Photochemical reactions of palladium(0) and platinum(0) phosphine complexes

Visible‐Light‐Driven Palladium‐Catalyzed Radical Alkylation of C−H Bonds with Unactivated Alkyl Bromides

“…As shown in Figures S5-S10, fluorescence quenching experiments and Stern-Volmer studies indicate that the alkyl bromide quenches the excited state of Pd(PPh 3 ) 4 ,where it presumably engages in single-electron transfer (SET) with the excited palladium(0) complex. [7] Based on the obtained results and previous reports, [11,12] we propose the following mechanism with 1 and 2 as the substrates (Scheme 3A). Under visible-light irradiation, the active palladium(0) complex A undergoes an SET process with 2 to provide the tert-butyl radical C and palladium complex B,which reacts with 1 to afford the radical cation D and regenerates the palladium(0) complex.…”

“…Based on previous reports, [11,12] our mechanistic hypothesis for the alkylation of heterocycles is shown in Scheme 3B. It starts from the SET from the excited Pd 0 L n *t ot he alkyl halide,t hus forming an alkyl radical and Pd I L n Br complex.…”

“…[10] Recently,abreakthrough has been independently realized by the groups of Fu, Zhou, and Alexanian for the palladium-catalyzed radical alkylation of (hetero)arenes with unactivated alkyl halides. [11,12] Palladium-catalyzed alkylation of C(sp 3 )ÀHb onds with unactivated tertiary and secondary alkyl halides,h owever,r emains unexplored. We wondered whether it was possible to resolve such challenges by introducing visible light as an energy source to activate the palladium-catalyst and facilitate the radical cross-couplings.A sac ontinuation of our interest in visible-light-driven transition-metal catalysis, [1f,13] herein, we report the discovery of au nique visible-light photoredox system with Pd(PPh 3 ) 4 as the sole catalyst to realize the first general cross-coupling of C(sp 3 ) À Hb onds in N-aryl tetrahydroisoquinolines with unactivated alkyl halides (Scheme 1B).…”

Copper(I) binap complexes (binap=(2,2′-bis(diphenylphosphino)-1,1′-binaphthyl). Luminescence from IL and LLCT states

“…Strongly reducing metals are required in this case. This applies, for example, to Pt 0 [10][11][12][13] and Re I [5] binap complexes while in Pt(II) [6], Ag(I) [8] and Au(I) binap [7] complexes the IL states are lowest and therefore emissive. It is difficult to predict a priori which of both states is lowest in Cu(I) binap complexes.…”

“…1) is determined by pp * IL bands of the binaphthyl chromophore [5][6][7][8][9]. Other absorptions such as MLCT bands which are the longest-wavelength absorptions of Pt 0 (binap) 2 [10][11][12][13] and Re I (binap)(CO) 3 Cl [5] should then occur at higher energies. Cu(I) is apparently a weaker CT donor than Pt(0) and Re(I) in these binap complexes.…”