Redetermination of the crystal structure of di-μ2-hydroxido-bis[di-tert-butylchloridotin(IV)] at 100 K

The crystal structure of the title compound was redetermined at 100 K in order to achieve improved structural data, especially with respect to the C—C distances and the hydrogen bonding.


Structure description
The title compound, [ t Bu 2 Sn(OH)Cl] 2 , belongs to the class of dimeric diorganotin(IV)hydroxides-halides, [R 2 Sn(OH)X] 2 , the first hydrolysis products of diorganotin(IV) dihalides, R 2 SnX 2 . The structure of the title compound has been determined previously at room temperature using point detector data as part of a paper describing the series of dimeric di-tert-butyltin(IV) hydroxide halides, [ t Bu 2 Sn(OH)X] 2 with X = F, Cl and Br (Puff et al., 1985). This series was completed when a second modification of the title compound was reported (Di Nicola et al., 2011) and more recently, when the crystal structures of the pure iodide compound, [ t Bu 2 Sn(OH)I] 2 (Reuter, 2022) and its DMSOadduct (Reuter & Wilberts, 2014) were published. With two well-resolved, lowtemperature crystal-structure determinations of the iodide derivative, it seemed reasonable to redetermine the structure of the chloride derivative using similar experimental conditions to enable a more valid comparison between structures.
As a result of the low-temperature measurement and the high data redundancy, combined with a multi-scan absorption correction, the new data improve the structural parameters of the title compound ( Fig. 1) (Reuter, 2022), and DMSOadduct: d(Sn-C) mean = 2.193 (10) Å (Reuter & Wilberts, 2014)].
These unusually long Sn-Cl bonds in the title compound arise from the fact that the chloride atoms are involved in intermolecular O-HÁ Á ÁCl hydrogen bonds (Table 1), resulting in a chain-like arrangement of the [ t Bu 2 Sn(OH)Cl] 2 molecules along [101], Fig. 3, a feature that had been recognized previously but now is confirmed unambiguously.

Synthesis and crystallization
For the synthesis of the title compound, see Puff et al. (1985). Ball-and-stick model of the inorganic framework of the [ t Bu 2 Sn(OH)Cl] 2 molecule highlighting selected bond lengths (Å ) and angles ( ). Positions of oxygen and chloride atoms within the trigonal-biypramidal coordination of the tin atoms are labelled by use of the abbreviation ax (= axial) and eq (= equatorial). For clarity, t Bu groups are stripped down to the Sn-C bonds drawn as shortened sticks. Intermolecular O-HÁ Á ÁCl hydrogen bonds are indicated by dashed sticks in green. Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x þ 1 2 ; Ày þ 1 2 ; z þ 1 2 ; (ii) x À 1 2 ; Ày þ 1 2 ; z À 1 2 .

Figure 3
Space     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.

data-2
IUCrData (2023). 8, x230056 Refinement. Six reflections, i.e. (-1 1 1), (1 1 0), (0 2 1), (0 1 1), (1 0 1) and (0 0 2), were omitted from the final cycles of refinement owing to poor agreement. The positions of all H atoms were clearly identified in difference Fourier syntheses. Those of the tert-butyl groups were refined with calculated positions (C-H = 0.98 Å) and common U iso (H) parameters for each of the methyl groups. The position of the H atoms of the OH groups were refined with a fixed O-H distance of 0.96 Å before they were fixed and allowed to ride on their parent atoms with a common U iso (H) parameter.