More on diphosphadithiatetrazocines and the importance of being bonded.

The cross-ring sulfur-sulfur bond for seven R'RP(NSN)2PRR' molecules 1a (R = R' = Me), 1b (R = R' = Ph), 1c (R = R' = Et), 1d (R = Cl, R' = CCl3), 1e (R = R'= Cl), 1f (R = R' = F), and 1g (R = R' = H) has been scrutinized by a topology analysis for a bond descriptor based on the kinetic energy density, supported by a fragment-based bond energy analysis. Contrary to a regular disulfide bond, the cross-ring connection is only a secondary electron-sharing bond, about half as strong as a common S-S linkage. The regular disulfide bond itself is best described as a charge-shift bond. These analyses are based on results obtained from B3PW91/def2-TZVP density functional calculations.