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Journal of Molecular Structure 886 (2008) 66–71 www.elsevier.com/locate/molstruc
[Chloro(difluoro)acetyl]phosphoramidic acid dichloride ClF2CC(O)NHP(O)Cl2, synthesis, vibrational and NMR spectra and theoretical calculations Ana G. Iriarte a,1, Mauricio F. Erben b,1, Khodayar Gholivand c, Jorge L. Jios d, Sonia E. Ulic b,e,1, Carlos O. Della Ve´dova b,d,*,1 a
Instituto de Quı´mica Fı´sica, Facultad de Bioquı´mica, Quı´mica y Farmacia, Universidad Nacional de Tucuma´n, San Lorenzo 456, 4000 Tucuma´n, Argentina b CEQUINOR (CONICET-UNLP), Departamento de Quı´mica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 esq. 115 (1900) La Plata, Argentina c Department of Chemistry, Faculty of Science, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran d Laboratorio de Servicios a la Industria y al Sistema Cientı´fico, LaSeISiC (UNLP-CIC-CONICET), Camino Centenario e/505 y 508, Gonnet, Buenos Aires, Argentina e Departamento de Ciencias Ba´sicas, Universidad Nacional de Luja´n, Rutas 5 y 7, 6700 Luja´n, Argentina Received 7 August 2007; received in revised form 23 October 2007; accepted 31 October 2007 Available online 7 November 2007
Abstract The synthesis of a new carbacylamidophosphate compound, [chloro(difluoro)acetyl]phosphoramidic acid dichloride (ClF2CC(O)NHP(O)Cl2), is reported along with its FTIR, Raman and mass spectra. The theoretical vibrational spectra were used to perform a tentative assignment of the observed bands. Quantum chemical calculations were realized with ab initio and density functional theory (DFT) methods using different levels of approximation. The title compound was analyzed as a dimer with Ci symmetry (C@O double bond in anti position with respect to the P@O double bond). The simulation of the potential energy surface was performed varying the dihedral angles /(ClACACAN) and x(CACANAP) using HF and B3LYP methods. The harmonic vibrations obtained by all theoretical methods are in good agreement with the experimental results. 1H, 13C and 31P NMR are also reported. Ó 2007 Elsevier B.V. All rights reserved. Keywords: [Chloro(difluoro)acetyl]phosphoramidic acid dichloride; Vibrational spectra; Theoretical calculations; NMR spectroscopy
1. Introduction The amount of data reported on compounds containing the AC(O)NHP(O)A unit has increased in recent years [1–6]. Probably, this interest is due to the growth of the application fields of imide compounds, beside their connection to structural and chemical properties [7–10]. In this
* Corresponding author. Address: CEQUINOR (CONICET-UNLP), Departamento de Quı´mica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 esq. 115 (1900) La Plata, Argentina. E-mail address:
[email protected] (C.O. Della Ve´dova). 1 Scholar and Member of the Carrera del Investigador Cientı´fico y Tecnolo´gico, CONICET, Repu´blica Argentina.
0022-2860/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2007.10.036
way, the major efforts were mainly focused on the biological area, where the species possessing the group under consideration play an important role as insecticides, pesticides and pharmacological agents, such as their urease inhibitor capacity [11–15]. Some imide compounds were submitted to tautomeric studies [16] and X-ray crystal diffraction and infrared analysis were reported for CF3C(O)NHP(O)Cl2 [17]. Recently, we have carried out the vibrational analysis and theoretical studies of CF3C(O)NHP(O)Cl2 and CCl3C(O)NHP(O)Cl2 [1]. For the perfluoroacetyl compound, previous X-ray diffraction data showed that this molecule exists as a dimer linked by intermolecular hydrogen bonds in the solid phase [17]. Moreover, several bands
A.G. Iriarte et al. / Journal of Molecular Structure 886 (2008) 66–71
2. Experimental 2.1. Chemical synthesis Commercial samples of ClF2CC(O)NH2 (Fluka, 98%) and phosphorus pentachloride in equimolar amounts were placed in a reaction flask and allow to react at refluxe temperature in CCl4 for 2 h. The reaction was carried out under a stream of dry nitrogen. The ClF2CC(O)NPCl3 intermediate was isolated by distillation under atmospheric conditions and the desired product was obtained by exposure of the distillate to ambient moisture. The crude product, a white solid, was purified by repeated recrystalizations from petroleum ether until the GC-chromatogram showed only the signal of the desired product. 2.2. Spectroscopic measurements Infrared spectra between 4000 and 400 cm1 (resolution 1 cm1) were recorded as KBr pellets with a Perkin Elmer 1600 series FTIR. Raman spectra between 3500 and 150 cm1 were recorded using a FT Bruker IFS85 spectrometer (spectral resolution 4 cm1). The 1064-nm radiation line of an Nd/YAG laser was used for excitation. The solid samples were handled in Pyrex capillaries at room temperature. 1 H, 13C and 31P NMR spectra were registered on a Bruker AC 250 NMR spectrometer (250.0, 62.9, 235.2 and 101.2 MHz, respectively) at room temperature using 5mm probes. CDCl3 was used as solvent and referenced internally to (CH3)4Si for 1H and 13C NMR, while for 31 P NMR the spectra H3PO4 85% was used as external reference.
3. Quantum chemical calculations Previous studies carried out for the related CF3CC(O)NHP(O)Cl2 and CCl3C(O)NHP(O)Cl2 molecules [1] showed that a dimeric form is present in the solid phase. The experimental data [1,10] are in good agreement with the theoretical results obtained by quantum chemical calculations, which treated both molecules as dimers in the solid phase. In order to prove that the most stable structure for the molecule under consideration is the proposed one, a simulation of the potential energy surface (PES) was performed varying the dihedral angles /(ClACACAN) and x(CACANAP) in steps of 30° using HF and B3LYP methods and a 6-31G* basis set. Figs. 1 and 2 depict the curves obtained from these calculations. 5 B3LYP/6-31G* HF/6-31G*
4
Energy (kcal/mol)
of low intensity in 3000–2500 cm1 range in the infrared spectrum are in accordance with these intermolecular bridges. N-acylphosphoramidates and N-acylphosphoramidic esters compounds have shown a similar behavior [10]. Taking into account previous results obtained for related compounds [1], we assumed in this work for the ClF2CC(O)HP(O)Cl2 molecule a dimer form as the unique species present in the solid phase, with the C@O double bond in anti position relative to the P@O double bond. In order to carry out the assignment of the vibrational spectra, geometrical parameters and theoretical wavenumbers were calculated with ab initio (HF) and DFT (B3LYP) methods.
67
3
2
1
0 -180 -150 -120
-90
-60
-30
0
30
60
90
120
150
180
ϕ (Cl-C-C-N) Fig. 1. Calculated potential energy curve for /(ClACACAN) torsion angle of ClF2C(O)NHP(O)Cl2 at the HF/6-31G* and B3LYP/6-31G* levels of theory.
2.3. Mass spectra A GC–MS-QP2010 Shimadzu Gas Chromatograph–Mass Spectrometer was used. The following are the mass numbers (species) and relative abundances for some of the most prominent peaks: 160 ðCðOÞNHPðOÞCl2 þ Þ 100; 117 ðPðOÞCl2 þ Þ 60 and 85 ðCClF2 þ Þ 20, which shows the characteristic chlorine isotopic distribution, and 47 (PO+) 35.
Fig. 2. Calculated potential energy curve obtained by rotation around the CAN single bond of ClF2C(O)NHP(O)Cl2 computed at the B3LYP/631G* levels of theory.
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A.G. Iriarte et al. / Journal of Molecular Structure 886 (2008) 66–71
the ClF2CC(O)A moiety is in agreement with the conformational preference observed for related species such as ClF2C(O)Cl, ClF2CC(O)SH and ClF2CC(O)SSC(O)F [18]. Table 1 shows calculated bond length and angles. Quantum chemical calculations were performed with the Gaussian 03 program suite [19]. The electronic delocalization was studied by a natural bond orbital (NBO) analysis, using the B3LYP/6-31G* level of approximation. 4. Vibrational analysis
Fig. 3. Molecular model for the dimer of ClF2C(O)NHP(O)Cl2.
The PES analysis shows that the most stable structure, predicted by ab initio (HF/6-31G*) and DFT (B3LYP/ 6-31G* and 6-31+G**) methods, is a dimer with a centrosymmetric structure possessing Ci symmetry. According to the different theoretical approaches, the values of the dihedral angle /(ClACACAN) are: 84.7° (HF), 87.5° (B3LYP/6-31G*) and 82.2° (B3LYP/6-31+G** basis set), while the x angle adopts a 180° value in the most stable conformation (see Fig. 3). The gauche orientation adopted for
Table 1 0 , degree) Calculated geometry parameters for ClF2C(O)NHP(O)Cl2 (A HF 6-31G*
B3LYP 6-31G*
6-31+G**
CACl FAC a CAC CAO CAN NAH NAP PACla PAO OAH
1.759 1.317 1.538 1.182 1.371 1.013 1.663 1.991 1.453 1.896
1.798 1.341 1.551 1.207 1.384 1.033 1.684 2.027 1.482 1.820
1.788 1.347 1.556 1.209 1.381 1.034 1.687 2.026 1.483 1.807
ClACAC FACACa FACACla FACAF CACAO CACAN OACAN CANAH CANAP PANAH NAHAO HAOAP NAPAO OAPACla ClACACAN CACANAP
110.2 109.6 109.4 108.4 120.9 114.4 124.7 120.5 126.0 113.4 166.4 148.9 111.0 113.2 84.7 177.1
109.6 110.0 109.1 108.8 121.2 113.7 125.1 120.8 125.6 113.6 167.0 148.0 111.2 113.5 87.5 177.2
110.4 109.9 109.2 108.1 120.8 114.1 125.1 121.0 125.6 113.4 167.8 147.7 110.9 113.5 82.2 177.6
a
Mean values for bond length and angles.
The IR and Raman spectra of solid ClF2CC(O)NHP(O)Cl2 are shown in Fig. 4. A tentative assignment of the observed bands was performed by comparison with the calculated spectra, and the approximated description of modes is based on the calculated displacement vectors for the fundamentals, as well as a comparison with spectra of related molecules [1,2,4,7]. Experimental and calculated (B3LYP/6-31G**) frequencies, intensities and their tentative assignments are given in Table 2. The vibrational spectra (IR and Raman) of ClF2CC(O)NHP(O)Cl2, molecule are consistent with the presence of a dimeric form in the solid phase; which belongs to Ci symmetry group with 3N 6 = 66 normal modes of vibrations split into Ag and Au blocks. The 33 Ag and 33 Au normal modes are both Raman and IR active. The title compound was fully analyzed on the basis of the vibrational assignment carried out for CF3C(O)NHP(O)Cl2 (1) and CCl3C(O)NHP(O)Cl2 (2) [1], and other related compounds [2,4,17]. The very weak band in the ClF2CC(O)NHP(O) Cl2 IR spectra located at 3083 cm1 with a Raman counterpart at 3064 cm1 was straightforward assigned to the NAH stretching mode. This relative low wavenumber for an NAH stretching vibrational mode can be explained by NAH intermolecular interactions as reported on related carbacylamidophosphate compounds [1–4,6,13,14]. In (1)
%T
A
I
B
3500
3000
2500
2000
1500
1000
500
-1
ν (cm ) Fig. 4. Solid phase infrared (A, as KBr pellet) and Raman (B, pure) spectra of ClF2CC(O)NHP(O)Cl2.
A.G. Iriarte et al. / Journal of Molecular Structure 886 (2008) 66–71
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Table 2 Tentative assignments, experimental and calculated Raman and IR wavenumbers and intensities of the fundamental observed modes for ClF2CC(O)NHP(O)Cl2 Mode
Approximate descriptiona
Experimental wavenumbers (cm1)b
Calculated wavenumbers (cm1) HF/
B3LYP/ *c
6-31G
6-31G*
6-31G**
Ag
mNAH mC@O dNAH mCAC mP@O masCF2 msCF2 mCACl mPAN mCAN qNAH qC@O dCClF2 masPCl2 msPCl2 xCClF2 dCClF2 dP(O)Cl2 sCClF2 qP(O)Cl2 dC@O xP(O)Cl2 Skel. torsion dP(O)Cl2 CClF2 torsion dCCN
3064 (2) 1747 (6) 1527 (9) 1290 (24) 1238 (35) 1183 (7) 1112 (7) 973 (10) 878 (18) 828 (23) 756 (4) 710 (35) 628 (19) 593 (19) 542 (100) 496 (75) 431 (24) 388 (26) 365 (28) 347 (15) 310 (37) 295 (42) 270 (27) 232 (98) 191 (51) 166 (57)
3251 1843 1515 1300 1248 1240 1132 999 870 836 730 702 615 599 543 490 425 384 361 351 310 294 268 227 183 149
3291 1842 1513 1293 1249 1232 1134 973 881 838 734 708 613 590 539 487 416 383 353 346 305 291 260 229 182 152
3251 1819 1514 1280 1231 1184 1116 968 871 834 742 713 610 586 535 482 419 379 352 346 306 293 264 227 183 148
Au
mNAH mC@O dNAH mP@O mCAC masCF2 msCF2 mCACl mPAN mCAN qNAH qC@O dClF2 masPCl2 msPCl2 xCClF2 dCClF2 dP(O)Cl2 sCClF2 qP(O)Cl2 dC@O xP(O)Cl2 Skel. torsion dP(O)Cl2 CClF2 torsion dCCN
3083 vw 1742 s 1465 s 1290 m 1254 vs 1171 vs 1119 vs 976 m 880 w 828 m – 717 s 624 sh 597 s 544 m 485 w – – – – – – – – –
3264d 1841 (45) 1491 (84) 1295 (17) 1254 (1) 1232 (100) 1137 (53) 1002 (43) 868 (35) 836 (3) 733 (1) 729 (44) 616 (16) 598 (15) 542 (13) 482 (3) 426 (
