Crystal structure of trimethyl({tris[(phenylsulfanyl)methyl]silyl}methoxy)silane and Hirshfeld surface analysis of 3-bromo-2,2-bis(bromomethyl)propan-1-ol

Trimethyl({tris[(phenylsulfanyl)methyl]silyl}methoxy)silane (3) is a new ligand for transition-metal coordination chemistry derived from 3-bromo-2,2-bis(bromomethyl)propan-1-ol (1) through silylation and following exchange of bromine groups with NaSPh. Analysis of the Hirshfeld surface shows structure-defining interactions for bromomethylalcohol 1, resulting in intermolecular hydrogen bonds between the hydroxyl groups along the a-axis direction.

Trimethyl({tris[(phenylsulfanyl)methyl]silyl}methoxy)silane (3), C 26 H 32 OS 3 Si, is a new ligand for transition-metal coordination chemistry derived from 3-bromo-2,2-bis(bromomethyl)propan-1-ol (1), C 5 H 9 Br 3 O, through silylation and following exchange of bromine groups with NaSPh. Silylated thioether ligand 3 crystallizes in the centrosymmetric space group C2/c. Bromomethylalcohol 1 crystallizes in the space group P1 in the triclinic crystal system with four molecules in the asymmetric unit. Analysis of the Hirshfeld surface shows structure-defining interactions for bromomethylalcohol 1, resulting in intermolecular hydrogen bonds between the hydroxyl groups along the a-axis direction.
In addition, thioether ligands are increasingly gaining interest for redox catalysis, as their stabilizing effect towards the metal centres differ from those of the common phosphine or amine ligands, and thus new catalytic accesses can be created (Petuker et al., 2017).
Furthermore, the solubility of ligands in polar and nonpolar solvents plays a major role. Polar hydroxyl groups, such as bromomethylalcohol 1, will reduce solubility in non-polar solvents and can cause problems like the reduced formation of catalytic species in the process. To prevent this, the hydroxyl group was silylated via conditions known from the literature, thus increasing the lipophilicity of ligand 3.
In the following, the structure of bromomethylalcohol 1 and silylated thioether ligand 3, as well as the surface interactions of 1 are discussed in terms of Hirshfeld surface analysis.

Structural commentary
Bromomethylalcohol 1 crystallizes at 243.15 K from diethyl ether in the centrosymmetric space group P1 with four molecules present in the asymmetric unit (Z 0 = 4, Z = 2). The molecular structure of bromomethylalcohol 1 is shown in Fig. 1 and selected bond lengths and angles are given in Table 1.
The bond lengths to be expected for a C(alkyl)-Br bond are in the range 1.880-1.940 Å (Allen et al., 1987). The C(alkyl)-Br bonds listed in Table 1 are located in the upper range of these bond lengths. The O1-C2 bond length of 1.432 (3) Å corresponds to an expected length for a C(alkyl)-OH bond of between 1.393-1.456 Å . Furthermore, the bond angles C1-C3-Br1, C1-C4-Br2 and C1-C5-Br3 are similar and in general comparable in size with similar structural motifs (Bukowska-Strzyżewska & Skoweranda, 1980). The molecular structure of silylated thioether ligand 3 is shown in Fig. 2 and selected bond lengths and angles are given in Table 2.

Supramolecular features
The crystal packing of bromomethylalcohol 1 is shown in Fig. 3 and is defined by intermolecular hydrogen bonds along the aaxis direction, which are given in Table 3 Table 1 Selected geometric parameters (Å , ) for 1.

Figure 1
The molecular structure of bromomethylalcohol 1 with displacement ellipsoids drawn at the 50% probability level.
To gain further insight into the supramolecular packing interactions, a Hirshfeld surface analysis was performed (Spackman & Jayatilaka, 2009). The Hirshfeld surfaces and fingerprint plots were generated and analysed using the program CrystalExplorer21 (Spackman et al., 2021). The Hirshfeld surface was mapped over d norm in the range À0.66 to 1.14 a.u. (Fig. 4). The contributions of the different intermolecular interactions for 1 are shown in the two-dimensional fingerprint plots (Fig. 5;McKinnon et al., 2007). The different strength of the interactions is reflected here by the colouring of the surface. The red dots represent close contacts, whereas blue areas represent no contact. The fingerprint plots show that the OÁ Á ÁH/HÁ Á ÁO interactions account for only 8.9% of the total surface area, although they are probably the strongest contributors to the intermolecular interactions. The largest contribution to the surface interactions comes from the BrÁ Á ÁH/HÁ Á ÁBr contacts at 50.4%. This is followed by the contributions of the HÁ Á ÁH/HÁ Á ÁH contacts (27.7%). There is no contribution to the surface interactions by CÁ Á ÁH/HÁ Á ÁC contacts, which is mainly due to the fact that the carbon atoms of the CH 2 groups in question are shielded from the outside by the terminal Br and OH groups so that they cannot make any contribution. The smallest contribution to the surface interactions is made by the BrÁ Á ÁO/OÁ Á ÁBr contacts (0.4%), which is due to the spatial arrangement of the bromine substituents in relation to the hydroxyl group.
The crystal packing of silylated thioether ligand 3 is shown in Fig. 6 and is characterized by propagation along the b-axis direction. For silylated thioether ligand 3, apart from the packing effects, there are no overriding intermolecular inter-  Table 3 Hydrogen-bond geometry (Å , ) for 1.

Figure 4
Hirshfeld surface analysis of 1 showing close contacts in the crystal. The hydrogen bonds between H1Á Á ÁO2 and H2Á Á ÁO3 are labelled.   actions between the molecules that influences the arrangement of the molecules.
Another related structure motif could be found where the thioether groups act as bridging ligands between Cu 2 I 2 rhomboids (Schlachter et al., 2022 Crystal packing of silylated thioether ligand 3 shown along the b-axis. Molecules are coloured by their symmetry relationship to the asymmetric unit. The relationships between colour and symmetry are as follows: grey -identity; light green -twofold rotation axis; dark green -twofold screw axis; golden yellow -inversion centre; magenta -glide plane.

Synthesis and crystallization
Bromomethylalcohol 1 is commercially available and was crystallized at 243.15 K from diethyl ether as clear and colourless plates. Methyllithium (1.6 M in n-hexane, 16.93 mmol) was dropped into diethyl ether (50 mL) at 273.15 K to 1 (15.39 mmol). The solution was stirred for 1 h at room temperature and then chlorotrimethylsilane (16.93 mmol) was added at 273.15 K. It was stirred again for 1 h at room temperature, then the reaction solution was quenched with water. The aqueous phase was extracted three times with dichloromethane and the combined organic layers were dried over magnesium sulfate. The volatiles were removed to give compound 2 crude. 1 H NMR (600 MHz, C 6 D 6 ) = 3.33 (s, 2H; OCH 2 C), 3.18 (s, 6H; CCH 2 Br), 0.03 (s, 9H; Si(CH 3 ) 3 ) ppm.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Trimethyl({tris[(phenylsulfanyl)methyl]silyl}methoxy)silane (3)
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.