Coordination of dimethyl methylphosphonate to the bidentate Lewis acid 1,2-bis(chloromercurio) tetrafluorobenzene

Incremental addition of the nerve gas simulant dimethyl methylphosphonate (DMMP) to an acetone solution of the bidentate Lewis acid 1,2-bis(chloromercurio)tetrafluorobenzene results in a downfield shift of the Hg-199 NMR resonance. This phenomenon is explained by the formation of a complex involving the bifunctional Lewis acid and DMMP with a stability of 3.7 (+/-0.4) M-1. Upon cooling of a hot solution of 1,2-bis(chloromercurio)tetrafluorobenzene in neat DMMP, needlelike crystals of a 1:2 complex are formed. This compound has been characterized by IR, P-31{H-1} CP/MAS NMR, elemental analysis, and X-ray single-crystal analysis. The structural data show that the phosphoryl oxygen atom of each DMMP bridges the two mercury centers of the bidentate Lewis acid. The individual adduct molecules interact by intermolecular Hg ... Cl contacts, which leads to the formation of polymeric chains. Each chain interacts with two neighboring chains via formation of offset pi-pi contacts. These weak interactions result in the formation of layers that sandwich the coordinated DMMP molecules.