The decisive role of ligand metathesis in Au/Pd bimetallic catalysis

Abstract

AuClL(1)/PdCl2L(2)2 cocatalyzed coupling of Ar(1)X and Ar(2)SnBu3 is feasible for bulky Ar(1), provided that at least one ligand on Pd is not strongly coordinating. This can be achieved in situ by Au/Pd ligand exchange if L(1) is weakly coordinating. When the exchange is slow, independent preparation of appropriate catalysts is recommended.

Mechanism-based enhancement of scope and enantioselectivity for reactions involving a copper-substituted stereogenic carbon centre

“…could not be improved by adjusting electrophile and co-catalyst concentration (see the Supplementary Information, Section 13, for details). This might be because the presence of achiral bis-phosphine Pd species causes an achiral Cu–B(pin) complex to be generated by ligand exchange 18 , and the resulting non-enantioselective pathways offset any advantage that might result from a change in conditions.…”

In Situ Generation of ArCu from CuF2 Makes Coupling of Bulky Aryl Silanes Feasible and Highly Efficient

“…Catalyst 5 is extremely efficient and quite general, as discussed below. It might appear that its composition (two different ligands, one of them AsPh 3 ) corresponds to a highly contaminant and not easily accessible catalyst, but it is very easy to make in two steps from simple precursors, and the isolated cross‐coupling reaction products analyzed by inductively coupled plasma mass spectrometry (ICP‐MS) show that the palladium or arsenic concentrations in the product are <1 μg g −1 (see the Supporting Information for details).…”

“…The use of linear gold complexes as "aryl carriers" in this bimetallic catalysis [15] leads to as equential Sn/Au/Pd bulky-aryl doublet ransmetalation,i nw hich eithero ft he two steps is much lessc ongested and has al ower transmetalation barriert han that of direct Sn/Pd transmetalation. [16,17] In this research we found that, for the facilitation of transmetalation to Pd II (Sn/Pdo rA u/Pd), it was important that Pd should contain an ancillary ligand that was easy to displace;a tt he same time, to stabilize the Pd 0 intermediate, good coordinating soft ligands should be availablet oc oordinate to Pd.T his led us to discover the excellent performance of [PdCl 2 (IDM)(AsPh 3 )] (IDM = 1,3-dimethylimidazol-2-ylidene), whichi sa na symmetric complex with one stronga nd one weak ligand that does not symmetrize to [PdCl 2 (IDM) 2 ]a nd [PdCl 2 (AsPh 3 ) 2 ]u nder the working conditions for that Au-cocatalyzed Stille process. Unfortunately,o ur attempts, at the be-ginningo ft his work, at extending this gold(I) cocatalysis to the Hiyama reactionhave been unsuccessful.…”

“…Unless specified otherwise, all compounds used were purchased from commercial sources and used without further purification. Compounds 3 , 8 , [PdCl 2 (IDM) 2 ], [PdCl 2 (AsPh 3 )(IDM)], 4 , PEPPSI, trans‐ [Pd(C 6 F 5 )(Br)(PPh 3 ) 2 ], trans‐ [Pd(C 6 H 4 CF 3 )(I)(PPh 3 ) 2 ], trans‐ [Pd(C 6 H 4 CF 3 )(F)(PPh 3 ) 2 ], [CuF 2 (bipy)] ⋅ 3 H 2 O (bipy=2,2′‐bipyridine), Cl−Si(OEt) 3 , and 1‐[2‐(diphenylphosphino)phenyl]‐ N , N ‐dimethylmethanamine were made by methods reported in the literature. Particularly, anhydrous CuF 2 was purchased from Alfa Aesar, Ph−Si(OEt) 3 was purchased from Aldrich, and (C 6 F 5 )Si(OEt) 3 from Fluorochem.…”

Multiple‐Metal (De‐)Hydrogenation‐Catalysed Processes

“…This microreview reports recent advances in the use of multiple organometallic complexes applied to catalytic reactions involving at least one hydrogenation or dehydrogenation process . There are multiple‐metal‐catalysed processes in which the hydrogen released in the first catalytic cycle is then used for a catalytic hydrogenation reaction in a second catalytic cycle.…”