Crystal structures of three (trichloromethyl)(carbamoyl)disulfanes

The present paper reports crystallographic studies on three related compounds that were of interest as precursors for synthetic and mechanistic work in organosulfur chemistry, as well as to model nitrogen-protecting groups.


Structural commentary
The three (trichloromethyl)(carbamoyl)disulfanes differ in the substituents on the carbamoyl nitrogen, but the bond lengths and angles of the common CCl 3 SS(C O)N moieties of each are markedly similar for the two molecules in the asymmetric units of (1) and (3), as well as for the single conformation of (2) (Tables 1 and 2). The corresponding structural features of (3) are also similar to the bond lengths and torsion angles of other carbamoyl disulfanes that include an SS(C O)N(Me)Ph chain, including, for example, bis(Nmethyl-N-phenylcarbamoyl)disulfane (ZAQWUL, formula [Ph(Me)N(C O)S] 2 ) (Schroll et al., 2012) and (N-methyl-N-phenylcarbamoyl) (N-methyl-N-phenylamino)disulfane [formula Ph(Me)N(C O)SSN(Me)Ph] (Henley et al., 2015).

Supramolecular features
The three compounds arrange in three distinct packing configurations. The two nearly superimposable molecular structures of (1) are alternately hydrogen-bonded (NHÁ Á ÁO C) in chains along [110] (Table 3). Successive molecules of each of two chains are linked by 3.162 (1) Å S1AÁ Á ÁO1B contacts, 0.157 Å less than their van der Waals radii sum (Fig. 4). Additional packing features result in a Z = 16 unit cell. A chlorine from each of four molecules -in separate hydrogen-bonded chains -form a short-contact skew quadrilateral with intermolecular contact distances of 1170 Goldenberg et al. C 3 H 4 Cl 3 NOS 2 , C 9 H 8 Cl 3 NOS 2 and C 9 H 8 Cl 3 NOS 2 Acta Cryst. The molecular structure of compound (1) showing the atom-labelling scheme, with two molecules (Z 0 = 2) per asymmetric unit. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The molecular structure of compound (2) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 4
Hydrogen-bonded chains of (1) are linked by S1AÁ Á ÁO1B contacts. Only H atoms involved in N-HÁ Á ÁO C bonds are shown.

Figure 5
A chlorine from each of four molecules of (1), in separate chains, form a short-contact skew quadrilateral. Only H atoms involved in N-HÁ Á ÁO C bonds are shown.

Figure 6
Packing structure of (2). Hydrogen-bonded chains are linked by pairs of O1Á Á ÁCl3 contacts. H atoms are not shown unless they participate in hydrogen bonding.
hydrogen-bonded chain has extensive links to two other chains. The resulting structure features alternating layers of trichloromethyl and benzyl groups (Fig. 6). Compound (3) has no available classical hydrogen bonding and lacks the chlorine-dense regions of (1) and (2). Of the two conformations available for (3), it is noteworthy that the four sulfurs of two adjacent molecules of (3b) are positioned in a parallelogram [angles 80.65 (2) and 99.35 (2) , torsion angle 0.00 (2) ] with intermolecular contact distances of 3.5969 (8) Å , slightly less than the sum of their van der Waals radii; no such configuration is evident for molecules of (3a).

Synthesis and crystallization
Compounds (1) (Harris, 1960;Barany et al., 2005), (2) (Barany et al., 2005), and (3) (Barany et al., 1983;Schroll & Barany, 1986) were synthesized and crystallized as outlined in Fig. 8 and described in the referenced publications. The reaction of (4) plus (5), shown in the top pathway of Fig. 8, is termed the Harris reaction (Harris, 1960). For the alternative Harris pathway shown in the middle of Fig. 8, compound (6), a thiocarbamate salt, is typically made by reaction of carbonyl sulfide (COS) with a primary or secondary amine HNR 1 R 2 . Therefore B + is usually the appropriate ammonium counterion H 2 N + R 1 R 2 . Finally, several variations of acylation chemistry are summarized in the bottom pathway of Fig. 8, as originally worked out by Barany et al. (2005). When R 3 = H, starting amine HNR 1 R 2 is present in sufficient excess so that a second equivalent of amine can absorb the HCl co-product. When R 1 and/or R 3 = TMS, stoichiometric ratios can be used, since co-product TMS-Cl is neutral. Note that for some reactions, a TMS group attached to N becomes an H after aqueous workup.

Special details
Experimental. Compound (2) (Barany et al., 2005) was synthesized and crystallized as outlined in the Scheme and described in the referenced publication. 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.

Special details
Experimental. Compound (3) (Barany et al., 1983;Schroll & Barany, 1986) was synthesized and crystallized as outlined in the Scheme and described in the reference publications. 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)