2,2,6,6-Tetramethylpiperidinium triisopropoxysilanethiolate

The crystal of the title compound, C9H20N+·C9H21O3SSi−, is built of aggregates, each made up of two 2,2,6,6-tetramethylpiperidinium cations and two triisopropoxysilanethiolate anions. The aggregates are linked by four N—H⋯S bonds and correspond to an R 2 4(8) graph-set motif.

relatively little attention, as these bonds are mostly weak and quite seldom lead to the proton transfer. One notable exception are silanethiolates, where ionization of the SH group is facilitated by the neighbouring silicon atom. The salts of these anions with primary amines as counter-ions often feature tetrameric aggregates with a cubane-like hydrogen bonded core (Becker et al., 2004). Secondary amines give derivatives with discrete dimeric units in the solid state (Baranowska, Chojnacki, Konitz et al. 2006).
We present here the crystal structure of the title compound, which was obtained by the reaction of tri-iso-propoxysilanethiol with 2,2,6,6-tetramethylpiperidine.

Experimental
Tri-iso-propoxysilanethiol (2 mmol) was dissolved in 8 ml of propanol-2 and 2,2,6,6-tetramethylpiperidine (0,338 ml, 2 mmol) was added. The solvent was then added gradually until a white deposit formed was completely dissolved. The solution was left to stand at 4 °C for a few days for crystallization. The obtained colourless crystals were suitable for X-ray diffraction analysis. The product is hygroscopic and slowly oxidizes in the air, therefore all operations were carried out using a vacuum-nitrogen line and Schlenk techniques.

Refinement
Hydrogen atoms were placed in geometrically calculated positions (C-H 0.98 Å for methyl, 0.99 Å for methylene and 1.00 Å for methine H atoms) and refined as riding on their parent atoms with U iso (H) = 1.2U eq (C) for methylene and methine and 1.5U eq (C) for methyl groups. Hydrogen atoms of ammonium group were found in the difference map and refined in isotropic approximation constrained to produce N-H bonds equal within 0.04 Å (SADI instruction of SHELXL97; Sheldrick, 2008) sup-2 Figures Fig. 1. Dimeric aggregates [C 9 H 20 N + C 9 H 21 O 3 SiS -] 2 in the structure of the title compound. The unlabeled atoms are derived from the reference atoms by the (1 -x, 1 -y, 1 -z) symmetry transformation. Displacement ellipsoids are drawn at the 50% probability level. C-bound H atoms have been omitted for clarity.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. 0.0169 (7) 0.0187 (7) 0.0178 (7) −0.0053 (6) −0.0033 (6) −0.0006 (6) Geometric parameters (Å, °)