F.R. Fortea-Pérez et al. / Inorganica Chimica Acta 443 (2016) 267–273
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2.2.2. (n-Bu4N)2[Pd(2,4,6-Me3pma)2]Á2CH3CONH2. (2), (n-Bu4N)4[Pd
(H2O)4][Pd(4-Brpma)2]3Á2CH3CONH2 (3) and (n-Bu4N)4[Pd(H2O)4][Pd
(4-Clpma)2]3Á2CH3CONH2 (4)
A methanolic solution of TBAOH (1.0 M, 2.4 mmol) was added
directly to a one-neck round flask suspension of the corresponding
N-substituted oxamate proligand (0.6 mmol) in 10 mL of acetoni-
trile at 60 °C. Then, an aqueous solution of K2[PdCl4] (100 mg,
0.3 mmol in 5 mL of water) was added dropwise to the reaction
mixture and resulting basic solution was heated at 60 °C for 10 h
under continuous stirring. The solution was allowed to evaporate
at room temperature. X-ray quality yellow prisms were grown
up after two weeks (2) and a couple of days (3 and 4). Their formu-
las were determined by X-ray diffraction on single crystals.
2: Yield: 90%; IR(KBr/cmÀ1): 3436–3309 (OÁ Á ÁH–N and N–H),
2965, 2936, 2873 (C–H), 1664, 1596 (C@Oamide/oxamato). Anal. Calc.
(found): C, 62.20 (62.04); H, 9.36 (9.25); N, 7.50 (7.43)%.
Scheme 2. Synthesis of proligands reaction pathway.
N-4-chlorophenyloxamate (4-Clpma) ligands were prepared by fol-
lowing a previously reported procedure (Scheme 2) [33,34]. The
corresponding aniline derivative (83 mmol) was dissolved in THF
(250 mL) under dinitrogen and the resulting solution was treated
with ethyl chlorooxoacetate (9.3 mL, 83 mmol) in presence of tri-
ethylamine (12 ml, 83 mmol) at room temperature under continu-
ous stirring for 30 min. The resulting solution was filtered and the
solvent was removed under vacuum to afford an oily crude, which
quickly became solid. The obtained white solid was suspended in
water and filtered off, then washed with a small amount of diethyl
ether and dried under vacuum.
3: Yield: 96%; IR (KBr/cmÀ1): 3464–3148 (O. . .H-N, O. . .H-O,
N–H), 2958, 2933, 2872 (C–H), 1670, 1576 (C@Oamide/oxamato). Anal.
Calc. (found): C, 45.86 (45.74); H, 6.17 (6.11); N, 5.53 (5.44)%.
4: Yield: 96%; IR (KBr/cmÀ1): 3463–3142 (OÁ Á ÁH–N, OÁ Á ÁH–O,
N–H), 2960, 2936, 2874 (C–H), 1671, 1568 (C@Oamide/oxamato). Anal.
Calc. (found): C, 50.28 (49.74); H, 6.77 (6.11); N, 6.07 (5.94)%.
2.3. X-ray crystallography
Single crystal X-ray diffraction data for 1–4 were collected at
296 K on a Bruker-Nonius X8-APEXII CCD area detector system
2.1.2. EtH-2,4,6-Me3pma
Yield: 96%; IR (KBr/cmÀ1): 3257 (N–H), 3019, 2977, 2919 (C–H),
1727, 1679 (C@O); 1H NMR (CDCl3) d ppm): 1.42–1.49 (t, 3H, CH3),
2.19 (s, 6H, CH3), 2.29 (s, 3H, CH3), 4.41–4.48 (q, 2H, CH2), 6.91
(s, 2H, Haromatics), 8.41 (s, 1H, NH); 13C NMR (CDCl3) d (ppm):
14.4,18.7, 21.3, 64., 129.5, 129.9, 135.1, 138.1, 155.2, 161.4. Anal.
Calc. (found): C, 66.08 (65.36); H, 7.68 (7.76); N, 5.93 (5.97).
using graphite-monochromated Mo K
a radiation (k = 0.71073 Å),
and processed through the SAINT [35] reduction and SADABS [36]
absorption software. Due to the poor crystal quality, a lower hmax
of diffraction (completeness to theta 25 only 79.3%) was obtained
for 1–2, even if all possible steps were undertaken to ensure that
the experiment was able to extract the best diffracting power from
the sample. All the structures were solved by direct methods and
2.1.3. EtH-4-Brpma
subsequently completed by Fourier recycling using the SHELXTL
-
Yield: 95%; IR (KBr/cmÀ1): 3334 (N–H), 3129, 2981, 2905, (C–H),
1729, 1705 (C@O); 1H NMR (CDCl3) d (ppm): 1.29–1.34 (t, 3H, CH3),
4.27–4.34 (q, 2H, CH2), 7.54–7.57 (m, 2H, Haromatics), 7.71–7.74 (m,
2H, Haromatics), 10.92 (s, 1H, NH); 13C NMR (CDCl3) d (ppm): 14.20,
62.85, 116.99, 122.75, 131.99, 137.26, 155.89, 160.77. Anal. Calc.
(found): C, 44.14 (47.74); H, 3.70 (4.99); N, 5.15 (5.42).
2013 [37] software packages, then refined by the full-matrix
least-squares refinements based on F2 with all observed reflections.
All non–hydrogen atoms were refined anisotropically. The hydro-
gen atoms on the phenyl-substituted oxamate ligand and on the
tetra-n-butylammonium cations and acetonitrile (1) and aceta-
mide (2–4) lattice molecules were included at geometrically calcu-
lated positions and refined using a riding model. The hydrogen
atoms on water molecules in 3 and 4 were neither found nor cal-
culated. Crystal data and refinements conditions for 1–4 are sum-
marized in Table S1, whereas selected bond lengths and angles and
hydrogen bonds are listed in Tables 1 and 2 and S2–S3, respec-
tively. CCDC reference numbers are 1056331 (1), 1056332 (2),
1056333 (3), 1400299 (4). The A-level alert in the Check Cif of 3
is related to expected disorder on tetra-n-butyl moieties. The final
graphical manipulations were carried out with the Crystal Maker
programs. [38]
2.1.4. EtH-4-Clpma
Yield: 90%. IR(KBr/cmÀ1): 3334 (N–H), 3122, 2984, 2908, (C–H),
1729, 1698 (C@O); 1H NMR (CDCl3) QUOTE d (ppm): 1.29–1.34 (t,
3H, CH3), 4.27–4.35 (q, 2H, CH2), 7.41–7.44 (d, 2H, Haromatics), 7.77–
7.80 (d, 2H, Haromatics), 10.93 (s, 1H, NH); 13C NMR (CDCl3) d (ppm):
14.20, 62.85, 122.40, 128.10, 129.08, 136.85, 155.87, 160.79; Anal.
Calc. (found): C, 52.76 (51.26); H, 4.43 (5,45); N, 6.15 (5.62).
2.2. Synthesis of the complexes
2.2.1. (n-Bu4N)2[Pd(2,4,6-Me3pma)2]Á2CH3CN (1)
A methanolic solution of n-Bu4NOH (1.0 M, 1.2 mmol) was
poured into a one-neck round flask containing a suspension of
the EtH-2,4,6-Me3pma proligand (0.6 mmol) in 10 mL of acetoni-
trile at 60 °C. Then, an aqueous solution of K2[PdCl4] (100 mg,
0.3 mmol, in 5 mL of water) was added dropwise to the resulting
solution and the reaction mixture was heated at 60 °C for 10 h
under continuous stirring. The neutral solution was allowed to
evaporate at room temperature and X-ray quality yellow prisms
of 1 were grown up after three weeks. Their stoichiometry was
established by X-ray diffraction on single crystals.
3. Results and discussion
3.1. Synthesis and X-ray crystal structure
Compound 1 was synthesized in neutral conditions using the
stoichiometric amount of [n-Bu4N]OH required to generate the
fully deprotonated 2,4,6-Me3pma2À ligand in an acetonitrile solu-
tion and adding an aqueous solution of K2[PdCl4] in a 2:1 ligand-
to-metal molar ratio. Complexes 2–4 were synthesized as 1 but
using the base in a twofold excess of that needed to afford the
deprotonated 2,4,6-Me3pma2À and 4-Xpma2À ligands, respectively
(Scheme 1). The structures of 1 and 2 consist of trans-[Pd(2,4,6-
Me2pma)2]2À anions, tetra-n-butylammonium cations, and either
1: Yield: 92%; IR(KBr/cmÀ1): 3437 (O–H), 2962, 2927, 2874 (C–
H), 1670, 1595 (C@O). Anal. Calc. (found): C, 64.27 (64.03); H, 9.30
(9.25); N, 7.75 (7.63)%.