Ligand displacement reactions with ketones

The mechanism of reversible (5-hydrogen elimination from square planar lr(l) alkoxide complexes with labile dative ligands, followed by associahve displacement of the coordinated ketone or aldehyde by incoming phosphine, which can be implied in TH reactions, was proposed by Hartwig and coworkers [36]. 

In contrast, for the oxy and thio analogues 106 and 107 only 1 equivalent of PPh3 was necessary to produce the neutral, pyridine-displaced products 130 and 131.52 Reaction of the ketone derivative 115 with an equimolar amount of PPh3 gave the neutral complex 132 formed by displacement of the pyridine ligand, while with 2 equivalents of PPh3 in the presence of Na[BF4] the cationic bis(phosphine) complex 133 is obtained.58... 

One or two minor points may be added to Table 8 above the adducts of aldehydes and ketones to palladium and platinum complexes react with SO2, CO2 and NO2 with displacement of the organic moiety to give the products expected for addition of these molecules to a dioxygen complex diphenylacetylene displaces both the carbonyl and the dloxygen ligand Adducts of CS2 and thiourea have also been reported The products obtained with NO2 depend on the reaction conditions, especially the solvent reaction of NO2 with (r-BuNC)2M02 gives a trans dinitrate for M = Ni and a cis dinitrate for M = Pd ). 

The following stoichiometric and catalytic reactions are based on the displacement of N. in CoH(N.)(PPh3)3 by alkenes. For example, replacement of the N7 ligand of CoH(N.)(PPh3)3to ethylene and the subsequent reaction of the ethylene complex with aeyl chloride give ketone stoichiometrically (eq (13)) [16]. 

Alkyl phenyl ketones are reduced to the (R) alcohols with greater selectivity than the alkyl methyl ketones are reduced to the (5) alcohols. Optical yields vary depending on the chiral ligand (4 being superior to 5) and increase on increasing the [i-PrOH]/[substrate] ratio (the reverse reaction becoming less thermodynamically favored). Formation of catalytically active species from the complex requires displacement of the cyclooctadiene from the coordination sphere of the metal. The enantioselectivity observed is explained in terms of the equilibria between the diastereoisomeric forms of this catalytically active species. 

---