Gomberg's dimer is the organic compound with the formula Ph2C=C6H5-CPh3, where Ph = C6H5.

It is a yellow solid that is air-stable for hours at room temperature and soluble in organic solvents.

[1] The compound achieved fame as the dimer of triphenylmethyl radical, which was prepared by Moses Gomberg in his quest for hexaphenylethane.

The C-C bond that reversibly breaks is rather long at 159.7 picometers.

[1] Gomberg's dimer can be prepared quantitatively by treating trityl bromide with powdered copper or silver:[2] Gomberg's dimer reversibly dissociates to the triphenylmethyl radical in organic solvents:[3]