Structure–Reactivity Relationships of Buchwald-Type Phosphines in Nickel-Catalyzed Cross-Couplings

The dialkyl-ortho-biaryl class of phosphines,
commonly known as Buchwald-type ligands, are among the most important
phosphines in Pd-catalyzed cross-coupling. These ligands have also
been successfully applied to several synthetically valuable Ni-catalyzed
cross-coupling methodologies and, as demonstrated in this work, are
top performing ligands in Ni-catalyzed Suzuki Miyaura Coupling (SMC)
and C–N coupling reactions, even outperforming commonly employed
bisphosphines like dppf in many circumstances. However, little is
known about their structure–reactivity relationships (SRRs)
with Ni, and limited examples of well-defined, catalytically relevant
Ni complexes with Buchwald-type ligands exist. In this work, we report
the analysis of Buchwald-type phosphine SRRs in four representative
Ni-catalyzed cross-coupling reactions. Our study was guided by data-driven
classification analysis, which together with mechanistic organometallic
studies of structurally characterized Ni(0), Ni(I), and Ni(II) complexes
allowed us to rationalize reactivity patterns in catalysis. Overall,
we expect that this study will serve as a platform for further exploration
of this ligand class in organonickel chemistry as well as in the development
of new Ni-catalyzed cross-coupling methodologies.