dppb (1,4-Bis(diphenylphosphino)butane) | CAS 7688-25-7 | ≥97%

Technical Specifications

Product Description & Scientific Applications

dppb (1,4-bis(diphenylphosphino)butane; tetramethylenebis(diphenylphosphine); butane-1,4-diylbis(diphenylphosphane)) is a bidentate diphosphine ligand whose four-carbon butane backbone binds a metal through both phosphorus donors in a seven-membered chelate ring, giving a wide natural bite angle of about 94° in its bidentate coordination mode. The flexible four-carbon backbone is conformationally floppy, so reported bite angles for dppb depend on the method of determination, with molecular-mechanics estimates of the natural bite angle running somewhat higher than the bidentate-complex value. In the short dppe–dppp–dppb series, dppb is the wider, more flexible member, reflecting its longer four-carbon linker. Because the bite angle set by the backbone influences the geometry at the metal, dppb occupies a distinct position in homogeneous catalysis and coordination chemistry. The longer backbone also lets dppb function as a chelating, bridging, or monodentate ligand depending on the metal and complex.

Bidentate ligand for Pd- and Ni-catalysed cross-coupling

PdCl2(dppb) is a well-defined precatalyst across Suzuki–Miyaura, Stille, Sonogashira, Negishi, Hiyama, Heck and Buchwald–Hartwig chemistry, while dppb-supported nickel systems are used more selectively in Kumada-type cross-coupling. dppb-supported palladium is also effective for coupling of alkyl Grignard reagents with organic halides, where the longer backbone helps favour reductive elimination over competing β-hydride elimination and so enables coupling of aliphatic substrates. It is further used for regio- and stereoselective monoalkylation and arylation of 1,1-dihalo-1-alkenes, including modification of the dihalovinyl motif en route to synthetic pyrethroids. Its wider bite angle makes dppb a useful comparison ligand when screening how diphosphine geometry affects oxidative addition, transmetalation and reductive elimination in a given coupling.

Palladium-catalysed carbonylation

PdCl2(dppb) is used in palladium-catalysed carbonylation of styrene, where carbon monoxide is incorporated into the organic product. This makes dppb a relevant ligand for carbonylation screening when comparing how diphosphine backbone length and bite angle affect palladium-catalysed CO insertion.

Rhodium-catalysed hydroformylation

Rhodium–dppb systems are used in alkene hydroformylation. In comparative 1-hexene hydroformylation studies across the dppe–dppp–dppb series, activity and selectivity increase with bite angle, with dppb the most active and selective of the three. This makes dppb useful for studying how wider diphosphine bite angles affect regioselectivity and rate in rhodium-catalysed hydroformylation.

Coordination chemistry and model complexes

dppb forms well-defined chelate complexes with nickel, palladium and platinum, including square-planar M(dppb)X2 species, as well as rhodium complexes relevant to its catalytic chemistry. Spanning a single metal through a seven-membered ring, dppb favours cis coordination of its two donors, and its wider bite angle makes these complexes standard reference points for relating diphosphine linker length to metal-complex geometry and reactivity.

Handling note

As a tertiary arylphosphine, dppb is mildly air-sensitive and can slowly oxidise to the corresponding phosphine oxide on prolonged air exposure; minimise air exposure and handle under inert atmosphere where ligand purity is critical.

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