The ubiquitous P(o-tol)3 ligand promotes formation of catalytically-active higher order palladacyclic clusters

TY - JOUR

T1 - The ubiquitous P(o-tol)3 ligand promotes formation of catalytically-active higher order palladacyclic clusters

AU - Husbands, David

AU - Tanner, Theo

AU - Whitwood, Adrian C.

AU - Hodnett, Neil S.

AU - Wheelhouse, Katherine M.P.

AU - Fairlamb, Ian James Stewart

PY - 2024/10/14

Y1 - 2024/10/14

N2 - The Herrmann-Beller catalyst, Pd(C^P)(µ2-OAc)]2, is readily formed by reaction of the cyclic trimer of ‘Pd(OAc)2’ with P(o-tol)3. In the presence of hydroxide, Pd(C^P)(µ2-OAc)]2 converts to [Pd(C^P)(µ2-OH)]2. Here, we report how this activated Pd precatalyst species, and related species, serve as a conduit for formation of higher order Pdn clusters containing multiple cyclopalladated P(o-tol)3 ligands. The catalytic competency of a Pd4-palladacyclic cluster is demonstrated in an arylated Heck cross-coupling, which is comparable to the base-activated form of Herrmann’s catalyst, namely [Pd(C^P)(µ2-OH)]2. The findings show that ‘simple’ ubiquitous phosphine ligands can promote higher order Pd speciation, moving beyond well-known phosphine-ligated Pd1 and Pd2 complexes. The findings challenge the status quo in the field, in that phosphine ligands can ligate higher order Pdn species which are catalytically competent species in cross-coupling reactions.

AB - The Herrmann-Beller catalyst, Pd(C^P)(µ2-OAc)]2, is readily formed by reaction of the cyclic trimer of ‘Pd(OAc)2’ with P(o-tol)3. In the presence of hydroxide, Pd(C^P)(µ2-OAc)]2 converts to [Pd(C^P)(µ2-OH)]2. Here, we report how this activated Pd precatalyst species, and related species, serve as a conduit for formation of higher order Pdn clusters containing multiple cyclopalladated P(o-tol)3 ligands. The catalytic competency of a Pd4-palladacyclic cluster is demonstrated in an arylated Heck cross-coupling, which is comparable to the base-activated form of Herrmann’s catalyst, namely [Pd(C^P)(µ2-OH)]2. The findings show that ‘simple’ ubiquitous phosphine ligands can promote higher order Pd speciation, moving beyond well-known phosphine-ligated Pd1 and Pd2 complexes. The findings challenge the status quo in the field, in that phosphine ligands can ligate higher order Pdn species which are catalytically competent species in cross-coupling reactions.

KW - palladium

KW - Catalysis

KW - cross-coupling

KW - Suzuki-Miyaura

KW - MECHANISM

KW - Sustainability

M3 - Article

SN - 2041-6520

SP - 1

EP - 6

JO - Chemical Science

JF - Chemical Science

ER -