The new ligand 1‐[2‐(diphenylphosphanyl)ethyl]‐3,5‐dimethylpyrazole (2) has been prepared by the reaction of 1‐(chloroethyl)‐3,5‐dimethylpyrazole and PPh₂Li. The bidentate N,N ligand 1‐[2‐(ethylamino)ethyl]‐3,5‐dimethylpyrazole (1) and 2 react with [Rh(COD)(THF)₂][BF₄] to give [Rh(COD)(1)][BF₄] (3) and [Rh(COD)(2)][BF₄] (4), respectively. Substitution of 1,5‐cyclooctadiene with carbon monoxide in the latter complexes generates [Rh(CO)₂(1)][BF₄] (5) and [Rh(CO)₂(2)][BF₄] (6), respectively. Treatment of [Rh(COD)(THF)₂][BF₄] with two equivalent amounts of 2 results in the complex [Rh(2)₂][BF₄] (7), which converts to [Rh(CO)(2)₂][BF₄] (8) on reaction with carbon monoxide. Ligand 2 in complex 8 exhibits a hemilabile character. The single‐crystal X‐ray structures of 3, 4, and 7 are reported. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)