Ni(II) and Pd(II) organometallic and coordination complexes with a new tridentate N,N,O-donor ligand

Article abstract of DOI:10.1016/j.poly.2012.04.002

Nickel and palladium organometallic [M(R)(NNO)] (R = CH₂CMe ₂C₆H₅; M = Pd, 1, Ni, 2; R = Me, M = Pd, 3, Ni, 4; R = CH₂SiMe₃, M = Ni, 5) and coordination [MCl(NNO)] (M = Pd(II), 6, Ni(II), 7), [Ni(NNO)₂], 8, complexes containing the potentially tridentate Schiff base NNO-donor ligand which is the condensation product of 2-hidroxynaphtaldehyde and N-benzylethylenediamine, were prepared and characterized by elemental analysis, IR and NMR spectroscopy. The crystal structure of 8 was determined by single X-ray diffraction measurements. Complexes 1-6 had a square planar structure with the ligand being tridentate through the NNO atoms. On the other hand compound 7 presented a conformational equilibrium in dissolution at room temperature and a rigid square-planar structure at 220 K. The crystal structure of 8 indicated a monoclinic lattice, with a P2(1)/c space group, a = 13.1799(8), b = 14.5556(9), c = 17.5018(11) ?, b = 98.0420 (10)°, Z = 4. The central Ni atom in 8 was in a N ₄O₂ coordination sphere formed by two NNO Schiff base ligands. In this structure two of the Ni-N bonds trans to the oxygen atoms were significantly longer than the other two Ni-N bonds, 2.0175(17), 2.2761(17) versus 2.0070(17), 2.1794(14) ?. The two oxygen phenol atoms of the chelating ligands were cis and the distances of the Ni(II)-O(phenol) bond were 2.0410(14) and 2.0415(14) ?, respectively.

Full text of DOI:10.1016/j.poly.2012.04.002

Polyhedron 40 (2012) 11–18
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Ni(II) and Pd(II) organometallic and coordination complexes with a new tridentate
N,N,O-donor ligand
Cristina Esqueda b, José C. Alvarado-Monzón b, Gabriel Andreu-de-Riquer b, J. Alfredo Gutiérrez b,
Luis M. De León-Rodríguez b, Oracio Serrano b, José G. Alvarado-Rodríguez a, Jorge A. López b,
⇑
a Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Hidalgo, Ciudad Universitaria, Km. 4.5 Carretera Pachuca-Tulancingo, Pachuca Hgo., Mexico
b Departamento de Química, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Cerro de la Venada s/n, Col. Pueblito de Rocha. Guanajuato,
Gto., C.P. 36040, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
Nickel and palladium organometallic [M(R)(NNO)] (R = CH2CMe2C6H5; M = Pd, 1, Ni, 2; R = Me, M = Pd, 3,
Ni, 4; R = CH2SiMe3, M = Ni, 5) and coordination [MCl(NNO)] (M = Pd(II), 6, Ni(II), 7), [Ni(NNO)2], 8, com-
plexes containing the potentially tridentate Schiff base NNO-donor ligand which is the condensation
product of 2-hidroxynaphtaldehyde and N-benzylethylenediamine, were prepared and characterized
by elemental analysis, IR and NMR spectroscopy. The crystal structure of 8 was determined by single
X-ray diffraction measurements. Complexes 1–6 had a square planar structure with the ligand being
tridentate through the NNO atoms. On the other hand compound 7 presented a conformational
equilibrium in dissolution at room temperature and a rigid square-planar structure at 220 K. The crystal
structure of 8 indicated a monoclinic lattice, with a P2(1)/c space group, a = 13.1799(8), b = 14.5556(9),
c = 17.5018(11) Å, b = 98.0420 (10)°, Z = 4. The central Ni atom in 8 was in a N4O2 coordination sphere
formed by two NNO Schiff base ligands. In this structure two of the Ni–N bonds trans to the oxygen atoms
were significantly longer than the other two Ni–N bonds, 2.0175(17), 2.2761(17) versus 2.0070(17),
2.1794(14) Å. The two oxygen phenol atoms of the chelating ligands were cis and the distances of the
Ni(II)–O(phenol) bond were 2.0410(14) and 2.0415(14) Å, respectively.
Received 16 December 2011
Accepted 11 April 2012
Available online 21 April 2012
Keywords:
Nickel
Palladium
Alkyl complexes
Schiff base ligand
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
mainly due to their facile syntheses, easily tunable steric and elec-
tronic properties and good solubility in common solvents [7–11].
Nickel and palladium alkyl and halide complexes constitute a
classical research area in organometallic and coordination inor-
ganic chemistry [1,2]. Interest in Ni and Pd alkyl and aryl com-
plexes has increased in recent years due to their application in a
variety of important processes especially in catalytic applications
such as oligomerization or polymerization of alkenes, alkynes
and dienes [3], carbonylation of several substrates such as alkyl ha-
lides and aryl or alkynes [4] and carbon–carbon bond formation
reactions [5]. Some of these processes (e.g. alkoxycarbonylation
of alkynes (Reppe reaction) or dimerization of ethylene) can be
considered classics in the field of industrial homogeneous catalysis
[6]. Most of these transformations use simple Ni or Pd catalysts
such as Ni(COD)2, Ni(CO)4, Pd(dba)2, Pd(PR3)4 or salts of these met-
als. Furthermore, by adding auxiliary ligands it is often possible to
adjust the electronic properties and stereo configuration of a cata-
lyst to suit a particular process. On the other hand, Schiff base (SB)
ligands have been extensively studied in coordination chemistry
Transition metal complexes with SBs containing oxygen and nitro-
gen donor atoms are of particular interest [12,13] because of their
(i) ability to present unusual configurations, (ii) structural lability
and (iii) sensitivity to molecular environments [14]. SB ligands
can also accommodate different metal centers with various coordi-
nation modes, thus allowing successful synthesis of homo and het-
erometallic complexes with varied stereochemistry [15]. Here we
report organometallic and coordination complexes containing a
new tridentate NNO-donor SB ligand.
2. Results and discussion
2.1. Synthesis of NNO ligand
The NNO ligand, 1-(2-(phenylamino)(phenylimino)methyl)
naphthalen-2-ol, was obtained in good yield as yellow crystals by
condensation of 2-hidroxy-1-naphthaldehyde with one equivalent
of N1-phenylbenzene-1,2-diamine in ethyl ether. The imine and
amine protons of the ligand were observed in 1H NMR solution
at 8.78 and 1.57 ppm, respectively, while the hydroxyl proton
⇑
Corresponding author.
E-mail address: albinol@ugto.mx (J.A. López).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.04.002

12
C. Esqueda et al. / Polyhedron 40 (2012) 11–18
appeared downfield at 14.42 ppm indicating the formation of an
intramolecular hydrogen bond. C@N and NH stretching vibration
IR bands were observed at 1620 and 3280 cmꢀ1, respectively.
Complexes 1–5 are diamagnetic, which is characteristic of a
complex with square planar geometry (Fig. 1). The 1H NMR spectra
of 1–5, showed a similar signal pattern. Furthermore, all signals
were sharp which indicates that the structures were static on the
NMR timescale. The absence of the phenol proton as well as signif-
icant chemical shift changes of some ligand’s protons can be ob-
served upon coordination of the ligand to the metal (Table 1). For
example, the signal of the H5 proton which appeared at 8.78 ppm
in the free ligand, is shifted to lower or higher fields in the com-
plexes, 8.50, 8.48, 8.81, 8.45 and 8.23 ppm for 1, 2, 3, 4 and 5,
respectively. Furthermore, all methylene signals of the ethylene
chain and benzyl group of the ligand appeared as unsymmetric
multiplets with the same intensity. This spectral feature can be
attributed to the presence of diasterotopic proton pairs within each
methylene group, which is the result of the chirality of the nitrogen
amino group and the conformational rigidity imposed to the struc-
ture upon metal coordination. Take for example complex 1 the
2.2. Preparation and characterization of alkyl complexes
Divalent metal organometallic complexes [M(R)(NNO)] (R =
CH2CMe2C6H5; M = Pd, 1, Ni, 2; R = Me, M = Pd, 3, Ni, 4;
R = CH2SiMe3, M = Ni, 5) (Scheme 1) were readily prepared in good
yield by reaction of metallacycles
(M = Pd,
L2 = PMe3; M = Ni, L = PMe3) or dialkyl complexes [ML2R2] {where
M = Pd, R = Me, L2 = TMEDA; M = Ni, L = Py, R = Me; M = Ni,
L = PMe3, R = CH2SiMe3} with one equivalent of NNO ligand. These
compounds were obtained pure as yellow (palladium) or red crys-
tals (nickel), by recrystallization from diethylether.
Scheme 1. Synthesis of nickel and palladium complexes.

C. Esqueda et al. / Polyhedron 40 (2012) 11–18
13
Fig. 1. Structure of the nickel and palladium complexes 1–7.
Table 1
1H NMR values of NNO ligand (in CDCl3) and complexes 1–6 (in C6D6) at 293 K.
Compound
1H NMR
H5
H1H1
3.83 (s)
H2H20–H3H3
M-CH2
CH3
H4
0
0
NNO ligand
8.78 (s)
2.97 (t, JHH = 5.6)
3.69 (t, JHH = 5.6)
2.89 (t. JHH = 12.7)
1.57 (bs)
2
2
2
[Pd(CH2CMe2C6H5)(NNO)], 1
8.50 (s)
8.48 (s)
3.64 (d, JHH = 14.3)
3.47 (t, JHH = 11.4)
2.40 (d, JHH = 8.6)
1.61 (d, JHH = 8.6)
2.02 (s)
1.68 (s)
1.75 (bs)
1.18 (bs)
2
2
2
2.28 (d, JHH = 14.0)
1.82 (m)
2
2
[Ni(CH2CMe2C6H5)(NNO)], 2
[Pd(CH3)(NNO)], 3a
[Ni(CH3)(NNO)], 4
3.91 (d, JHH = 13.4)
3.39 (d, JHH = 13.5)
2.06 (t, JHH = 13.4)
2.61 (d, JHH = 13.3)
1.38 (d, JHH = 14.1)
0.95 (t, JHH = 14.2)
3.52 (d, JHH = 13.1)
3.40 (t, JHH = 13.1)
2.66 (d, JHH = 13.8)
2.81 (t, JHH = 13.7)
2.85 (d, JHH = 14.2)
2.63 (d, JHH = 14.0)
2.48 (t, JHH = 14.2)
2.19 (d, JHH = 14.1)
2.81 (d, JHH = 13.6)
1.88 (t, JHH = 13.9)
2.17 (d, JHH = 14.1)
1.43 (t, JHH = 14.0)
1.58, 0.72 (dd,2JHH = 14.2)
2.21 (s)
1.64 (s)
2
2
2
2
2
2
8.81 (s)
8.45 (s)
8.43(s)
8.45(s)
4.62 (d, JHH = 13.2)
0.40 (s)
0.19 (s)
0.62 (s)
6.19 (bs)
1.63 (bs)
2
2
2
3.80 (d, JHH = 13.1)
2
2
2
3.73 (d, JHH = 11.7)
4.24 (d, JHH = 11.5)
2
2
2
2
2
2
2
[Ni(CH2SiMe3)(NNO)], 5
[Pd(NNO)Cl], 6b
4.21 (d, JHH = 13.2)
3.61 (t, JHH = 13.2)
0.06 (d, JHH = 13.9)
ꢀ0.52 (d, JHH = 13.8)
2
2
2
2
2
2
2
4.18 (d, JHH = 13.2)
4.33 (d, JHH = 13.2)
3.83 (t, JHH = 13.9)
3.95 (t, JHH = 13.9)
2.40 (m)
6.63 (bs)
2
2
a
In CDCl3.
In DMSOd.
b
diasterotopic proton H1 of the benzyl group appeared as a doublet
Infrared spectroscopy also provides supplementary evidence on
the tridentate coordination nature of the NNO ligand. Thus, in com-
plexes 1–5 the signal corresponding to C@N stretching vibration
was observed at higher energies relative to the free ligand
(1623–1632 cmꢀ1), whereas the stretching vibration of the NH
group was found between 3150 and 3250 cmꢀ1, in addition the
phenolic proton vibration was absent.
As mentioned above alkyl complexes 2–5 showed very similar
ligand spectroscopic features relative to compound 1 and therefore
the former will not be discussed in detail. The 1H and 13C{1H} NMR
data for these complexes are shown in Tables 1 and 2, respectively.
A general observation is that the metal atom provokes a chemical
shift displacement of carbons and protons of the ligand in the com-
plex relative to the free ligand, for instance, in the nickel complexes
the methylene protons of alkyl groups appeared displaced 0.3 ppm
at higher fields, while the other aliphatic protons moved to lower
fields.
0
0
at 3.64 ppm (2JHH = 14.3) due to coupling with H1 and H1 appeared
as one virtual triplet at 3.47 ppm (2JHH = 11.40) due to coupling with
H1 and NH (Fig. 2). On the other hand, protons of the bridge ethyl-
ene appeared as partially resolved multiplets at 2.89 (dt, 1H), 2.28
(dd, 1H), 1.81 (m, 1H) and 1.77 (m, 1H) ppm, given the coupling
among themselves and with the proton of the amine. The methy-
lene protons of the neophyl group were also diasterotopic and a
2
AX spin system can be observed at 2.40 (d, JHH = 8.60, 1H) and
2
1.61 (d, JHH = 8.60, 1H) ppm, while the methyl protons are found
as two singlets at 2.02 (s, 3H) and 1.68 (s, 3H) ppm.
13C{1H} and 13C NMR (C6D6, 300 MHz) of 1 provided additional
information on the structure of the complex. There were four sig-
nals in the aliphatic region of the carbon spectra at 29.9, 33.0,
36.7 and 42.3 ppm, which were assigned to the methyl, methylene
and quaternary carbons of the neophyl ligand, respectively. The
methylene carbons of NNO were located at lower field at 53.6 (s,
JCH = 140.1, CH2), 50.3 (s, JCH = 131.3, CH2) and 53.8 (s, JCH = 133.5,
CH2) ppm. The complete assignment of carbon and protons was
carried out using the monodimensional NMR techniques discussed
herein together with bidimensional NMR techniques such as
1H–1H COSY, 1H–13C HETCOR and NOESY (see Supplementary
information).
2.3. Preparation and characterization of Ni(II) and Pd(II) coordination
complexes
The coordination complexes of formula [MCl(NNO] (M = Pd(II),
6; Ni(II), 7), were prepared by mixing equimolar amounts of

14
C. Esqueda et al. / Polyhedron 40 (2012) 11–18
Fig. 2. 1H NMR spectrum (300 MHz, C6D6) of [Pd(CH2CMe2-o-C6H5)(NNO)], 1.
Table 2
13C{1H} NMR values of NNO ligand (in CDCl3) and complexes 1–6 (in C6D6) at 293 K.
Compound
13C NMR
IR (cmꢀ1
)
C@N
NH
HC@N
CH2-Ph
N-CH2-CH2-N
M-CH2
C(CH3)2
CH3
NNO ligand
158.9
169.1
167.5
166.0
166.4
167.9
163.9
53.6
53.6
50.1
56.5
51.9
52.1
54.4
48.7, 53.8
50.3, 53.8
45.9, 50.2
53.0, 57.2
47.8, 54.1
47.2, 53.6
50.4, 60.2
1620
1630
1628
1623
1628
1632
1617
3280
3150
3250
3220
3190
3150
3105
[Pd(CH2CMe2C6H5)(NNO)], 1
[Ni(CH2CMe2C6H5)(NNO)], 2
[Pd(CH3)(NNO)], 3a
[Ni(CH3)(NNO)], 4
36.7
31.9
42.3
41.8
29.9, 33.0
29.3, 33.1
ꢀ4.0
ꢀ7.4
[Ni(CH2SiMe3)(NNO], 5
-0.9
3.2
[Pd(NNO)Cl], 6b
a
In CDCl3.
In DMSOd.
b
PdCl2(COD) or NiCl2ꢁ6H2O and NNO in dichloromethane followed
by addition of KOH in excess. The diamagnetic square–planar pal-
ladium yellow complex 6 showed very similar spectroscopic fea-
tures to analogous organometallic compounds, vide supra,
particularly with the methyl palladium compound 3 and therefore
its spectroscopic features will not be discussed further. The room
temperature 1H NMR (CDCl3, 300 MHz) spectrum of the brown
complex 7 exhibited only broad signals between 0 and 10 ppm.
When the temperature was progressively lowered, the broad sig-
nals progressively sharpened and at 220 K distinct sharp signals
appeared for all protons. Seven unsymmetrical multiplets assigned
to the methylene –CH2CH2– chain, benzyl group and amine pro-
tons were observed at 220 K (see Supplementary information).
The imine proton H5 was not observed even at the lowest temper-
ature, but the stretching vibration of the C@N bond was observed
at 1621 cmꢀ1 by IR spectroscopy.
tetrahedral structures has been proposed in the literature [16],
we first considered that the broad signals in the 1H NMR spectrum
of 7 could be attributed to the presence of the paramagnetic Ni(II)
species [17,18] (Scheme 2a). However, we measured the magnetic
moment of 7 in solution (CDCl3) at 298 K (using Evans’ method) as
well as in solid state and we found that complex 7 was diamagnetic
agreeing with a square–planar structure. This finding is also sup-
ported by the fact that there was no color change of the solution
of 7 in the studied temperature range (323–250 K). Therefore, we
suggest that the dynamic process observed for complex 7 in solu-
tion is due to a conformational flexibility of the two chelating rings
as depicted in Scheme 2b which has been observed for other Ni(II)
complexes [19].
Complex Ni(NNO)2, 8, was prepared by reaction of any of the
alky complex precursors used in this work with two equivalents
of NNO ligand (Scheme 1). Crystals of 8 suitable for X-ray diffrac-
tion were obtained by crystallization in a mixture of Et2O/petro-
leum ether at ꢀ30 °C. Crystalline complex 8 was quite insoluble
Given that for some Ni(II) complexes a temperature-dependent
equilibrium between diamagnetic square–planar and high-spin

C. Esqueda et al. / Polyhedron 40 (2012) 11–18
15
Scheme 2. (a) Representation of the equilibrium between diamagnetic square–planar and high-spin tetrahedral structures of 7. (b) Proposed conformational rearrangement
for 7, certain atoms have been omitted for clarity proposes.
Fig. 3. ORTEP drawing of the molecular structure of [Ni(NNO)2], 8. Selected interatomic distances (Å) and angles (°): Ni(1)–N(1) = 2.0070(17), Ni(1)–N(3) = 2.0175(17), Ni(1)–
O(1) = 2.0410(14), Ni(1)–O(2) = 2.0415(14), Ni(1)–N(2) = 2.1794(17), Ni(1)–N(4) = 2.2761(17); N(1)–Ni(1)–N(3) = 177.12(6), N(1)–Ni(1)–O(1) = 88.81(6), N(3)–Ni(1)–O(1) =
93.86(6), N(1)–Ni(1)–O(2) = 93.00(6), N(3)–Ni(1)–O(2) = 87.99(6), O(1)–Ni(1)–O(2) = 92.43(6), N(1)–Ni(1)–N(2) = 81.23(6), N(3)–Ni(1)–N(2) = 96.10(7), O(1)–Ni(1)–
N(2) = 170.04(6), O(2)–Ni(1)–N(2) = 88.04(7), N(1)–Ni(1)–N(4) = 97.99(6), N(3)–Ni(1)–N(4) = 81.11(7), O(1)–Ni(1)–N(4) = 86.12(7), O(2)–Ni(1)–N(4) = 168.88(6),
N(2)–Ni(1)–N(4) = 95.29(7).
in most common solvents and had high thermal and thermody-
namic stability.
late rings of six and five members. A distortion of the NiN4O2 pseu-
do octahedron was clearly evident from the bond distances and
angles given in Fig. 3. The crystal structure also shows that the
nitrogen atoms of the amine group of the two NNO ligands bonded
to the metal center are chiral. Interestingly, the H attached to N(4)
was pointing towards O(1) while the H bound to N(2) was opposite
to O(2), so that the absolute configuration of one amine nitrogen of
one ligand is ‘‘R’’ and the amine nitrogen of the other ligand is ‘‘S’’.
Fig. 3 shows a perspective drawing of complex 8 indicating
selective atom labels and relevant bond lengths and angles. The
Ni(II) ion appeared in a N4O2 coordination sphere. Each of the
two meridionally spanning ligands (NNO) coordinated the metal
ion via imine-N, amine-N and deprotonated phenol-O, with the
oxygen atoms being in cis position, so each ligand forms two che-

16
C. Esqueda et al. / Polyhedron 40 (2012) 11–18
The bond lengths of Ni-N(2) and Ni-N(4) [2.1794(17), 2.2761(17)]
were longer than Ni-N(1) and N(3) [2.0070(17), 2.0175(17)] due to
bigger trans influence of the oxygen atoms. These data are in
agreement to the values found for known six coordinated Ni com-
plexes with nitrogen donor ligands [20]. Moreover, only one of the
two phenyl rings of the benzyl group was oriented over the five
ring chelate. It should be noted that the six membered chelate
rings are almost planar suggesting an aromatic character.
4.3. Synthesis of [Pd(NNO)(CH2CMe2C6H5)], 1
A Schlenk flask containing 504.84 mg (2 mmol) of palladium
neophyl metallacycle
and 592 mg
(2 mmol) of NNO ligand was cooled to ꢀ78° C, followed by addi-
tion of 60 ml of Et2O. The mixture was stirred for 15 min at this
temperature and then 1.5 h at room temperature. The solvent
was evaporated to dryness and the residue was extracted with
30 ml of Et2O, the solute was concentrated by reduced pressure
and the product crystallized at ꢀ30 °C. The reaction was almost
quantitative. Anal. Calc. for C30H32N2OPd: C, 66.36, H, 5.94; N,
5.16. Found: C, 66.15; H, 5.71; N, 5.03%. IR spectrum (selected
bands, Nujol, cmꢀ1): 3150 (NH), 1630 (C@N). 1H NMR (C6D6):
3. Conclusions
In this study, we prepared alkyl and chloro Ni(II) and Pd(II)
compounds containing a Schiff base ligand having N2O donor
atoms. The complexes were characterized by analytical, IR and
NMR spectroscopic methods. Structural characterization by sin-
gle-crystal diffraction analysis of one Ni(II) octahedral complex
was also discussed where the main feature was that the central
Ni(II) ion possesses a distorted octahedral geometry.
2
1.68(s, CH3, 3H), 2.02 (s, CH3, 3H), 1.61 (d, JHH = 8.60 Hz,Cq-CH2,
1H), 1.77 (m, N-CH2, 2H), 1.81 (m, N-CH2, 1H), 2.28 (dd, CN-CH2,
2
1H), 2.40 (d, JHH = 8.60 Hz, Cq-CH2, 1H), 2.89 (dd, NH, 1H), 3.47
2
2
(d, JHH = 11.40 Hz,Ph-CH2, 1H), 3.64 (d, JHH = 14.26 Hz,Ph-CH2,
1H), 6.80–7.80 (m, 16H), 8.50(s, HC = N, 1H). 13C NMR (C6D6):
29.9 (Cq-Me2), 33.0 (Cq-Me2), 36.7 (Cq-CH2), 42.3 (Cq-Me2), 53.6
(CH2-Ph), 50.3 (CH2NH), 53.8 (s, CH2C@N), 109.3 (Car), 118.0 (CHar),
121.3 (CHar), 124.8(CHar), 125.2 (Car), 125.7 (CHar), 126.0–130.0
4. Experimental
(Car), 152.5 (CHar), 155.8 (Car), 169.1 (C@N).
4.1. General procedures
4.4. Synthesis of [Ni(NNO)(CH2CMe2C6H5)], 2
Unless otherwise stated, operations for synthesis of
organometallic compounds were carried out under strictly inert
atmosphere conditions using standard Schlenk techniques and
the solvents were distilled under N2 atmosphere, employing as
drying agents CaH2(CH2Cl2, Hexane), Na/benzophenone (Et2O,
THF, Toluene). The starting materials were reagent grade and were
A
Schlenk flask containing 399.5 mg (1.16 mmol) of
and 338.7 mg (1.16 mmol) of NNO
ligand was cooled to ꢀ78 °C and then 50 ml of Et2O were added.
The mixture was continuously stirred for 15 min at ꢀ78 °C fol-
lowed by 1.5 h at room temperature. The solvent was evaporated
to dryness. Subsequently, the product was extracted with a mini-
mum amount of Et2O and then petroleum ether was slowly added
until the product began to precipitate as a red solid. Yield: 419 mg
(73%). Anal. Calc. for C30H32N2NiO: C, 72.75; H, 5.66; N, 6.51.
Found: C, 72.65; H, 5.51; N, 6.23%. IR spectrum (selected bands,
Nujol, cmꢀ1): 3250 (NH), 1628 (C@N). 1H NMR (C6D6): 1.64 (s,
purchased from Aldrich. The
[21],
[22], Pd(cod)(Cl)(Me) [23], Pd(TME-
DA)Me2 [24], Ni(Py)2Me2 [25] and Ni(PMe3)2(CH2SiMe3)2 [26],
were prepared following reported procedures.
FT-IR spectra were recorded using a Perkin-Elmer 710-B spec-
trophotometer, in 4000–400 cmꢀ1 region. 1H, 13C and bidimen-
sional NMR experiments were obtained either in an NMR Brucker
300 spectrometer (300 MHz) or a Varian Gemini 200 MHz Unity
plus. Chemical shits (d) are expressed in ppm downfield from
TMS at d = 0 ppm, and coupling constants (J) are expressed in Hz.
Elemental Analysis were carried out in the Chemical Research Cen-
ter at Universidad Autónoma del Edo. Hidalgo and Universidad
Autónoma de Morelos. X-ray diffraction data of compound [Ni(N-
NO)2] was obtained at the Chemical Research Center of the Uni-
versidad Autónoma del Edo. Hidalgo.
2
CH3, 3H), 2.21 (s, CH3, 3H), 0.72 (d, JHH = 8.05 Hz,Cq-CH2, 1H),
2
0.95 (dd, JHH = 4.69 Hz, N-CH2, 1H), 1.18 (sa, NH, 1H), 1.38 (m, N-
2
2
CH2, JHH = 4.94 Hz, 1H), 2.06 (t, CN-CH2, JHH = 13.36 Hz,1H), 1.58
2
2
(d, JHH = 8.05 Hz, Cq-CH2, 1H), 2.61 (t, JHH = 14.10 Hz, CN-CH2,
2
2
1H), 3.39 (d, JHH = 13.37 Hz,Ph-CH2, 1H), 3.91 (d, JHH = 14.26 Hz,
Ph-CH2, 1H), 6.70–7.90 (m, 16H), 8.48 (s, HC@N, 1H). 13C NMR
((C6D6): 29.3 (Cq-Me2), 33.1 (Cq-Me2), 31.9 (Cq-CH2), 41.8
(Cq-Me2), 50.1 (CH2-Ph), 45.9 (CH2NH), 52.1 (s, CH2C = N), 109.7
(Car), 118.0–136.0 (Car), 154.5 (CHar), 156.8 (Car), 167.5 (C@N).
4.2. Synthesis of [NNO] ligand, 1-((2-
4.5. Synthesis of [Pd(NNO)(Me)], 3
benzylamino)ethylimino)methyl)naphthalene-2-ol
Five hundred and ninety two milligrams (2 mmol) of NNO
ligand was added to a solution of dialkyl palladium complex,
[PdMe2(TMDA)], 504.84 mg (2 mmol) in 30 ml of Et2O maintained
at ꢀ30 °C. The mixture was allowed to stir 15 min at this temper-
ature and then 1 h at room temperature. The solvent was evapo-
rated under reduced pressure, the product was extracted with
30 ml of CH2Cl2, filtered and the solution was concentrated. The fil-
trate was stored at ꢀ30 °C yielding yellow crystals. Yield: 100 mg
(47%). Anal. Calc. for C21H22N2OPd: C, 59.37; H, 5.22; N, 6.59.
Found: C, 59.15; H, 5.11; N, 6.23. IR spectrum (selected bands, Nu-
jol, cmꢀ1): 3220 (NH), 1623 (C@N). 1H NMR (CDCl3): 0.40 (s, CH3,
3H), 2.66 (m, N-CH2, 1H), 2.81 (m, N-CH2, 1H), 3.40 (m, CN-CH2,
A solution of 2-hydroxy-1-naphthaldehyde (910 mg, 5 mmol) in
30 ml of dichloromethane was added to a solution of N-benzyleth-
ylenediamine (751 mg, 5 mmol) in 20 ml of Et2O. The mixture was
allowed to react at room temperature for 1 h, then filtered and
washed whit Et2O (2 ꢂ 5 ml). Yield: 1.49 g, 90%. Anal. Calc. for
C
20H20N2O: C, 78.92; H, 4.82; N, 9.20. Found: C, 78.80; H, 4.80; N,
9.03%. 1H NMR (CDCl3): 1.57(s, NH, 1H), 2.97(t, J = 5.6 Hz, HN-
CH2, 2H), 3.69(t, J = 5.6 Hz,CN-CH2, 2H), 3.83(s, CH2Ph, 2H),
6.91(d, J = 9.3 Hz, 1H), 7.20–7.40(m, 5H), 7.40(t, J = 7.2 Hz, 1H),
7.59(d, J = 7.8 Hz, 1H), 7.67(d, J = 9.3 Hz, 1H), 7.82 (d J = 8.4 Hz,
1H), 8.78(s, HC = N, 1H), 14.42 (sa, OH, 1H). 13C NMR (CDCl3):48.7,
53.6, 53.8, 117.8, 122.7, 124.8, 127.2, 128.1, 128.5, 128.8, 129.3,
137.2, 158.9. FAB-MS: m/z 304(62%, NNO). IR spectrum (selected
bands, KBr, cmꢀ1): 3280 (NH), 1620(C@N).
2
1H), 3.52 (m CN-CH2, 1H), 3.80 (dd, JHH = 11.70 Hz,Ph-CH2, 1H),
2
4.62 (dd, JHH = 11.16 Hz, Ph-CH2, 1H), 6.15 (sa, NH, 1H), 7.15–
7.75 (m, 11H), 8.81 (s, HC = N, 1H). 13C NMR (CDCl3): ꢀ4.0 (CH3),

C. Esqueda et al. / Polyhedron 40 (2012) 11–18
17
56.5 (CH2-Ph), 53.0 (CH2NH), 57.2 (s, CH2C@N), 110.5 (Car), 115.0–
4.9. Synthesis of [Ni(NNO)Cl], 7
140.0 (Car), 152.5 (CHar), 166.0 (C@N).
This compound was obtained as a brown solid following the
same route used in the preparation of complex 6. Yield:
286.5 mg (73.0%). Anal. Calc. for C20H19ClN2NiO: C, 60.43; H,
4.82; N, 7.05. Found: C, 60.27; H, 4.66; N, 6.88%. IR spectrum (se-
lected bands, KBr, cmꢀ1): 3285 (NH), 1621 (C@N). 1H NMR (CDCl3,
220 K): 1.61 (d, N-CH2, 2H), 3.02 (d, N-CH2, 2H), 3.33 (t, CN-CH2,
1H), 3.60 (t, CN-CH2, 1H), 3.98 (t, Ph-CH2, 1H), 4.76 (d, Ph-CH2,
1H), 4.75 (sa, NH, 1H), 6.50–7.50 (m, 12H).
4.6. Synthesis of [Ni(NNO)(Me)], 4
A suspension of NiCl2Py4 (880 mg, 2 mmol) in 50 ml of Et2O was
cooled to ꢀ78 °C and 1 ml of pyridine was added. The mixture was
allowed to stir 15 min and then 3.5 ml (2 mmol) of a solution LiMe
(1.4 M in Et2O) was added. The mixture was stirred 15 min at
ꢀ78 °C followed by 1 h at room. Again, the mixture was cooled at
ꢀ78 °C and 292 mg (1 mmol) of NNO ligand was added, stirred
15 min at this temperature and then 1.5 h at room temperature.
The solvent was evaporated under reduced pressure and the prod-
uct was extracted with 50 ml of Et2O, filtered and concentrated.
The concentrated solution was stored at ꢀ30 °C yielding orange
crystals. Yield: 460 mg (61%). Anal. Calc. for C21H22N2NiO: C,
66.88; H, 5.88; N, 7.43. Found: C, 66.53; H, 5.75; N, 7.23%. IR spec-
trum (selected bands, Nujol, cmꢀ1): 3190 (NH), 1628 (C@N). 1H
NMR (C6D6): 0.19 (s, CH3, 3H), 1.63 (sa, NH, 1H),2.19 (m, N-CH2,
1H), 2.48 (m, N-CH2, 1H), 2.63 (sa, CN-CH2, 1H), 2.85 (m CN-CH2,
1H), 3.73 (dd,Ph-CH2, 1H), 4.24 (dd, Ph-CH2, 1H), 7.00–8.00 (m,
11H), 8.45 (s, HC@N, 1H). 13C NMR (C6D6): -7.4 (CH3), 47.8 (CH2-
Ph), 51.9 (CH2NH), 54.1 (s, CH2C@N), 108.5 (Car), 115.0–140.0
(Car), 152.5 (CHar), 166.4 (C = N).
4.10. Synthesis of [Ni(NNO)2], 8
This compound can be obtained by double protonation of any
dialkyl nickel complex with two equivalents of NNO ligand. i.e.
152 mg (0.5 mmol) of NNO ligand was added to a solution of
[Ni(NNO)CH3] 188 mg (0.5 mmol) in 30 ml of Et2O and the reaction
mixture was stirred 1 h at room temperature. The solution was
concentrated to half of its original volume under reduced pressure.
The product crystallized as dark red crystals by diffusion with
petroleum ether after 72 h at ꢀ30 °C. Anal. Calc. for C40H38N4NiO2:
C, 72.20; H, 5.76; N, 8.42. Found: C, 71.98; H, 5.68; N, 8.25%. IR
spectrum (selected bands, KBr, cmꢀ1): 1621 (C@N).
4.11. X-ray structure analyses for compound 8
An X-ray-quality red crystal was glued onto the tip of a glass fi-
ber, and reflections were collected on a Bruker-SMART 5000 CCD
4.7. Synthesis of [Ni(NNO)(CH2SiMe3)], 5
based diffractometer, using
x scans and a rotating anode with
Mo K radiation (k = 0.71073 Å) at room temperature. The frames
a
Two hundred and ninety two milligrams (1 mmol) of ligand
NNO was added to a solution of [Ni(PMe3)2(CH2SiMe3)2] (383 mg,
1 mmol) in 50 ml of Et2O which was kept at ꢀ78 °C The mixture
was stirred for 15 min at ꢀ78 °C and then 1.5 h at room tempera-
ture. The solution color changed from orange to yellow. The reac-
tion mixture was filtered and the solvent evaporated giving a red
oil which was dissolved in petroleum ether and concentrated by
reduced pressure until an orange precipitate appeared. Yield:
359.2 (80%). Anal. Calc. for C24H38N2NiOSi: C, 64.16; H, 6.73; N,
6.24. Found: C, 66.03; H, 6.20; N, 6.12%. IR spectrum (selected
bands, Nujol, cmꢀ1): 3150 (NH), 1632 (C@N). 1H NMR (C6D6):
were integrated with the SAINT software package[27], using a nar-
row-frame algorithm, and the structure was solved by direct meth-
ods, completed by subsequent difference Fourier synthesis, and
refined by full-matrix least-squares procedures with SHELXTL 5.1
[28]. The structure was checked with PLATON [29] or SXGRAPH included
in the WINGX VI.6 [30] crystallographic software package. Non-H
atoms were refined with anisotropic thermal parameters.
Table 3
Crystal Data and Structure Refinement Details for Compound 8.
2
Formula
C40H38N4NiO2
665.45
291(2)
0.62 (s, CH3, 9H), 1.81 (sa, NH, 1H), -0.52 (m, JHH = 10.60 Hz, Si-
2
Molecular weight
Temperature (K)
Color
CH2, 1H), 0.06 (m, JHH = 10.60 Hz, Si-CH2, 1H),1.43 (dd,
2
2JHH = 5.97 Hz,N-CH2, 1H), 2.17 (m, JHH = 13.90 Hz, N-CH2, 1H),
red
2
2
1.88 (dd, JHH = 6.37 Hz,CN-CH2, 1H), 2.81 (t, JHH = 14.30 Hz, CN-
CH2, 1H), 3.61 (t, 2JHH = 1.70 Hz,,Ph-CH2, 1H), 4.21 (d,
2JHH = 13.18 Hz, Ph-CH2, 1H), 6.80–8.00 (m, 11H), 8.43 (s, HC = N,
1H). 13C NMR (C6D6): -0.9 (CH2-Si), 3.2 (CH3), 51.9 (CH2-Ph), 47.8
(CH2NH), 53.6 (s, CH2C@N), 110.3 (Car), 115.0–140.0 (Car), 153.1
(CHar), 167.9 (C@N).
Crystal size (mm)
Symmetry, space group
a, (Å)
b (Å)
c (Å)
.55 ꢂ 0.60 ꢂ 0.60
monoclinic, P2(1)/c
13.1799(8)
14.5556(9)
17.5018(11)
90
98.0420 (10)
90
3324.5(4)
4,
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g cmꢀ3
)
1.330
4.8. Synthesis of [Pd(NNO)Cl], 6
Diffractometer
k (Mo K ) (Å)
Monochromator
Scan type
Theta range for data collection (°)
Limiting indices
Bruker SMART 5000 CCD
0.71073
graphite
x scan
1.56–24.01
a
PdCl2(cod) (285 mg, 1 mmol) was added to a suspension of NNO
(304 mg, 1 mmol) in 30 ml of EtOH. The mixture was allowed to re-
act at room temperature for 1 h giving a yellow precipitate. The so-
lid was filtered and washed with cold EtOH (2 times/10 ml). Yield:
393 mg (88.0%). Anal. Calc. for C20H19ClN2OPd: C, 53.95; H, 4.30; N,
6.29. Found: C, 53.87; H, 4.22; N, 6.21. IR spectrum (selected bands,
KBr, cmꢀ1): 3105 (NH), 1617 (C@N). 1H NMR (DMSOd): 2.30–2.50
(m, N-CH2, 2H), 3.83 (t, CN-CH2, 1H), 3.95 (t, CN-CH2, 1H), 4.18 (dd,
Ph-CH2, 1H), 4.33 (dd, Ph-CH2, 1H), 6.63 (ta, NH, 1H), 7.00–8.00 (m,
11H), 8.45 (s, HC@N, 1H). 13C NMR (C6D6): 54.4 (CH2-Ph), 50.4
(CH2NH), 60.2 (s, CH2C@N), 109.5 (Car), 120.0–140.0 (Car and CHar),
153.0 (CHar), 163.9 (C@N).
ꢀ14 6 h 6 15, ꢀ16 6 k 6 16,
ꢀ13 6 l620
Number of data collected
Number of unique data (Rint
Number of parameters/restraints
Final R indices [I > 2
R indices (all data)
18119
)
5223 (0.0502)
557/0
R1 = 0.0371, wR2 = 0.0886
R1 = 0.0459, wR2 = 0.0938
0.0233 (10)
0.325 and ꢀ0.330
r
(I)]
Extinction coefficient
Largest difference in peak and hole
(eAꢀ3
)

18
C. Esqueda et al. / Polyhedron 40 (2012) 11–18
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Hydrogen atoms were treated as idealized contributions. Pertinent
crystallographic data are collected in Table 3.
(g) G. Hilt, T. Vogler, W. Hess, F. Galbiati, Chem. Commun. (2005) 1474;
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Acknowledgements
(i) P. Tagliatesta, B. Floris, P. Galloni, A. Leoni, G. D’Arcangelo, Inorg. Chem. 42
(2003) 7701;
(j) K. Yoshida, I. Morimoto, K. Mitsudo, H. Tanaka, Chem. Lett. 36 (2007) 998;
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This research was supported by grants from the Universidad de
Guanajuato (UG-2010) and SEP/CONACYT (México) (02-44420).
Appendix A. Supplementary data
(l) E.S. Johnson, G.J. Balaich, P.E. Fanwick, I.P. Rothwell, J. Am. Chem. Soc. 119
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CIF file giving details for the crystal structure determinations of
8 and figures giving a 1H NMR 13C{1H}, COSY, HETCOR and NOESY
spectra for compound 1, as well as 1H NMR of temperature variable
of 7. CCDC 855860 contains the supplementary crystallographic
data for [Ni(NNO)2], 8. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.poly.2012.04.002.
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