Crystal structure of O-isopropyl [bis(trimethylsilyl)amino](tert-butylamino)phosphinothioate

[Bis(trimethylsilyl)amino](tert-butylimino)thiophosphorane reacts in benzene with isopropyl alcohol via 1,2-addition of an iPrO–H bond across the P=N bond, resulting in the title compound, C13H35N2OPSSi2. In the molecule, the P atom possesses a distorted tetrahedral environment involving two N atoms from (Me3Si)2N– and tBuNH– groups, one O atom from an iPrO group and one S atom, therefore the molecule has a stereocenter on the P atom but crystal symmetry leads to a racemate. In the crystal, a pair of enantiomers form a centrosymmetric dimer via a pair of N—H⋯S hydrogen bonds.


Data collection
Oxford Xcalibur PX -geometry diffractometer with a CCD area detector 36939 measured reflections 7436 independent reflections 5938 reflections with I > 2(I) R int = 0.033

Refinement
R[F 2 > 2(F 2 )] = 0.041 wR(F 2 ) = 0.115 S = 1.08 7436 reflections 184 parameters H atoms treated by a mixture of independent and constrained refinement Á max = 0.84 e Å À3 Á min = À0.34 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).  Scherer & Kuhn (1974), and later some general chemical reactivity of this compound was studied, see: Scherer et al. (1978). Based on these early results, pentavalent tricoordinated σ 3 λ 5 -phosphoranes recommended themselves as promising ligands for the obtaining of new organometallic metallacycles with specific features. Recently we have reported and characterized series of transition metal metallacycles, containing phosphorus atom in cyclic moiety, see: Kovalenko et al. (2011aKovalenko et al. ( , 2011bKovalenko et al. ( , 2011cKovalenko et al. ( , 2012; Rusanov et al. (1992). In current communication we reported the reactivity of [bis(trimethylsilyl)amino](tert-butylimino)-thiophosphorane with isopropyl alcohol. The reaction proceeds through a 1,2-addition of i PrO-H bond across the P=N bond, resulting in the title compound. Resulted product was characterized by single X-ray analysis and 1 H, 13 C and 31 P NMR spectroscopy. In these latter days it was discovered that low-coordinate phosphorus compounds are catalytically active and might be efficiently applied in catalysis, see: (tert-butylamino)phosphinothioate are consistent with the values reported earlier (Rusanov et al., 1992;Kovalenko et al., 2011aKovalenko et al., , 2011b for the compounds containing analogous phosphinothioates, but deprotonated and coordinated to metal centers.

S2. Experimental
All procedures were carried out under a dry argon atmosphere using standard Schlenk and glovebox techniques. Benzene and hexane were distilled from sodium-potassium alloy directly before use. Isopropyl alcohol was dried and distilled from magnesium and stored over 4 Å molecular sieves prior to use.
In a Schlenk flask, (0.884 g, 3.0 mmol) of [bis(trimethylsilyl)amino](tert-butylimino)thiophosphorane was dissolved in 3 ml of benzene and the solution of isopropyl alcohol (0.23 ml, 3.0 mmol) in 1 ml of benzene was added dropwise. The mixture was stirred for 1.5 h at room temperature, thereafter solvent was removed in vacuo producing an almost colorless tar. The residue was dissolved in 1 ml of hexane and kept at 252 K in order to induce further crystallization.

S3. Refinement
Positions of hydrogen atoms bonded to carbon were generated in idealized geometries using a riding model with U iso (H) = 1.5U eq (C) or 1.2U eq (C). The fractional coordinates of the H atom attached to N2 were identified from a difference Fourier map and refined freely with isotropic thermal displacement parameter.

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