α-Tetraphosphorus trichalcogenide diiodide compounds containing both sulfur and selenium

Abstract

T w o isomers of each of a-P,S,Sel, and a-P,SSe,l, have been identified by ,'P and "Se NMR spectroscopy in mixtures made by direct combination of the elements. The same compounds were formed as a result of a photochemical redistribution reaction between a-P, S, I , and a-P, Se, I , in solution in CS, . Systematic changes in chemical shifts and in coupling constants with alterations in molecular geometry, as sulfur was replaced by selenium in the series a-P, S, I , 1a-P,S,Sel ,

α‐Tetraphosphorus Trichalcogenide Diamides and Imides containing both Sulfur and Selenium

“…The ratios within the two pairs of isomers followed the trends reported previously for a photolytically-induced equilibrium in a system with equimolar quantities of sulfur and selenium [4]. The predicted ratio (Ͱ-P 4 S 2 Se b I 2 ϩ Ͱ-P 4 S 2 Se d I 2 ) : Ͱ-P 4 S 2 Se a I 2 , based on energy difference calculated at the MPW1PW91/LanL2DZ(d) level (see below) was 9.84 : 1, compared with 13.3 : 1 observed, while Ͱ-P 4 S a Se 2 I 2 : (Ͱ-P 4 S b Se 2 I 2 ϩ Ͱ-P 4 S d Se 2 I 2 ) was predicted as 1.66 : 1 and measured as 2.16 : 1.…”

“…A mixture of red phosphorus, sulfur, grey selenium and iodine in atomic ratio 4 : 2 : 1 : 2 was sealed under vacuum in a glass ampoule and heated in stages to 320°C over two days, then annealed at 280°C (see Experimental). The resulting sticky glass at room temperature was extracted and crystallised from CS 2 , as described previously [4], to give orange crystals. A sample of this product dissolved completely in CS 2 to give a solution shown by 31 P NMR integration to contain the following exo,exo-Ͱ-P 4 S n Se 3Ϫn I 2 species 2 (mole% in parentheses): Ͱ-P 4 S 3 I 2 (27), Ͱ-P 4 S 2 Se a I 2 (3), Ͱ-P 4 S 2 Se b I 2 (45), Ͱ-P 4 S a Se 2 I 2 (14), Ͱ-P 4 S d Se 2 I 2 (7) and Ͱ-P 4 Se 3 I 2 (3), along with traces of Ͱ-P 4 S 4 , P 4 S 7 , PI 3 and P 3 S 2 Se 2 I [6].…”

“…To obtain evidence for or against this hypothesis, there remains the possibility of breaking the C 2 symmetry by endocyclic replacement of the asymmetrically placed S b by selenium. We reported previously the preparation of inseparable mixtures of diiodides exo,exo-Ͱ-P 4 S n Se 3Ϫn I 2 2 (E ϭ S or Se, X ϭ Y ϭ I), and assigned the 31 P NMR spectra of the compounds [4]. Because NMR couplings were transmitted through a different cage as a result of each endocyclic replacement, there was no simple balancing of changes in coupling constants, as in the case of replacing exocyclic substituents.…”

Endo- and Exocyclic Substitutions inα-P4S3I2

“…± Systematic changes in the 31 P-NMR parameters with endocyclic substitution have been reported for the bicyclic a-P 4 S 3 I 2 [1] and b-P 4 E 3 I 2 [2], a-P 4 E 3 R 2 [3] (E S, Se; R carboxylate) and b-P 4 E 3 I(CHI 2 ) [4], as well as for the tricyclic P 5 E 2 X (X Cl, Br, I) [5]. The influence of an exocyclic ligand exchange was investigated for a-P 4 E 3 XY [6] and P 5 E 2 X [5] (X, Y Cl, Br, I).…”

“…It is completed by corresponding data of P 4 E 3 I 2 [1]. The values in these tables are obtained by subtracting each of the 31 P-NMR data of the Se-rich isomers from those of the corresponding S-rich isomers.…”