The Effect of N-Donor Ligands on the Reaction of Ruthenium Hydrides with 1-Alkynes

Ruthenium-Catalyzed C-C Coupling of Terminal Alkynes with Primary Alcohols or Aldehydes: α,β-Acetylenic Ketones (Ynones) via Oxidative Alkynylation

The first metal-catalyzed oxidative alkynylations of primary alcohols or aldehydes to form α,β-acetylenic ketones (ynones) are described. Deuterium labelling studies corroborate a novel reaction mechanism in which alkyne hydroruthenation forms a transient vinylruthenium complex that deprotonates the terminal alkyne to form the active alkynylruthenium nucleophile.

Stereo- and Site-Selective Conversion of Primary Alcohols to Allylic Alcohols via Ruthenium-Catalyzed Hydrogen Auto-Transfer Mediated by 2-Butyne

The first enantioselective ruthenium-catalyzed carbonyl vinylations via hydrogen autotransfer are described. Using a ruthenium-JOSIPHOS catalyst, primary alcohols 2a-2m and 2-butyne 1a are converted to chiral allylic alcohols 3a-3m with excellent levels of absolute stereocontrol. Notably, 1°,2°-1,3-diols participate in site-selective C-C coupling, enabling asymmetric carbonyl vinylation beyond premetalated reagents, exogenous reductants, or hydroxyl protecting groups. Using 2-propanol as a reductant, aldehydes dehydro-2a, 2l participate in highly enantioselective 2-butyne-mediated vinylation under otherwise identical reaction conditions. Regio-, stereo-, and site-selective vinylations mediated by 2-pentyne 1b to form adducts 3n, 3o, and epi-3o also are described. The tiglyl alcohol motif obtained upon butyne-mediated vinylation, which is itself found in diverse secondary metabolites, may be converted to commonly encountered polyketide stereodiads, -triads, and -tetrads, as demonstrated by the formation of adducts 4a-4d. The collective mechanistic studies, including deuterium labeling experiments, corroborate a catalytic cycle involving alcohol dehydrogenation to form a transient aldehyde and a ruthenium hydride, which engages in alkyne hydrometalation to form a nucleophilic vinylruthenium species that enacts carbonyl addition. A stereochemical model for carbonyl addition invoking formyl CH···I[Ru] and CH···O≡C[Ru] hydrogen bonds is proposed based on prior calculations and crystallographic data.

Heteromultimetallic compounds based on polyfunctional carboxylate linkers

Polyfunctional linkers bearing carboxylate, bipyridine and alkyne functionalities allow the stepwise construction of multimetallic assemblies incorporating redox and photophysical properties.

Ligand controlled switchable selectivity in ruthenium catalyzed aerobic oxidation of primary amines

A ligand controlled catalytic system for the aerobic oxidation of 1° amines to nitriles and imines has been developed where the varying π-acidic feature of BIAN versus phen in the frameworks of ruthenium catalysts facilitates switchable selectivity.

Temperature-Dependent Coordination of Phosphine to Five-Coordinate Alkenylruthenium Complexes

The red, five-coordinate complexes Ru(CO)Cl(PPh(3))2(CH=CHPh) and [Ru(CO)Cl(PPh(3))2]2(mu-CH=CHC(6)H(4)CH=CH) undergo reversible coordination of PPh(3) at low temperature to produce the pale yellow, six-coordinate complexes Ru(CO)Cl(PPh(3))3(CH=CHPh) and [Ru(CO)Cl(PPh(3))3]2(mu-CH=CHC(6)H(4)CH=CH). X-ray crystal structures of the latter complex and of the hydride complex RuH(CO)Cl(PPh(3))3 were obtained. 1H and 31P NMR spectra between 20 and -70 degrees C exhibit large changes in both equilibrium constants and dynamic effects. Thermodynamic parameters, DeltaH = -17.5 +/- 2.0 kcal/mol and DeltaS = -57.5 +/- 7.6 eu, were obtained for PPh(3) coordination to the monoruthenium complex, and activation parameters, DeltaH = 20.6 +/- 0.7 kcal/mol and DeltaS = 41.6 +/- 2.0 eu, were obtained for the reverse decoordination. Coordination of PPh(3) was not observed upon cooling of the shorter bridged complex, [Ru(CO)Cl(PPh(3))2]2(mu-CH=CHCH=CH).

σ-Organyl complexes of ruthenium and osmium supported by a mixed-donor ligand

A series of vinyl, aryl, acetylide and silyl complexes [Ru(R)(kappa2-MI)(CO)(PPh3)2] (R = CH=CH2, CH=CHPh, CH=CHC6H4CH3-4, CH=CH(t)Bu, CH=2OH, C(C triple bond CPh)=CHPh, C6H5, C triple bond CPh, SiMe2OEt; MI = 1-methylimidazole-2-thiolate) were prepared from either [Ru(R)Cl(CO)(PPh3)2] or [Ru(R)Cl(CO)(BTD)(PPh3)2](BTD = 2,1,3-benzothiadiazole) by reaction with the nitrogen-sulfur mixed-donor ligand, 1-methyl-2-mercaptoimidazole (HMI), in the presence of base. In the same manner, [Os(CH=CHPh)(kappa2-MI)(CO)(PPh3)2] was prepared from [Os(CH=CHPh)(CO)Cl(BTD)(PPh3)2]. The in situ hydroruthenation of 1-ethynylcyclohexan-1-ol by [RuH(CO)Cl(BTD)(PPh3)2] and subsequent addition of the HMI ligand and excess sodium methoxide yielded the dehydrated 1,3-dienyl complex [Ru(CH=CHC6H9)(kappa2-MI)(CO)(PPh3)2]. Dehydration of the complex [Ru(CH=CHCPh2OH)(kappa2-MI)(CO)(PPh3)2] with HBF4 yielded the vinyl carbene [Ru(=CHCH=CPh2)(kappa2-MI)(CO)(PPh3)2]BF4. The hydride complexes [MH(kappa2-MI)(CO)(PPh3)2](M = Ru, Os) were obtained from the reaction of HMI and KOH with [RuHCl(CO)(PPh3)3] and [OsHCl(CO)(BTD)(PPh3)2], respectively. Reaction of [Ru(CH=CHC6H4CH3-4)(kappa2-MI)(CO)(PPh3)2] with excess HC triple bond CPh leads to isolation of the acetylide complex [Ru(C triple bond CPh)(kappa2-MI)(CO)(PPh3)2], which is also accessible by direct reaction of [Ru(C triple bond CPh)Cl(CO)(BTD)(PPh3)2] with 1-methyl-2-mercaptoimidazole and NaOMe. The thiocarbonyl complex [Ru(CPh = CHPh)Cl(CS)(PPh3)2] reacted with HMI and NaOMe without migration to yield [Ru(CPh= CHPh)(kappa2-MI)(CS)(PPh3)2], while treatment of [Ru(CH=CHPh)Cl(CO)2(PPh3)2] with HMI yielded the monodentate acyl product [Ru{eta(1)-C(=O)CH=CHPh}(kappa2-MI)(CO)(PPh3)2]. The single-crystal X-ray structures of five complexes bearing vinyl, aryl, acetylide and dienyl functionality are reported.

Diimine−Acetylide Compounds of Ruthenium: The Structural and Spectroscopic Effects of Oxidation

The reaction of Ru(Me(2)bipy)(PPh(3))(2)Cl(2) 1 with terminal alkynes HCCR in the presence of TlPF(6) leads to the formation of the vinylidene compounds [Ru(Me(2)bipy)(PPh(3))(2)Cl(=C=CHR)][PF(6)] (2) (2a, R = Bu(t); 2b, R = p-C(6)H(4)-Me; 2c, R = Ph). These compounds decompose in oxygenated solution to form the carbonyl compound [Ru(Me(2)bipy)(PPh(3))(2)Cl(CO)][PF(6)] (3), and may be deprotonated by K(2)CO(3) to give the ruthenium(II) terminal acetylide compounds Ru(Me(2)bipy)(PPh(3))(2)Cl(CC-R) (4) (4a, R = Bu(t); 4b, R = p-C(6)H(4)-Me; 4c, R = Ph). Cyclic voltammetry shows that 2a-c may also be reductively dehydrogenated to form 4a-c. 4a-c are readily oxidized to their ruthenium(III) analogues [4a](+)-[4c](+), and the changes seen in their UV/visible spectra upon performing this oxidation are analyzed. These show that whereas the UV/visible spectra of 4a-c show MLCT bands from the ruthenium atom to the bipyridyl ligand, those of [4a](+)-[4c](+) contain LMCT bands originating on the acetylide ligands. This is in agreement with the IR and ESR spectra of [4a](+)-[4c](+). The X-ray crystal structures of the redox pair 4a and [4a][PF(6)()] have been determined, allowing the bonding within the metal-acetylide unit to be analyzed, and an attempt is made to determine Lever electrochemical parameters (E(L)) for the vinylidene and acetylide ligands seen herein. Room temperature luminescence measurements on 4a-c show that the compounds are not strongly emissive.

Direct addition of TMS-acetylene to aldimines catalyzed by a simple, commercially available Ir(I) complex

A new, convenient procedure for the addition reaction of trimethylsilylacetylene to imines is described. Simply treating a solution of aldimine and trimethylsilyl acetylene with catalytic [IrCl(COD)](2) furnishes the adduct in preparatively useful yields. Interestingly, the reaction may be conducted in the absence of solvent. [reaction: see text]