Co-crystallization of dimethyl N-cyanodithioiminocarbonate and bis[(aqua)-µ₂-hydroxy-n-butyldichlorotin(IV)]

2.1 General

Reagents were purchased from Aldrich Company, Germany, and used without any further purification.

2.2 Synthesis of {[Sn(n-Bu)Cl₂(OH)(H₂O)]₂·2[(MeS)₂C=N–C≡N]} (1)

In a 50:50 acetonitrile/ethanol solvent, one equivalent of dimethyl N-cyanodithioiminocarbonate (90%), [(MeS)₂C=N–C≡N] (0.221 g; 1.36 mmol) and one equivalent of n-butyltin trichloride, Sn(n-Bu)Cl₃ (95%) (0.404 g; 1.36 mmol) were dissolved and the mixture stirred at room temperature (T = 300 K) for 2 h. After several days of slow evaporation, colorless tablet-like crystals suitable for single-crystal X-ray structure determination were collected.

2.3 X-ray crystallography

The X-ray crystallographic data was collected using a Bruker Apex-II diffractometer operating at T = 120(2) K. Data was measured using φ and ω scans using MoKα radiation (λ = 0.71073 Å) using a collection strategy to obtain a hemisphere of unique data determined by Apex2 [18]. Cell parameters were determined and refined using the program Saint [19]. Data was numerically corrected for absorption and polarization effects and analyzed for space group determination [20]. The structure was solved by dual-space analysis using Shelxt [21] and refined using least-squares minimization with Shelxl [22]. The dimethyl N-cyanodithioiminocarbonate molecule [(MeS)₂C=N–C≡N] was found to exhibit a small amount of positional disorder. This was evident from the presence of two ∼1.8 e^– peaks near the S atoms, in positions that mirrored the S atoms on the opposite side of C6. There were also two additional Fourier peaks that pointed to alternative positions of N2 and C5. These positions were all included as split-atom model with occupancies for the two components summed to unity yielding an approximately ratio of 0.95–0.05. While this is only a small percentage inclusion of the split atoms reduced R₁ from 0.0202 to the final 0.0154. The refinement of the minor component carbon (C5A) resulted in a smaller than normal atomic displacement parameter. Programs used for the representation of the molecular and crystal structures: Olex2 [23] and Mercury [24]. Crystal data, data collection and structure refinement details for compound 1 are summarized in Table 1. Selected bond lengths and angles for 1 are listed in the caption of Figure 1.

Figure 1:

View of compound 1 in the crystal and crystallographic numbering scheme adopted (atom color code: C, black; H, white; Cl, green; O, red; S, yellow; N, blue; Sn, turquoise). Only one position of the disordered atoms S1, S2, N2, C5 has been drawn. Selected bond lengths and angles (Å, deg) (symmetry code: (i) −x + 1, −y + 1, −z + 2): Sn1–O1 2.0526(10), Sn1–O1ⁱ 2.1421(10), Sn1–O2 2.2247(12), Sn1–C1 2.1402(14), Sn1–Cl1 2.4424(4), Sn1–Cl2 2.4718(4), O1–Sn1ⁱ 2.1421(10), C1–C2 1.525(2), C2–C3 1.5287(19), C3–C4 1.529(2), N1–C5 1.156(2), N2–C5 1.327(2), N2–C6 1.304(2), S1–C6 1.7364(16), S1–C7 1.8007(18), S2–C6 1.7331(15), S2–C8 1.7931(18); O1–Sn1–C1 168.29(5), O1–Sn1–O1ⁱ 69.34(5), C1–Sn1–O1ⁱ 100.88(5), O1–Sn1–O2 81.35(4), C1–Sn1–O2 91.77(5), O1ⁱ–Sn1–O2 85.93(4), O1–Sn1–Cl1 88.04(3), C1–Sn1–Cl1 101.20(4), O1ⁱ–Sn1–Cl1 157.15(3), O2–Sn1–Cl1 87.59(3), O1–Sn1–Cl2 90.10(3), C1–Sn1–Cl2 96.42(4), O1ⁱ–Sn1–Cl2 89.77(3), O2–Sn1–Cl2 171.34(3), Cl1–Sn1–Cl2 93.534(13), Sn1–O1–Sn1ⁱ 110.66(5), C6–S1–C7 104.21(8), C6–S2–C8 101.40(8), C6–N2–C5 120.08(16), N1–C5–N2 173.2(2), N2–C6–S2 119.20(12), N2–C6–S1 122.34(12), S2–C6–S1 118.45(9), C2–C1–Sn1 113.27(9), C1–C2–C3 112.56(12), C2–C3–C4 111.89(13).

CCDC 2165147 (1) contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

3.1 Synthesis

Compound 1 was isolated from the reaction of a 1:1 molar ratio of dimethyl N-cyanodithioiminocarbonate, [(MeS)₂C=N–C≡N] and n-butyltin trichloride, Sn(n-Bu)Cl₃ in a mixed solvent of acetonitrile and ethanol, which were not of anhydrous quality. Colorless single crystals grew from the solution (Eq. (1)) and have been characterized as 1, [Sn(n-Bu)Cl₂(OH)(H₂O)]₂·2[(MeS)₂C=N–C≡N]. To date, only one single crystal X-ray investigation involving the dinuclear [Sn(n-Bu)Cl₂(OH)(H₂O)]₂ molecule, co-crystallized with 3-methylbenzothiazole, [Sn(n-Bu)Cl₂(OH)(H₂O)]₂·4(C₈H₇NS) has previously been reported in the literature [25]. The reactions involved partial hydrolysis by water contained in the solvents.

3.2 Crystal and molecular structure

The co-crystal 1 crystallizes about the inversion centre at [0.5, 0.5, 1], thus, only half of the molecule is observed in the asymmetric unit. The dinuclear organotin complex, depicted in Figure 1, consists of two [Sn(n-Bu)Cl₂(H₂O)]⁺ cations coordinated to two OH⁻ hydroxide bridges to complete the octahedral coordination sphere at the Sn centers. The bridging hydroxide form an almost symmetric bridge with Sn–O bond lengths of 2.0526(10) and 2.1421(10) Å, as earlier encountered in the literature [2, 3, 25, 26]. The Sn–C bond length of 2.1402(14) Å is in the range of those found in other n-butyltin(IV)-based complexes [25, 27], [28], [29], [30], [31], and the Sn–Cl bond lengths of 2.4424(4) and 2.4718(4) Å are also in accordance with previously reported values [25], [26], [27], [28], [29], [30]. The bond angles at the tin center (see caption of Figure 1) indicate a distorted octahedron as expected. The water molecules coordinated to the tin atoms feature a Sn–O bond length of 2.2247(12) Å slightly longer than those of the hydroxide groups [2, 3, 25]. The dimethyl N-cyanodithioiminocarbonate molecules adopt a general position showing cyanide triple C≡N and imine double C=N bonds as reported for this ligand [1, 11], [12], [13, 17]. The sum of the angles at the central carbon atom (see Table 2) indicates, as expected, a perfect trigonal geometry [1, 11], [12], [13, 17]. The molecule exhibits a minor positional disorder. Moreover, dimethyl N-cyanodithioiminocarbonate molecules are in an isotactic disposition forming a dihedral angle of 40.48(4)° between the (N1C5N2C6S1S2C7C8) and [Cl₂CSn(O)₂SnCCl₂] core planes. From a supramolecular point of view, the water molecule is connected to the Cl2 chlorine atom through an inner O2–HO2B⋯Cl2 hydrogen bond and also to the cyanide nitrogen atom of the dimethyl N-cyanodithioiminocarbonate molecule through an O2–HO2A⋯N1 hydrogen bond (Table 2 and Figure 2). These hydrogen bonding interactions afford R 1 1 ( 6 ) rings involving the Cl2 chlorine atom and a water molecule, and R 2 2 ( 8 ) rings involving two Cl2 chlorine atoms and two water molecules as well as a hydrogen bond string of D type (Table 2 and Figure 2). Neighboring binuclear tin(IV) components interact via the hydroxide groups and chlorine Cl1 atoms through symmetrically equivalent O–H⋯Cl hydrogen bonds, leading to infinite chains parallel to the crystallographic (100) direction (Figure 3). These inter-species O–H⋯Cl hydrogen bond patterns describe R 2 2 ( 8 ) rings in the (100) direction (Figure 3). Dimethyl N-cyanodithioiminocarbonate molecules, through O2–H2OA⋯N1 (see Table 2 for details) hydrogen bonds, are connected to the chains of the dinuclear complexes (Figure 4). Weak C–H⋯Cl hydrogen bonds involving methyl groups of the dimethyl N-cyanodithioiminocarbonate molecule are also present in the structure. The molecular packing diagram is depicted in Figure 5. Numerical details of the most prominent hydrogen bond interactions are summarized in Table 2.

Figure 2:

Selected hydrogen bonding interactions in crystals of compound 1.

Figure 3:

The infinite chain extending in the (100) direction featuring R 2 2 ( 8 ) rings.

Figure 4:

The interactions of the chain shown in Figure 3 with the dimethyl N-cyanodithioiminocarbonate molecules.

Figure 5:

The isotactic positioning of the dimethyl N-cyanodithioiminocarbonate molecules between the chains of the dinuclear complexes.