Abstract
Several new monobutyltin(IV) derivatives containing both oximes and N-protected amino acids have been generated. The compounds having the general formulae BuSn[(L)2A], where LH=cyclohexanoneoxime, acetophenoneoxime and
Introduction
In recent years, the synthesis of organotin(IV) compounds containing a large variety of different substituents have attracted considerable interest. These compounds have interesting structural features (Sharma et al., 2007, 2010; Gupta et al., 2010; Maheshwari et al., 2014) and demonstrate potential applications in catalysis, sorption (Adachi et al., 1997) and organic light emitting diodes (Garcia-Lopez et al., 2014). It has been reported that a new dimethyltin(IV) complex was used as a precursor for the preparation of SnO2 nanoparticles which show photoluminescence (Najafi et al., 2013). SnO2 nanoparticles exhibit significant industrial applications such as catalyst supports (Jang et al., 2008; Dehbashi et al., 2013; Higuchi et al., 2014; Rabis et al., 2014; Zhao et al., 2014), transparent conducting electrodes (Kleinjan et al., 2008) and gas sensors (Wang et al., 2011; Kim et al., 2012; Xing et al., 2013). Some organotin(IV) compounds are used as PVC stabilizers (Xu et al., 1990), catalysts (Ashfaq et al., 2011; Devendra et al., 2013; Tariq et al., 2013), antioxidants (Jabbar et al., 2012; Sirajuddin et al., 2014), fungicides (Menezes et al., 2005; Singh and Kaushik 2008; Aziz-ur-Rehman et al., 2011; Parrilha et al., 2011; Dias et al., 2012) and as potential antitumor agents (Gleeson et al., 2008; Arjmand et al., 2011; Sun et al., 2011; Verginadis et al., 2011; Khandani et al., 2013; Nath et al., 2013; Carraher and Roner, 2014). These organic-inorganic organotin(IV) complexes may possess a rich diversity of structural motifs. In the present communication, we have endeavored to design and assemble organic-inorganic hybrid complexes of monobutyltin(IV) by the reactions of monobutyltin(IV) trichloride with oximes and N-protected amino acids.
Results and discussion
The monobutyltin(IV) derivatives 1–10 were synthesized by the reactions of BuSnCl3 with the sodium salts of the oximes and N-protected amino acids in 1:2:1 (Schemes 1 and 2) and 1:1:2 (Schemes 3 and 4) molar ratios in dry refluxing benzene.
Synthesis of monobutyltin(IV) derivatives 1–3.
Synthesis of monobutyltin(IV) derivative 4.
Synthesis of monobutyltin(IV) derivatives 5–7.
Synthesis of monobutyltin(IV) derivatives 8–10.
These derivatives are white solids and are soluble in common organic solvents such as chloroform, methanol, tetrahydrofuran and benzene. The isolated products were purified by recrystallization from benzene and hexane mixture in 69–80% yield. Suitable quality of crystals was not obtained under experimental conditions. These derivatives are monomers as revealed by molecular weight measurements. Plausible structures of these complexes were suggested using physico-chemical and spectroscopic [IR and NMR (1H, 13C and 119Sn)] studies.
Spectroscopic studies
IR spectra
In the IR spectra of monobutyltin(IV) derivatives, two medium intensity bands appeared in the regions 530–540 cm-1 and 630–660 cm-1, which may be assigned to Sn-O bonds (Sharma et al., 2007). The IR spectra of the free ketoximes exhibit a weak intensity band in the region (Sharma et al., 2007) 1560–1570 cm-1, which may be due to >C=N- bond. In the IR spectra of these derivatives, this band is shifted towards lower wave numbers and appears in the region 1520–1550 cm-1. In the IR spectra of free ketoximes, a strong band was observed in the region 920 cm-1, which may be assigned to N-O absorption. This band is shifted to lower wave numbers in the region 870–890 cm1 in the IR spectra of the derivatives.
In the IR spectra of monobutyltin(IV) derivatives, ν(COO)asym vibration appeared as a medium intensity band at 1640–1660 cm-1, and ν(COO)sym vibration was observed at 1390–1410 cm-1. The magnitude of Δν [Δν=ν(COO)asym-ν(COO)sym] is an important factor in deciphering the mode of bonding of N-protected amino acids with the central tin atom in these compounds. The value of Δν was of the order of 240–270 cm-1, which indicates the chelating bidentate nature of N-protected amino acids (Sharma et al., 2007). The bands appearing in the regions 410–440 cm-1 and 490 cm-1 may be assigned to Sn-C vibrations.
1H NMR spectra
The 1H NMR spectra of monobutyltin(IV) derivatives were recorded in CDCl3 solution. The hydroxyl group of the ketoximes and carboxylic OH of N-protected amino acids were absent in the 1H NMR spectra of these derivatives. This reveals the deprotonation of oximes and N-protected amino acids and formation of Sn-O bond. The butyl protons attached to tin atom appeared in the region 0.77–2.16 ppm. The aromatic protons of ketoxime are overlapping with the aromatic protons of N-protected amino acids and appeared as a complex pattern in the region 7.00–7.97 ppm.
13C NMR spectra
The 13C NMR spectra of monobutyltin(IV) derivatives were recorded in CDCl3 solution. In the 13C NMR spectra of cyclohexanoneoxime and acetophenoneoxime, >C=N- signals were observed at 160.66 ppm and 156.02 ppm, respectively. There is some shift in the positions of these signals in 13C NMR spectra of the corresponding derivatives. The carboxylic carbon signal shows some shift in the 13C NMR spectra of these derivatives as compared to its position in the ligands. This clearly shows the bidentate nature of N-protected amino acids (Saxena et al., 1990a,b; Saxena et al., 1992; Sharma et al., 2007). The butyl carbon atoms attached to tin appeared in the region 12.51–35.01 ppm.
119Sn NMR spectra
119Sn NMR spectra of monobutyltin(IV) derivatives were recorded in CDCl3 solution. 119Sn NMR spectra of monobutyltin(IV) derivatives 1–4 exhibit signals in the region -473 to -495 ppm, whereas the monobutyltin(IV) derivatives 5–10 show signals in the region -520 to -535 ppm. 119Sn NMR chemical shift values indicate the presence of five (Pettinari et al., 1997) and six (Swamy et al., 1998; Lloyd et al., 2006; Gupta et al., 2010) coordinated tin centers in the monobutyltin(IV) derivatives 1–4 and 5–10, respectively.
Mass spectrometry
Mass spectra of the two representative monobutyltin(IV) derivatives 4 and 5 were recorded. Molecular ion peak was not observed in the mass spectrum of monobutyltin(IV) derivative 4. The fragments of monobutyltin(IV) derivatives 4 and 5 are given in the Experimental section.
Conclusion
Monobutyltin(IV) derivatives of oximes and N-protected amino acids are monomeric in nature. The physico-chemical and spectroscopic (119Sn NMR) data suggest a trigonal bipyramidal geometry and a distorted octahedral geometry for monobutyltin(IV) derivatives 1–4 and 5–10, respectively. 119Sn NMR chemical shift values reveal the presence of five and six coordinated tin centers in monobutyltin(IV) derivatives 1–4 and 5–10, respectively.
Experimental
All the reactions for the generation of monobutyltin(IV) derivatives were carried out under anhydrous conditions. Standard methods were used for the synthesis of ketoximes, and N-protected amino acids were synthesized by Sheehan method (Sheehan et al., 1952). BuSnCl3 is commercially available and distilled before use. Tin was estimated as tin(IV) oxide. Molecular weights were determined by the Rast method (Furniss et al., 1989). FT-IR spectra of the ligands and organotin compounds were recorded as KBr pellets on a SHIMADZU FTIR 8400s spectrophotometer in the range 4000–400 cm-1. 1H, 13C and 119Sn NMR spectra were recorded in CDCl3 solution on BRUCKER AVANCE II 400 NMR spectrometer operating at 400.13, 100.61 and 149.21 MHz, respectively.
Synthesis of monobutyltin(IV) derivatives of oximes and N-protected amino acids
These derivatives were synthesized by a similar method. The synthesis of one representative derivative is described in detail, and analytical data for other derivatives are given.
Synthesis of compound 1:
A benzene solution (~10 mL) of cyclohexanoneoxime (0.59 g, 5.21 mmol) and a benzene solution (~10 mL) of N-phthaloylvaline (0.64 g, 2.60 mmol) were added to methanolic solution (~5 mL) (sodium reacts with methanol) of sodium (0.18 g, 7.82 mmol), and the reaction contents were refluxed for ~5 h. Subsequently, a benzene solution (~10 mL) of BuSnCl3 (0.73 g, 2.60 mmol) was added to sodium salt of the two ligands (sodium salts of both the ligands were formed in situ), and the reaction contents were further refluxed for ~8 h. The precipitated NaCl was filtered out. After removing the excess solvent under reduced pressure, a white solid was obtained which was purified by recrystallization from benzene and hexane mixture. Yield: 76%. M.P. 168–170°C. NaCl: calc., 0.45; found, 0.44. Anal. calc. for C29H41N3O6Sn: C, 53.88; H, 6.39; N, 6.50; Sn, 18.36. Found: C, 53.71; H, 6.31; N, 6.52; Sn, 18.34. Molecular weight: calc., 646.36; found, 629. IR (KBr, cm-1): 1770, ν (CO)asym; 1720, ν (CO)sym; 1650, ν (COO)asym; 1530, ν (>C=N-); 1400, ν (COO)sym; 890, ν (N-O); 660, 540, ν (Sn-O); 490, 430, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.18 (t, 4H, CyC2-H), 2.48 (t, 4H, CyC6-H), 7.27–7.85 (m, 4H, aromatic ring), 4.50 (d(unresolved), 1H, C2′-H), 3.76 (st, 1H, C3′-H), 0.88–1.65 (m, 9H, Sn-butyl), CyC3,4,5-H, C3′-CH3 and C4′-H are merged with butyl region. 13C NMR (CDCl3, 100.62 MHz) δ: 175.59 (C1′), 167.83 (CO), 159.59 (C1), 134.21, 131.81, 123.56 (aromatic carbon atoms), 56.21 (C2′), 28.52, 27.08, 25.11, 13.22 (Sn-butyl carbon atoms), 31.04, 27.55, 23.18 (cyclohexyl carbon atoms), 25.22 (C3′), 23.14 (C3′-CH3), 20.98 (C4′). 119Sn NMR (CDCl3, 149.21 MHz) δ:-475, -485.
Synthesis of compound 2:
Stoichiometric amounts: sodium (0.17 g, 7.39 mmol), cyclohexanoneoxime (0.57 g, 4.92 mmol), N-phthaloylisoleucine (0.64 g, 2.46 mmol) and monobutyltin(IV) trichloride (0.69 g, 2.46 mmol). Yield: 80%. M.P. 158–159°C. NaCl: calc., 0.43; found, 0.41. Anal. calc. for C30H43N3O6Sn: C, 54.56; H, 6.56; N, 6.36; Sn, 17.97. Found: C, 54.51; H, 6.53; N, 6.39; Sn, 17.96. Molecular weight: calc., 660.39; found, 641. IR (KBr, cm-1): 1760, ν (CO)asym; 1720, ν (CO)sym; 1640, ν (COO)asym; 1540, ν (>C=N-); 1400, ν (COO)sym; 870, ν (N-O); 640, 530, ν (Sn-O); 490, 420, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.18 (t, 4H, CyC2-H), 2.43 (t, 4H, CyC6-H), 7.21–7.76 (m, 4H, aromatic ring), 4.30 (d, 1H, C2′-H), 3.77 (m, 1H, C3′-H), 0.77–1.96 (m, 9H, Sn-butyl), CyC3,4,5-H, C3′-CH3, C4′-H and C5′-H are merged with butyl region. 13C NMR (CDCl3, 100.62 MHz) δ: 173.21 (C1′), 167.93 (CO), 160.86 (C1), 134.01, 131.77, 123.43 (aromatic carbon atoms), 57.54 (C2′), 41.97 (C3′), 34.50, 26.73, 25.58, 13.36 (Sn-butyl carbon atoms), 31.74, 25.86, 24.89 (cyclohexyl carbon atoms), 25.46 (C4′), 16.91 (C3′-CH3), 11.04 (C5′). 119Sn NMR (CDCl3, 149.21 MHz) δ:-478, -495.
Synthesis of compound 3:
Stoichiometric amounts: sodium (0.20 g, 8.69 mmol), cyclohexanoneoxime (0.65 g, 5.79 mmol), N-phthaloylphenylalanine (0.85 g, 2.90 mmol) and monobutyltin(IV) trichloride (0.82 g, 2.90 mmol). Yield: 72%. M.P. 165–166°C. NaCl: calc., 0.51; found, 0.50. Anal. calc. for C33H41N3O6Sn: C, 57.07; H, 5.95; N, 6.05; Sn, 17.09. Found: C, 57.22; H, 6.01; N, 6.12; Sn, 17.07. Molecular weight: calc., 694.40; found, 676. IR (KBr, cm-1): 1760, ν (CO)asym; 1710, ν (CO)sym; 1630, ν (COO)asym; 1550, ν (>C=N-); 1400, ν (COO)sym; 890, ν (N-O); 660, 530, ν (Sn-O); 490, 430, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.24 (t, 4H, CyC2-H), 2.48 (t, 4H, CyC6-H), 7.00–7.94 (m, 9H, aromatic ring), 5.73 (t, 1H, C2′-H), 3.56 (d, 2H, C3′-H), 0.86–1.97 (m, 9H, Sn-butyl). 13C NMR (CDCl3, 100.62 MHz) δ: 175.80 (C1′), 167.84 (CO), 159.04 (C1), 134.25, 131.98, 129.88, 127.69 (phenyl carbon atoms), 134.12, 131.61, 123.47 (aromatic carbon atoms), 57.79 (C2′),34.01 (C3′), 32.46, 27.75, 23.05, 13.62 (Sn-butyl carbon atoms), 30.94, 29.47, 28.95, 23.12 (cyclohexyl carbon atoms). 119Sn NMR (CDCl3, 149.21 MHz) δ:-473, -492.
Synthesis of compound 4:
Stoichiometric amounts: sodium (0.19 g, 8.26 mmol), acetophenoneoxime (0.74 g, 5.50 mmol), N-phthaloylisoleucine (0.71 g, 2.75 mmol) and monobutyltin(IV) trichloride (0.77 g, 2.75 mmol). Yield: 71%. M.P. 162–164°C. NaCl: calc., 0.48; found, 0.46. Anal. calc. for C34H39N3O6Sn: C, 57.97; H, 5.58; N, 5.96; Sn, 16.85. Found: C, 57.89; H, 5.52; N, 5.92; Sn, 16.84. Molecular weight: calc., 704.40; found, 689. ESI-MS, m/z (%): [C34H39N3O6Sn]+ 704.40 (n.o.), [C27H28N3O6Sn]+ 609.26 (22), [C27H29N3O6Sn]+ 610.26 (8), [C27H30N3O6Sn]+ 611.26 (6), [C26H26N3O6Sn]+ 595.24 (1), [C18H28N2O3Sn]+ 439.26 (13), [C8H10N2O4Sn]+ 316.12 (100), [C8H4NO2]+ 146.12 (12), [C5H12N]+ 86.10 (20). IR (KBr, cm-1): 1770, ν (CO)asym; 1710, ν (CO)sym; 1660, ν (COO)asym; 1540, ν (>C=N-);1400, ν (COO)sym; 880, ν (N-O); 630, 540, ν (Sn-O); 490, 440, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.20 (s, 6H, C2-H), 7.18–7.75 (m, 14H, aromatic ring), 4.51 (d(unresolved), 1H, C2′-H), 3.70 (m(unresolved), 1H, C3′-H), 0.79–1.43 (m, 9H, Sn-butyl), C3′-CH3, C4′-H and C5′-H are merged with butyl region. 13C NMR (CDCl3, 100.62 MHz) δ: 174.87 (C1′), 167.01 (CO), 154.88 (C1), 135.41, 130.76, 128.18, 126.90 (phenyl carbon atoms), 133.02, 127.30, 125.03 (aromatic carbon atoms), 56.98 (C2′), 31.01, 28.69, 24.85, 12.51 (Sn-butyl carbon atoms), 25.88 (C4′), 15.94 (C3′-CH3), 11.42 (C2), 10.63 (C5′). 119Sn NMR (CDCl3, 149.21 MHz) δ:-479, -488.
Synthesis of compound 5:
Stoichiometric amounts: sodium (0.18 g, 7.82 mmol), cyclohexanoneoxime (0.29 g, 2.60 mmol), N-phthaloylvaline (1.29 g, 5.21 mmol) and monobutyltin(IV) trichloride (0.73 g, 2.60 mmol). Yield: 78%. M.P. 148–150°C. NaCl: calc., 0.45; found, 0.44. Anal. calc. for C36H43N3O9Sn: C, 55.40; H, 5.55; N, 5.38; Sn, 15.21. Found: C, 55.32; H, 5.42; N, 5.31; Sn, 15.20. Molecular weight: calc., 780.45; found, 761. ESI-MS, m/z (%): [C36H44N3O9Sn]+ 781.32 [M+ +1] (1), [C34H38N3O9Sn]+ 751.33 (40), [C34H39N3O9Sn]+ 752.34 (18), [C34H33N3O9Sn]+ 746.38 (12), [C30H31N2O8Sn]+ 666.28 (10), [C24H18N2O8Sn]+ 581.22 (5), [C18H21N2O7Sn]+ 496.28 (10), [C13H13NO4Sn]+ 365.18 (100), [C13H14NO4]+ 248.10 (60), [C12H12NO2]+ 202.09 (30), [C8H4O2]+ 132.11 (18). IR (KBr, cm-1): 1760, ν (CO)asym; 1720, ν (CO)sym; 1650, ν (COO)asym; 1520, ν (>C=N-); 1410, ν (COO)sym; 870, ν (N-O); 630, 540, ν (Sn-O); 490, 440, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.14 (t, 2H, CyC2-H), 2.46 (t, 2H, CyC6-H), 7.27–7.83 (m, 8H, aromatic ring), 4.49 (d, 2H, C2′-H), 3.75 (st, 2H, C3′-H), 0.94–1.59 (m, 9H, Sn-butyl), CyC3,4,5-H, C3′-CH3 and C4′-H are merged with butyl region. 13C NMR (CDCl3, 100.62 MHz) δ: 174.79 (C1′), 167.89 (CO), 160.71 (C1), 134.40, 131.74, 123.47 (aromatic carbon atoms), 57.69 (C2′), 31.89, 29.69, 22.03, 12.58 (Sn-butyl carbon atoms), 31.32, 26.79, 25.61, 25.52, 24.63 (cyclohexyl carbon atoms), 28.35 (C3′), 19.50(C3′-CH3), 17.99 (C4′). 119Sn NMR (CDCl3, 149.21 MHz) δ: -529, -533.
Synthesis of compound 6:
Stoichiometric amounts: sodium (0.16 g, 6.95 mmol), cyclohexanoneoxime (0.26 g, 2.31 mmol), N-phthaloylisoleucine (1.21 g, 4.63 mmol) and monobutyltin(IV) trichloride (0.65 g, 2.31 mmol). Yield: 69%. M.P. 153–154°C. NaCl: calc., 0.40; found, 0.38. Anal. calc. for C38H47N3O9Sn: C, 56.45; H, 5.85; N, 5.19; Sn, 14.68. Found: C, 56.39 H, 5.81; N, 5.21; Sn, 14.66. Molecular weight: calc., 808.50; found, 796. IR (KBr, cm-1): 1770, ν (CO)asym; 1720, ν (CO)sym; 1660, ν (COO)asym; 1540, ν (>C=N-); 1390, ν (COO)sym; 870, ν (N-O); 650, 530, ν (Sn-O); 490, 440, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.19 (t, 2H, CyC2-H), 2.51 (t, 2H, CyC6-H), 7.26–7.83 (m, 8H, aromatic ring), 4.66 (d(unresolved), 2H, C2′-H), 3.84 (m, 2H, C3′-H), 0.79–1.64 (m, 9H, Sn-butyl), CyC3,4,5-H, C3′-CH3, C4′-H and C5′-H are merged with butyl region. 13C NMR (CDCl3, 100.62 MHz) δ: 174.86 (C1′), 167.87 (CO), 159.83 (C1), 134.01, 131.77, 123.40 (aromatic carbon atoms), 59.02 (C2′), 34.46 (C3′), 35.01, 26.72, 25.46, 13.43 (Sn-butyl carbon atoms), 33.73, 25.85, 24.87 (cyclohexyl carbon atoms), 25.57 (C4′), 15.47 (C3′-CH3), 11.06 (C5′). 119Sn NMR (CDCl3, 149.21 MHz) δ: -523, -528.
Synthesis of compound 7:
Stoichiometric amounts: sodium (0.19 g, 8.26 mmol), cyclohexanoneoxime (0.31 g, 2.75 mmol), N-phthaloylphenylalanine (1.62 g, 5.50 mmol) and monobutyltin(IV) trichloride (0.77 g, 2.75 mmol). Yield: 79%. M.P. 138–139°C. NaCl: calc., 0.48; found, 0.47. Anal. calc. for C44H43N3O9Sn: C, 60.29; H, 4.94; N, 4.79; Sn, 13.54. Found: C, 60.42; H, 5.02; N, 4.99; Sn, 13.52. Molecular weight: calc., 876.53; found, 860. IR (KBr, cm-1): 1760, ν (CO)asym; 1710, ν (CO)sym; 1640, ν (COO)asym; 1550, ν (>C=N-); 1400, ν (COO)sym; 870, ν (N-O); 640, 540, ν (Sn-O); 490, 430, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.19 (t, 2H, CyC2-H), 2.50 (t, 2H, CyC6-H), 7.13–7.68 (m, 18H, aromatic ring), 5.11 (t, 2H, C2′-H), 3.58 (d, 4H, C3′-H), 1.21–1.86 (m, 9H, Sn-butyl). 13C NMR (CDCl3, 100.62 MHz) δ: 175.87 (C1′), 167.04 (CO), 159.44 (C1), 134.27, 131.98, 129.18, 127.39 (phenyl carbon atoms), 134.22, 131.65, 123.17 (aromatic carbon atoms), 57.71 (C2′),34.21 (C3′), 30.74, 28.75, 27.65, 13.22 (Sn-butyl carbon atoms), 32.16, 29.26, 29.77, 23.62, 22.25 (cyclohexyl carbon atoms). 119Sn NMR (CDCl3, 149.21 MHz) δ: -522, -531.
Synthesis of compound 8:
Stoichiometric amounts: sodium (0.21 g, 9.13 mmol), acetophenoneoxime (0.41 g, 3.04 mmol), N-phthaloylvaline (1.50 g, 6.08 mmol) and monobutyltin(IV) trichloride (0.86 g, 3.04 mmol). Yield: 73%. M.P. 142–144°C. NaCl: calc., 0.53; found, 0.51. Anal. calc. for C38H41N3O9Sn: Sn, 14.79. Found: Sn, 14.77. Molecular weight: calc., 802.46; found, 782. IR (KBr, cm-1): 1770, ν (CO)asym; 1720, ν (CO)sym; 1640, ν (COO)asym; 1530, ν (>C=N-); 1400, ν (COO)sym; 870, ν (N-O); 660, 540, ν (Sn-O); 490, 430, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.20 (s, 3H, C2-H), 7.28–7.97 (m, 13H, aromatic ring), 4.57 (d, 2H, C2′-H), 3.87 (st, 2H, C3′-H), 0.79–1.58 (m, 9H, Sn-butyl), C3′-CH3 and C4′-H are merged with butyl region. 13C NMR (CDCl3, 100.62 MHz) δ: 174.78 (C1′), 167.74 (CO), 155.78 (C1), 137.01, 129.89, 128.58, 127.65 (phenyl carbon atoms), 134.18, 131.64, 123.52 (aromatic carbon atoms), 57.54 (C2′), 31.38, 28.66, 25.48, 15.24 (Sn-butyl carbon atoms), 26.64 (C3′), 19.47 (C3′-CH3), 17.50 (C4′), 11.50 (C2). 119Sn NMR (CDCl3, 149.21 MHz) δ:-526, -532.
Synthesis of compound 9:
Stoichiometric amounts: sodium (0.17 g, 7.39 mmol), acetophenoneoxime (0.33 g, 2.46 mmol), N-phthaloylisoleucine (1.28 g, 4.92 mmol) and monobutyltin(IV) trichloride (0.69 g, 2.46 mmol). Yield: 75%. M.P. 145–146°C. NaCl: calc., 0.43; found, 0.42. Anal. calc. for C40H45N3O9Sn: C, 57.84; H, 5.46; N, 5.05; Sn, 14.29. Found: C, 57.81; H, 5.42; N, 5.03; Sn, 14.28. Molecular weight: calc., 830.51; found, 819. IR (KBr, cm-1): 1770, ν (CO)asym; 1720, ν (CO)sym; 1650, ν (COO)asym; 1540, ν (>C=N-); 1400, ν (COO)sym; 890, ν (N-O); 650, 540, ν (Sn-O); 490, 430, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.29 (s, 3H, C2-H), 7.28–7.82 (m, 13H, aromatic ring), 4.50 (d(unresolved), 2H, C2′-H), 3.78 (m, 2H, C3′-H), 0.83–1.50 (m, 9H, Sn-butyl), C3′-CH3, C4′-H and C5′-H are merged with butyl region. 13C NMR (CDCl3, 100.62 MHz) δ: 175.98 (C1′), 167.82 (CO), 155.98 (C1), 136.10, 129.35, 128.53, 126.09 (phenyl carbon atoms), 134.02, 132.73, 123.42 (aromatic carbon atoms), 56.85 (C2′), 37.96 (C3′), 34.43, 25.83, 25.68, 13.34 (Sn-butyl carbon atoms), 25.25 (C4′), 15.42 (C3′-CH3), 11.65 (C2), 11.47 (C5′). 119Sn NMR (CDCl3, 149.21 MHz) δ: -526, -535.
Synthesis of compound 10:
Stoichiometric amounts: sodium (0.2 g, 8.69 mmol), acetophenoneoxime (0.39 g, 2.90 mmol), N-phthaloylphenylalanine (1.71 g, 5.80 mmol) and monobutyltin(IV) trichloride (0.82 g, 2.90 mmol). Yield: 70%. M.P. 172–174°C. NaCl: calc., 0.51; found, 0.49. Anal. calc. for C46H41N3O9Sn: Sn, 13.21. Found: Sn, 13.19. Molecular weight: calc., 898.54; found, 872. IR (KBr, cm-1): 1760, ν (CO)asym; 1710, ν (CO)sym; 1650, ν (COO)asym; 1550, ν (>C=N-); 1390, ν (COO)sym; 870, ν (N-O); 640, 530, ν (Sn-O); 490, 420, ν (Sn-C). 1H NMR (CDCl3, 400 MHz) δ: 2.29 (s, 3H, C2-H), 7.14–7.77 (m, 23H, aromatic ring), 5.10 (t(unresolved), 2H, C2′-H), 3.56 (d, 4H, C3′-H), 0.81–2.16 (m, 9H, Sn-butyl). 13C NMR (CDCl3, 100.62 MHz) δ: 175.13 (C1′), 167.38 (CO), 155.60 (C1), 136.17, 136.09, 128.68, 128.44, 128.29, 128.16, 128.05, 126.24 (phenyl carbon atoms), 132.89, 128.47, 125.68 (aromatic carbon atoms), 53.31 (C2′),33.21, 26.97, 25.97, 13.34 (Sn-butyl carbon atoms), 12.14 (C2). 119Sn NMR (CDCl3, 149.21MHz) δ:-520, -530.
Acknowledgments
One of the authors (Manish Kumar Srivastava, M.K.S.) is thankful to the University of Rajasthan, Jaipur, for awarding a UGC UPE Non-NET fellowship. M.K.S. is also thankful to Dr. Asha Jain, Associate Professor, Department of Chemistry, University of Rajasthan, Jaipur for helping in recording the NMR spectra of the complexes from an outside institution.
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