1,1- and 1,4-Addition Reactions with 3a,6a-Diaza-1,4-diphosphapentalene Containing Two-Coordinate and Formally Divalent Phosphorus

3a,6a-Diaza-1,4-diphosphapentalene (DDP) reacts with halocarbons to give addition products to one or both phosphorus atoms depending on the substrate. Chlorotriphenylmethane affords a 1,4-addition product, which slowly decomposes in solution to form the Ph3C radical and the chloro-DDP coupling product with a P–P bond. Benzyl chloride is added to one phosphorus atom to form hypervalent (trivalent, four-coordinate) phosphorus with a N···P distance (nonvalent interaction) of 2.191(2) A. A workup of the latter with GeCl2 results in a complex salt containing the GeCl3– anion and cation with covalent N–P bonding.