Figure 1.
The structure of Compounds IVa-c.
The active alkyltin groups were first attached to the
meta position of the benzene ring [
9,
10] and the resulting aldehyde was then allowed to react with aniline and with a selected substituted aniline [
9] such as
p-chloroaniline,
m-trifluoromethylaniline, and
m-methoxyaniline giving a highly substituted Schiff base (imine) which is reacted directly with a phosphate ester such as diphenyl phosphate to give solid producs IV
a-c (
Scheme 1).
Scheme 1.
Synthesis of organotin-phosphorus compounds.
The titled compounds were isolated in almost quantitative yield (
Table 1). The stoichiometry of the compounds was established by elemental analysis (
Table 2) which showed agreement with the calculated values; further evidence was obtained from the corresponding
13C-,
1H-NMR and FT-IR spectra.
2.1. 13C-NMR Spectra
Generally, the assignments of the
13C-NMR resonances for tin-phosphorous compounds (
Table 3) in which there are more than three benzene rings are much more difficult than for the starting compounds (I, II, benzaldehyde, aniline,
p-chloroaniline,
m-trifluoromethylaniline,
m-methoxyaniline, and diphenyl phosphite) (
Table 4), because excluding the quaternary carbons, the
13C chemical shifts for the ring carbons in 1, 2 and 3 and its derivatives are spread over 18 ppm, compared with the
13C of the starting material in which only one benzene ring is found. Assignments of the
13C chemical shifts of rings 1, 2 and 3 were based on comparisons with reported values [
9,
11,
12,
13,
14].
The quaternary carbons C-1, C-3, C'-1, C'-3, C'-4, C'-5, and C''-1 are readily identified since they are less intense and almost invariant in position compared with other signals, as a result of long relaxation times of the quaternary carbons [
9,
15].
For example, the
13C-NMR spectrum of diphenyl-1-(4-chloroanilino)-1-[3-(tri-
n-butylstannyl)-phenyl]methyl phosphonate (
IVa) in CDCl
3, shows that the
13C signal of C
0 (for the numbering refer to
Figure 1) appears at δ 53.15 and 59.32 ppm, which indicates a clear spin-spin coupling between
31P and
13C.
The ring carbon values were confirmed by using the substituent chemical shift (SCS) effect of the ‑SnBu3n, -N-R, and (Ph-O)2P(O)-CH groups on the ring carbons, in comparison with the parent compounds. However, it has been found that the SCS effects for the above mentioned groups are additive in all positions. It is worth noting that the 13C chemical shift of C0 in which the phosphorous atom appears directly bonded to it generally appears as a doublet centered at δ 55.5 ppm. As expected the carbon of C0, appears as a single peak coupled with the adjacent 31P atom (I = 0.5, 100%).
13C spin-spin coupling constants involving
31P have been determined during the rapid growth of organophosphorous chemistry, particularly for biological molecules such as the nucleotides, phospholipids, and the titled compounds which contain phosphorous.
13C-
31P spin-spin interactions have frequently been used as a probe and also used to identify carbons near the phosphorous atom. The
13C-NMR signal of the imine group (–C=N) of compound III (
Scheme 1) shows only one signal at δ 161.0 ppm, which indicates the existence of only one isomer.
Table 3.
13C-NMR data of the titled compounds.
Table 3.
13C-NMR data of the titled compounds.
R group | δ (ppm) |
---|
Sn-CH2- | -CH2CH2- | -CH3 | C0 | C1 | C2 | C3 | C4 | C5 | C6 |
---|
4-Cl | 29.0 | 27.8 | 9.6 | 59.2 | 136.0 | 136.5 | 146.8 | 143.3 | 128.2 | 129.5 |
13.6 | 53.0 |
3-CF3 | 29.0 | 27.3 | 9.6 | 59.4 | 136.4 | 137.0 | 142.4 | 142.4 | 128.3 | 129.5 |
13.6 | 53.2 |
3-OCH3 | 29.0 | 27.3 | 9.6 | 60.1 | 134.3 | 136.3 | 142.4 | 142.4 | 127.9 | 128.3 |
13.5 | 54.0 |
R group | δ (ppm) | |
C'1 | C'2 | C'3 | C'4 | C'5 | C'6 |
4-Cl | 147.4 | 113.9 | 135.0 | 118.1 | 129.7 | 112.2 |
3-CF3 | 146.4 | 115.1 | 139.0 | 119.3 | 129.0 | 120.8 |
3-OCH3 | 142.6 | 91.9 | 153.8 | 120.4 | 153.8 | 91.9 |
R group | δ (ppm) | |
C''1 | C''2,6a | C''3,5a | C''4 |
4-Cl | 150.4 | 120.7 | 130.2 | 127.3 |
149.8 | 120.5 | 130.2 |
3-CF3 | 150.5 | 120.6 | 129.5 | 127.9 |
150.1 | 120.4 | 129.5 |
3-OCH3 | 150.5 | 120.7 | 130.9 | 127.8 |
150.4 | 120.6 | 130.9 |
Table 4.
13C NMR data of the starting compounds.
Table 4.
13C NMR data of the starting compounds.
Compound | δ (ppm) |
---|
Sn-CH2- | -CH2CH2- | -CH3 | C0 | C1 | C2 | C3 | C4 | C5 | C6 |
---|
Sn-(CH2-CH2-CH2-CH3)3 | 27.8 | 26.8 | 13.6 | - | - | - | - | - | - | - |
18.0 |
III | 29.1 | 27.4 | 9.7 | 192.2 | 135.6 | 137.7 | 143.6 | 142.6 | 128.4 | 129.5 |
13.7 |
Compound | δ (ppm) | |
C'1 | C'2 | C'3 | C'4 | C'5 | C'6 |
4-Chloroaniline | 147.7 | 114.8 | 134.7 | 118.2 | 130.3 | 113.2 |
3-Trifluoromethaneaniline | 146.4 | 115.8 | 138.9 | 119.3 | 129.7 | 112.2 |
3-Methoxyaniline | 143.3 | 98.8 | 152.9 | 119.0 | 152.9 | 98.8 |
Compound | δ (ppm) | |
C''1 | C''2,6a | C''3,5a | C''4 |
Diphenyl phosphite | 149.3 | 120.8 | 131.8 | 127.6 |
149.0 | 120.5 | 131.8 |
2.3. FT-IR Spectra
The structures of the titled compounds were further confirmed by their FT-IR spectra as shown in (
Table 6).
Table 6.
FT-IR data of the titled compounds.
Table 6.
FT-IR data of the titled compounds.
Compound | Wavenumber (cm-1) |
---|
-(CH2)3CH3 | Aromatic ring | P-O-Aryl | -P=O | C-O-C | -C=O |
---|
| C-H stretching | C-H bending | C=C stretching | Stretching |
II | 2860, 2910, 2940 | 1350, 1370 | 1420, 1455 | - | - | 1080 | - |
III | 2840, 2910, 2950 | 1360 | 1450 | - | - | - | 1700 |
IVa | 2900, 2940 | 1290 | 1480 | 1180 | 1200 | - | - |
IVb | 2840, 2900, 2960 | 1340 | 1480 | 1100 | 1200 | - | - |
IVc | 2920, 2940 | 1300 | 1470 | 1040 | 1200 | - | - |
Generally, the conversion of compound II into compound III was confirmed by the disappearance of the peak at 1080 cm-1 and the appearance of a peak at 1700 cm-1 which was assigned to C=O stretching. Moreover the formation of compounds IVa-c was confirmed by peaks at 760, 1150 and 1260 cm-1 which were assigned to C-Cl, C-F and -O-CH3 stretching, respectively. In addition, the formation of compounds IVa-c was confirmed via the FT-IR spectra by the disappearance of peaks at 1700 cm-1 and the appearance of peaks at 3290, 3310, 3320 cm-1 and at 1580 cm-1 assigned to N-H stretching and bending, respectively.