New Acyclic Neutral Phosphorus Sulfides and Sulfide Oxides

A great number of binary neutral phosphorus sulfides was discovered and investigated. However all stable representatives of this family of compounds adopt a polycyclic structure in contrast to their lighter homologues, the nitrogen oxides. Acyclic representatives can be stabilized by adduct formation with a nitrogen base. The bis(pyridine) adduct py 2 P 2 S 5 of the unstable acyclic phosphorus sulfide P 2 S 5 is readily obtained stirring P 4 S 10 in pyridine at ambient temperature. X‐ray diffraction studies on single crystals of py 2 P 2 S 5 · 0.5 py ( 1b ) show a N 2 O 5 like structure for the P 2 S 5 framework. The long P–N distances of 1.86 Å indicate only weak coordination of the pyridine molecules to phosphorus. Single crystal X‐ray diffraction studies on py 2 P 2 S 4.34 O 0.66 ( 2 ) reveal the presence of py 2 P 2 S 4 O ( 3 ) together with py 2 P 2 S 5 in the crystal. Compound 3 contains the mixed phosphorus oxide sulfide molecule P 2 S 4 O stabilized as bis(pyridine) adduct. It is readily obtained from pyP 2 S 5 by oxidation with KMnO 4 in pyridine. The oxygen atom occupies the bridging position between the two phosphorus atoms. Quantum chemical calculations at the MPW1PW91 level of theory as well as DTA/TG thermal analyses confirm the weak coordination of the pyridine molecules in py 2 P 2 S 5 , py 2 P 2 S 4 O, and py 2 P 2 S 7 to phosphorus.