Microwave‐Assisted C–C and C–S Couplings Catalysed by Organometallic Pd‐SCS or Coordination Ni‐SNS Pincer Complexes

Abstract

A family of SCS and SNS pincer compounds of the type [PdCl{C6H3‐2,6‐(CH2SR)2}] {R = tBu (3a), sBu (3b), iBu (3c)} and [NiCl2{C5H3N‐2,6‐(CH2SR)2}] {R = tBu (4a), sBu (4b)} have been prepared. Among these, complexes 3b, 3c, 4a–4c are reported for the first time. Dimeric compounds such as [NiCl{C5H3N‐2,6‐(CH2SiBu)2}μ‐Cl]2 (4c) were found in the solid state for the nickel complexes with lower steric hindrance exhibiting octahedral metal centers, whereas other nickel structures such as [NiCl2{C5H3N‐2,6‐(CH2StBu)2}(iPrOH)] (4d) could also expand their coordination number by coordinating to solvents. The single crystal X‐ray diffraction results for 4a, 4c and 4d are presented. The catalytic activity of the six compounds was studied in C–C and C–S cross‐coupling reactions under conventional heating and under microwave irradiation conditions. The palladium catalysts enabled good to excellent conversions in Suzuki–Miyaura couplings of p‐substituted halobenzenes with phenylboronic acid. Comparable yields resulted from application of the nickel complexes in the thioetherification of iodobenzene with different disulfides. The fast increase in reaction temperature associated with microwave irradiation, in combination with the robust pincer catalysts, allowed for quantitative conversions in only minutes.

Eco-Friendly Physical Activation Methods for Suzuki–Miyaura Reactions

“…An enhanced TOF of 24,000 was obtained for acyl and formyl substituents. Morales-Morales [76] have reported the preparation of a family of SCS pincer compounds, of the [PdCl{C6H3-2,6-(CH2SR)2}] {R = tBu, sBu, iBu} type, which are suitable for SMC reaction, under both conventional and MW heating. These series of alkyl-substituted SCS-Pd II pincer complexes (Scheme 43) were prepared via the direct C-H activation of a series of α,α-bis(butylthio)metaxylene proligands Morales-Morales [76] have reported the preparation of a family of SCS pincer compounds, of the [PdCl{C 6 H 3 -2,6-(CH 2 SR) 2 }] {R = tBu, sBu, iBu} type, which are suitable for SMC reaction, under both conventional and MW heating.…”

“…Morales-Morales [76] have reported the preparation of a family of SCS pincer compounds, of the [PdCl{C6H3-2,6-(CH2SR)2}] {R = tBu, sBu, iBu} type, which are suitable for SMC reaction, under both conventional and MW heating. These series of alkyl-substituted SCS-Pd II pincer complexes (Scheme 43) were prepared via the direct C-H activation of a series of α,α-bis(butylthio)metaxylene proligands Morales-Morales [76] have reported the preparation of a family of SCS pincer compounds, of the [PdCl{C 6 H 3 -2,6-(CH 2 SR) 2 }] {R = tBu, sBu, iBu} type, which are suitable for SMC reaction, under both conventional and MW heating. These series of alkyl-substituted SCS-Pd II pincer complexes (Scheme 43) were prepared via the direct C-H activation of a series of α,α-bis(butylthio)metaxylene proligands (C 6 H 4 -1,3-(CH 2 SR) 2 , for R = tBu, sBu, iBu substituents) starting from a PdCl 2 suspension in toluene.…”

Instituto de Química de la UNAM: catalizando la química con paso firme

“…Este tipo de ligantes se aplican a la investigación en los campos de la hidrogenación asimétrica, polimerización y reacciones de acoplamiento cruzado tipo Heck y Suzuki-Miyaura [19]. Al respecto, el grupo del doctor Morales ha estudiado y desarrollado la química de este tipo de ligantes, no sólo con paladio como metal sino con rutenio [19], níquel [ 20] e iridio [21]. En el esquema 3 se presenta la aplicación de un complejo tipo pinza de iridio con átomos de arsénico como donadores y la aplicación a reacciones de dehidrogenación catalítica.…”

Halide exchange studies of novel Pd(ii) NNN-pincer complexes

“…18,20 Among various metals, palladium is one of the most studied owing mainly to its importance in organic synthesis. While formation of a carbon-palladium bond provides stability, replacing carbon with other elements such as Si, P, N have been shown to lead to signicant changes in reactivity and an lead to signicant developments in catalysis 4,8,[21][22][23][24][25][26][27] and cytotoxicity studies. 18,20,[28][29][30][31][32] A key factor in reactivity is the general lability of the fourth coordination site.…”