Fluoroarene tricarbonylchromium complexes

It has been found that ( 7 -fluoroarene)tricarbonylchromium complexes undergo Suzuki reactions with arylboronic acids to form (77 -biaryl)tricarbonylchromium complexes in the presence of PMe3/[Pd2(dba)3] and GsF or GS2GO3 (Scheme 43). Comparable Stille couplings have been developed. DFT calculations have been performed... 

The optically pure secondary phosphine boranes are easily deprotonated, giving extremely nucleophilic phosphide borane anions, which preserve the absolute configuration at the P atom at low temperatures. This fact prompted Danjo, Imamoto and co-workers to couple the phosphide boranes derived from 9 with aryl cation equivalents. In particular, they found that fluoroarene tricarbonylchromium complexes such as 17 were excellent substrates for the SNAr process due to the high electron deficiency of the arene ring and significant electrophilicity of the ipso carbon (Scheme 5.9). 

There are only a few examples of displacement of a fluorine atom in a cross-coupling reaction. With tricarbonylchromium complexes of fluoroarenes as substrates, cross-coupling with both boronic acids and vinylstannanes has been realized. Interestingly, only PMe3 is effective as ligand in this reaction (89).2" See Section 9.6.3.4.10 for an example of the involvement of unactivated fluoroarenes in cross-coupling reactions. 

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