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

Article abstract of DOI:10.1080/15533170802255351

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 = CO3-- (carbonate), (2),2- - OC6H4CO2- (salicylate, Sal), (3),-O2CCH2CH2 CH(NH2)CO2- (glutamate, Glu), (4), -O2 CCH2CH2CO2- (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. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533170802255351

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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: 24 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, 38:5, 445-447
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 38:445–447, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533170802255351
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
derivative (1a), the desired product was not obtained from (1b).
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−2 (salicylate, Sal), (3),−O2CCH2CH2 CH(NH2)CO−2
−
(glutamate, Glu), (4), −O2 CCH2CH2CO−2 (succinicate, Suc), (5);
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, which might
be potentially useful in biomedicine and industry.[7] In addi-
tion to our previous work, this article presents the synthesis of
nickel-phophine complexes containing carbonate or carboxylate
groups at one site. The preparation of the carbonate and carboxy-
late complexes provides the opportunity to develop further the
chemistry of these systems.
SCHEME 1.
The carboxy late 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
the 31P-{ H} NMR data, selected IR data and melting points
1
RESULTS AND DISCUSSION
In order to investigate the reactivity of dichloro derivatives
of nickel(II) aminomethylphosphine complexes, the reactions
Received 23 May 2007; accepted 11 January 2008.
We would like to thank 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, Adana
01330, Turkey. E-mail: osmanser@cu.edu.tr
445

446
O. SERINDAG AND M. KELES
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
of these complexes (2)–(5). The reactions carried out with 1b tinct from the starting cyclohexyl substitued phosphine-nickel
resulted in unreacted starting compound.
complex was also indicative of novel carboxylate derivative
1
The 31P-{ H} NMR spectra of the complexes obtained complexes.
showed more shielded signals as compared to the dichloride
The visible electronic spectra of the complexes in
derivative (1a). Table 1 also shows the coordination shifts of the dichlomethane show only one absorption band in the range
complexes (2)–(5) along with the chemical shift of the free lig- of 438–470 nm. On comparision with the starting compound,
and. The coordination shift values of the complexes (ꢀ), which which has a absorption maximum , λmax, at 473 nm. A dis-
is defined as ꢀ = δ (complex- δ free ligand, vary depending tinct blue shift has been observed for each complex due to
on the metal and the ligand itself. The values of ꢀ have been coordination of oxygen. These bands are consistent with those
correlated for many metal phosphine complexes.[8−11] Thus de- reported for nickel-diphosphine complexes and they correspond
pending on the type of the phosphine ligand such as being mono to square-planar geometry[11]. The broad bands observed al-
dentate or chelating ligand giving various ring size, the chemi- most at the same wave length in the ultraviolet spectra of both
cal shifts of the compund could be estimated for a certain metal complexes and and the starting compound are assigned to the
1
complex.[12,13] In their solution 31P-{ H} NMR spectra, sali- electronic transitions of n-π∗ and to the π − π∗.
cylate complex (3) exhibited the highest chemical shift with a
Magnetic susceptibility measurements of the complexes
broad peak at 19.72 ppm. In fact, this singlet peak can be as- showed no paramagnetism, another indication of the square-
sumed as a doublet of doublets having two different phosphorus palnar geometry of the complexes.
atoms with a distinctly different chemical environment.[4,8−11]
Attempts to obtain and characterize phenyl substitued
The prepared complexes (2)–(5) were further characterized phosphine-nickel complexes having chelated carboxylates at
by their IR spectra which showed characteristic C=O symmetric one site were unsuccessful.The spectroscopic investigations of
streching bands in the range of 1640–1540 cm−1 whereas the the products showed starting dichloride derivative 1b.
asymmetric ones assigned in the range of 1410–1380 cm−1
,
(Table 1). The frequencey difference between symmetric and
asymmetric vibration of carboxylate group is given as ꢀν which
indicates bonding to metal center.
EXPERIMENTAL
Materials and Methods
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)
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.[15−16]
The separation value indicates the vibration mode of the co-
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.
ordinated carboxylate group and defined as ꢀν = νasym
−
νsym. The salyclate complex (3) presents an aromatic-H vi-
bration at 3090 cm−1. The mass spectra of the complexes
showed a characteristic peak of the Cy2PCH+2 ion at 211
due to the dcpam ligand and also a characteristic [M(dcpam)]
peak for Ni(dcpam)+2 at 510. Obtaining melting points dis-
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.

SYNTHESIS OF SOME NICKEL(II) DIPHOSPHINE COMPLEXES
447
and used without further purification. [NiCI2(dcpam)] and cinic acid addition (0.017 g, 0.143 mmol) the mixture was
[NiCI2(dppam)] were prepared by treating NiCI.26H2O with refluxed for 8h.On cooling the mixture was filtered through
the phosphines (Cy2PCH2)2NMe, dcpam and (Ph2PCH2)2NMe, Celite. The product was precipitated with diethyl ether to give
dppam, respectively, which were obtained by treating phos- a pale orange powder. Yield: 0.082 g (93.6 %, based on Ni).
phonium salts of the type [R2P(CH2OH)2]CI (R=Cy, Ph) with [Ni(suc)(Cy2PCH2)2NMe]: C, 53.40; H, 8.24; N, 2.01. Found:
methylamine in the presence of triethylamine as described in C, 53.8; H, 8.60; N: 2.35. M.p= 212 ◦C decomp. 31P-1H NMR:
the literature (5).
δ =9.08 ppm. IR: ν(C-H aliph.) 2929, 2850, 2788; ν(C=O)
1585 (asym), 1330 (sym); ν(CH2) 1445; ν(C-C) 1212; ν(C-
O) 1094; ν(Cyclohexyl) 1005; ν(N-CH3) 850 cm−1. Electronic
spectrum: λmax 458 nm.
Synthesis of Compounds
[Ni(CO3)(Cy2PCH2)2NMe] (2). Silver carbonate (0.066 g,
0.241 mmol) was added to a stirred solution of [NiCI2(dcpam)]
(1a) (0.08 g, 0.42 mmol) in dichloromethane (20 mL). The
mixture was refluxed for 8h. The solution was filtered through
Celite. A red solute was obtained on addition of diethyl ether.
Yield, 0.053 g (67.5 % based on Ni). Anal. cal. for [Ni(CO3)
(Cy2PCH2)2NMe]: C, 59.53; H, 9.42; N, 2.53. Found: C, 58.9;
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1
H, 9.01; N: 2.46. M.p = 213◦C decomp. 31P-{ H} NMR: δ =
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%) [Ni(dcpam)], 211 (89.6 %) [Cy2PCH2]. IR: ν(C-H aliph.)
2940, 2789; ν(C=O) 1540 (asym), 1360 (sym); ν(CH2) 1446;
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2.17. Found: C, 63.50; H, 8.76; N: 2.36. M.p = 225◦C decomp.
1
31P-{ H} NMR: δ = 19.72. Mass spectrum: m/z : 646; 646
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◦
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