## 3 Results and Discussion  
### Synthesis of Complexes **1-4**  
The treatment of of nefenamic acid and the appropriate substituted tin chloride gave the corresponding tin complexes **1-4** as white solids. The reaction of a 1:1 mixture of nefenamic acid and triphenyltin chloride in boiling MeOH for 8 h provided **1** (Scheme 1) in a 70% yield. Similarly, the reaction of two mole equivalents of nefenamic acid and di-substituted tin chloride gave compounds **2-4** (Scheme 2) in 71-77% yields. Table 1 presents the elemental analyses, melting points, and yields of complexes **1-4**.  
The absorption peaks appeared at the 520-526 cm\({}^{-1}\) and 447-449 cm\({}^{-1}\) regions in the FTIR spectra of complexes (Table 2) and were attributed to the Sn-C and Sn-O vibrations, respectively [48; 49]. The asymmetric (v asym) and symmetric (v sym) vibrations of the carbonyl group were observed at the 1641-1643 cm\({}^{-1}\) and 1506-1508 cm\({}^{-1}\) regions, respectively. The difference between the asymmetric and symmetric vibrations of the C=O group (vasym \(-\)\(\
u\)sym) ranged from 133 to 137 cm\({}^{-1}\). The \(\Delta\)\(\sigma\) value is evidence for the bidentate chelation mode between the tin atom and the O=C-O group of nefenamic acid [50; 51; 52]. The microanalytical results confirmed the structures and purity of **1-4**.  
The \({}^{1}\)H NMR spectra showed the presence of an exchangeable singlet at the 9.45-9.77 ppm region corresponding to the NH proton (Table 3). Multiplet signals were seen within the 7.90-6.67 ppm region due to aromatic protons. The methyl protons attached to the aryl ring appeared as singlet signals at approximately 2.5 and 2.1 ppm regions. Meanwhile, the methyl protons attached to the tin atom in complex **4** appeared as a singlet at a very high field (0.78 ppm) as a result of the shielding effect.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Complex**} & \multicolumn{8}{c}{**FTIR (v, cm\({}^{-1}\))**} \\ \cline{2-8}  & \multicolumn{8}{c}{**C=O**} \\ \cline{2-8}  & **NH** & **asym** & **sym** & \(\Delta\)\(\sigma\) **(asym – sym)** & **C=C** & **Sn–C** & **Sn–O** \\ \hline
**1** & 3312 & 1643 & 1508 & 135 & 1452 & 525 & 449 \\
**2** & 3312 & 1641 & 1508 & 133 & 1450 & 520 & 448 \\
**3** & 3333 & 1643 & 1506 & 137 & 1456 & 526 & 447 \\
**4** & 3312 & 1643 & 1506 & 137 & 1454 & 524 & 447 \\ \hline \end{tabular}
\end{table}
Table 2: FTIR data of **1-4**.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Complex**} & \multicolumn{2}{c}{**1H (\(\delta\), ppm, Hz)**} \\ \hline
**1** & 9.46 (s, 1H, NH), 7.90–7.84 (m, 3H, Ar), 7.44–7.41 (m, 6H, Ar), 7.33–7.29 (m, 9H, Ar), 7.13–6.67 (m, 4H, Ar), 2.50 (s, 3H, Me), 2.09 (s, 3H, Me) \\
**2** & 9.45 (s, 2H, 2 NH), 7.89–7.80 (m, 6H, Ar), 7.36–7.10 (m, 1 OH, Ar), 7.03–6.67 (m, 6H, Ar), 2.50 (s, 6H, 2 Me), 2.50 (s, 6H, 2 Me) \\
**3** & 9.77 (s, 2H, 2 NH), 7.89–7.85 (m, 6H, Ar), 7.46–6.96 (m, 8H, Ar), 2.50 (s, 6H, 2 Me), 2.04 (s, 6H, 2 Me), 1.64–1.29 (m, 12H, 6 CH\({}_{2}\)), 0.81 (t, 7.6 Hz, 6H, 2 Me) \\
**4** & 9.45 (s, 2H, 2 NH), 7.89–7.84 (m, 6H, Ar), 7.32–6.98 (m, 8H, Ar), 2.50 (s, 6H, 2 Me) \\
**2.08 (s, 6H, 2 Me)**, 0.78 (s, 6H, 2 Me) \\ \hline \end{tabular}
\end{table}
Table 3: \({}^{1}\)H NMR data (DMSO-\(d_{6}\)) of **1-4**.