Facile Ni(II)/Ketoxime-Mediated Conversion of Organonitriles into Imidoylamidine Ligands. Synthesis of Imidoylamidines and Acetyl Amides

Article abstract of DOI:10.1021/ic0349813

Treatment of alkyl nitriles with NiX₂·6H₂O (X = Cl, NO₃) and 2-propanone oxime, followed by (X = Cl) addition of [i-Pr₄N](NO₃) for precipitation of the product, resulted in the formation of amidinium nitrates [RC(=NH₂)NH ₂]-(NO₃) (R = Me, Et, n-Pr). The reaction went to another direction with NiX₂·2H₂O, i.e., the reaction between neat RCN (R = Me, Et, n-Pr, i-Pr, n-Bu, CH₂Cl, CH ₂C₆H₄OMe-p) and NiCl₂·2H ₂O/2-propanone oxime (other ketoximes can also be used) gave the (imidoylamidine)Ni(II) complexes [Ni{N(H)=C(R)NHC(R=NH}₂] ²⁺ (1²⁺-7²⁺). The latter were isolated in good yields (65-91%) as the bis-chloride salts 1·Cl₂-6· Cl₂ and the mixed salt 7·(Cl)(p-MeOC₆H ₄-CH₂CO₂). Remarkably, the latter transformation does not proceed at all if NiCl₂·2H ₂O or the ketoxime are taken alone. Liberation of imidoylamidines was performed for one alkyl-containing complex [2·Cl₂] and one benzyl-containing complex [7·(Cl)(p-MeOC₆H ₄CH₂CO₂)], by (i) addition of HBF ₄·Et₂O to the acetonitrile solution of the complexes to yield [N(H)=C(R)NHC(R)=NH]·2HBF₄ (R = Et 8 and R = CH₂C₆H₄OMe-p 9) or (ii) substitution for ethanediamine (en) with following precipitation of the complex [Ni(en) ₃]Cl₂ with formation of free N(H)=C(R)NHC(R)=NH (R = Et 10 and R = CH₂C₆H₄OMe-p 11). In contrast to the liberation in nonaqueous media, treatment of 2·Cl₂ and 7· (Cl)(p-MeOC₆H₄CH₂CO₂)with Na₂EDTA·2H₂O in water-methanol solutions led to substitution and hydrolysis to furnish the acyl amides {EtC(=O)}₂NH (12) and {p-MeOC₆H₄CH₂C(=O)}₂NH (13). Alternatively, 12 and 13 were obtained by hydrolysis of 10 and 11 in water at pH ca. 8.5. It was shown that the oxime complexes trans-[NiCl ₂-(C₄H₈C=NOH)₄] (14) or cis-[Ni(O,O-NO₃)₂(C₄H₈C=NOH) ₂] (15) can be intermediates in the formation of amidines and imidoylamidines. The sequence of the Ni(II)/oxime mediated formation of (imidoylamidine)Ni complexes and liberation (or hydrolytic liberation) of the ligands opens up a novel, facile and environmentally benign route to imidoylamidines and acyl amides.

Full text of DOI:10.1021/ic0349813

Inorg. Chem. 2003, 42, 7239−7248
Facile Ni(II)/Ketoxime-Mediated Conversion of Organonitriles into
Imidoylamidine Ligands. Synthesis of Imidoylamidines and Acetyl
Amides
,†
Maximilian N. Kopylovich,† Armando J. L. Pombeiro,* Andreas Fischer,‡ Lars Kloo,‡ and
,§
Vadim Yu. Kukushkin*
Centro de Qu´ımica Estrutural, Complexo I, Instituto Superior Te´cnico, AV. RoVisco Pais,
1049-001 Lisbon, Portugal, Inorganic Chemistry, Royal Institute of Technology,
100 44 Stockholm, Sweden, and Department of Chemistry, St. Petersburg State UniVersity,
198504 Stary Petergof, Russian Federation
Received August 18, 2003
Treatment of alkyl nitriles with NiX ‚6H O (X ) Cl, NO ) and 2-propanone oxime, followed by (X ) Cl) addition
2
2
3
of [i-Pr4N](NO ) for precipitation of the product, resulted in the formation of amidinium nitrates [RC(dNH )NH ]-
3
2
2
(NO ) (R ) Me, Et, n-Pr). The reaction went to another direction with NiX ‚2H O, i.e., the reaction between neat
3
2
2
RCN (R ) Me, Et, n-Pr, i-Pr, n-Bu, CH Cl, CH C H OMe-p) and NiCl2‚2H O/2-propanone oxime (other ketoximes
2
2
6
4
2
can also be used) gave the (imidoylamidine)Ni(II) complexes [Ni{N(H)dC(R)NHC(R)dNH}2]2+ (12+−72+). The latter
were isolated in good yields (65−91%) as the bis-chloride salts 1‚Cl2−6‚Cl2 and the mixed salt 7‚(Cl)(p-MeOC H -
6
4
CH CO ). Remarkably, the latter transformation does not proceed at all if NiCl2‚2H O or the ketoxime are taken
2
2
2
alone. Liberation of imidoylamidines was performed for one alkyl-containing complex [2‚Cl2] and one benzyl-containing
complex [7‚(Cl)(p-MeOC H CH CO )], by (i) addition of HBF ‚Et2O to the acetonitrile solution of the complexes to
6
4
2
2
4
yield [N(H)dC(R)NHC(R)dNH]‚2HBF (R ) Et 8 and R ) CH C H OMe-p 9) or (ii) substitution for ethanediamine
4
2 6 4
(en) with following precipitation of the complex [Ni(en)3]Cl2 with formation of free N(H)dC(R)NHC(R)dNH (R ) Et
10 and R ) CH C H OMe-p 11). In contrast to the liberation in nonaqueous media, treatment of 2‚Cl2 and 7‚
2
6 4
(Cl)(p-MeOC H CH CO ) with Na2EDTA‚2H O in water−methanol solutions led to substitution and hydrolysis to
6
4
2
2
2
furnish the acyl amides {EtC(dO)}2NH (12) and {p-MeOC H CH C(dO)}2NH (13). Alternatively, 12 and 13 were
6
4
2
obtained by hydrolysis of 10 and 11 in water at pH ca. 8.5. It was shown that the oxime complexes trans-[NiCl2-
(C H CdNOH)4] (14) or cis-[Ni(O,O-NO ) (C H CdNOH)2] (15) can be intermediates in the formation of amidines
4
8
3 2
4 8
and imidoylamidines. The sequence of the Ni(II)/oxime mediated formation of (imidoylamidine)Ni complexes and
liberation (or hydrolytic liberation) of the ligands opens up a novel, facile and environmentally benign route to
imidoylamidines and acyl amides.
Introduction
favorable giving versatile imino compounds with new C-N,
C-O, C-C, C-P, and C-S bonds. Despite that some of
the imino complexes are important by themselves, e.g., as
antitumor agents,3 it is rather likely that the most promising
The activation of organonitriles by metal centers toward
nucleophilic or electrophilic additions or cycloaddition is a
frontier area of studies targeted on the exploration of
synthetic transformations of RCN species, and this subject
has recently been reviewed by two of us1 and previously by
others.2 Literature up to date clearly shows that in the vast
majority of cases coordination of organonitriles to metal
centers makes their reactions with nucleophilic reagents
(1) (a) Kukushkin, V. Y.; Pombeiro, A. J. L. Chem. ReV. 2002, 102, 1771
and references therein. (b) Pombeiro, A. J. L.; Kukushkin, V. Y. In
ComprehensiVe Coordination Chemistry, 2nd Edition, Elsevier: New
York; Vol. 1, in press.
(2) (a) Michelin, R. A.; Mozzon, M.; Bertani, R. Coord. Chem. ReV. 1996,
147, 299. (b) Boyd, G. V. The Chemistry of Amidines and Imidates;
Patai, S., Rappoport, Z., Eds.; Wiley: Chichester, 1991; Vol. 2, p
339.
(3) For recent examples see: (a) Natile, G.; Coluccia, M. Coord. Chem.
ReV. 2001, 216-217, 383. (b) Liu, Y.; Pacifico, C.; Natile, G.; Sletten,
E. Angew. Chem., Int. Ed. 2001, 40, 1226. (c) Liu, Y.; Sivo, M. F.;
Natile, G.; Sletten, E. Met.-Based Drugs 2000, 7, 169. (d) Leng, M.;
* Authors to whom correspondence should be addressed. E-mail:
pombeiro@ist.utl.pt (A.J.L.P.) and kukushkin@VK2100.spb.edu (V.Yu.K.).
† Instituto Superior Te´cnico.
‡ Royal Institute of Technology.
§ St. Petersburg State University.
10.1021/ic0349813 CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/02/2003
Inorganic Chemistry, Vol. 42, No. 22, 2003 7239

Kopylovich et al.
subdirection of the research on organonitriles is the synthesis
of organic species involving metal compounds.
As far as the formation of C-N bonds via nucleophilic
addition to metal-bound nitriles is concerned, the known
types of reactions include the coupling between ligated
nitriles and primary and secondary amines giving amidines,
hydrazines leading to amidrazones, heterocycles resulting in
their iminoacylation,1 and addition of imines1 and sulfimides4
to yield 1,3-diazadienes. A rather small, albeit of practical
importance, fraction of these results is relevant to metal-
mediated or metal-catalyzed amidation5,6 or hydrolytic ami-
dation of nitriles.7
In particular, within the framework of our project on metal-
mediated nitrile-oxime coupling,8-10 an unusual transforma-
tion of sterically unhindered alkyl nitriles RCN which can
be easily converted to the appropriate amidines (I, Figure
1) and carboxylic acids in the presence of Co(II)/ketoxime
systems has recently been found.11 This route opens up a
good stoichiometric access to amidines which otherwise are
conventionally obtained by the hazardous two-step Pinner
synthesis.1 Moreover, further development of the systems,
comprising a metal salt and a ketoxime, have shown that
Figure 1.
when Zn(II) instead of Co(II) is employed, the transformation
of RCN is metal-catalyzed and gives either carboxamides
(II, Figure 1) or amidines (both types of compounds of
superior industrial and/or pharmacological significance),
depending on the presence or absence of water in the
system.12
Our interest in further exploration of the metal/ketoxime
systems for C-N bond formation has recently been sparked
by the report of the reaction between acetonitrile and the
dinuclear nickel(II) complex [Ni2(µ-OH)2(tpa)2](ClO4)2 [where
tpa is the tetradentate tris(2-pyridylmethyl)amine] giving a
novel imidoylamidine (III, Figure 1) compound [Ni{HNC-
(Me)NC(Me)NH}2],13 in which the ligand III (R ) Me) is
in a deprotonated form. The mechanism of this remarkable
conversion has not yet been established, but the authors13
suggested that MeCN, activated by the Ni(II) center, converts
to an (amidine)Ni(II) intermediate followed by the known14,15
metal-templated condensation of two amidines (and elimina-
tion of NH3) to give the imidoylamidine complex.
Inspired by these observations, we attempted to apply a
system of high simplicity, i.e., Ni(II)/ketoxime, to the
conversion of organonitriles to imidoylamidines. The chem-
istry of the latter compounds is very little developed despite
the well-established interest of amidines as synthons for
further transformations16 as well as in biology and medicine.17
We anticipated a dual benefit for the present work: (i) to
get an entry into the almost unexplored field of coordination
chemistry of imidoylamidines, and (ii), in organic chemistry,
to find an easy and environmentally benign access to
imidolylamidines and to acetyl amides (IV, Figure 1), the
latter via hydrolysis of the former. In the course of these
studies, we observed a novel Ni(II)/ketoxime-mediated
transformation of RCN to accomplish new (imidoylamidine)-
Ni(II) complexes from which the ligands can be liberated
and, if necessary, converted to acetyl amides by hydrolysis.
Locker, D.; Giraud-Panis, M.-J.; Schwartz, A.; Intini, F. P.; Natile,
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M.; Natile, G.; Sletten, E. Met.-Based Drugs 2000, 7, 23. (f) Intini, P.
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597, 2000; Chem. Abstr. 2000, 132, 102832.
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D. C.; Xue, S. Tetrahedron Lett. 1995, 36, 8761. Towle, M. J.; Lee,
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Cancer Res. 1993, 53, 2553.
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J. H.; Spaziano, V. T.; Balasubramanian, T. M.; Liu, G. K.; Kinsley,
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R.; Wagner, G.; Pombeiro, A. J. L. Inorg. Chem. 1998, 37, 6511.
Kukushkin, V. Y.; Pakhomova, T. B.; Bokach, N. A.; Wagner, G.;
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2000, 39, 216. Wagner, G.; Pakhomova, T. B.; Bokach, N. A.; Frau´sto
da Silva, J. J. R.; Vicente, J.; Pombeiro, A. J. L.; Kukushkin, V. Y.
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J. J. R.; Pombeiro, A. J. L. Inorg. Chem. 2002, 41, 4798.
(13) Kryatov, S. V.; Nazarenko, A. Y.; Smith, M. B.; Rybak-Akimova, E.
V. Chem. Commun. 2001, 1174.
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(9) Ferreira, C. M. P.; Guedes da Silva, M. F. C.; Frau´sto da Silva, J. J.
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V.; Wagner, G.; Frau´sto da Silva, J. J. R.; Pombeiro, A. J. L. J. Chem.
Soc., Dalton Trans. 1999, 3047. Kukushkin, V. Y.; Ilichev, I. V.;
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Soc., Perkin Trans. 1 2001, 1569.
7240 Inorganic Chemistry, Vol. 42, No. 22, 2003

ConWersion of Organonitriles into Imidoylamidine Ligands
Scheme 1
In this work, all these results along with structural studies
of the imidoylamidine nickel compounds and of possible
oxime intermediate complexes are reported.
fragmentation/isotopic patterns in FAB+-MS; (ii) by IR and
1H and 13C{1H} NMR spectroscopies [in the IR spectra of
all compounds there are characteristic stretches of ν(NH) in
the range 3100-3300 cm-1, strong δ(NH) peaks at ca. 1550
cm-1, and also strong ν(CdN) vibrations at ca. 1600 cm-1;
in the NMR spectra, the chemical shifts for the peaks are
close (within 0.01-0.15 ppm in the 1H and 1-4 ppm in the
13C{1H} NMR spectra) to those observed for the correspond-
ing amidinium nitrates]; and (iii) by X-ray crystallographic
studies for six complexes indicated in Scheme 1 in their
biscationic [4‚Cl2, 5‚Cl2, 7‚(p-MeOC6H4CH2CO2)2‚MeOH]
and deprotonated monocationic forms ([2 - H]Cl, [3 - H]-
Cl, [6 - H]Cl); the latter compounds formed upon slow
crystallization of 2‚Cl2, 3‚Cl2, and 6‚Cl2, correspondingly,
from aqueous solutions (a water-acetone solution for 2‚Cl2).
A view of the cation 72+, as a representative of these groups
of complexes, is given in Figure 2, and crystallographic data
for all six complexes are summarized in Table 1. The study
Results and Discussion
We have recently reported an unusual reaction between a
nitrile and an oxime, mediated by a Co(II) center, providing
a facile conversion of an alkyl nitrile, RCN, to the appropriate
amidine, RC(dNH)NH2, and carboxylic acid, RC(dO)OH.11
This reaction has now been extended to a Ni(II)/oxime
system, and it has been observed that treatment of alkyl
nitriles with Ni(NO3)2‚6H2O or NiCl2‚6H2O, in the presence
of 2-propanone oxime, followed by, in the latter case,
addition of isopropylammonium nitrate for precipitation of
the product, under the same experimental conditions (50 °C
for 8 h) as for the Co(II)/oxime system, results in the
formation of amidinium nitrates [RC(dNH2)NH2](NO3) [R
) Me, Et, n-Pr] (Scheme 1, route A) isolated in 60-80%
yields. All these nitrates were identified by comparison of
their melting points and IR and NMR spectra with those of
genuine samples. The former product was additionally
characterized by comparison of the space group and crystal
lattice parameters with those previously found for
[MeC(dNH2)NH2](NO3).11
When the less hydrated NiCl2‚2H2O was employed, the
Ni(II)/oxime/nitrile system opened a new type of reaction.
Thus, the reaction between neat RCN (R ) Me, Et, n-Pr,
i-Pr, n-Bu, CH2Cl, CH2C6H4OMe-p) and NiCl2‚2H2O/2-
propanone oxime (other ketoximes, e.g., 2-butanone or
cyclopentanone oximes, can also be used) proceeds under
reflux conditions (R ) Me, Et), at room temperature for R
) CH2Cl or at 100 °C (for the other nitriles) for 24 h to
give the (imidoylamidine)Ni(II) complexes [Ni{N(H)dC(R)-
NHC(R)dNH}2]2+ (12+-72+, Scheme 1, route B). The latter
were isolated in good yields (65-91%) as the bis-chloride
salts 1‚Cl2-6‚Cl2 and the mixed salt 7‚(Cl)(p-MeOC6H4CH2-
CO2). Remarkably, the above reactions do not proceed at
all if the nickel(II) salt or Me2CdNOH is taken alone; the
process is efficient when the molar ratio NiCl2‚2H2O:2-
propanone oxime is 1:4. However, with less oxime, e.g., a
ratio of 1:2, a significant retardation of the reaction rate and
decrease of yield (to ca. 15%) are observed.
-
also revealed the formation of the p-MeOC6H4CO2 anion
(Figure 3) which obviously originates from the two-step
hydrolysis of the appropriate nitrile (see Final Remarks).
Inspection of the X-ray data along with the available
literature data13,14 shows that the N-C bond order in the Ni-
(H)NdC and C-N-C moieties does not depend on the
degree of deprotonation. Indeed, the CdN bond is in the
range 1.282(3)-1.294(3) Å for the bis-cationic 4‚Cl2, 5‚Cl2,
and 7‚(p-MeOC6H4CH2CO2)2‚MeOH complexes, 1.277(4)-
1.304(4) Å for the monocationic complexes [2 - H]Cl,
Figure 2. The complex 72+. Thermal ellipsoids represent a 70%
probability. H atoms omitted. Only the crystallographically independent
atoms are labeled. Selected bond lengths: Ni-N(1) 1.861(2), N(1)-C(1)
1.291(4), C(1)-N(2) 1.357(4), N(2)-C(10) 1.374(4), C(10)-N(3) 1.282-
(3), N(3)-Ni 1.853(3) Å.
The (imidoylamidine)Ni(II) complexes were characterized
(i) by satisfactory C, H, N elemental analyses and expected
Inorganic Chemistry, Vol. 42, No. 22, 2003 7241

Kopylovich et al.
7242 Inorganic Chemistry, Vol. 42, No. 22, 2003

ConWersion of Organonitriles into Imidoylamidine Ligands
20
known compound [Ni(en)3]Cl2 (Scheme 2), separation of
the solid by filtration, and evaporation of the filtrate.
Hydrolytic Liberation of Acyl Amides. We have also
studied the reaction between the (imidoylamidine)Ni(II)
complexes and 1 equiv of the disodium EDTA salt in
aqueous methanolic solution, illustrated also for one alkyl-
containing complex [2‚Cl2, R ) Et] and one benzyl-
containing complex [7‚(Cl)(p-MeOC6H4CH2CO2), R )
CH2C6H4OMe], followed by extraction of the organic mate-
rial from the water-methanol phase with diethyl ether. In
contrast to the liberation with HBF4/MeCN, the reaction with
Na2EDTA furnishes the amides, i.e., {RC(dO)}2NH (12, 13),
in ca. 70% yield, which are derived from hydrolysis of the
initially formed free imidoylamidines as proved by the
hydrolysis of {RC(dNH)}2NH (R ) Et, p-CH2C6H4OMe)
in water-methanol (1:1, v/v) media at pH ca. 8.5 (Scheme
2). The dipropionamide {EtC(dO)}2NH (12) was identified
by comparison of its melting point and IR spectrum with
those given in the literature,21-23 and its crystal structure was
determined by X-ray crystallography (Figure 4), while the
other amide (13) was characterized by conventional methods
(see Experimental Section).
Figure 3. The unit cell of 7‚(p-MeOC6H4CH2CO2)2‚MeOH in a view along
the crystallographic a-axis.
The acetyl amides {RC(dO)}2NH exhibit a biological
activity24 and have previously been used as agents for
molecular recognition (host-guest chemistry)25 and synthons
for further organic synthesis.26 The conventional synthesis
of these compounds involves acylation of the corresponding
carboxamides, RC(dO)NH2, with the acetyl chlorides RC-
(dO)Cl or interaction of the amides with the appropriate
lithium alkyls followed by treatment with RC(dO)Cl.21,26
The observed sequence of the Ni(II)/oxime-mediated reaction
and EDTA/H2O substitution/hydrolysis suggests an alterna-
tive and more environmentally friendly route to this class
of organic compounds.
Trapping and Characterization of Ketoxime Plausible
Intermediates. When the nickel salt NiCl2‚2H2O or Ni-
(NO3)2‚6H2O was dissolved in acetonitrile in the presence
of 4 equiv of C4H8CdNOH, subsequent evaporation of the
solvent to dryness in a vacuum at 20-25 °C and careful
washing with diethyl ether, as well as drying in a vacuum,
led to the isolation of the stable blue-colored oxime nickel-
(II) complex trans-[NiCl2(C4H8CdNOH)4] (14) or cis-[Ni-
(O,O-NO3)2(C4H8CdNOH)2] (15). These oxime complexes
were prepared by independent syntheses via heating the
appropriate nickel salts with 4 or 2 equiv, respectively, of
the oxime in acetone (see Experimental Section); the latter
complex is also formed when 10 equiv of the oxime is used.
These complexes gave satisfactory C, H, and N elemental
analyses and expected fragmentation/isotopic patterns in the
[3 - H]Cl, and [6 - H]Cl, 1.282(6)-1.285(6) Å for the
previously characterized complex [C8H17.5N6Ni1.5+]Cl1.5‚
3H2O,14 and 1.296(3) Å for the fully deprotonated [2 - 2H].13
Concurrently, the C-N bond in the C-N-C functionality
lies between 1.357(4) and 1.374(4) Å for the biscationic
complexes, 1.346(5) and 1.374(4) Å for the monocationic
[2 - H]Cl, [3 - H]Cl, and [6 - H]Cl, and 1.362(5) and
1.367(5) Å for [C8H17.5N6Ni1.5+]Cl1.5‚3H2O,14 and in the range
1.353(3)-1.360(3) Å for the neutral compound.13 Moreover,
the NdC and N-C bond distances perfectly agree with the
typical double and single NC bonds and all these observations
favor the lack of significant electron delocalization within
the chelate ring.
Liberation of Imidoylamidines. Known methods for the
preparation of imidoylamidines RC(dNH)NHCR1(dNH)
include a reaction between the first [i.e., imino ester RC(d
NH)OR2] and the second [i.e., amidine R1C(dNH)NH2]
products of the Pinner synthesis (the reaction proceeds at
25-35 °C for 2 days in the presence of NaOMe18), or,
alternatively, imidoylamidines can be obtained by treating
1,2,4-dithiazolium salts with RNH2, optionally in the pres-
ence of an oxidizing agent.19 In our case, the liberation of
the corresponding ligand (imidoylamidine) was exemplified
for one alkyl-containing complex [2‚Cl2, R ) Et] and one
benzyl-containing complex [7‚(Cl)(p-MeOC6H4CH2CO2), R
) CH2C6H4OMe], by (i) addition of HBF4‚Et2O to the
acetonitrile solution of the corresponding complex (Scheme
2; the liberated imidoylamidine is conditionally presented
in the parent tautomeric form) or (ii) substitution for
ethanediamine (en) with following precipitation of the well-
(20) Ihara, Y.; Toda, R. Thermochim. Acta 1994, 237, 167. Evans, J.;
Levason, W.; Perry, R. J. J. Chem. Soc., Dalton Trans. 1990, 3691.
De, G.; Biswas, P. K.; Chaudhuri, N. R. Bull. Chem. Soc. Jpn. 1983,
56, 3145.
(21) Reutzel, S. M.; Etter, M. C. J. Phys. Org. Chem. 1992, 5, 44.
(22) Noe, E. A.; Raban, M. J. Am. Chem. Soc. 1975, 97, 581.
(23) Kuroda, Y.; Machida, K.; Uno, T. Spectrochim. Acta A 1974, 30, 47.
(24) Krohn, K.; Franke, C.; Jones, P. G. Liebigs Ann. Chem. 1992, 789.
(25) Etter, M. C.; Reutzel, S. M. J. Am. Chem. Soc. 1991, 113, 2586.
(26) Richter, R.; Temme, G. H. J. Org. Chem. 1981, 46, 3015. Flitsch,
W.; Pandl, K.; Russkamp, P. Liebigs Ann. Chem. 1983, 529.
(18) Oto, K.; Ichikawa, E. Patent Japan 73 03,811, 1973; Chem. Abstr.
1973, 79, 18443.
(19) Liebscher, J.; Knoll, A.; Berger, A.; Krenzke, A. Patent East Ger.
DD 219,479, 1985; Chem. Abstr. 1985, 103, 195834.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7243

Kopylovich et al.
Scheme 2
FAB mass spectra; they were also characterized by IR
spectroscopy as well as by X-ray diffraction studies (Figures
5 and 6). It is noteworthy to mention that the structures of
14 and 15 are rare examples of nickel(II) complexes with
so-called “simple” oximes which merely have only one
oxime group as the coordination site. The only relevant Ni-
(II) structure previously reported is the aldoxime complex
[NiCl2(MeCH)NOH)4].27
In the NiCl2‚2H2O/C4H8CdNOH/ClCH2CN system, the
blue powder of [NiCl2(C4H8CdNOH)4] (14) is formed at
room temperature after ca. 10 min of stirring, and the
complex can be separated by filtration and characterized as
described in Experimental Section. However, if the reaction
is continued without separation of [NiCl2(C4H8CdNOH)4]
(14), the blue precipitate is fully dissolved after ca. 30 min,
the reaction mixture becomes brown, and a yellow precipitate
of [Ni{N(H)dC(CH2Cl)NHC(CH2Cl)dNH}2]Cl2 (6‚Cl2) is
obtained after ca. 10 h. It can be isolated in approximately
60% yield. The latter product can also be obtained by mixing
1 equiv of the nickel complex [NiCl2(C4H8CdNOH)4] (14),
2 equiv of water, and 16 equiv of ClCH2CN. This experiment
gives evidence that the complex 14 can be at least one of
the intermediates involved in the conversion depicted in
Scheme 1, route B. However, with other studied nitriles the
reaction does not proceed at room temperature. Heating the
mixture at ca. 50 °C resulted in the formation of a broad
spectrum of yet unidentified products.
We have also observed that the complex cis-[Ni(O,O-
NO3)2(C4H8CdNOH)2] (15) promotes the conversion of the
nitriles to amidinium salts (Scheme 1, route A). Thus, the
amidinium nitrates were obtained by mixing 1 equiv of 15,
6 equiv of water, and 16 equiv of RCN (R ) Me, Et, n-Pr)
and heating the mixture at 50 °C.
The oxime complexes 14 and 15 are so far the only
isolable intermediates for the conversion, and our attempts
to detect other species involved in the process have not yet
been successful. Thus, in preparative experiments, treatment
of 14 or 15 with an additional amount of the oxime (the
complex:oxime molar ratio has been varied from 1:2 to 1:10)
in acetone followed by removal of the solvent in vacuo and
of the excess of the oxime by washing with diethyl ether
led to recovery of the intact metal complexes. Paramagnetic
properties of these complexes precluded NMR studies.
Figure 4. The molecule of dipropionamide 12 in the crystal structure.
Thermal ellipsoids represent a 70% probability. Bond lengths (Å) and angles
(deg): N(1)-C(1) 1.378(3), C(1)-O(1) 1.208(3), C(1)-C(2) 1.503(4),
C(2)-C(3) 1.501(5); N(1)-C(1)-O(1) 123.0(3), N(1)-C(1)-C(2) 113.7-
(2), C(1)-N(1)-C(1i) 128.6(3), O(1)-C(1)-C(2) 123.4(2), C(1)-C(2)-
C(3) 113.9(3).
Figure 5. The complex 14. Thermal ellipsoids represent a 70% probability.
Bond lengths (Å) and angles (deg): Ni-N(1) 2.108(2), Ni-N(2) 2.123(2),
Ni-Cl 2.4402(8), N(1)-O(1) 1.402(3), N(1)-C(7) 1.269(4), N(2)-O(2)
1.405(3), N(2)-C(12) 1.271(4); Ni-N(1)-O(1) 113.8(2), Ni-N(1)-C(7)
135.4(2), Ni-N(2)-O(2) 114.0(2), Ni-N(2)-C(12) 135.0(2).
Figure 6. The complex 15. Thermal ellipsoids represent a 70% probability.
Bond lengths (Å) and angles (deg): Ni-N(1) 2.031(2), N(1)-O(1) 1.399-
(3), N(1)-C(1) 1.270(4); Ni-N(1)-O(1) 117.8(2), Ni-N(1)-C(1) 129.2-
(2).
7244 Inorganic Chemistry, Vol. 42, No. 22, 2003

ConWersion of Organonitriles into Imidoylamidine Ligands
Scheme 3
include only the conversion of nitriles to carboxamides
without further transformation to NH3 and RCO2H. Hence,
one more plausible pathway should be taken into account,
i.e., Ni(II)-mediated coupling of complexed RCN species
with an oxime (step C2; such iminoacylated oximes were
recently detected at Ni(II) centers33 and previously by two
of us at Pt(IV), Pt(II), Re(IV), and Rh(III) centers1) followed
by their hydrolysis (step C3; the hydrolysis of this type was
recently observed at a Pt(IV) center34). (ii) Ammonia, formed
in step C, couples with the nitrile to give the amidine (step
D). This step is also metal-mediated insofar as nonactivated
nitriles do not react with amines without metal ions (ref 1a,
section V). The formation of amidines has also been detected
in this work when NiCl2‚6H2O was employed instead of
NiCl2‚2H2O (Scheme 1). Moreover, the metal-mediated
formation of amidines directly from nitriles, in nondried
solvents, was observed at Co(II)11 and Pt(II)35 centers. (iii)
Further conversion of amidines to imidoylamidines can
proceed by Ni(II)-templated coupling with nitriles (step E;
recently the nitrile-amidine coupling at Pt(IV) center has
been observed36), by coupling with one more molecule of
amidine (step F; the Ni(II)-templated coupling of amidines
to achieve (imidoylamidine)Ni complex and NH3 has been
reported14), or by coupling with iminoacylated oxime species
(step G). We believe that all steps in Scheme 3 are metal-
mediated, while C3 and/or G are additionally oxime-
catalyzed thus explaining the oxime involvement in the
overall process. Studies on trapping of other intermediates
and elucidation of the mechanism of this new conversion in
more detail are on the way in our group.
Hence, the lack of additional experimental data on intermedi-
ates involved in the studied system makes the interpretation
of the mechanism somewhat ambiguous.
Final Remarks
Based on the relevant worksspreviously done by us and
by the other groupssand as an extension of the scheme
suggested earlier,13 we propose here a number of metal-
mediated and oxime-catalyzed steps that might lead to the
formation of imidoylamidines: (i) The boxed nitrile (Scheme
3) is subject to the two-step hydrolysis. Thus, when 72+ is
formed, the carboxylic anion p-MeOC6H4CH2CO2- (Figure
3) was unambiguously identified, thus confirming the oc-
currence of the suggested process. The latter might occur
via route C1. However, although the conversion of a nitrile
to ammonia and carboxylic acid has been detected at Pt-
(IV),28 Nb(V),29 Os(IV),30 and Re2(III)31 metal centers, all
reported examples of Ni(II)-mediated hydrolysis of RCN32
It is anticipated that the method of synthesis developed in
this work for the preparation of imidoylamidines will make
them more accessible, expand their number, and encourage
further research on their chemical and biological properties.
We also believe that significant progress can be achieved
by the application of imidoylamidines, as triaza analogues
of acetylacetone, for chelation of metal ions exhibiting soft
character and forming rather weak complexes with hard
O-donor acetylacetone(ate). It is also noteworthy to mention
that imidoylamidines are useful synthons for the preparation
of triazines37 and imidoylamidine-terminated polymers are
widely used as precursors for triazine-containing polymers,38
exhibiting a range of useful properties, e.g., as good heat
resisting39 or water- and oil-proofing ones.40 Moreover,
imidoylamidines are precursors for the facile syntheses of
sulfur-41 and phosphorus-nitrogen42 heterocycles by their
treatment with S or P chlorides.
(27) Stone, M. E.; Robertson, B. E.; Stanley, E. J. Chem. Soc. A 1971,
3632.
(28) Kuznetsov, M. L.; Bokach, N. A.; Kukushkin, V. Y.; Pakkanen, T.;
Wagner, G.; Pombeiro, A. J. L. J. Chem. Soc., Dalton Trans. 2000,
4683.
(29) Lee, G. R.; Crayston, J. A. Polyhedron 1996, 15, 1817.
(30) Bennett, B. K.; Lovell, S.; Mayer, J. M. J. Am. Chem. Soc. 2001,
123, 4336.
(31) Cutler, A. R.; Esjornson, S. M. V.; Fanwick, P. E.; Walton, R. A.
Inorg. Chem. 1988, 27, 287.
(32) Sanchez, G.; Ruiz, F.; Garcia, J.; Ramirez de Arellano, M. C.; Lopez,
G. HelV. Chim. Acta 1997, 80, 2477. Suh, M. P.; Oh, K. Y.; Lee, J.
W.; Bae, Y. Y. J. Am. Chem. Soc. 1996, 118, 777. Meyer, F.; Kaifer,
E.; Kircher, P.; Heinze, K.; Pritzkow, H. Chem. Eur. J. 1999, 5, 1617.
Meyer, F.; Hyla-Kryspin, I.; Kaifer, E.; Kircher, P. Eur. J. Inorg. Chem.
2000, 771. Caneschi, A.; Dei, A. Inorg. Chim. Acta 1988, 141, 3.
Clark, C. R.; Hay, R. W. J. Chem. Soc., Dalton Trans. 1974, 2148.
Breslow, R.; Fairweather, R.; Keana, J. J. Am. Chem. Soc. 1967, 89,
2135. Kang, S.-G.; Song, J.; Jeong, Jong H. Bull. Korean Chem. Soc.
2002, 23, 824; Chem. Abstr. 2002, 137, 256821.
(33) Pavlishchuk, V. V.; Kolotilov, S. V.; Addison, A. W.; Prushan, M.
J.; Butcher, R. J.; Thompson, L. K. Chem. Commun. 2002, 468.
Pavlishchuk, V. V.; Kolotilov, S. V.; Addison, A. W.; Prushan, M.
J.; Butcher, R. J.; Thompson, L. K. Inorg. Chem. 1999, 38, 1759.
(34) Bokach, N. A.; Haukka, M.; Pombeiro, A. J. L.; Morozkina, S. N.;
Kukushkin, V. Y. Inorg. Chim. Acta 2002, 336, 95.
(35) Longato, B.; Bandoli, G.; Mucci, A.; Schenetti, L. Eur. J. Inorg. Chem.
2001, 3021.
(36) Kuznetsova, T. V.; Simanova, S. A.; Bokach, N. A.; Kukushkin, V.
Y. Unpublished results.
(37) Shmel’kova, T. K.; Ignatenko, A. V.; Krukovskii, S. P.; Ponomarenko,
V. A. IzV. Akad. Nauk SSSR, Ser. Khim. 1989, 928. Davtyan, M. M.;
Krukovskii, S. P.; Ignatenko, A. V.; Ponomarenko, V. A. IzV. Akad.
Nauk SSSR, Ser. Khim. 1980, 1414.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7245

Kopylovich et al.
an oil bath at 100 °C (refluxing for acetonitrile and propionitrile;
in the case of ClCH2CN the reaction is performed at room
temperature) for 1 day. In all the cases, the reaction mixture
homogenizes for 10 min after the addition of the oxime, giving a
greenish-blue solution. The color of the reaction mixture changes
with time from greenish-blue to brown (ca. 1 h), and a yellow
powder begins to form after ca. 3 h, which is then (after 24 h)
separated by filtration, washed with three 5-mL portions of acetone,
and dried in a vacuum at room temperature.
Experimental Section
Materials and Instruments. Nickel(II) hexaaquachloride (Mer-
ck), acetonitrile (Lab-Scan), propionitrile (Aldrich), butyronitrile
(Aldrich), isobutyronitrile (Merck), valeronitrile (Aldrich), chloro-
acetonitrile (Merck), p-methoxybenzoacetonitrile (Lancaster), 2-pro-
panone oxime (Lancaster), and cyclopentanone oxime (Aldrich)
were obtained from commercial sources and used as received.
Preparation of NiCl2‚2H2O: NiCl2‚6H2O (2.38 g, 10 mmol) is finely
grounded and partially dehydrated by refluxing in acetone (75 mL)
for 3 h and then with a new portion of acetone (75 mL) for 1 h.
The solid is then filtered off and dried under vacuum at room
temperature. The yield is almost quantitative. In NiCl2‚2H2O, the
water content was determined by EDTA titration.
[Ni{N(H)dC(Me)NHC(Me)dNH}2]Cl2 (1‚Cl2). Yield is 65%,
based on Ni. Yellow powder is insoluble in acetone and chloroform,
slightly soluble in methanol and DMSO, and soluble in water. Anal.
Calcd for C8H18N6Cl2Ni: C, 29.31; H, 5.53; N, 25.63. Found: C,
29.30; H, 5.50; N, 25.69. FAB+-MS, m/z: 255 [M - 2Cl - 2H]+.
The compound does not have a characteristic melting point (mp),
and upon heating it decomposes at >300 °C. IR spectrum, selected
bands, cm-1: 3165 s ν(NH), 2958 s νas(CH), 2918 s νs(CH), 1665
vs ν(CdN), 1542 s F(NH). 1H NMR in D2O, δ: 2.02 (s, Me), NH
groups were not observed. 13C{1H} NMR in D2O, δ: 21.9 (CH3),
162.4 (CdN).
C, H, and N elemental analyses were carried out by the
Microanalytical Service of the Instituto Superior Te´cnico. Melting
points were determined on a Kofler table. Positive-ion FAB mass
spectra were obtained on a Trio 2000 instrument by bombarding
3-nitrobenzyl alcohol (NBA) matrices of the samples with 8 keV
(ca. 1.18 × 1015 J) Xe atoms. Mass calibration for data system
acquisition was achieved using CsI. Infrared spectra (4000-400
cm-1) were recorded on a BIO-RAD FTS 3000MX instrument in
[Ni{N(H)dC(Et)NHC(Et)dNH}2]Cl2 (2‚Cl2). Yield is 83%,
based on Ni. Yellow powder is insoluble in acetone and chloroform
and soluble in water, methanol, and DMSO. Anal. Calcd for
C12H26N6Cl2Ni: C, 37.54; H, 6.83; N, 21.89. Found: C, 37.59; H,
6.16; N, 21.91. FAB+-MS, m/z: 659 [2M - Cl - 2H], 311 [M -
2Cl - 2H]+. Mp ) 260 °C (sublimation) and 264 °C (dec). IR
spectrum, selected bands, cm-1: 3298 and 3156 s ν(NH), 2978 s
νas(CH), 2920 s νs(CH), 1655 vs ν(CdN), 1529 s F(NH). 1H NMR
in D2O, δ: 1.01 (t, J 7.7 Hz, 3H, Me), 2.29 (q, J 7.7 Hz, 2H, CH2),
NH groups were not observed. 13C{1H} NMR in D2O, δ: 11.2
(CH3), 29.6 (CH2), 167.3 (CdN). Crystallization of 2‚Cl2 from a
water-acetone mixture (1:1, v/v) at ca. 25 °C results in dehydro-
chlorination and release of the monocationic complex [2 - H]Cl
as the solid. The X-ray structure of the latter was determined by
X-ray crystallography.
1
KBr pellets. H and 13C{1H} NMR spectra were measured on a
Varian UNITY 300 spectrometer at ambient temperature.
X-ray Structure Determinations. Diffraction data for all crystals
were collected using a Bruker-Nonius KappaCCD diffractometer
(Mo KR, λ ) 0.71073 Å). Structural models were obtained using
direct methods.43 H atoms were refined on calculated positions using
a riding model. All structure models were refined on F2 using
anisotropic displacement parameters for all non-H atoms.44 The
crystallographic data and the results of the structure determinations
are summarized in Table 1.
Synthetic Work and Characterization. Conversion of RCN
-
to RC(dNH2)NH2+NO3 (R ) Me, Et, n-Pr) Mediated by the
Ni(II)/2-Propanone Oxime System. The amidinium nitrates were
obtained in accord with the previously described method,11 by using
Ni(NO3)2‚6H2O instead of the cobalt(II) salt. Yields are 60-80%,
based on Ni.
Formation of the (Imidoylamidine)Ni(II) Complexes. General
procedure: NiCl2‚2H2O (166 mg, 1.00 mmol) is stirred in the
corresponding nitrile (5 mL) for 5 min, whereupon 2-propanone
oxime (4.00 mmol) is added and the reaction mixture is heated in
[Ni{N(H)dC(n-Pr)NHC(n-Pr)dNH}2]Cl2 (3‚Cl2). Yield is
85%, based on Ni. Yellow powder is insoluble in acetone and
chloroform and soluble in water, methanol, and DMSO. Anal. Calcd
for C16H32N6Cl2Ni: C, 43.86; H, 7.36; N, 19.18. Found: C, 43.66;
H, 7.34; N, 19.23. FAB+-MS, m/z: 402 [M - Cl - 2H]+, 367 [M
- 2Cl - 2H]+. Mp ) 249 (sublimation) °C and 257 °C (dec). IR
spectrum, selected bands, cm-1: 3153 s ν(NH), 2963 s νas(CH),
2911 s νs(CH), 1659 vs ν(CdN), 1527 s F(NH). 1H NMR in D2O,
δ: 0.91 (t, J 7.3 Hz, 3H, Me), 1.62 (sextet, J 7.5 Hz, 2H, CH2),
2.43 (t, J 7.6 Hz, 2H, CH2), NH groups were not observed. 13C-
{1H} NMR in D2O, δ: 12.9 (CH3), 20.8 (CH2), 37.8 (CH2), 166.0
(CdN). Slow evaporation of water solution of 3‚Cl2 at ca. 25 °C
results in dehydrochlorination and release of the monocationic
complex [3 - H]Cl as the solid. The X-ray structure of the latter
was determined by X-ray crystallography.
(38) Ding, J.-F.; Khan, A. R.; Proudmore, M.; Mobbs, R. H.; Heatley, F.;
Price, C.; Booth, C. Macromol. Chem. Phys. 1994, 195, 3137. Frosch,
R. A.; Rosser, R. W.; Psarras, T. Patent U.S. 4,234,715, 1980; Chem.
Abstr. 1981, 94, 48032. Rosser, R. W.; Korus, R. A. Patent US 60,434,
1980; Chem. Abstr. 1980, 93, 221738. Rosser, R. W.; Psarras, T. Patent
US 37,066, 1979; Chem. Abstr. 1980, 92, 95419. Rosser, R. W.; Korus,
R. A. Patent US 28,300, 1979; Chem. Abstr. 1980, 92, 43145. Mitsch,
R. A.; Zollinger, J. L. Patent Can. 960,400, 1974; Chem. Abstr. 1975,
82, 171913.
(39) Watakabe, A.; Shirota, N.; Nakamura, H. Patent Japan 07,268,031,
1995; Chem. Abstr. 1995, 124, 148863.
(40) Fukui, H.; Ikeda, M.; Suzuki, Y. Patent Japan 02,269,737, 1990; Chem.
Abstr. 1991, 114, 248063.
[Ni{N(H)dC(i-Pr)NHC(i-Pr)dNH}2]Cl2 (4‚Cl2). Yield is 63%,
based on Ni. Yellow powder is insoluble in acetone and chloroform
but slightly soluble in water, methanol, and DMSO. Anal. Calcd
for C16H34N6Cl2Ni: C, 43.67; H, 7.79; N, 19.10. Found: C, 43.44;
H, 7.67; N, 18.75. FAB+-MS, m/z: 404 [M - Cl]+, 367 [M - 2Cl
(41) Torroba, T. J. Prakt. Chem. 1999, 341, 99. Kornuta, P. P.; Derii, L.
I.; Markovskii, L. N. Zh. Org. Khim. 1980, 16, 1308.
(42) Paciorek, K. J. L.; Nakahara, J. H.; Smythe, M. E.; Harris, D. H.;
Kratzer, R. H. J. Fluorine Chem. 1985, 28, 441. Paciorek, K. J. L.;
Ito, T. I.; Nakahara, J. H.; Harris, D. H.; Kratzer, R. H. J. Fluorine
Chem. 1983, 22, 185. Paciorek, K. J. L.; Ito, T. I.; Nakahara, J. H.;
Kratzer, R. H. J. Fluorine Chem. 1980, 16, 431. Paciorek, K. J. L.
Patent US 601,874, 1984; Chem. Abstr. 1985, 102, 116423. Kornuta,
P. P.; Kolotilo, N. V. Zh. Obshch. Khim. 1978, 48, 1181.
(43) Sheldrick, G. S. SHELXS97, a Program for Crystal Structure Solution;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
- 2H]+. Mp ) 267 °C (dec). IR spectrum, selected bands, cm-1
:
3159 s ν(NH), 2965 s νas(CH), 2925 s νs(CH), 1655 vs νas(CdN),
1
1523 s F(NH). H NMR in D2O, δ: 1.02 (d, J 7.2 Hz, 6H, 2Me),
2.60 (septet, Japparent 7.2 Hz, 1H, CH), NH groups were not observed.
13C{1H} NMR in D2O, δ: 19.3 (2CH3), 35.5 (CH), 170.8 (CdN).
Crystals for the X-ray study were obtained by slow evaporation of
methanol solution of the complex at ca. 25 °C.
(44) Sheldrick, G. S. SHELXL97, a Program for Crystal Structure
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
7246 Inorganic Chemistry, Vol. 42, No. 22, 2003

ConWersion of Organonitriles into Imidoylamidine Ligands
[Ni{N(H)dC(n-Bu)NHC(n-Bu)dNH}2]Cl2 (5‚Cl2). Yield is
91%, based on Ni. Yellow powder is insoluble in acetone and
chloroform, slightly soluble in water, and soluble in methanol and
DMSO. Anal. Calcd for C20H42N6Cl2Ni: C, 48.41; H, 8.53; N,
16.94. Found: C, 48.81; H, 8.65; N, 16.42. FAB+-MS, m/z: 423
[M - 2Cl - 2H]+. Mp ) 246 °C (dec). IR spectrum, selected
bands, cm-1: 3150 s ν(NH), 2958 s νas(CH), 2870 s νs(CH), 1658
vs ν(CdN), 1525 s F(NH). 1H NMR in D2O, δ: 0.72 (t, J 7.3 Hz,
3H, Me), 1.21 (sextet, Japparent 7.3 Hz, 2H, CH2), 1.41 (quintet,
H, 5.16; N, 13.91. FAB+-MS, m/z: 129 [M - 2BF4]+. Mp ) 126
°C (dec). IR spectrum, selected bands, cm-1: 3290 s, br ν(NH),
2958 s νas(CH), 2910 s νs(CH), 1633 vs ν(CdN), 1090 s, br δ(BF4).
1H NMR in CDCl3, δ: 1.05 (t, J 7.3 Hz, 3H, Me), 2.32 (q, J 7.3
Hz, 2H, CH2), 8.34 (s, br, NH), 8.90 (s, br, NdH). 13C{1H} NMR
in CDCl3, δ: 10.5 (CH3), 24.2 (CH2), 170.0 (CdN).
[N(H)dC(CH2C6H4OMe-p)NHC(CH2C6H4OMe-p)dNH]‚
2HBF4 (9). Yield is 57%, based on Ni. Colorless crystalline material
is soluble in acetone, chloroform, water, methanol, dichloromethane,
and DMSO. Anal. Calcd for C18H23N3B2F8O2: C, 44.39; H, 4.76;
N, 8.63. Found: C, 44.09; H, 5.00; N, 8.82. FAB+-MS, m/z: 312
Japparent 7.6 Hz, 2H, CH2), 2.29 (t, J 7.6 Hz, 2H, CH2), NH groups
were not observed. 13C{1H} NMR in D2O, δ: 13.5 (CH3), 21.83
(CH2), 29.3 (CH2), 35.9 (CH2), 166.2 (CdN). Crystals for the X-ray
study were obtained by slow evaporation of methanol solution of
the complex at ca. 25 °C.
[M - 2HBF4]+. Mp ) 165 °C. IR spectrum, selected bands, cm-1
:
3275 s, br ν(NH), 2969 m-w νas(CH), 2840 m-w νs(CH), 1614 s
1
ν(CdN), 1515 s F(NH), 1080 vs, br δ(BF4). H NMR in DMSO-
[Ni{N(H)dC(CH2Cl)NHC(CH2Cl)dNH}2]Cl2 (6‚Cl2). Yield is
65%, based on Ni. Yellow powder is insoluble in acetone and
chloroform but soluble in water, methanol, and DMSO. Anal. Calcd
for C8H14N6Cl6Ni: C, 20.64; H, 3.03; N, 18.05. Found: C, 20.66;
H, 3.07; N, 18.02. FAB+-MS, m/z: 393 [M - 2Cl - 2H]+. The
compound has no specific mp, and it is slowly sublimated at ca.
200 °C and decomposes above 300 °C. IR spectrum, selected bands,
cm-1: 3094 s ν(NH), 2968 s νas(CH), 2851 s νs(CH), 1664 vs
d6, δ: 3.55 (s, 2H, CH2), 3.74 (s, 3H, OMe), 7.17 (d, J 8.4 Hz, 2H,
CH), 7.35 (d, J 8.4 Hz, 2H, CH), NH groups were not observed.
13C{1H} NMR in DMSO-d6, δ: 34.1 (CH2), 55.1 (OCH3), 114.1
(CH), 130.5 (CH), 168.2 (CdN).
2. Liberation of Imidoylamidines via Substitution. Ethanedi-
amine (3 mmol) is added to the corresponding (imidoylamidine)-
Ni(II) complex (1 mmol) dissolved in a methanol:chloroform (4
mL, 3:1 v/v) solution, and the reaction mixture is refluxed for 1 h,
whereupon diethyl ether (4 mL) is added and a pink powder of
[Ni(en)3]Cl2 complex20 is precipitated, which is separated by
filtration, and the filtrate is dried under vacuum at room temperature.
1
ν(CdN), 1538 s F(NH). H NMR in D2O, δ: 3.96 (s, 2H, CH2),
NH groups were not observed. 13C{1H} NMR in D2O, δ: 41.9
(CH2), solubility is insufficient to observe CdN groups even at
high acquisition time. Slow evaporation of water solution of 6‚Cl2
at ca. 25 °C results in dehydrochlorination and release of the
monocationic complex [6 - H]Cl as the solid. The X-ray structure
of the latter was determined by X-ray crystallography.
N(H)dC(Et)NHC(Et)dNH (10). Yield is 43%, based on Ni.
Colorless, hygroscopic, crystalline material is unstable toward the
hydrolysis and soluble in acetone, chloroform, water, methanol,
dichloromethane, and DMSO. Anal. Calcd for C6H13N3: C, 52.91;
H, 10.36; N, 30.85. Found: C, 52.95; H, 10.50; N, 30.75. FAB+-
MS, m/z: 129 [M + 2H]+. Mp ) 86 °C. IR spectrum, selected
bands, cm-1: 3160 s br ν(N-H), 2953 m-w νas(CH), 2890 m-w
[Ni{N(H)dC(CH2C6H4OMe-p)NHC(CH2C6H4OMe-p)dNH}2]-
(Cl)(p-MeOC6H4CH2CO2) [7‚(Cl)(p-MeOC6H4CH2CO2)]. Yield
is 87%, based on Ni. Yellow powder is insoluble in chloroform,
acetone, and water, slightly soluble in methanol and dichlo-
romethane, and well soluble in DMSO. Anal. Calcd for C45H49-
ClN6NiO7: C, 61.41; H, 5.61; N, 9.55. Found: C, 61.32; H, 5.65;
N, 9.69. FAB+-MS, m/z: 679 [Mcation - 2H]+. Mp ) 257 °C. IR
spectrum, selected bands, cm-1: 3387 m-w and 3121 m-w ν(NH),
2958 m-w νas(CH), 2837 m-w νs(CH), 1672 s ν(CdO), 1612 s
1
νs(CH), 1643 s νas(CdN), 1524 s F(NH). H NMR in CDCl3, δ:
1.01 (t, J 7.2 Hz, 3H, Me), 2.36 (q, J 7.2 Hz, 2H, CH2), NH groups
were not observed. 13C{1H} NMR in CDCl3, δ: 10.4 (CH3), 31.7
(CH2), 169.3 (CdN).
N(H)dC(CH2C6H4OMe-p)NHC(CH2C6H4OMe-p)dNH (11).
Yield is 57%, based on Ni. Colorless crystalline material is soluble
in acetone, chloroform, water, methanol, dichloromethane, and
DMSO. Anal. Calcd for C18H21N3O2‚1/2H2O: C, 67.48; H, 6.92;
N, 13.12. Found: C, 67.25; H, 7.05; N, 13.08. FAB+-MS, m/z:
307 [M - 4H]+. Mp ) 113 °C (with partial sublimation at ca. 105
°C). IR spectrum, selected bands, cm-1: 3423 ν(OH), 3136 m-w
ν(NH), 2933 m-w νas(CH), 2853 m-w νs(CH), 1610 s νas(CdN),
1
ν(CdN). H NMR in DMSO-d6, δ: 3.50 (s, 2H, CH2), 3.72 (s,
3H, OMe), 6.84 (d, J 8.5 Hz, 2H, CH), 7.22 (d, J 8.5 Hz, 2H, CH),
ca. 8.90 (s, br, NH), ca. 9.10 (s, br, NH). 13C{1H} NMR in DMSO-
d6, δ: 37.0 (CH2), 55.0 (OCH3), 113.8 (CH), 129.6 (CH), 164.0
(CdN). Signals from p-MeOC6H4CH2CO2- counterion: 1H NMR
in DMSO-d6, δ, 3.60 (s, 0.5H, CH2), 3.74 (s, 0.75H, OMe), 6.93
(d, J 8.4 Hz, 0.5H, CH), 7.33 (d, J 8.4 Hz, 0.5H, CH); 13C{1H}
NMR in DMSO-d6, δ, 37.0 (CH2), 55.1 (OCH3), 114.2 (CH), 130.0
(CH), signal for -C(dO)O- group was not observed. Slow
evaporation of methanol solution of 7‚(Cl)(p-MeOC6H4CH2CO2)
at ca. 25 °C results in the release of the solvate 7‚(p-MeOC6H4-
CH2CO2)2‚MeOH. The X-ray structure of the latter was determined
by X-ray crystallography.
Liberation and Hydrolytic Liberation of the Ligands. 1.
Liberation of the Imidoylamidines via Protonation. HBF4‚Et2O
(4 mmol; 50% solution in Et2O) is added dropwise and with
vigorous stirring to a solution of the corresponding complex (1
mmol) dissolved in a mixture of dry acetonitrile and methanol (4
mL, 3:1, v/v), whereupon the reaction mixture is refluxed with
stirring for 1 h, the solvent is evaporated under vacuum to dryness,
and the product is recrystallized from methanol at 50 °C.
[N(H)dC(Et)NHC(Et)dNH]‚2HBF4 (8). Yield is 37%, based
on Ni. Colorless crystalline material is soluble in acetone, chloro-
form, water, methanol, dichloromethane, and DMSO. Anal. Calcd
for C6H15N3B2F8: C, 23.80; H, 4.99; N, 13.88. Found: C, 23.99;
1
1514 s F(NH). H NMR in DMSO-d6, δ: 3.36 (s, 2H, CH2), 3.67
(s, 3H, OMe), 6.81 (d, J 8.1 Hz, 2H, CH), 7.16 (d, J 8.1 Hz, 2H,
CH), NH groups were not observed. 13C{1H} NMR in DMSO-d6,
δ: 34.4 (CH2), 55.5 (OCH3), 114.2 (CH), 130.4 (CH), 158.4 (Cd
N).
3. Hydrolytic Liberation. (i) Na2EDTA‚2H2O (2 mmol) is added
to a water-methanol (1:1, v/v) solution (5 mL) of the corresponding
complex (1.00 mmol), whereupon the reaction mixture is refluxed
with stirring for 1 h and cooled to room temperature, the organic
product is extracted with diethyl ether, the solvent is evaporated
under vacuum at 20-25 °C, and the product is purified by
dissolution in 5 mL of acetone at 50 °C and evaporation of the
solvent at room temperature to ca. 0.5 mL. (ii) Water (5 mL) is
added to the corresponding imidoylamidinium tetrafluoroborate
(1.00 mmol), and the reaction mixture is refluxed for 1 h. In the
case of R ) CH2C6H4OMe-p, the product precipitates, while for R
) Et, the solvent should be removed under vacuum at 20 °C and
the residue is purified as indicated above.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7247

Kopylovich et al.
{EtC(dO)}2NH (12). Mp ) 156 °C from acetone [mp lit.21 155
°C]. This compound has been characterized by X-ray diffraction
study (see above).
IR spectrum, selected bands, cm-1: 3278 s ν(OH), 2961 s νas(CH),
2871 m-w νs(CH), 1668 m-w ν(CdN).
cis-[Ni(O,O-NO3)2(C4H8CdNOH)2] (15). Anal. Calcd for
C10H18N4O8Ni: C, 31.56; H, 4.77; N, 14.74. Found: C, 31.21; H,
5.01; N, 14.54. FAB+-MS, m/z: 319 [M - NO3]+, 255 [M - 2NO3
- 2H]+. This complex has no specific mp and gradually decom-
{p-MeOC6H4CH2C(dO)}2NH (13). Yield is 57%, based on Ni.
Colorless crystalline material is soluble in acetone, chloroform,
water, methanol, dichloromethane, and DMSO. Anal. Calcd for
C9H10NO3: C, 59.99; H, 5.59; N, 7.77. Found: C, 59.95; H, 6.05;
N, 7.65. Mp ) 96 °C. IR spectrum, selected bands, cm-1: 3419 vs
ν(NH), 2954 m-w νas(CH), 2836 m-w νs(CH), 1671 vs (CdO),
poses on heating above 100 °C. IR spectrum, selected bands, cm-1
:
3420 s br ν(OH), 2980 m-w νas(CH), 2888 m-w νs(CH), 1632 s
ν(CdN) + νas(NO3), 1383 vs, br νs(NO3) + δ(CH), 825 s δ (NO3).
1
1509 F(NH), 1250 s δ(CH3). H NMR in CDCl3, δ: 3.49 (s, 2H,
Acknowledgment. M.N.K. expresses gratitude to the
PRAXIS XXI program (Portugal) for the grant BPD/20169/
99. V.Yu.K. thanks the Russian Fund for Basic Research
for the grant 03-03-32363 and the International Science
Foundation (Soros Foundation) for the Soros Professorship.
A.J.L.P. and V.Yu.K. are grateful to the FCT (Foundation
for Science and Technology) (Portugal) and the POCTI
program (POCTI/QUI/43415/2001) (FEDER funded) for
financial support of these studies. The authors also thank
Dr. M. Caˆndida Vaz for the elemental analysis service and
Mr. Indale´cio Marques for running the FAB+-MS spectra.
CH2), 3.78 (s, 3H, OMe), 6.86 (d, J 8.1 Hz, 2H, CH), 7.16 (d, J
8.1 Hz, 2H, CH), NH was not observed. 13C{1H} NMR in CDCl3,
δ: 41.3 (CH2), 56.3 (OCH3), 114.4 (CH2) 130.5 (CH2), solubility
is insufficient to observe the CdN groups.
Preparation of (Ketoxime)Ni(II) Complexes. The ketoxime
C4H8CdNOH (4 mmol) is added to NiCl2‚2H2O or Ni(NO3)2‚6H2O
(1 mmol), whereupon acetone or acetonitrile (10 mL) is added.
The reaction mixture is refluxed for 1 h on stirring (or stirred at
room temperature for 10 min if nitrile is used as solvent). The
solvent is removed under vacuum to dryness at room temperature,
and the precipitate is washed with three 5-mL portions of diethyl
ether. Yields are 90-97%, based on Ni. These complexes can also
be isolated when any of the nitriles is used as the solvent.
trans-[NiCl2(C4H8CdNOH)4] (14). Anal. Calcd for C20H36N4-
Cl2O4Ni: C, 45.66; H, 6.90; N, 10.65. Found: C, 45.84; H, 6.83;
N, 10.43. FAB+-MS, m/z: 425 [M - oxime - 2H]+, 356 [M -
oxime - 2Cl]+, 329 [M - 2oxime + H]+. This complex has no
specific mp and gradually decomposes on heating above 100 °C.
Supporting Information Available: Crystallographic data
including positional parameters, thermal parameters, and bond
lengths and angles (CIF). This material is available free of charge
via the Internet at http://pubs.acs.org.
IC0349813
7248 Inorganic Chemistry, Vol. 42, No. 22, 2003