Bis(diphenylphosphino)methane

1,1-Bismethane, is an organophosphorus compound with the formula CH₂₂. Dppm, a white, crystalline powder, is used in inorganic and organometallic chemistry as a ligand. It is more specifically a chelating ligand because it is a ligand that can bond to metals with two phosphorus donor atoms. The natural bite angle is 73°.

Synthesis and reactivity

1,1-Bismethane was first prepared by the reaction of sodium diphenylphosphide with dichloromethane:
The methylene group in dppm is mildly acidic. The ligand can be oxidized to give the corresponding oxides and sulfides CH₂₂. The methylene group is even more acidic in these derivatives.

Coordination chemistry

As a chelating ligand, 1,1-bismethane forms a four-membered ring with the constituents MP₂C. The ligand promotes the formation of bimetallic complexes that feature five-membered M₂P₂C rings. In this way, dppm promotes the formation of bimetallic complexes. One such example is the dipalladium chloride, Pd₂Cl₂₂. In this complex, the oxidation state for the Pd centres are I. Bismethane gives rise to a family of coordination compounds known as A-frame complexes.