Influence of Noncovalent Se∙∙∙Se, N∙∙∙P, and Se∙∙∙H Interactions on the Structures of 1,4-Bis(phenylselenyl)-3a,6a-diaza-1,4-diphosphapentalene in Crystal and Solution

The reaction of annelated 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalene (DDPCl₂, I) with 2 equivalents of lithium phenyl selenolate (PhSeLi) results in the substitution of the chlorine atoms by the PhSe group and formation of exclusively cis isomer of annelated 1,4-bis(phenylselenyl)-3a,6a-diaza-1,4-diphosphapentalene (II) according to the XRD data. The noncovalent Se···Se interaction (3.968 Å) is observed in the crystal of compound II. The cis-II isomer is by 6.0 kcal/mol thermodynamically more favorable than trans-I according to the DFT/B3LYP/6-31G(d) calculations. The cis-1,4-bis(phenylselenyl) and 1,1-bis(phenylselenyl) isomers (the latter is formed due to the easy migration of the PhSe group) are equilibrated in the solution. Noncovalent N∙∙∙P and Se∙∙∙H interactions participate in the stabilization of the 1,1-isomer. The crystallographic structural information is available at the Cambridge Crystallographic Data Centre (CIF file CCDC no. 2357640).