Typical ligands include olefins, phosphines, and CO. It belongs to the reactive groups of&colon; amines, phosphines and pyridines. It readily undergoes substitution by tertiary phosphines and other Lewis-bases. Secondary phosphines are prepared analogously to the primary phosphines. Examples of tetradentate tripodal phosphines include tris[2-(diphenylphosphino)ethyl]phosphine (pp3). Compared to tertiary phosphines, diphenylphosphine is weakly basic. The hydrophosphination of alkenes is versatile route to a variety of phosphines. These salts are versatile precursors to tertiary phosphines. Most chiral phosphines are C-symmetric diphosphines. The azide can act as a soft electrophile that prefers soft nucleophiles such as phosphines. Normally, ligands of intermediate donicity, such as phosphines, are utilized. Basic phosphines, such as trialkyl derivatives, are prone to this reaction. Borane adducts with phosphines and amines are also available, but are not widely used. The catalyst, when combined with optically active phosphines, can produce optically active dimers. Examples of L type ligands that have been studied are amines and phosphines (ref).