Palladium complexes arsenic ligands

Polar, aprotic solvents such as DMF were necessary for the formation of (126). [Pd(diphos)2] (104) gave the best performance as catalyst. Using [Pd(DBA)2] (105) as palladium source, a number of mono- and bi-dentate nitrogen, phosphorus and arsenic ligands were investigated and Me2PCH2CH2PMe2 was found to be nearly as effective as diphos. The reaction of C02 with a bis(i73-allyl) complex of palladium was believed to be a key step in the process (equation 158). 

D. PALLADIUM COMPLEXES CONTAINING NITROGEN AND ARSENIC LIGANDS... 

The corresponding palladium compound (157) must be formulated as [Pd(TA)Br]+Br. The cation is essentially square-planar, but the bromine atom is displaced 10° out of the arsenic-palladium plane. Such a distortion is very unusual for palladium, and may be due to a steric effect of the alkyl chains in the arsine ligand. This might similarly account for the distortion of the nickel complex from a square pyramidal shape. 

The ligands triphos or/ and np in presence of compounds of iron, cobalt, nickel, rhodium, iridium and palladium, by reaction with THF solutions of white phosphorus, P, or yellow arsenic, As, form mononuclear or dinuclear sandwich complexes containing the cyclo-triphosphorus or cyclo-triarsenic units which behave as 3n-electrons rings. 

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