Trifunctional phosphines

Bifunctional and trifunctional phosphines can be used to link two metal or three centers, and this reactivity can be controlled to give metal-metal bonds. 

Balch, Alan L., Construction of Small Polynuclear Complexes with Trifunctional Phosphine-Based Ligands as Backbones. 41 239... 

Scheme 13.23 Asymmetric aza MBH reaction catalyzed by trifunctional phosphine catalyst.

N Tosylimine (0.5 mmol), trifunctional phosphine catalyst 27 (10 mol%, 0.05 mmol),... 

Palladium-phosphine complexes such as Pd [PPh3 ]4 or, most conveniently, Pd(OAc)2 and PPh3 are used. Usually, these telomers are obtained in high yields. Nucleophiles such as water, carboxylic acids, alcohols, phenols, ammonia, amines, enamines, nitroalkanes, and active methylene and methyne compounds participate in telomerization. Also, carbon monoxide and hydrosilanes are involved in the reaction to give telomers. These easily available telomers are trifunctional and extremely useful starting materials for simple synthesis of certain types of natural products. 

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