Phenyl substituted indenylphosphine ruthenium complexes as catalysts for dehydrogenation of alcohols

Abstract

Thermal treatment of (1H-inden-3-yl)dicyclohexylphosphinium tetrafluoroborate (1) and (3-mesityl-1H-inden-3-yl)dicyclohexylphosphinium tetrafluoroborate (3) with tBuONa followed by [(η(6)-cymene)RuCl(2))](2) in methanol gave the adduct {(η(6)-cymene)RuCl(2)[(1H-inden-3-yl)PCy(2)]} (6) and {(η(6)-cymene)RuCl(2)[(3-mesityl-1H-inden-3-yl)PCy(2)]} (7), respectively. Thermal treatment of (2-phenyl-1H-inden-3-yl)dicyclohexylphosphinium tetrafluoroborate (4) with tBuONa followed by [(η(6)-cymene)RuCl(2))](2) or RuCl(3)·3H(2)O in methanol gave {Ru[κ(P):(η(6)-2-phenyl-1H-inden-3-yl)PCy(2)]Cl(2)} (8). Whereas (2-mesityl-1H-inden-3-yl)dicyclohexylphosphine (5) reacted with [(η(6)-cymene)RuCl(2))](2) (in toluene) or RuCl(3)·3H(2)O (in ethanol) to afford {Ru[κ(P):(η(6)-2-mesityl-1H-inden-3-yl)PCy(2)]Cl(2)} (9). The molecular structures of complexes 6, 8 and 9 have been determined by single-crystal X-ray diffraction analysis. In addition, complexes 8 and 9 have been found to catalyze the acceptorless dehydrogenation of alcohols in toluene. 9 displayed high activity and different substrates, including cyclic and linear alcohols, were efficiently oxidized to ketones by using 2.0 mol% of catalyst.

Facile Arene Ligand Exchange in p-Cymene Ruthenium(II) Complexes of Tertiary P-Chiral Ferrocenyl Phosphines

“…Here, phosphines with pendant aromatic groups in close proximity to the phosphorus atom are predominantly used as polydentate ligands for the formation of tethered ruthenium complexes. 18−26 Utilizing the chelate effect to stabilize the arene–metal interaction is one major benefit of tethered complexes compared to nontethered complexes. 21,27 In the case of chiral ligands, another advantage is a restrained stereochemical situation which raises the racemization barrier of the chiral tethered complex.…”

“…Tethered complexes are an interesting subset of metal–arene complexes which emerge when the π-coordinating neutral arene ligand is connected with one of the coordinating donor groups. Here, phosphines with pendant aromatic groups in close proximity to the phosphorus atom are predominantly used as polydentate ligands for the formation of tethered ruthenium complexes. − Utilizing the chelate effect to stabilize the arene–metal interaction is one major benefit of tethered complexes compared to nontethered complexes. , In the case of chiral ligands, another advantage is a restrained stereochemical situation which raises the racemization barrier of the chiral tethered complex. ,− The arene coordination to form tethered complexes can be triggered thermally, but usually requires high temperatures . In contrast, tethering triggered by light is a milder alternative in cases where thermal racemization needs to be avoided, for example, with P -stereogenic phosphines …”

Indenyl Ruthenium Complexes with an Unusual η3 Coordination Mode

“…We found that (2-phenyl-1 H -inden-3-yl)­dicyclo­hexyl­phosphine ( 1 ) and (2-mesityl-1 H -inden-3-yl)­dicyclo­hexyl­phosphine ( 2 ) could react with the cluster Ru 3 (CO) 12 in heptane at about 100 °C to afford the simply substituted products [(2-phenyl-1 H -inden-3-yl)PCy 2 ]­Ru 3 (CO) 11 ( 3 ) and [(2-mesityl-1 H -inden-3-yl)PCy 2 ]­Ru 3 (CO) 11 ( 4 ) in 64% and 52% yields, respectively. Phosphine ligands 1 and 2 reacted with Ru 3 (CO) 12 in p -xylene at about 138 °C to afford dinuclear ruthenium carbonyl complexes (μ 2 -η 1 :η 3 -2-phenyl-3-Cy 2 PC 9 H 4 )­Ru 2 (CO) 6 ( 5 ) and (μ 2 -η 1 :η 3 -2-mesityl-3-Cy 2 PC 9 H 4 )­Ru 2 (CO) 6 ( 6 ).…”

A ruthenium cis-dihydride with 2-phosphinophosphinine ligands catalyses the acceptorless dehydrogenation of benzyl alcohol

“…NaO t Bu gave benzaldehyde as the product at 110°C (2 mol%, 36 h, 80% yield). 59 [RuH 2 (PPh 3 ) 4 ] (2 mol%) at 180°C in refluxing mesitylene gave 60% benzyl benzoate. 15 We note that the use of [RuCl 2 (PPh 3 ) 3 ] did not lead to substantial amounts of ester formation (2.4%) even with the addition of KO t Bu.…”