Gold Complexes with ADAP Ligands: Effect of Bulkiness in Catalytic Carbene Transfer Reactions (ADAP = Alkoxydiaminophosphine)

Abstract

A family of gold(I) complexes of composition AuCl(ADAP) (ADAP = alkoxydiaminophosphine) has been prepared through a one-pot simple protocol in which the ADAP ligand is in situ prepared before reaction with the Au(I) source. Structural data demonstrate that these ADAP ligands exert a trans effect superior to those of phosphine or phosphite ligands. Evaluation of the buried volume (%V Bur ) indicates a steric hindrance higher than several NHC-, PR 3 or P(OR 3 ) ligands, in the context of AuCl(L) complexes. These complexes promote the catalytic transfer of a carbene group from ethyl diazoacetate to alkenes and alkanes. In the case of styrene, both the C sp 2-H bonds as well as the C=C bond are functionalized, the relative ratio depending of the catalyst employed, correlating well with the (%V Bur ). Data available allow proposing that these compounds display quite similar electronic properties but differ in steric, a variable that can be readily controlled upon modifying the alkoxy group at the ADAP ligand by simply replacing the starting alcohol employed in their synthesis.

Planar Chiral 1,3-Disubstituted Ferrocenyl Phosphine Gold(I) Catalysts

“…As a comparison, buried volumes of [(PR 3 )AuCl] complexes with R = t Bu, o Tol, and Mes are 38.1, 39.4, and 45.0%, respectively (2.28 Å, Au–P length). 21 Buried volumes of 45–53% have been reported for other gold(I) complexes bearing bulky alkoxydiaminophosphine 22 or acyclic diaminocarbene ligands. 23 …”

“…As a comparison, buried volumes of [(PR 3 )AuCl] complexes with R = tBu, oTol, and Mes are 38.1, 39.4, and 45.0%, respectively (2.28 Å, Au−P length). 21 Buried volumes of 45−53% have been reported for other gold(I) complexes bearing bulky alkoxydiaminophosphine 22 or acyclic diaminocarbene ligands. 23 To compare the reactivity of the new ferrocenyl phosphine gold(I) complexes with that of 1, 17 we studied the [4 + 2] cycloaddition of 1,6-arylenynes 7 (Scheme 3).…”

Selective Functionalization of Arene C(sp2)–H Bonds by Gold Catalysis: The Role of Carbene Substituents

“…Computational studies have revealed the crucial role of the arene group in the selectivity, explaining the large differences in comparison with the widely employed ethyl diazoacetate reagent. 13 We have recently described 12 the synthesis and characterization of a series of compounds of general formula (ADAP)AuCl, bearing alkoxydiaminophosphine ligands containing a five-membered ring that resembles that of NHC ligands. In view of our previous work with (NHC)AuCl compounds as precatalysts for carbene transfer reactions to C(sp 3 )−H and C(sp 2 )−H bonds 3,14,15 Regarding the functionalization of the C(sp 2 )−H bonds, both diazo compounds provide products derived from the formal insertion of the carbene group into such bonds; however, whereas EDA gives a mixture of the three o-, m-, and p-isomers, only the para isomer (2-p) is observed with PhEDA as the carbene precursor under the applied reaction conditions.…”

“…In this contribution, we report the catalytic properties of a family of gold complexes containing alkoxydiaminophosphine ligands (ADAP) which promote the exclusive incorporation of carbene units into the C–H bond located at the para position of monosubstituted alkylbenzenes with the readily available ethyl 2-phenyldiazoacetate as the carbene source (Scheme d), not needing the elaboration on the diazo reagent. Computational studies have revealed the crucial role of the arene group in the selectivity, explaining the large differences in comparison with the widely employed ethyl diazoacetate reagent …”

“…We have recently described the synthesis and characterization of a series of compounds of general formula (ADAP)­AuCl, bearing alkoxydiaminophosphine ligands containing a five-membered ring that resembles that of NHC ligands. In view of our previous work with (NHC)­AuCl compounds as precatalysts for carbene transfer reactions to C­(sp 3 )–H and C­(sp 2 )–H bonds ,, and the above-mentioned success ,, of phosphite-containing gold catalysts for selective C­(sp 2 )–H bond functionalization, we decided to test their catalytic properties toward this transformation.…”