Ferrocenyl iminophosphine ligands in Pd-catalysed Suzuki couplings

A mixture of Pd2(dba)3/{η-C5H4CHN[CH(CH3)(Nap)]}Fe[η-C5H4P(tBu)2] efficiently catalyzes the Suzuki reactions of a variety of bulky aryl halides and aryl- and alkyl-boronic acids, affording the desired cross-coupling biaryl products in quantitative isolated yields under mild conditions and at low (1 × 10−6–1 mol%) Pd loadings. Spectroscopic (NMR & ESI) analysis of the mixture of Pd2(dba)3, the hybrid [P,N] ligands, and aryl halides revealed different structural forms of oxidative addition products that are dependent on the substituent on the imino nitrogen.

Graphical abstractA mixture of Pd2(dba)3/{η-C5H4CHN[CH(CH3)(Nap)]}Fe[η-C5H4P(t-Bu)2] efficiently catalyzes the Suzuki reactions of a variety of bulky aryl halides and aryl- and alkyl-boronic acids, affording the desired cross-coupling biaryl products in quantitative isolated yields under mild conditions and at low (1 × 10−6–1 mol% Pd) loadings.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Facile method of synthesizing biaryls with four-ortho organo substituents. ► Use of P, N ligands that promote Suzuki cross-coupling efficiently. ► Influence of hemilabile donor site in determining catalytic performance. ► Structural effect on the oxidative addition intermediates are demonstrated.