Origin of Stability and Inhibition of Cooperative Alkyne Hydrofunctionalization Catalysts

Abstract

New entries to the [Ru(Cp/Cp*)(P R 2 N R' 2 )(MeCN)]PF 6 catalyst family were synthesized, including a Cp complex (R=Cy; R'=Ph) and two Cp* complexes (R=Cy, Ph; R'=Ph). These and other derivatives were used for the intramolecular hydroamination of 2-ethynylaniline to elucidate trends in catalytic lifetime and rate. The readily accessible [Ru(Cp)(P Cy 2 N Ph 2 )(MeCN)]PF 6 derivative showed comparable lifetime to [Ru(Cp)(P tÀ Bu 2 N Ph 2 )(MeCN)] PF 6 , the previous optimal catalyst. Donor-free 'active' catalysts, [Ru(Cp/Cp*)(P Cy 2 N Ph 2 )]PF 6 , were prepared and their thermal stability was assessed. The relatively high stability of the Cp derivative was explained by the capacity of the P Cy 2 N Ph 2 ligand to coordinate in a k 3 -(P,P,Ar) mode, which protects the lowcoordinate species. This coordination mode is inaccessible with the Cp* derivative. Additionally, [Ru(Cp*)(P Cy 2 N Ph 2 )]PF 6 readily activated the CÀ Cl bond of the solvent dichloromethane. Variable time normalization analysis (VTNA) revealed that the indole product inhibited the catalyst [Ru(Cp)(P Cy 2 N Ph 2 )(MeCN)] PF 6 , which slowed catalytic rates.

Catalytic Aldehyde and Alcohol Arylation Reactions Facilitated by a 1,5-Diaza-3,7-diphosphacyclooctane Ligand

“…Despite being distant from the metal center, the CF 3 group can have a profound effect on the Ni, suggesting simple electronic tuning may be occurring . The pendant nitrogen arm of aniline-derived P 2 N 2 ligands has also been found to interact with and stabilize metal centers in a manner similar to how the arene ring on Buchwald-type ligands are known to interact with Pd . Furthermore, the sterically bulky cyclohexyl­phosphine fragments on our optimal ligand have been shown to result in distortion of square-planar Ni­(II) complexes in related complexes, which may be important for reactivity .…”

Reagent-free intramolecular hydrofunctionalization: a regioselective 6-endo-dig cyclization of o-alkynoylphenols

“…11 The intramolecular hydrofunctionalizations of alkynes are catalyzed by transition metal and inner transition metal complexes, which primarily activate electrophiles such as alkynes or nucleophiles such as the O-H or N-H group (Scheme 1A and B). 6,10,[12][13][14] Besides, a few metal-free synthetic methods for acid-or base-catalyzed reactions have been studied, particularly for the intramolecular alkoxylation of o-alkynoylphenols (Scheme 1C). 8,[15][16][17][18][19] The alkoxylation might be achieved owing to the presence of both the reactive carbonyl and the polarized α,β-alkyne moieties (i.e., ynones).…”

Molecular Catalysts with Diphosphine Ligands Containing Pendant Amines

“…The nucleophilicity of the pendant amines is not high enough to impede further transformation of the Ru vinylidene. Cyclization of 2-ethynylaniline to give indole (eq ) is catalyzed by [CpRu­(P Ph 2 N Bn 2 )­(NCMe)] + (1 mol %) at 55 °C …”

“…Intramolecular hydroamination of 2-ethynylaniline is catalyzed by [CpRu­(P R 2 N Ph 2 )­(NCMe)] + (R = Cy, Ph, t -Bu) at 70 °C. , These studies led to the isolation and crystallographic characterization of [CpRu­(P Cy 2 N Ph 2 )] + (Figure ), which has a weak bond between the phenyl ring and the Ru . This structure was determined for the complex with a Cp ligand, but studies on [(C 5 Me 5 )­Ru­(P Cy 2 N Ph 2 )] + did not give evidence for arene coordination.…”

“…Cyclization of 2-ethynylaniline to give indole (eq 26) is catalyzed by [CpRu(P Ph 2 N Bn 2 )(NCMe)] + (1 mol %) at 55 °C. 310 Acceptorless dehydrogenation of amines is catalyzed at 110 °C by [CpRu(P Ph 2 N Bn 2 )(NCMe)] + ; 63 eq 27 shows the imine and benzonitrile products and their stoichiometry for dehydrogenation reactions. The imine was favored about 3:1 over the nitrile.…”