Sulfurisation of Amino Tetraphosphorus Trichalcogenide Compounds

Abstract

Amino tetraphosphorus trisulfides α‐P4S3(NR1R2)2 reacted with S8 under photolysis using visible light, in moderate or low conversion, to give α‐P4S3(S)(NR1R2)2, in which the added sulfur atom was exocyclic. For NR1R2 = NPr2i, three isomers were found: a pair of diastereomers corresponding to attachment of the sulfur atom to a nitrogen‐carrying phosphorus atom either with retention or with inversion of its configuration, and an isomer containing a sulfurised bridgehead phosphorus atom. For NR1R2 = NMePh, only the two diastereomers were seen. Photolysis of a mixture of α‐P4Se3(NMePh)2 and α‐P4Se3(NMePh)I with S8 gave as major products α‐P4SSe2(NMePh)2 and α‐P4SSe2(NMePh)I, in which sulfur had replaced the bridging selenium atom in the starting compounds. This provides a synthesis of compounds α‐P4SSe2XY in which sulfur occupies a specific skeletal position, rather than being randomly distributed. All products were characterised by 31P NMR in unseparated solutions. Ab initio MO calculations of geometry and of GIAO NMR chemical shifts at the 3‐21G* level for three isomers of the unknown model compound α‐P4S3(S)(NH2)2, and two isomers of α‐P4S3(NH2)2, allowed identification of the observed isomer of α‐P4S3(S)(NPr2i)2 with a sulfurised bridgehead, but relative assignment of the two diastereomers to their NMR parameters remains a hypothesis.

Insertion of Methylthiirane into the P–I Bonds of α‐P4S3I2

“…Diastereomer C. This had an internal diastereomeric shift δ(P A )-δ(P C ) of 1.22 ppm, and a coupling constant 2 J(P A P C ) of 60.4 Hz, giving J/δ 0.244 at 202.5 MHz. In contrast, although δ(P B )-δ(P D ) was only 0.33 ppm, 3 J(P B P D ) was -8.20, so the corresponding J/δ was only 0.122. The spin system could be analysed as AFMN and the MN region (P A and P C , region (iv), above) treated by subspectral analysis.…”

“…The high and low shifts are characteristic of addition of a terminal sulfur atom at P B , as is the large coupling they share [3]. The P C and P D multiplets could then be identified as sharing other couplings with P A or P B .…”

“…There were correlation peaks to the same part of region (iii), from regions (i) and (ii), but no correlation peak could be found between regions (i) (P D ) and (ii) (P B ). This was because the corresponding coupling for α-P 4 S 3 (SCHMeCH 2 I)I, 3 J(P B P D ), was very small (-1 Hz, Table 1). A third set of correlation peaks in region (i) linked it to region (iv), and were attributed to α-P 4 S 3 (SCHMeCH 2 I)(SCH 2 CHIMe), for which the P D multiplets were found in region (i) of the product of the 1 : 4 reaction, and the P A , P C multiplets were believed as a result of the present COSY experiment to be in region (iv).…”

“…Sulfurisation at P B , however, could go either with retention or inversion of configuration, as found for sulfurisation of α-P 4 S 3 amides [3]. Each such isomer would consist of two diastereomers, R(2a) and S(2a), for α-P 4 S 3 (S)(SCHMeCH 2 I)I, as in the unsulfurised compound, but for α-P 4 S 3 (S)(SCHMeCH 2 I) 2 there would now be four, since the P B and P D sides of the molecule are differentiated, as for α-P 4 S 3 (SCHMeCH 2 I)(SCH 2 CHIMe) above.…”

“…α-P 4 S 3 (NPr i 2 ) 2 , reacted with S 8 under photolysis by visible light, to give three isomers of α-P 4 S 3 (S)(NPr i 2 ) 2 2, in which one of the phosphorus atoms carried a terminal sulfur atom [3]. A similar reaction of α-P 4 S 3 I 2 itself gave no corresponding new phosphorus sulfide iodides, which could have been valuable intermediates in making new families of derivatives.…”