Bridging the Gap from Mononuclear Pd^IIPrecatalysts to Pd Nanoparticles: Identification of Intermediate Linear [Pd₃(XPh₃)₄]²⁺Clusters as Catalytic Species for Suzuki-Miyaura Couplings (X = P, As)

TY - JOUR

T1 - Bridging the Gap from Mononuclear PdIIPrecatalysts to Pd Nanoparticles

T2 - Identification of Intermediate Linear [Pd3(XPh3)4]2+Clusters as Catalytic Species for Suzuki-Miyaura Couplings (X = P, As)

AU - Appleby, Kate M.

AU - Dzotsi, Evans

AU - Scott, Neil W.J.

AU - Dexin, Guan

AU - Jeddi, Neda

AU - Whitwood, Adrian C.

AU - Pridmore, Natalie E.

AU - Hart, Sam

AU - Duckett, Simon B.

AU - Fairlamb, Ian J.S.

N1 - Funding Information: We are grateful for financial support from the EPSRC (grant no. EP/G009546/1) and Bruker BioSpin (CASE studentship for K.M.A. and equipment). N.W.J.S. was funded by Bayer AG (Ph.D. studentship). S.B.D. and I.J.S.F. thank the Wellcome Trust for funding (Reference Grants 092506 and 098335). © 2021 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

PY - 2021/11/8

Y1 - 2021/11/8

N2 - Tripalladium clusters of the type [Pd3(PPh3)4]2+, wherein three linearly connected Pd atoms are stabilized by phosphine and arsine ligands, have been detected and isolated as intermediates during the reduction of well-defined mononuclear [Pd(OTf)2(XPh3)2] (X = P and X = As, respectively) to Pd nanoparticles (PdNPs). The isolated [Pd3(PPh3)4]2+ cluster isomerizes on broad-band UV irradiation to form an unexpected photoisomer, produced by a remarkable change in conformation at one of the bridging PPh3 ligands. A catalytic role for these [Pd3(XPh3)4]2+ species is exemplified in Suzuki-Miyaura cross-coupling (SMCC) reactions, with high activity seen in the arylation of a brominated heterocyclic 2-pyrone. Use of the [Pd3(PPh3)4]2+ cluster enables a switch in site selectivity for SMCC reactions involving 2,4-dibromopyridine from the typical C2-bromide site (seen previously for mononuclear Pd catalysts) to the atypical C4-bromide site, thereby mirroring recently reported cyclic Pd3 clusters and PdNPs. We have further determined that the thermal isomer and photoisomer of [Pd3(PPh3)4]2+ are similarly catalytically active in the Pd-catalyzed hydrogenation of phenylacetylene to give styrene. Our findings link the evolution of mononuclear Pd(II) salts to PdNPs via the intermediacy of linear [Pd3(XPh3)4]2+ clusters.

AB - Tripalladium clusters of the type [Pd3(PPh3)4]2+, wherein three linearly connected Pd atoms are stabilized by phosphine and arsine ligands, have been detected and isolated as intermediates during the reduction of well-defined mononuclear [Pd(OTf)2(XPh3)2] (X = P and X = As, respectively) to Pd nanoparticles (PdNPs). The isolated [Pd3(PPh3)4]2+ cluster isomerizes on broad-band UV irradiation to form an unexpected photoisomer, produced by a remarkable change in conformation at one of the bridging PPh3 ligands. A catalytic role for these [Pd3(XPh3)4]2+ species is exemplified in Suzuki-Miyaura cross-coupling (SMCC) reactions, with high activity seen in the arylation of a brominated heterocyclic 2-pyrone. Use of the [Pd3(PPh3)4]2+ cluster enables a switch in site selectivity for SMCC reactions involving 2,4-dibromopyridine from the typical C2-bromide site (seen previously for mononuclear Pd catalysts) to the atypical C4-bromide site, thereby mirroring recently reported cyclic Pd3 clusters and PdNPs. We have further determined that the thermal isomer and photoisomer of [Pd3(PPh3)4]2+ are similarly catalytically active in the Pd-catalyzed hydrogenation of phenylacetylene to give styrene. Our findings link the evolution of mononuclear Pd(II) salts to PdNPs via the intermediacy of linear [Pd3(XPh3)4]2+ clusters.

UR - http://www.scopus.com/inward/record.url?scp=85118675223&partnerID=8YFLogxK

U2 - 10.1021/acs.organomet.1c00452

DO - 10.1021/acs.organomet.1c00452

M3 - Article

AN - SCOPUS:85118675223

SN - 0276-7333

VL - 40

SP - 3560

EP - 3570

JO - Organometallics

JF - Organometallics

IS - 21

ER -