Intermolecular aryl ligand transfer

Studies of intermolecular aryl ligand transfer of nickel complexes [149] started almost at the same time as the first preparation of the arylnickel complexes because they were regarded to be involved in Ni complex promoted intermolecular coupling of aryl halides to give biaryls. Kochi reported the reaction of bromoarene with NiBr(ArXPEt3)2 at elevated temperature in THF to produce biaryl as the 

Monoarylnickel(III) complexes were obtained from the reaction of NBS N-bromosuccinic imide) with arylnickel(II) complex (Eq. 5.41) or its electrochemical oxidation [152,153]. 

The complex exhibits unique properties originating from the Ni(I) center, such as a T-shaped three coordination structure, longer Ni-N (2.007(3) A) and Ni-C (2.205(3) A) bonds than those of organonickel(II) complexes, and paramagnetism confirmed by ESR measurement. 

Pd(II) complexes with perhalogenated aryl ligands, C6F2CI3 and CeFs, have stable Pd-C bonds and do not cause coupling reactions even when the two 

Neutral arylnickel(II) complexes, NiBr(Ar)(bpy) (Ar = Ph, C6H4Me, C6H40Me, etc.), form biaryls when they are dissolved in DMF at room temperature [161,162] (Eq 5.45). 

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It is more facile than the reaction of NiBr(Ar)(bpy), whose disproportionation via intermolecular aryl ligand transfer requires polar solvents to assist Ni-halogeno bond activation as mentioned in a previous section. Methylplatinum complexes with monodentate phosphine, arsine and thioether hgands cause methyl ligand transfer leading to disproportionation and cis-trans isomerization [207] (Eq. 5.63). 

Intermolecular alkynyl ligand transfer of transition metal complexes is more common than the aryl and alkyl ligand transfer. Alkynyl compounds of Cu(I) and Hg(II) transport the ligand to other transition metals, giving various alkynyl transition metal complexes. [Cu(C=CR)] [171], isolated or generated in situ from the reaction of alkyne, Cul, and base, was employed in preparation of a number of alkynyl complexes of group 5-10 transition metals. The alkynyl hgand transfer is depicted schematically in Eq. 5.46 [172-175]. 

Transmetallation, involving intermolecular transfer of the aryl ligand, also provides convenient routes for synthesis of arylplatinum(ii) complexes. Reactions of 2-methoxyphenyllithium with Pt complexes having optically active diphosphines, DIOP, BINAP, and chiraphos, produce the corresponding diarylplatinum complexes. NMR spectra show the presence of isomers due to restricted rotation around the Pt-G bond of the 2-methoxyphenyl ligand. Anionic... 

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