University of Cukurova ,
Adana, Turkey
Published online: 05 Sep 2008.
To cite this article: Osman Serindag & Mustafa Keles (2008) Synthesis of Some Nickel(II) Diphosphine Complexes Having
Coordinated Carboxylates, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 38:7, 580-583
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 38:580–583, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533170802293238
Synthesis of Some Nickel(II) Diphosphine Complexes
Having Coordinated Carboxylates
Osman Serindag and Mustafa Keles
Department of Chemistry, Faculty of Science and Letters, University of Cukurova, Adana, Turkey
of nickel-phosphines with carbonate and carboxylic acids were
carried out. [NiCl2(dcpam)] (1a) or [NiCl2(dppam)] (1b) were
refluxed with Ag2CO3 in dichloromethane to give the carbonate
compound only in the case of (1a), as shown in Scheme 1. The
insoluble silver salt was filtered off and diethyl ether was added
to give a brownish-red, powdery sample of [Ni(CO3)(dcpam)]
(2). The diphenyl derivative (1b) gave an uncharacterized white
powder. Even with longer reaction times than cyclohexyl deriva-
tive (1a) the desired product was not obtained from (1b).
The carboxylate derivatives of the nickel-phosphines (3), (4),
and (5) were synthesized by treating the dichloride derivatives of
the Ni(II) phosphine complexes with the respective carboxylic
acids in the presence of silver(I) oxide (Scheme 2). The desired
products were obtained from the reaction of 1a in good yield and
characterized using spectroscopic techniques. Table 1 presents
Treatment of aminobis(methylphosphine) complexes of nickel
(II) with carboxylic acids in the presence of silver(I) salts in
dichloromethane gives the corresponding nickel(II) complexes
of the type [NiA(P-P] where A = CO−3 (carbonate), (2), 2-
−OC6H4CO− (salicylate, Sal), (3), −O2CCH2CH2CH(NH2)CO−2
(glutamate, 2Glu), (4), −O2CCH2CH2CO− (succinicate, Suc), (5);
2
P-P = (Cy2PCH2)2NMe (dcpam), (Ph2PCH2)2NMe (dppam). The
complexes have been characterized by spectroscopic techniques
1
such as 31P-{ H} NMR, FT-IR, UV-Vis, and mass spectrometry.
Keywords Phosphine, Nickel (II), Carboxylic Acids
INTRODUCTION
In view of the importance of phosphine complexes in
medicine and in industry, we were interested in the synthesis of
novel aminobis(methylphosphine) complexes of platinum group
metals.[1−4] The phoshine metal carbonate and carboxylate com-
plexes are useful starting compounds for the synthesis of M(0)
and M(II) complexes.[5,6] Although there have been many re-
ported studies on phosphine platinum or phospine palladium
complexes, a relatively limited number of nickel-phosphine
complexes and their chemistry have been reported that might
be potentially useful in biomedicine and industry.[7] In addi-
tion to our previous work, this article presents the synthesis of
nickel-phosphine complexes containing carbonate or carboxy-
late groups at one site. The preparation of the carbonate and
carboxylate complexes provides the opportunity to develop fur-
ther the chemistry of these systems.
1
the 31P-{ H} NMR data, selected IR data, and melting points
of these complexes (2)–(5). The reactions carried out with 1b
resulted in unreacted starting compound.
1
The 31P-{ H} NMR spectra of the complexes obtained
showed more shielded signals as compared to the dichloride
derivative (1a). Table 1 also shows the coordination shifts of the
complexes (2)–(5) along with the chemical shift of the free lig-
and. The coordination shift values of the complexes (ꢀ), which
is defined as ꢀ = δ (complex-δ) (free ligand), vary depending
on the metal and the ligand itself. The values of ꢀ have been
correlated for many metal phosphine complexes.[8−11] Thus,
depending on type of the phosphine ligand such as mono den-
tate or chelating ligand giving various ring size, the chemical
shifts of the compound could be estimated for a certain metal
1
complex.[12,13] In their solution 31P-{ H} NMR spectra, sali-
cylate complex (3) exhibited the highest chemical shift with a
broad peak at 19.72 ppm. In fact this singlet peak can be as-
sumed as a doublet of doublets having two different phosphorus
atoms with a distinctly different chemical environment.[4,8−11]
The prepared complexes (2)–(5) were further characterized
by their IR spectra, which showed characteristic C O symmet-
ric streching bands in the range of 1640–1540 cm−1, whereas
the asymmetric ones assigned in the range of 1410–1380 cm−1
(Table 1). The frequence difference between symmetric and
asymmetric vibration of carboxylate group is given as ꢀν, which
indicates bonding to metal centre.
RESULTS AND DISCUSSION
In order to investigate the reactivity of dichloro derivatives
of nickel(II) aminomethylphosphine complexes, the reactions
Received 3 August 2007; accepted 1 April 2008.
We are grateful to the Research Fund of C¸ ukurova University for
support to this project and the University of Leicester, UK, for providing
some of the spectroscopic measurements.
Address correspondence to Osman Serindag, Department of Chem-
istry, Faculty of Science and Letters, University of Cukurova, 01330
Adana, Turkey. E-mail: osmanser@cu.edu.tr
580

SYNTHESIS OF NICKEL(II) DIPHOSPHINE COMPLEXES
581
exhibit this band at 1640, 1590, and 1585 cm−1, respectively.
The separation values of the asymmetric and the symmetric
bands, ꢀν, are observed in the range of 185–230 cm−1, which
is in agreement with the values reported in the literature.[14,15]
The separation value indicates the vibration mode of the coor-
Cy2
P
O
O
Ni
O
CH2Cl2
reflux
P
[NiCl2(dcpam)]
+
+
Ag2CO3
Cy2
N
H3C
(2)
(1a)
dinated carboxylate group and defined as ꢀν = νasym − νsym
.
The salyclate complex (3) presents an aromatic-H vibration at
3090 cm−1. The mass spectra of the complexes showed a charac-
teristic peak of the Cy2PCH2+ ion at 211 due to the dcpam ligand
and also a characteristic [M(dcpam)] peak for Ni(dcpam)+2 at
510. Obtaining melting points distinct from the starting cyclo-
hexyl substituted phosphine-nickel complex was also indicative
of novel carboxylate derivative complexes.
CH2Cl2
reflux
[NiCl2(dppam)]
Ag2CO3
product was not isolated
(1b)
Scheme 1.
The relevant IR bands of the carboxylate complexes (3),
(4), and (5) were compared with that of silver(I) acetate,
Ag(OCOCH3), for which the asymmetric C O vibration oc-
curs at 1574 cm−1, whereas the complexes (3), (4), and (5)
The visible electronic spectra of the complexes in
dichlomethane show only one absorption band in the range of
438–470 nm. On comparison with the starting compound, which
Cy2
P
O
HO
Ag2O
Ni
HO
O
P
(2)
+
O
Cy2
reflux
N
O
H3C
(3)
O
Cy2
P
NH2
O
O
O
O
Ag2O/CH2Cl2
reflux
Ni
(2)
HO
OH
+
P
N
Cy2
NH2
H3C
(4)
Cy2
P
O
O
O
O
Ni
Ag2O/CH2Cl2
reflux
P
Cy2
O
N
(2)
HO
OH
+
H3C
O
(5)
Scheme 2.
TABLE 1
1
31P-{ H} NMR (in ppm), IR (in cm−1), UV-Vis (in nm) spectra and melting points of the complexes (2)–(5)
1
31P-{ H} NMR
IR (C O, cm−1
)
UV-Vis
λmax
M.p.
(◦C)
Compound
δ (ppm)
ꢀa
asym
sym
ꢀνb
dcpam
−16.15
16.8
17.8
19.7
16.4
60
[NiCl2(dcpam)]
[Ni(CO3)(dcpam)] (2)
[Ni(Sal)(dcpam)] (3)
[Ni(Glu)(dcpam)] (4)
[Ni(Suc)(dcpam)] (5)
Ag(OAc)
32.95
33.65
35.85
32.55
25.23
473
470
438
468
458
251
213
225
250
212
1540
1640
1590
1585
1574
1355
1410
1380
1380
1338
185
230
210
205
236
9.08

582
O. SERINDAG AND M. KELES
has an absorption maximum, λmax, at 473 nm. A distinct blue [Cy2PCH2]. IR: ν(C H aliph.) 2940, 2789; ν(C O) 1540
shift has been observed for each complex due to coordination (asym), 1360 (sym); ν(CH2) 1446; ν(C C) 1206; ν(C O)
of oxygen. These bands are consistent with those reported for 1095; ν(Cyclohexyl) 1001, ν(N CH3) 847 cm−1. Electronic
nickel-diphosphine complexes and they correspond to square- spectrum: λmax 470 nm.
planar geometry.[11] The broad bands observed almost at the
same wavelength in the ultraviolet spectra of both complexes [Ni(sal){(Cy2PCH2)2NMe}] (3). Ag2O (0.12 g, 0.72 mmol)
and the starting compound are assigned to the electronic transi- was added to a stirred solution of [NiCI2(dcpam)] (0.04 g, 0.068
tions of n-π∗ and to the π-π∗.
mmol) in dichloromethane (20 mL). After addition of salicylic
Magnetic susceptibility measurements of the complexes acid (0.026 g, 0.0144 mmol) the mixture was refluxed for 8 h
showed no paramagnetism, another indication of the square- and filtered through Celite. A yellow product was precipitated
planar geometry of the complexes.
with diethyl ether, filtered, and dried. Yield: 0.026 g (58.5%
Attempts to obtain and characterize phenyl-substituted based on Ni). Anal. Calcd. for [Ni(sal)(dcpam)]: C, 63.20; H,
phosphine-nickel complexes having chelated carboxylates at 8.56; N, 2.17. Found: C, 63.50; H, 8.76; N: 2.36. M.p = 225◦C
1
one site were unsuccessful. The spectroscopic investigations decomp. 31P-{ H} NMR: δ = 19.72. Mass spectrum: m/z: 646;
of the products showed starting dichloride derivative 1b.
646 (100%)[M+]; 569 (1.5%) [M-Ph]; 510 (8.2%) [Ni(dcpam)];
211 (61.9%) [Cy2PCH2]. IR: ν(ar-H) 3090; ν(C H aliph.)
2990, 2850; ν(C O) 1640 (asym), 1410 (sym); ν(CH2) 1445;
ν(C C) 1212; ν(C O) 1097; ν(Cyclohexyl) 1007, ν(N CH3)
852 cm−1. Electronic spectrum: λmax 438 nm.
EXPERIMENTAL
Materials and Methods
The melting points of the prepared complexes were recorded
on a Gallenkamp melting point apparatus. The mass spectra
of the compounds were obtained by the FAB technique on a
Kratos Concept Double Focusing Sector Mass Spectrometer.
The 31P NMR spectra were recorded in dichloromethane on a
JEOL JMM-FX60 operating at 24.15 MHz with H3PO4 in D2O
as external reference The IR spectra were recorded on a Perkin-
Elmer 580 FTIR spectrophotometer as KBr discs. Magnetic
susceptibility measurements were carried out on a Sherwood
Scientific Magnetic Susceptibility Balance at room temperature.
The solvents dichloromethane and diethyl ether were dried prior
to use by using sodiumwire/benzophenone.
Preparations were carried out under a dry, oxygen-free ni-
trogen atmosphere using standart Schlenk techniques. Ag2O
and Ag2CO3 were purchased from Aldrich Chemicals Inc.
and used without further purification. [NiCI2(dcpam)] and
[NiCI2(dppam)] were prepared by treating NiCI2·6H2O with
the phosphines (Cy2PCH2)2NMe, dcpam and (Ph2PCH2)2NMe,
dppam, respectively, which were obtained by treating phos-
phonium salts of the type [R2P(CH2OH)2]CI (R=Cy, Ph) with
methylamine in the presence of triethylamine as described in
the literature.[5]
[Ni(Glu){(Cy2PCH2)2NMe}](4). Ag2O (0.25 g, 1.13
mmol) was added to a stirred solution of [NiCI2(dcpam)] (0.05
g, 0.086 mmol) in dichloromethane (20 mL). After addition of
glutamic acid (0.015 g, 0.10 mmol) the mixture was refluxed
for 8 h and then filtered through Celite. The solvent volume
was reduced to 5 mL and the product was then precipitated with
diethyl ether, filtered, and dried. Yield: 0.45 g (80.0% based on
Ni). [Ni(Glu){(Cy2PCH2)2NMe}]: C, 58.60; H, 8.92; N, 2.14.
Found: C, 58.20; H, 8.97; N: 2.41. M.p. = 250◦C decomp.
1
31P-{ H} NMR: δ = 16.4 ppm. Mass spectrum: m/z: 654;
654 (2.2%) [M+]; 580 (3.2%) [M-OCOCH2NH2]; 510 (6.2%)
[Ni(dcpam)]; 211 (100%) [Cy2PCH2]. IR: ν(N H) 3450–3370
ν(C H aliph.) 2931, 2854, 2782; ν(C O) 1590 (asym), 1380
(sym); ν(CH2) 1446; ν(C C) 1211, 1174; ν(Cyclohexyl) 1009;
ν(N CH3) 854 cm−1. Electronic spectrum: λmax 468 nm.
[Ni(Suc){(Cy2PCH2)2NMe}] (5). Ag2O (0.16 g, 1.07
mmol) was added to a stirred solution of [NiCI2(dcpam)] (0.08
g, 0.14 mmol) in dichloromethane (20 mL). Following suc-
cinic acid addition (0.017 g, 0.143 mmol) the mixture was re-
fluxed for 8 h. On cooling the mixture was filtered through
Celite. The product was precipitated with diethyl ether to
give a pale orange powder. Yield: 0.082 g (93.6%, based on
Ni). [Ni(suc){(Cy2PCH2)2NMe}]: C, 53.40; H, 8.24; N, 2.01.
Found: C, 53.8; H, 8.60; N: 2.35. M.p. = 212◦C decomp.
Synthesis of Compounds
[Ni(CO3){(Cy2PCH2)2NMe}] (2). Silver carbonate (0.066 31P-{ H} NMR: δ = 9.08 ppm. IR: ν(C H aliph.) 2929,
g, 0.241 mmol) was added to a stirred solution of 2850, 2788; ν(C O) 1585 (asym), 1330 (sym); ν(CH2) 1445;
[NiCI2(dcpam)] (1a) (0.08 g, 0.42 mmol) in dichloromethane ν(C C) 1212; ν(C O) 1094; ν(Cyclohexyl) 1005; ν(N CH3)
(20 mL). The mixture was refluxed for 8 h. The solution was 850 cm−1. Electronic spectrum: λmax 458 nm.
filtered through Celite. A red solute was obtained on addition
1
of diethyl ether. Yield, 0.053 g (67.5% based on Ni). Anal.
Calcd. for [Ni(CO3){(Cy2PCH2)2NMe}]: C, 59.53; H, 9.42; N,
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SYNTHESIS OF NICKEL(II) DIPHOSPHINE COMPLEXES
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