Bis(3,5-dimethylpyridine-κN)bis(tri-tert-butoxysilanethiolato-κS)chromium(II) toluene solvate

In the title chromium silanethiolate, [Cr(C12H27O3SSi)2(C7H9N)2]·C7H8, the CrII atom is coordinated by two S and two N atoms in a distorted square-planar geometrical arrangement. The mononuclear molecule lies on a twofold axis that passes through the pyridine N atoms. The toluene solvent molecule is equally disordered about a twofold axis.

In the title chromium silanethiolate, [Cr(C 12 H 27 O 3 SSi) 2 -(C 7 H 9 N) 2 ]ÁC 7 H 8 , the Cr II atom is coordinated by two S and two N atoms in a distorted square-planar geometrical arrangement. The mononuclear molecule lies on a twofold axis that passes through the pyridine N atoms. The toluene solvent molecule is equally disordered about a twofold axis.

Experimental
Crystal data [Cr(C 12

Data collection
Oxford Diffraction KM-4-CCD diffractometer Absorption correction: none 18436 measured reflections 5260 independent reflections 4788 reflections with I > 2(I) R int = 0.031 Refinement R[F 2 > 2(F 2 )] = 0.048 wR(F 2 ) = 0.148 S = 1.11 5260 reflections 296 parameters 1 restraint H-atom parameters constrained Á max = 1.14 e Å À3 Á min = À0.78 e Å À3 Table 1 Selected bond lengths (Å ). The large development of transition-metal silanethiolate chemistry results from its potential to form new types of complexes with interesting chemical properties. These complexes may be used in model studies on structural and catalytic metal centers in proteins (Becker et al. 2002;Dołęga et al. 2008). Here we present the synthesis and molecular structure of the chromium(II), tri-tert-butoxysilanethiolate complex [Cr(C 12 H 27 O 3 SSi) 2 (C 7 H 9 N) 2 ] C 7 H 8 .The crystal structure of the title compound (I) is one of the few structurally defined four-coordinate Cr II thiolate complexes (Dorfman et al. 1985;Ciborska et al. 2008). This complex was obtained as light-blue crystals in the reaction of anhydrous Cr II chloride with sodium tri-tert-butoxysilanethiolate and 3,5-dimethylpyridine. The Cr II ion is coordinated by two S atoms from the tri-tert-butoxysilanethiolate ligands and two N atoms from the 3,5-dimethylpyridine molecules. The trans angles of the square base are then described by S-Cr-S and N-Cr-N, which are very close to 180°. The Cr-S bond lengths in (I) are very similar to the corresponding values of ca 2.4 Å observed in the other silanethiolates (Ciborska et al.2007). The Cr-N bond lengths are like these found in the [Cr(C 12 H 27 O 3 SSi) 2 (C 6 H 15 N) 2 ]. Selected data of important bond lengths and angles are compared in Table 1.
After that the mixture was concentrated and cooled (250 K) to afford light-blue crystals.

S3. Refinement
All C-H hydrogen atoms were refined as riding on carbon atoms with methyl C-H = 0.98 Å, aromatic C-H = 0.95 Å and U ĩso (H)=1.2 U eq (C) for aromatic CH and 1.5U eq (C) for methyl groups.
The toluene molecule was allowed to refine off the twofold axis. The aromatic ring was refined as a rigid hexagon of 1.39 Å sides. The phenyl-methyl distance was restrained to 1.50±0.01 Å.  A view of the molecule of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms have been omitted.

Bis(3,5-dimethylpyridine-κN)bis(tri-tert-butoxysilanethiolato-κS)chromium(II) toluene solvate
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.14 e Å −3 Δρ min = −0.78 e Å −3 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 cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 R-factors(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.