[CpRu(η6-naphthalene)]PF6 as Precursor in Complex Synthesis and Catalysis with the Cyclopentadienyl-Ruthenium(II) Cation

Ruthenium-Catalyzed Cycloadditions to Form Five-, Six-, and Seven-Membered Rings

Ruthenium-catalyzed cycloadditions to form five-, six-, and seven-membered rings are summarized, including applications in natural product total synthesis. Content is organized by ring size and reaction type. Coverage is limited to processes that involve formation of at least one C-C bond. Processes that are stoichiometric in ruthenium or exploit ruthenium as a Lewis acid (without intervention of organometallic intermediates), ring formations that occur through dehydrogenative condensation-reduction, σ-bond activation-initiated annulations that do not result in net reduction of bond multiplicity, and photochemically promoted ruthenium-catalyzed cycloadditions are not covered.

Synthesis and Reactivity of Cyclopentadienyl Ruthenium(II) Complexes with Tris(alkylthio)benzenes: Transformation between Dinuclear and Sandwich-Type Complexes

To explore the structural transformation of cyclopentadienyl ruthenium (CpRu) complexes in response to external stimuli, the reaction of [RuCp(MeCN)₃][X] (X = PF₆, (FSO₂)₂N [= FSA]) and tris(alkylthio)benzenes (1,3,5-C₆H₃(SR)₃; L ¹ : R = Pr, L ² : R = Me) was investigated, and the crystal structures and thermal properties of the products were examined. The reaction produced the sandwich complexes [RuCpL ⁿ ][X] or dinuclear complexes [Ru₂Cp₂(μ-L ⁿ )₂(CH₃CN) _m ][X]₂ (X = PF₆, FSA) depending on the reaction conditions. The sandwich complex [RuCpL ¹ ][FSA] was an ionic liquid. The solids of dinuclear complexes transformed into the thermodynamically stable sandwich complexes upon heating accompanied by acetonitrile loss. This change resulted in a transformation from crystal to ionic liquid for complexes with the FSA anion. UV irradiation of the sandwich complex [RuCpL ¹ ][PF₆] in methanol produced the dinuclear complex [Ru₂Cp₂(μ-L ¹ )₂ L ¹ ₂][PF₆]₂. The complex transformed into the sandwich complex upon heating.

Anthracene-rhodium complexes with metal coordination at the central ring - a new class of catalysts for reductive amination

A new class of anthracene complexes with a metal coordinated at the central ring was applied in catalysis for the first time. As a result, a simple and efficient protocol for reductive amination that involves CO as a reducing agent has been developed. The rhodium complex [(cyclooctadiene)Rh(C10H4Me2(OMe)4)]+ (1 mol%) catalyses such reactions under mild conditions (40-130 °C) and produces a variety of amines in good yields (74-95%) without affecting the functional groups. The protocol is acceptable for all combinations of aldehydes (aromatic and aliphatic), ketones (aromatic and aliphatic) and amines (aromatic and aliphatic; primary and secondary).

Cyclopentadienyl-Ru(II)-Pyridylamine Complexes: Synthesis, X-ray Structure, and Application in Catalytic Transformation of Bio-Derived Furans to Levulinic Acid and Diketones in Water

A series of cationic half-sandwich cyclopentadienyl-ruthenium(II)-pyridylamine complexes, [(η⁵-C₅H₅)Ru(κ²-L)(PPh₃)]⁺ (L = N_amine-substituted pyridylamine ligands) ([Ru]-1-[Ru]-6), along with the analogous cyclopentadienyl-ruthenium(II)- N-isopropylpyridylimine complex [(η⁵-C₅H₅)Ru(κ²-L)(PPh₃)]⁺ (L = N-isopropylpyridylimine) ([Ru]-7), have been synthesized in good yields. Structural identities of all the complexes have been authenticated by ¹H, ¹³C, and ³¹P NMR, mass spectrometry, and X-ray crystallography. The synthesized complexes exhibited high catalytic activity for the transformation of the bio-derived furans, 2-furfural (furfural), 5-methyl-2-furfural (5-MF), and 5-hydroxymethyl-2-furfural (5-HMF) to levulinic acid (LA) and the diketones, 3-hydroxyhexane-2,5-dione (3-HHD), 1-hydroxyhexane-2,5-dione (1-HHD), and hexane-2,5-dione (HD) in water. Efficient transformation of furfural to LA over a range of η⁵-Cp-Ru-pyridylamine complexes is substantially affected by the N_amine-substituents, where a η⁵-Cp-Ru- N-propylpyridylamine complex ([Ru]-2) exhibited higher catalytic activity in comparison to other η⁵-Cp-Ru-pyridylamine and η⁵-Cp-Ru-pyridylimine complexes. The relative catalytic activity of the studied complexes demonstrated a substantial structure-activity relationship which is governed by the basicity of N_amine, steric hindrance at N_amine, and the hemilabile nature of the coordinated pyridylamine ligands.

Facile Synthesis of Pentamethylcyclopentadienyl Ruthenium Half-Sandwich Complexes by Naphthalene Displacement

Ruthenium half-sandwich complexes are central in a wide range of diverse applications in the field of organometallic chemistry. As such, exploration of their preparation and reactivity is crucial for development of their chemistry. Herein, we present alternative synthetic methods for the preparation of Cp*Ru(dppm)Cl, Cp*Ru(dppe)Cl, Cp*Ru(dppf)Cl, [Cp*Ru(COD)(MeCN)]BF4, and [Cp*Ru(bpy)(MeCN)]BF4 (dppm = 1,2-bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino) ethane; dppf = 1,2-bis(diphenylphosphino)ferrocene; COD = 1,5-cyclooctadiene; bpy= 2,2′-bipyridine), starting from the easily accessible [Cp*Ru(η6-C10H8)]BF4. The single-crystal X-ray structure determinations for [Cp*Ru(COD)(MeCN)]BF4, and [Cp*Ru(bpy)(MeCN)]BF4 are also presented.

Exploring the Ruthenium-Ligands Bond and Their Relative Properties at Different Computational Methods

We report some experimental bond distances and computational models of six ruthenium bonds obtained from DFT to higher computational methods like MP2 and CCSD. The bonds distances, geometrical RMSD, and the thermodynamic properties of the models from different computational methods are similar. It is observed that optimization of molecules of many light atoms with different functional methods results in significant geometrical variation in the values and order of the computed properties. The values of the hyperpolarizabilities, HOMO, LUMO, and isotropic and anisotropic shielding are found to depend greatly on the type of the functional used and the geometrical variation rather than on the nature of basis set used. However, all the methods rated modelled Ru-S, Ru-Cl, and Ru-O bonds as having the highest hyperpolarizabilities values. The infrared spectra data obtained from the different computational methods are significantly different from each other except for MP2 and CCSD which are found to be very similar.

Mixed phosphane η5-CpRuCl(PR3)2 complexes as ambifunctional catalysts for anti-Markovnikov hydration of terminal alkynes

The catalytic activity of [CpRu(L)(2)(MeCN)]PF(6) (L = 2-diphenylphosphinopyridine with bulky groups at C-6) for anti-Markovnikov hydration of terminal alkynes to aldehydes is retained when one heterocyclic ligand L is replaced by L' = PPh(3). Equal amounts of CpRuCl(PPh(3))(2) (1) and phosphane L in acetone solution equilibrate to a mixture of 1, CpRuCl(L)(PPh(3)) (2), and CpRuCl(L)(2) (3), which acts as highly active in situ catalyst for preparative anti-Markovnikov hydration of alkynes in water-rich media (2 mol % [Ru], 60 °C, 3-18 h in 4:1 (v/v) acetone/water). Reactions were completed in <15 min at 160 °C.

Simple synthesis of ruthenium pi complexes of aromatic amino acids and small peptides

The interaction of [Ru(eta(6)-C(10)H(8))(Cp)](+) (Cp=C(5)H(5)) with aromatic amino acids (L-phenylalanine, L-tyrosine, L-tryptophane, D-phenylglycine, and L-threo-3-phenylserine) under visible-light irradiation gives the corresponding [Ru(eta(6)-amino acid)(Cp)](+) complexes in near-quantitative yield. The reaction proceeds in air at room temperature in water and tolerates the presence of non-aromatic amino acids (except those which are sulfur containing), monosaccharides, and nucleotides. The complex [Ru(eta(6)-C(10)H(8))(Cp)](+) was also used for selective labeling of Tyr and Phe residues of small peptides, namely, angiotensin I and II derivatives.