The reactivity of bidentate P-donors with dirhodium(II) complexes, leading to a further example of orthometalation across the Rh-2(4+) core, is reported. The dirhodium(II) formamidinate complex Rh-2(form)(2)(O-2-CCF3)(2)(H2O)(2) (form = N,N’-di-p-tolylformamidinate anion) easily reacts with diphosphines giving products whose nature is critically dependent on the aliphatic chain length. While the short-bite dppm is able to coordinate in equatorial position across the Rh-2(4+) core, the reaction with dppe proceeds via ortho-metalation of the diphosphine giving a further evidence of the versatility of the above fragment toward ortho-metalation.