3,3 -Bipyridyl diphosphine

Chan et al. reported the preparation and resolution of closely related 3,3 -bipyridyl diphosphine atropisomers that differed by the aryl group on the phosphorous. The synthetic route which was used for Ar = Ph (99USP5886182, 00JA11513), R = p-tolyl (01SL1050) and R = 3,5-dimethyl-phenyl (02TL1539) is reported in Figure 13. 

Carbon monoxide insertion in a palladium-carbon bond is a fairly common reaction [21]. Under polymerization conditions, CO insertion is thought to be rapid and reversible. Olefin insertion in a palladium-carbon bond is a less common reaction, but recent studies involving cationic palladium-diphosphine and -bipyridyl complexes have shown that olefin insertion also, particularly in palladium-acyl bonds, appears to be a facile reaction [22], Nevertheless, it is likely that olefin insertion is the slowest (rate-determining) and irreversible step vide infra) in polyketone formation. 

The 3,3 -bipyridyl-based axially chiral diphosphine ligand (P-Phos) has found several applications in rhodium- and ruthenium-catalyzed homogeneous reactions (50). 

Scheme 4.5 Ni-catalyzed dehalogenative polycondensation of p-dihalobenzene with Mg. Ni(II)Lm divalent Ni complexes such as NiCl2(bpy) (bpy = 2,2 -bipyridyl) and NiCl2(diphosphine). X = Br, Cl, etc.

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