Synthesis, structural characterization and crystal structure of some dimethyltin complexes containing substituted 1,10-phenanthroline

Journal of Molecular Structure 1142 (2017) 156e167

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Synthesis, structural characterization and crystal structure of some dimethyltin complexes containing substituted 1,10-phenanthroline Badri Z. Momeni*, Fahimeh Haghshenas, Saba Hadi Faculty of Chemistry, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran 15418, Iran

a r t i c l e i n f o

a b s t r a c t

Article history: Received 4 February 2017 Received in revised form 12 April 2017 Accepted 12 April 2017

The reaction of dimethyltin dichloride with four substituted 1, 10- phenanthroline has been studied. The reactions of dimethyltin dichloride with 5-methyl-1,10-phenanthroline (Mephen); 5,6-dimethyl-1,10phenanthroline (Me2phen); 5-nitro-1,10-phenanthroline (NO2phen); 5-chloro-1,10-phenanthroline (Clphen) resulted in the formation of the hexa-coordinated complexes of [SnMe2Cl2(NN)] {Mephen (1), Me2phen (2), NO2phen (3), Clphen (4)}. The resulting products have been fully characterized by elemental analysis, multinuclear (1H, 13C, 119Sn) NMR, DEPT-135, HHCOSY and HSQC NMR spectroscopy. The solid state X-ray determination of complexes [SnMe2Cl2(Mephen)] (1) and [SnMe2Cl2(Me2phen)] (2) revealed that the complexes 1 and 2 contain the hexa-coordinated tin(IV) atom in an octahedral geometry with the trans-[SnMe2] configuration. The SneN bond distances in 1e2 are 2.47e2.48 Å which are almost among the largest values. © 2017 Elsevier B.V. All rights reserved.

Keywords: Organotin Phenanthroline Adduct NMR Crystal structure

1. Introduction The various derivatives of organotin compounds such as diimines, terpyridines or carboxylates display potential applications such as a variety of biological activities, particularly, antibacterial, anti-tumour and anti-cancer activity [1e8]. Three factors of organic group R, the halide or pseudohalide and the nature of donor ligand are important in the activity of organotin compounds. For example, most dibromo complexes are active than the corresponding dichloro or diiodo analogues. The majority of the investigation of the activity of the organotin complexes has been focused on the bidentate ligand with cis-halogens, since they are structurally similar to those of active platinum complexes [9]. For example, [SnEt2Cl2(phen)] (phen ¼ 1,10-phenanthroline) containing cis-Cl2 as a leaving group, can intercalate into DNA, resulting in the unwinding of the DNA or interacts with DNA by ion binding or hydrophobic interacting which stabilize the metal complex-DNA system [1]. It has been shown that the active Sn(IV) complexes containing N-donor atoms have the average SneN bond lengths > 2.39 Å which reveals the pre-dissociation of the ligand as an important step in these complexes [10]. The use of chelating pyridyl ligand in the coordination

* Corresponding author. E-mail address: [email protected] (B.Z. Momeni). http://dx.doi.org/10.1016/j.molstruc.2017.04.042 0022-2860/© 2017 Elsevier B.V. All rights reserved.

chemistry of tin adducts has grown rapidly, with the various substituted 2,2'-bipyridine and 1,10-phenanthroline as the bidentate ligands [11e16]. The trans-configuration of R2 have been observed in [SnR2Cl2(phen)] {R ¼ p-Clbenzyl, p-methylbenzyl, benzyl) [17e19]. The unusual feature of cis-[SnPh2] configuration in 0 0 [SnPh2Cl2(bu2bpy)] (bu2bpy ¼ 4,4 -di-tert-butyl-2,2 -bipyridine) has been assigned to the steric hindrance between bu2bpy group and phenyl group on the tin atom [16]. On the other hand, trans[SnMe2] and trans-[SnCl2] configurations in [SnMe2Cl2(bupy)] (bupy ¼ 4-tert-butylpyridine) was observed which differs from cis[SnCl2] configuration in the corresponding diimine ligand of bu2bpy [16]. In spite of the well-known chemistry of organotin complexes, the variety of structures containing the phenanthroline ligand is more diverse than those of substituted phenanthroline ligands [20]. For example, trans-configuration of phenyl groups in [SnPh2Cl2(5Mephen)] and [SnPh2Cl2(4,7-Me2phen)] has been known [21]. Trans- or distorted trans-[SnR2] configuration were observed for the dialkyltin dihalide complexes [22,23]. The functionalization of the phenanthroline moiety enables the formation of the complexes which change the spectroscopic and electronic properties of the products and therefore, broadening the potential application for the biological studies. Herein, we report on the preparation, NMR data and crystal structures of new organotin(IV) complexes containing a series of the substituted chelating ligand of 1,10-phenanthroline to provide more information about

B.Z. Momeni et al. / Journal of Molecular Structure 1142 (2017) 156e167

their structural properties. Four different types of substituted phenanthroline were examined (5-methyl, 5,6-dimethyl, 5-NO2 and 5-Cl) that ranged from electron-donating to electronwithdrawing, as shown in Scheme 1.

2. Experimental 2.1. General remarks Elemental analyses were performed on a Costech ECS 4010 elemental analyzer. The 1H, 13C, 119Sn, HH-COSY, HSQC and DEPT135 NMR spectra were recorded using Bruker DPX 300 and Biospin GmbH 400 spectrometers. All the chemical shifts and coupling constants are reported in ppm and Hz, respectively. The 1H, 13C and 119 Sn NMR spectra are reported relative to TMS (1H, 13C) and SnMe4 119 ( Sn).

2.2. Preparation of [SnMe2Cl2(Mephen)] (1) A solution of Mephen (30 mg, 0.15 mmol) in acetone (5 mL) was added to a solution of SnMe2Cl2 (34 mg, 0.15 mmol) in diethyl ether (5 mL). The reaction mixture was stirred for 24 h at room temperature. The solvent was removed under reduced pressure and the resulting residue was solidified with dichloromethane/n-hexane to  give a white solid. Yield: 54%; m.p. 212e214 C. Anal. Calc. for C15H16Cl2N2Sn: C, 43.53; H, 3.90; N, 6.77. Found: C, 43.73; H, 3.99; N, 7.12%. NMR data in CDCl3: d(1H) 2.94 [s, 3H, CH3 of Mephen], 1.12 [s, 6H, 2J(119SneH) ¼ 113.3, 2J(117SneH) ¼ 108.5 Hz, SneMe]; (Mephen group) 7.95 [s, 1H, H6], 8.00 [dd, 1H, J ¼ 8.0, 8.0 Hz, H8], 8.09 [dd, 1H, J ¼ 8.0, 8.0 Hz, H3], 8.60 [dd, 1H, J ¼ 8.4, 1.6 Hz, H7], 8.82 [dd, 1H, J ¼ 8.8, 1.6 Hz, H4], 9.77 [dd, 1H, J ¼ 4.8, 1.6 Hz, H9], 9.86 [dd, 1H, J ¼ 4.8, 1.6 Hz, H2]; d(13C) 19.4 [s, CH3 of Mephen], 25.7 [s, 1 119 J( SneC) ¼ 1097 Hz, 1J(117SneC) ¼ 1049 Hz, SneMe]; (Mephen group) 125.3 (C3), 125.5 (C8), 126.8 (C6), 130.0 (C13), 130.4 (C14), 135.3 (C5), 136.7 (C4), 138.9 (C12), 139.2 (C7), 139.8 (C11), 147.5 (C2), 147.9 (C9); d(119Sn) in CDCl3: 262. Crystals suitable for X-ray structure determination were grown from a dichloromethane/nhexane solution.

Me

Me 5

6 14

13

4 3

7

2

N

9

N

N

Following the same procedure as the preparation of 1, this was prepared using Me2phen (30 mg, 0.14 mmol) and SnMe2Cl2 (32 mg,  0.14 mmol) to afford a white solid. Yield: 75%; m.p. 258e260 C (dec). Anal. Calc. for C16H18Cl2N2Sn: C, 44.91; H, 4.24; N, 6.55. Found: C, 44.06; H, 4.84; N, 6.09%. NMR data in CDCl3: d(1H) 2.90 [s, 6H, CH3 of Me2phen], 1.11 [s, 6H, 2J(119SneH) ¼ 110.5 Hz, 2 117 J( SneH) ¼ 106.5 Hz, SneMe]; (Me2phen group) 8.05 [dd, 2H, J ¼ 8.8, 8.8 Hz, H3,8], 8.87 [dd, 2H, J ¼ 8.8, 1.6 Hz, H4,7], 9.81 [dd, 2H, J ¼ 4.8, 1.2 Hz, H2,9]; d (13C) 15.7 [s, CH3 of Me2phen], 25.0 [s, 1J(119/ 117 SneC) not resolved, SneMe]; (Me2phen group) 125.2 (C3,8), 130.4 (C5,6), 131.6 (C13,14), 136.2 (C4,7), 138.8 (C11,12), 147.1 (C2,9); d(119Sn) in CDCl3: 264. Crystals suitable for X-ray structure determination were grown from a dichloromethane/n-hexane solution. 2.4. Preparation of [SnMe2Cl2(NO2phen)], (3) This was prepared similarly using NO2phen (30 mg, 0.13 mmol) and SnMe2Cl2 (29 mg, 0.13 mmol) to afford a pale yellow solid.  Yield: 84%; m.p. 220e224 C (dec). Anal. Calc. for C14H13Cl2N3O2Sn: C, 37.80; H, 2.95; N, 9.45. Found: C, 38.07; H, 3.18; N, 9.62%. NMR data in DMSO-d6: d(1H) 1.04 [s, 6H, 2J(119SneH) ¼ 114.1, 2 117 J( SneH) ¼ 109.3 Hz, SneMe]; (NO2phen group) 7.97 [dd, 1H, J ¼ 8.4, 8.4 Hz, H8], 8.00 [dd, 1H, J ¼ 8.4, 8.4 Hz, H3], 8.81 [dd, 1H, J ¼ 8.4, 2.0 Hz, H7], 8.92 [dd, 1H, J ¼ 8.4, 1.6 Hz, H4], 9.05 [s, 1H, H6], 9.28 [dd, 1H, J ¼ 4.4, 1.6 Hz, H9], 9.30 [dd, 1H, J ¼ 4.4, 1.6 Hz, H2]; d (13C) 23.6 [s, 1J(119SneC) ¼ 1026 Hz, 1J(117SneC) ¼ 981 Hz, SneMe]; (NO2phen group) 121.0 (C13), 125.2 (C8), 125.3 (C6), 126.2 (C14), 126.6 (C3), 133.0 (C4), 139.4 (C7), 144.3 (C5), 145.3 (C12), 146.6 (C11), 151.4 (C2), 153.5 (C9); d(119Sn) in DMSO-d6: 244. 2.5. Preparation of [SnMe2Cl2(Clphen)], (4) This was prepared similarly using Clphen (30 mg, 0.14 mmol) and SnMe2Cl2 (31 mg, 0.14 mmol) to afford a white solid. Yield:  77%; m.p. 231e233 C. Anal. Calc. for C14H13Cl3N2Sn: C, 38.72; H, 3.02; N, 6.45. Found: C, 38.56; H, 3.21; N, 6.56%. NMR data in CDCl3: d(1H) 1.15 [s, 6H, 2J(119SneH) ¼ 110.2, 2J(117SneH) ¼ 105.6 Hz, SneMe]; (Clphen group) 8.04 [dd, 1H, J ¼ 8.4, 8.4 Hz, H8], 8.14 [dd, 1H, J ¼ 8.8, 8.4 Hz, H3], 8.24 [s, 1H, H6], 8.60 [dd, 1H, J ¼ 8.0, 1.6 Hz, H7], 9.07 [dd, 1H, J ¼ 8.4, 1.6 Hz, H4], 9.80 [dd, 1H, J ¼ 4.8, 1.6 Hz, H9], 9.88 [dd, 1H, J ¼ 4.8, 1.6 Hz, H2]; d (13C) 25.3 [s, 1 119 J( SneC) ¼ 1074 Hz, 1J(117SneC) ¼ 1044 Hz, SneMe]; (Clphen group) 125.9 (C8), 126.0 (C3), 126.7 (C6), 128.4 (C13), 129.6 (C14), 131.7 (C5), 136.9 (C4), 138.8 (C7), 139.1 (C12), 140.7 (C11), 148.8 (C2), 149.3 (C9); d(119Sn) in CDCl3: 238.

Cl

NO2

N

N

N Clphen

NO2phen Scheme 1.

2.6. X-ray crystal structure determination Crystallographic data for 1e2 and were collected on a MAR345 dtb diffractometer equipped with image plate detector using MoKa X-ray radiation. The structure was solved by direct methods using SHELXS-97, and refined using full-matrix least-squares method on F2, SHELXL-97 [24]. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were added at ideal positions and refined using a riding model. A summary of the crystal data, experimental details and refinement parameters for 1e2 is given in Table 1.

Me2phen

Mephen

N

2.3. Preparation of [SnMe2Cl2(Me2phen)], (2)

8

12 11 N

Me

157

3. Results and discussion 3.1. NMR studies The reaction of dimethyltin(IV) dichloride with substituted 1,

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10- phenanthroline 5-methyl-1,10-phenanthroline (Mephen), 5,6dimethyl-1,10-phenanthroline (Me2phen), 5-nitro-1,10phenanthroline (NO2phen), 5-chloro-1,10-phenanthroline (Clphen) resulted in the formation of complexes [SnMe2Cl2(NN] {NN ¼ Mephen (1), Me2phen (2), NO2phen) (3), Clphen (4)} as shown in Scheme 2. These complexes were prepared by mixing the diethyl ether solution of dimethyltin dichloride and the acetone solution of the appropriate ligand in a 1:1 M ratio to give a white or pale yellow solid. The 1H NMR spectra of 1e4 show the expected integration and signal multiplicities. The complex [SnMe2Cl2(Mephen)] (1) was fully characterized by elemental analysis, 1H, 13C{1H}, 119Sn, HHCOSY, HSQC and DEPT-135 NMR spectroscopy and single crystal X-ray diffraction analysis. The 1 H NMR of complex 1 in CDCl3 shows a singlet at d ¼ 1.12 ppm which is accompanied by tin satellites with 2J(119SneH) ¼ 113.3 Hz and 2J(117SneH) ¼ 108.5 Hz (Fig. 1), while the starting complex SnMe2Cl2 in CDCl3 indicates 2J(119SneH) ¼ 69.8 Hz and 2 117 J( SneH) ¼ 66.8 Hz with d ¼ 1.23 ppm [25]. The 13C NMR spectrum of 1 in CDCl3 displayed a signal at d ¼ 25.7 with 1J(119SneC) ¼ 1097 Hz and 1J(117SneC) ¼ 1049 Hz (Fig. 2). The DEPT-135 spectrum of complex 1 confirms the structural information (Fig. 2). The assignments of the diimine ligand are made by a correlation in the HH COSY and HSQC spectra. For example, the HH COSY and HSQC spectra of 1 are shown in Figs. 3 and 4, respectively.

Table 1 Crystal data and structure refinement for complexes 1 and 2.

Empirical formula Formula weight Temperature (K) Crystal system Space group Z a (Å) b (Å) c (Å) b (º) V (Å3) Dcalc (g/cm3) Absorption coefficient (mm1) Crystal size (mm) Crystal color q range (º) Index ranges

Reflections collected Independent reflections Observed reflections Goodness-of-fit on F2 (GOF) Final R indices (I > 2 s (I)) Largest diff. peak and hole (eÅ3)

1

2

C15H16Cl2N2Sn 413.89 293(2) Monoclinic P21/c 4 8.0130(16) 21.272(4) 10.811(2) 105.66(3) 1774.4(6) 1.549 1.73 0.15  0.08  0.05 colorless 2.2 to 25.0 9  h  9, 25  k  25, 12  l  11 10316 3029 (Rint ¼ 0.048) 2662 (I > 2s(I)) 1.166 R1 ¼ 0.0798, wR2 ¼ 0.1454 0.65 and 0.85

C16H18Cl2N2Sn 427.93 293(2) Orthorhombic P n ma 4 10.139(2) 12.191(2) 15.004(3) 90 1854.6(6) 1.533 1.66 0.15  0.10  0.03 colorless 2.2 to 25.0 11  h  12 14  k  14 17  l  17 9448 1707 (Rint ¼ 0.047) 1516 (I > 2s (I)) 1.091 R1 ¼ 0.0447, wR2 ¼ 0.0762 0.29 and 0.42

Me Me

N

Cl Sn Cl

N Me (1)

Me N

Cl Cl

Cl Clphen

Sn

Me

Mephen

Cl

SnMe2Cl2

Me2phen

Me

Me NO2phen (2)

(4) Me N

Cl Sn Cl

N Me (3) Scheme 2.

Me

N

Me

Sn Cl

N

N

NO2

B.Z. Momeni et al. / Journal of Molecular Structure 1142 (2017) 156e167

159

(a)

(b)

Fig. 1. 1H NMR spectrum of [SnMe2Cl2(Mephen)](1) in the (a) aliphatic and (b) aromatic region in CDCl3.

On the other hand, it has been found that 1J(119Sne13C) depends linearly on the MeeSneMe angle for a number of tetra-, penta-, and hexa-coordinated di, tri and tetramethyltin(IV) compounds using eq. (1), where q ¼ MeeSneMe angle (deg) and 1J is measured in Hz [26]. This empirical relationship can be used for determination of the uncharacterized structures of the compounds in solution by the Lockhart and Manders equation. 1 119

J(

Sne13C) ¼ 11.4q875

(1)

Therefore, the coupling constant of 1J(119SneC) ¼ 1097 Hz was used to calculate q (CeSneC) by eq. (1), which is (172.98 ). The magnitude of q is very close to the observed value in the solid state from analysis of the X-ray crystallography (175.5(4) ). The 119Sn NMR spectrum of complex 1 showed a sharp signal at d ¼ 262 ppm in CDCl3. It has been reported d values from þ200 to 60 for four-coordinated, 90 to 190 for five-coordinated and 210 to 400 for six-coordinated tin atoms in solution [27]. Thus, the signal at 262 ppm is consistent with those reported for

the other hexa-coordinated organotin(IV) complexes. Additional confirmation of the geometry of trans-[SnMe2Cl2(Mephen)] (1) comes from the X-ray structure determination. Similarly, the 1H NMR of complex [SnMe2Cl2(Me2phen)] (2) in CDCl3 shows a chemical shift in d ¼ 1.11 ppm with 2 119 J( SneH) ¼ 110.5 and 2J(117SneH) ¼ 106.5 Hz. The 13C NMR spectrum of 2 shows a signal at d ¼ 25.0 ppm, however, the 1J(119/ 117 SneC) ¼ were not resolved. On the other hand, coordination number of tin atom in dimethyltin compounds has been related to the 2J(119SneH) coupling constant according to the Lockhart-Manders equation (eq. (2)) [26]. For complex [SnMe2Cl2(Me2phen)] (2), comparison between the calculated value of the CH3eSneCH3 angle (184.12 ) from 2 119 J( SneH) ¼ 110.5 Hz and solid state structure (175.2(2) ) implies that the solid state structure is retained in solution.

q ¼ 0.0161 [2J(119SneH)]21.32 [2J(119SneH)] þ 133.4

(2)

On the basis of eq. (2), the solution 2J(119SneH) for complex 1

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(a)

(b)

(c)

Fig. 2. (a)

13

C NMR spectrum of [SnMe2Cl2(Mephen)] (1) in the aliphatic and (b) in the aromatic region and (c) DEPT-135 spectrum of (1) in the aromatic region in CDCl3.

indicates a larger value for CH3eSneCH3 angle (190.14 ) which is different from those of observed by eq. (1) (172.98 ) and X-ray structure determination (175.5(4) ). We suggest that these deviation from the observed values from X-ray structure in solid state and corresponding solution data by using eq. (2) are due to the presence of methyl substituents on the phenanthroline ligands. Therefore, eq. (1) can be used with more confidence to estimate

CH3eSneCH3 angle in solution in the case of more crowding substituted phenanthroline ligand. Compound [SnMe2Cl2(NO2phen)] (3) is almost insoluble in all common organic solvents except DMSO. In the 1H NMR spectrum of 3 in DMSO-d6, the SneMe signal was observed at d ¼ 1.04 ppm with 2 119 the coupling constant J( SneH) ¼ 114.1 and 2 117 J( SneH) ¼ 109.3 Hz (Fig. 5). The 13C NMR of complex 3 in DMSO-

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161

(a)

(b)

Fig. 3. HHCOSY spectrum of complex [SnMe2Cl2(Mephen)] (1) in the (a) aliphatic and (b) aromatic region in CDCl3.

d6 displays a signal at d ¼ 23.6 ppm flanked by tin satellites with 1 119 J( SneC) ¼ 1026 and 1J(117SneC) ¼ 981 Hz (Fig. 6) which is slightly different with those of SnMe2Cl2 in DMSO. The values of d(119Sn) and d(H) for SnMe2Cl2 in DMSO-d6 are 246 and 1.06 ppm, respectively, while 2J(119SneH) and 2J(117SneH) are 117.8 and 113 Hz [25,28]. The above data indicates that the interaction

between SnMe2Cl2 and NO2phen is maintained in solution. It should be noted that the 119Sn chemical shift and nJ values for [SnEtPhCl2(phen)] in DMSO-d6 are close to those obtained for SnEtPhCl2 in the same solvent which can be assigned to the similar effects of the DMSO and phen on the NMR parameters [29]. Similarly, the 1H and 13C NMR spectra for complex

162

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Fig. 4. HSQC spectrum of complex [SnMe2Cl2(Mephen)] (1) in CDCl3.

[SnMe2Cl2(Clphen)] (4) are given in Figs. 7 and 8, respectively. The 2 119 J( SneH) and 2J(117SneH) values for 4 are 110.2 and 105.6 Hz, respectively, which implies an octahedral geometry for 4. The 1 119 J( SneC) coupling constants of 1026 and 1074 Hz for 3 and 4 were used to determine q (CeSneC) by eq. (1), which are 166.75 and 170.96 , respectively. The CeSneC angles for 3 and 4 were also estimated by using the coupling constant of 2J(119SneH) ¼ 114.1 and 110.2 Hz by application of eq. (2) which are 192.39 and 183.46 , respectively. Details of 1H and 13C NMR data for complexes 1e4 are given in the Experimental Section. In conclusion, four different types of substituted phenanthroline were examined (5-methyl, 5,6-dimethyl, 5-Cl, and 5-NO2) that ranged from electron-donating to electron-withdrawing. The results show that the 2J(119SneH) coupling constant values for 1e4 are d ~ 110e114 Hz which supports the octahedral environment around tin atom for all complexes. The 119Sn NMR spectra of all complexes 1e4 displayed the expected hexa-coordinated compounds consist of one resonance with the chemical shift values of d ¼ 262 in CDCl3 for 1, -264 in CDCl3 for 2, -244 in DMSO-d6 for 3 and -238 in CDCl3 for 4, typical of the hexa-coordinated species, which is in accordance with the structures in the solid state for 1e2. The 119Sn chemical shift of 1e4 exhibit an upfield shift of about

(a)

(b)

Fig. 5. 1H NMR spectrum of [SnMe2Cl2(NO2phen)] (3) in the (a) aliphatic (b) aromatic region in DMSO-d6.

B.Z. Momeni et al. / Journal of Molecular Structure 1142 (2017) 156e167

Fig. 6.

13

163

C NMR spectrum of [SnMe2Cl2(NO2phen)] (3) in the (a) aliphatic and (b) aromatic region in DMSO-d6.

20 ppm for 1e2 respect to 3e4, due to the electron-donating of alkyl groups. 3.2. Crystal structures of complexes 1e2 The crystal structures and unit cell packing diagrams for 1e2 are shown in Figs. 9e12. The crystal structure of complex [SnMe2Cl2(Mephen)] (1) shows that the geometry about tin atom is best described as a slightly distorted octahedral with the C16eSneC17 angle of 175.5 (4)º which deviates insignificantly from the linearity (Fig. 9). The SneN bond distances of SneN1 (2.465(6) Å) and SneN2 (2.483(6) Å) are not equal and longer than those observed for [SnPh2Cl2(Mephen)] (2.356 (5) Å) [21]. The SneC bond distances of 2.169(11) and 2.176(10) Å are also equal within the experimental error. On the other hand, the SneCl bond distances of 2.569(2) and 2.603(3) Å are the same. The methyl group on the phenanthroline ligand is nearly planar with a 0.393 Å (C15) deviation from the equatorial plane. As shown in Fig. 11, the crystal structure of complex [SnMe2Cl2(Me2phen)] (2) is similar to that of [SnMe2Cl2(Mephen)] (1). The tin atom is six-coordinated in a slightly distorted octahedral geometry in 2. In this arrangement, the chlorine atoms are cis, while the methyl groups are trans to each other. The formation of

trans-[SnMe2] in complexes 1e2 is consistent with the other dialkyltin adducts containing diimine ligands. The axial C9eSneC8 angle is 175.2 (2)º which deviates slightly from the linearity. The most notable difference in the structure of 1 and 2 is the symmetrization of 2 which has a 2-fold axis of symmetry with the axis bisecting the SnCl2N2 basal plane, passing through CleSneCl. Therefore, the equivalent SneC bond lengths (2.203(6) Å), SneCl bond lengths (2.5906(12) Å) and SneN bond lengths (2.477(3) Å) found in the crystal structure of 2. The NeSneN bite angles for 1 and 2 are 69.2(2) and 68.69(15) , respectively, which are consistent with those observed for the other chelating diimine ligands [11,12,16] Complexes 1e2 display different views of the packing of molecules as shown in Figs. 10 and 12. Interestingly, there is some p-p stacking between the parallel aromatic rings of 1 and 2 with the centroid-centroid distance of 3.690 and 3.903 Å, respectively. The interesting features of the crystal structures of 1e2 are intermolecular CeH/Cl contacts which link the neighboring molecules of 1 or 2 together into chains along the a axis. There are four intermolecular Cl/H interactions of Cl(1) … H(12) ¼ 2.99, Cl(2) ¼ H(6) ¼ 3.11, Cl(2) … H(7) ¼ 2.99 and Cl(2) … H(17C) ¼ 2.97 Å for 1 while there are two intermolecular Cl/H interaction of Cl(1) … H(3) ¼ 3.10 and Cl(1) … H(7A) ¼ 3.06 Å for 2, which seems to be effective in the stabilization of the crystal

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Fig. 7. 1H NMR spectrum of [SnMe2Cl2(Clphen)] (4) in the (a) aliphatic and (b) aromatic region in CDCl3.

Fig. 8.

13

C NMR spectrum of [SnMe2Cl2(Clphen)] (4) in the aromatic region in CDCl3.

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165

Fig. 9. ORTEP diagram for [ SnMe2Cl2(Mephen)] (1). Selected parameters: Sn1eCl6 2.169(11), Sn1eC17 2.176(10), Sn1eN1 2.465(6), Sn1eN2 2.483(6), Sn1eCl2 2.569(2), Sn1eCl1 2.603(3), C16eSn1eC17 175.5(4), C16eSn1eN1 89.9(3), C17eSn1eN1 87.9(3), C16eSn1eN2 89.3(3), C17eSn1eN2 86.3(3), N1eSn1eN2 69.2(2), C16eSn1eCl2 92.1(3), C17eSn1eCl2 91.9(3), N1eSn1eCl2 91.74(17), N2eSn1eCl2 160.90(18), C16eSn1eCl1 90.6(3), C17eSn1eCl1 90.2(3), N1eSn1eCl1 161.60(18), N2eSn1eCl1 92.41(18), Cl2eSn1eCl1 106.62(10).

Fig. 10. Stacking of molecules of [SnMe2Cl2(Mephen)] (1) along a axis.

packing (Figs. 10 and 12). The SneCl bond lengths of complexes [SnMe2Cl2(Mephen)] (1) (2.569(2) and 2.603(3) Å) and [SnMe2Cl2(Me2phen)] (2) (2.5906 (12) Å) and [SnMe2Cl2(phen)] (2.521(3) Å) [30], reflecting the trans influence follows this sequence: Me2phen > Mephen > phen. The results of the SneN bond length in 1 and 2 suggest that these

complexes can be good candidate for anti-tumour activity. From the above, clearly, the steric and electronic effects of these substituted ligands can influence on the stereochemistry of adducts as well as the SneN bond length. In complexes 1e2, the average SneN bond length are 2.47e2.48 Å more than that [SnMe2Cl2(phen)] (2.385(9) Å) [30] which are almost among the largest values [31].

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Fig. 11. ORTEP diagram for [SnMe2Cl2(Me2phen)] (2). Selected bond lengths (Å) and angles ( ): Sn1eC9 2.203(6), Sn1eC8 2.203(6), Sn1eN1 2.477(3), Sn1eCl1 2.5906(12), C9eSn1eC8 175.2(2), C9eSn1eN1 87.38(17), C8eSn1eN1 88.61(16), N1i-Sn1-N1 68.69(15), C9eSn1eCl1 91.68(12), C8eSn1eCl1 91.28(11), N1i-Sn1-Cl1 161.92(8), N1eSn1eCl1 93.24(8), Cl1eSn1eCl1i 104.84 (6).

Fig. 12. Stacking of molecules of [SnMe2Cl2(Me2phen)] (2) along a axis.

B.Z. Momeni et al. / Journal of Molecular Structure 1142 (2017) 156e167

Acknowledgements We would like to thank the Science Research Council of K.N. Toosi University of Technology for financial support. Supplementary data CCDC 1513977 and 1513976 contain the supplementary crystallographic data for 1 and 2, respectively. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/ retrieving.html or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (þ44) 1223 336 033; or e-mail: deposit@ ccdc.cam.ac.uk. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

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