[Rh(1,5-cyclooctadiene)(1,4-bis(diphenylphosphino)butane)]BF4, also known as [Rh(cod)(dppb)]BF4, is a cationic rhodium(I) complex. It features a square planar geometry where the rhodium center is coordinated by a chelating 1,4-bis(diphenylphosphino)butane (dppb) ligand and a bidentate 1,5-cyclooctadiene (cod) ligand, with a tetrafluoroborate (BF4-) counterion. This complex is typically supplied as an orange to red-brown solid and is air-sensitive, requiring storage under an inert atmosphere. This complex is a versatile and highly active homogeneous catalyst precursor. Its primary application is in catalytic hydrogenation reactions, particularly for the selective reduction of alkenes, alkynes, and other unsaturated functional groups. The cod ligand is labile and can be easily displaced under reaction conditions (e.g., by hydrogen), generating the active catalytic species. The chelating dppb phosphine ligand provides stability and influences the catalyst's selectivity. It is also employed in hydroformylation, hydrosilylation, and various carbon-carbon bond-forming reactions in both academic research and fine chemical synthesis. Due to its sensitivity, handling requires a nitrogen or argon atmosphere. It is a valuable tool for synthetic chemists developing efficient and selective catalytic processes. The complex is commercially available from major suppliers of organometallic and catalytic reagents.