Synthesis,characterization, and reactivity of ruthenium(II) complexes containing η6-arene-η1-pyrazole ligands

New ruthenium(II) complexes containing η⁶-arene-η¹-pyrazole ligands were synthesized and characterized by elemental analysis and spectroscopic methods. In addition, the molecular structure of dichloro-3,5-dimethyl-1-(pentamethylbenzyl)-pyrazole–ruthenium(II), [Ru]L_3b, was determined by X-ray diffraction studies. These complexes were applied in the transfer hydrogenation of acetophenone by isopropanol in the presence of potassium hydroxide. The activities of the catalysts were monitored by NMR.     

The interconversion of η5 and η3 hapticities in cycloheptadienyl complexes of molybdenum and tungsten

[Mo(CO)₄(η⁵-C₇H₉)]⁺ (1) reacts with acetonitrile to give [Mo(CO)₂(NCMe)₃(η³-C₇H₉)]⁺ (3), which is precursor of a wide reange of η⁵-cycloheptadienyl complexes [Mo(CO)₂L₂(η⁵-C₇H₉)]⁺ [6, L = PPH₃; 7, L₂ = Ph₂PCH₂PPh₂; 8, L₂ = 1,3-cyclohexadiene; 9, L₂ = 2,2′-dipyridyl]; 9 reacts reversibly with NCMe to give [Mo(CO)₂(NCMe)(dipy)(η³-C₇H₉)]⁺ (10).     

Redox-induced η5 ⇔ η3 haptotropy of the fluorenyl ligand in 9-substituted η5-fluorenylmanganesetricarbonyl complexes

It has been shown by cyclic voltammetry in THF within the –90 to 40 °C temperature range that fluorenyl (⁵-9-R-C₁₃H₈)Mn(CO)₃ complexes (R=Bu^t (3) and Ph (4)) undergo two-electron reduction to form allyl type [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– dianions as final products. At low temperatures complexes3 and4 are reduced in two one-electron steps according to the EEC-scheme. The first step is reversible and corresponds to the formation of 19-radical anions 3^–. and 4^–.. TheE ⁰ values for redox pairs3 ^0/–. and4 ^0/–. are –1.88 and –1.73 V, respectively. The further reduction of radical anions3 ^–. and4 ^–. at more negative potentials is accompanied by fast ^{5 3} haptocoordination of the fluorenyl ligand to form 18-dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2–. These dianions obtained by the reduction of complexes3 and4 by the radical anion of pyrene are stable at –80 °C and are characterized by their IR spectra. At room temperature the ^{5 3} hapticity change is a fast and reversible process occurring at the step of 19-radical anions3 ^–. and4 ^–. and leading to the electron deficient 17-species [(³-9-R-C₁₃H₈)Mn(CO)₃]^–., which are reduced easier than the initial complexes. As a result, complexes3 and4 are reduced to the corresponding dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– at room temperature in one reversible two-electron step according to the ECE-scheme. Reactivities of 19e^–-species of the isomeric ⁵- and ⁶-fluorenylmanganesetricarbonyl complexes are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1347–1353, July, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-05209) and the International Science Foundation (Grant No. REV 000).     

The rate of substitution from η6-arene ruthenium(II) complexes

Transition Metal Chemistry - The rate and mechanism of substitution in the Ru(II) complexes (C1–C6) by thiourea nucleophiles was studied at pH 2 and rate constants measured as a function of...     

Mixed ligand complexes of ruthenium(II) containing α,β-unsaturated-β-ketoaminesand their antibacterial activity

Hexacoordinated Ru^II complexes of the [RuX(CO)(PPh₃)(B)(LL)] type [X = Cl; B = PPh₃, pyridine (py), piperidine (pip) or morpholine (morph); LL = ,-unsaturated--ketoaminate] have been synthesised by reacting [RuHCl(CO)(PPh₃)(B)] (B = PPh₃, py, pip or morph) with the appropriate -ketoamine in a 1:1 molar ratio. The replacement of hydride ion and the triphenylphosphine group by a bidentate chelating ligand from the starting compounds occurs. The complexes were characterised by elemental analyses and spectral (i.r., electronic, ¹H- and ³¹P-n.m.r.) data. Antibacterial activity were also tested for in these new complexes.     

Two-photon-excited fluorescence of zinc(II), cadmium(II) complexes containing phenothiazine ligand

Shortly after the experimental verification of two-photon absorption by Kaiser et al.[1] with aCaF2:Eu2+ crystal in 1961, two-photon processes have been used to create a number of chemical or physical processes including optical data storage[2], lithographic fabrication[3], and fluorescence imaging[4]. In fluorescence imaging, two-photon excitation (TPE) has developed as an importantalternative to the traditional one-photon excitation (OPE) in the fluorescence microscopy and spectroscopy[5,…     

Part 1: 1,3-Dipolar addition of activated alkyne towards coordinated azido group in ruthenium(II) complexes containing η-cyclichydrocarbons

The indenyl and pentamethylcyclopentadienyl ruthenium(II) complexes [(η⁵-L₃)Ru(L₂)Cl] (L₃ = C₉H₇, L₂ = dppe (1a), L₂ = dppm (1b); L₃ = C₅Me₅, L₂ = dppe (2a); L₂ = dppm (2b) (where, dppe = Ph₂PCH₂CH₂PPh₂ and dppm = Ph₂PCH₂PPh₂) reacts with NaN₃ to yield the azido complexes [(η⁵-C₉H₇)Ru(L₂)N₃], L₂ = dppe (3a), dppm (3b) and [(η⁵-C₅Me₅)Ru(L₂)N₃], L₂ = dppe (4a), dppm (4b), respectively. The azido complexes undergo [3 + 2] dipolar cycloaddition reaction with dimethylacetylenedicarboxylate to yield triazole complexes [(η⁵-C₉H₇)Ru(L₂)(N₃C₂(CO₂Me)₂)], L₂ = dppe (5a), dppm (5b) and [(η⁵-C₅Me₅)Ru(L₂)(N₃C₂(CO₂Me)₂)], L₂ = dppe (6a), dppm (6b), respectively. The complexes were fully characterized on the basis of microanalyses, FT-IR and NMR spectroscopy. The crystal structures of the starting complex (1a) and representative complexes 5a, 5b and 6a have been established by single X-ray study.     

Studies of η5-cyclichydrocarbon ruthenium(II) complexes containing para-amino-N-(pyrid-2-ylmethylene)phenylamine ligand: molecular structure of [(η5-C5H5)Ru(PPh3)(C5H4NCH=N-C6H4-p-NH2)]BF4

Reaction of [(η⁵-Cp)Ru(PPh₃)₂Cl] (1) with excess para-amino-N-(pyrid-2-ylmethylene)-phenylamine ligand (app) in methanol in the presence of NH₄BF₄ leads to the formation of [η⁵-CpRu(PPh₃)(aap)]BF₄ (6BF₄). Similarly, [(η⁵-ind)Ru(PPh₃)₂(CH₃CN)]BF₄ (4BF₄) and [(η⁵-Cp*)Ru(PPh₃)₂(CH₃CN)]BF₄ (5BF₄) react with app to yield the cationic complexes [(η⁵-ind)Ru(PPh₃)(app)]BF₄ (7BF₄) and [(η⁵-Cp*)Ru(PPh₃)(app)]BF₄ (8BF₄), respectively. The complexes were characterized by analysis and spectroscopic data. The structure of a representative complex (6BF₄) was established by single-crystal X-ray methods.     

Solid-state (15)N CPMAS NMR and computational analysis of ligand hapticity in rhodium(η-diene) poly(pyrazolyl)borate complexes

Novel [Rh(η-diene)Tp(x)] complexes of sterically encumbered Tp(x) ligands (Tp(x) = Tp(4Bo), diene = cod, 1; nbd, 2; Tp(x) = Tp(4Bo,5Me), diene = cod, 3; nbd, 4; Tp(x) = Tp(a,3Me), diene = cod, 5; nbd, 6; Tp(x) = Tp(a*,3Me), diene = cod, 7; nbd, 8) have been prepared by treatment of [Rh(η-diene)(μ-Cl)](2) with TlTp(x) (Tp(x) in general, in detail: Tp(4Bo) = hydrotris(indazol-1-yl)borate, Tp(4Bo,5Me) = hydrotris(5-methyl-indazol-1-yl)borate, Tp(a,3Me) = hydrotris(3-methyl-2H-benz[g]-4,5-dihydroindazol-2-y1)borate, Tp(a*,3Me) = hydrotris(3-methyl-2H-benz[g]indazol-2-yl)borate), and characterized by analytical and spectral data (IR, (1)H, (11)B, and (13)C NMR solution). The structures adopted by [Rh(nbd)Tp(4Bo)] 2, [Rh(cod)Tp(4Bo,5Me)] 3, [Rh(nbd)Tp(a,3Me)] 6, [Rh(nbd)Tp(a*,3Me)] 8, and [Rh(nbd)Tp(a*,3Me*)] 8* (incorporating a borotropomeric ligand), have been investigated. Low steric hindrance between the ligands in 2 and 3 permits κ(3) coordination of the pyrazolylborate while the high steric encumbrance present in 6, 8, and 8* results in κ(2) ligands. The coordination modes of the ligands to the metal have also been established by (15)N CPMAS studies of selected ligands and their corresponding Rh complexes. These spectroscopic data are in agreement with the (15)N chemical shifts obtained by using quantum-chemical methods to assist reliable assignments of the experimental values, affording new insights into the extraction of structural information concerning the hapticity (κ(2) or κ(3)) of the poly(pyrazolyl)borate ligands to the Rh metal.     

New chiral ruthenium(II)–phosphinite complexes containing a ferrocenyl group in enantioselective transfer hydrogenations of aromatic ketones

A new and versatile class of unsymmetrical ferrocenyl-phosphinite ligands possessing a stereogenic center has been prepared from commercially available, inexpensive aminoacids such as, d-, l-phenylglycine and d-, l-phenylalanine, through a concise synthetic procedure. These ligands are not very sensitive to air and moisture, and display good enantioselectivities in the ruthenium-catalyzed asymmetric transfer hydrogenation of acetophenone derivatives, in which up to 91% ee was obtained. A comparison of the catalytic properties of amino alcohols and other analogues based on a ferrocenyl backbone is also discussed briefly. The structures of these ligands and their corresponding complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy, and elemental analysis.     

Synthesis and structure of η6-(biphenyl)-η5- (cyclopentadienyl)iron(II) hexaflourophosphates

A series of η⁶-(biphenyl)-η⁵-(cyclopentadienyl)iron(II) hexafluorophosphates have been prepared. Demethylation occured during the synthesis of the 2′-OMe derivatives to yield the correspoding 2′-OH product. The mechanism of this process is discussed. In all cases the complexation involved the unsubstituted phenyl ring. From ¹³C NMR data, values of Hammett resonance parameters σ_R, were calculated which show that the [CpfeC₆H₅]⁺ group behaves as an electron-withdrawing substituent comparable in strength to the cyano group. Approximate values of the biphenyl interplanar angle (θ) were obtained. θ appeared to be significantly lower when electron-releasing substituents were present. ⁵⁷ Fe Mössbauer data support the strong electron acceptor properties of the [CpFe⁺C₆H₅] moiety. In particular the quadrupole splitting (QS) shows a marked increase for the 4-OMe derivative relative to the unsubstituted comples. This is in direct contrast to the aryl ferrocenes. Here, the ferrocenyl and OMe substituents are electronically and so there is no (QS) enhancement.     

Diastereoisomeric (η6-arene)ruthenium(II) chiral Schiff base complexes: crystal structure of a triphenylphosphine adduct

Reaction of [(η⁶-p-cymene)RuCl(L*)] with AgClO₄ in Me₂CO gives a perchlorate complex which on subsequent treatment with PPh₃, γ-picoline or Cl⁻ yields adducts showing that there can be retention as well as inversion of configuration at the metal centre. The (R)_Ru,(S_C absolute configurations of the chiral centres in the triphenylphosphine adduct have been established by an X-ray diffraction study [HL*, (S-α-methylbenzylsalicylaldimine]. The CD spectral study reveals that there is an inversion of configuration during formation of the PPh₃ adduct.     

Syntheses, structures, and reactivity of ruthenium(II) hydride complexes containing Kläui’s oxygen tripodal ligand

Treatment of Ru(CO)(Cl)(H)(PPh₃)₃ with NaL_OEt (L_OEt ^? = [CpCo{P(O)(OEt)₂}₃]^?) afforded the hydride complex (PPh₃)(CO)-L_OEtRu(H) (1), which has been characterized by X-ray crystallography. Similarly, the tricyclohexylphosphine analogue, (PCy₃)(CO)L_OEtRu(H) (2), was synthesized from Ru(CO)Cl(H)(PCy₃)₂ and NaL_OEt. Treatment of complex 1 with R’sO₂N₃ afforded the (arylsulfonyl)amido complexes L_OEtRu(CO)(PPh₃)(NHSO₂R) (R = 2,4,6-i-Pr₃C₆H₂ (3), 4-t-BuC₆H₄ (4)). The crystal structure of complex 3 has been determined. The Ru-N distance and Ru-N-S angle in 3 are 2.076(3) Å and 126.14(16)°, respectively. Reactions of complex 1 with acids have been studied.     

Reaction of alkenyl carbonyl ruthenium(II) complexes with t-butyl isocyanide. Synthesis of η1-acylruthenium(II) complexes by intramolecular CO insertion

Reaction of Ru(CO)Cl(CHCHR)(PPh₃)₂ or Ru(CO)Cl(CHCHR)(PPh₃)₂L (L = py, Me₂Hpz) with 1 equivalent of t-butyl isocyanide gives the alkenyl derivatives Ru(CO)Cl(CHCHR)(PPh₃)₂(t-BuNC). When an excess of isocyanide is used, further reaction results in intramolecular CO insertion to yield η¹-acyl complexes [Ru(COCHCHR) (t-BuNC)₃(PPh₃)₂]Cl. Related complexes were obtained from [Ru(CO)(CHCHR)(MeCN)₂(PPh₃)₂]PF₆ and an excess of isocyanide.     

Novel (η-arene)-ruthenium(II) complexes containing bis(iminophosphorano)methanide and methandiide ligands

The novel bis(iminophosphorano)methanes CH₂[P{NP(S)(OR)₂}Ph₂]₂ (R = Ph (1a), Et (1b)) have been obtained by oxydation of dppm with the corresponding thiophosphorylated azides (RO)₂P(S)N₃. Deprotonation of 1a,b with KH generates the methanide species KCH[P{NP(S)(OR)₂}Ph₂]₂ (R = Ph (2a), Et (2b)). The ruthenium(II) dimer [{Ru(η⁶-p-cymene)(μ-Cl)Cl}₂] reacts with 2a,b to afford the cationic complexes [Ru(η⁶-p-cymene)(κ³-C,N,S-CH[P{NP(S)(OR)₂}Ph₂]₂)]⁺ (R = Ph (3a), Et (3b)), via selective κ³-C,N,S-coordination of the bis(iminophosphorano)methanide anions to ruthenium. The structure of [Ru(η⁶-p-cymene)(κ³-C,N,S-CH[P{NP(S)(OEt)₂}Ph₂]₂)][PF₆] (3b) has been confirmed by single-crystal X-ray crystallography. Deprotonation of complexes 3a,b with NaH leads to the neutral carbene derivatives [Ru(η⁶-p-cymene)(κ²-C,N-C[P{NP(S)(OR)₂}Ph₂]₂)] (R = Ph (4a), Et (4b)).     

Dinuclear hexamethylbenzene ruthenium cations containing η:η-2-(ferrocenyl)ethen-1-yl ligands: Synthesis, structure, electrochemistry

The cationic ferrocenyl-containing complexes [(η⁶-C₆Me₆)₂Ru₂(μ-η¹:η²-CH-CHFc)₂(μ-H)]⁺ (3) and [(η⁶-C₆Me₆)₂Ru₂(μ-PPh₂)(μ-η¹:η²-CH-CHFc)(μ-H)]⁺ (4) have been synthesised in ethanol from ethynylferrocene and the dinuclear precursors [(η⁶-C₆Me₆)₂Ru₂(μ-H)₃]⁺ (1) and [(η⁶-C₆Me₆)₂Ru₂(μ-PPh₂)(μ-H)₂]⁺ (2) respectively, and isolated as tetrafluoroborate salts. The spectroscopic data of 3 and 4 as well as the single-crystal X-ray diffraction analysis of [4][BF₄] show that the alkyne function of ethynylferrocene has been converted to a σ/π-ethenyl ligand by transfer of a bridging hydride from the diruthenium backbone onto the α-carbon of the triple bond in ethynylferrocene. The ferrocenyl-containing diruthenium compounds [3][BF₄] and [4][BF₄] as well as their parent compounds [1][BF₄] and [2][BF₄] have been studied by voltammetric techniques: Whereas 1 shows only an irreversible Ru(II)/Ru(III) oxidation, the phosphido-bridged derivative 2 displays two well-separated one-electron redox processes. In the case of 3 and 4, the ferrocenyl substituents give rise to additional reversible ferrocene/ferrocenium waves.     

Inter-ring η6⇌η5 haptotropic rearrangements of 18ē and 19ē (η5-pentamethylcyclopentadienyl)(η6-9-methylfluorenyl)iron complexes

New cationic complexes [(⁶-C₁₃H₁₀)Fe(⁵-Cp^*)]PF₆ and [(⁶-9-CH₃-C₁₃H₉)Fe(⁵-Cp^*)]PF₆ were obtained by the reaction of Cp^*Fe(CO)₂Br with fluorene and 9-methylfluorene, respectively. Deprotonation of these complexes byt-BuOK in THF affords zwitter-ionic compounds (⁶-C₁₃H₉)Fe(⁵-Cp^*) and (⁶-9-CH₃-C₁₃H₈)Fe(⁵-Cp^*) (A). WhenA is heated in nonane at 150 °C it undergoes ⁶⁵ inter-ring rearrangement with the formation of hexamethyldibenzoferrocene (B). The electrochemical behavior ofA andB was studied by cyclic voltammetry. One-electron reduction ofA andB to the corresponding radical anions induces inter-ring haptotropic rearrangementA ^.–B ^.–. The equilibrium in the 19 state is shifted to the ⁶-isomeric radical anionA ^.–, while in the 18 precursors, it shifts to the ⁵-isomerB.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 319–324, February, 1994.The authors are grateful to D. V. Zagorevskii (A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences) for recording and interpreting the mass spectra, and to A. A. Borisenko (Moscow State University) for recording the NMR spectra.This work was financially supported by the Russian Foundation for Basic Research (Grant 93-03-5209).     

Chiral discrimination at the η3-allyl units of rhodium(I) η3-cyclo-octenyl complexes containing chiral bidentate phosphanes

A three step synthesis of rhodium(I) η³-cyclooctenyl complexes [(P₂*)Rh(η³-C₈H₁₃)] (P₂*=chiral bidentate phosphane) starting from commercially available [{(cod)Rh(μ-Cl)}₂] is described. Examination of these complexes by multinuclear NMR-spectroscopy reveals a distinct stereochemical differentiation of the terminal positions of the η³-allyl unit. Preliminary results on the reactivity of these compounds towards various electrophiles are reported.     

Syntheses and crystal structure of binuclear μ-oxamido copper(II) complexes containing 1,4,7-triazacyclononane as a terminal ligand

Two new binuclear copper(II) complexes, Cu(tacn)Cu(oxpn)(ClO₄)₂·C₂H₅OH (1), and Cu(tacn)Cu(oxap)(ClO₄)₂·CH₃OH (2), have been prepared from the planar fragment Cu(oxpn) and Cu(oxap) (tacn denotes 1,4,7-triazacyclononane, oxpn and oxap stand for the dianions of N,N′-bis(3-aminopropyl)oxamide, and N,N′-bis(2-aminopropyl)oxamide, respectively). The complexes have been characterized by means of elemental analyses and IR, and UV spectra. The crystal structure of compound 1 shows that copper(II) coordinates to the four nitrogen atoms of oxpn in a square-planar environment and the other copper(II) ion is in a distorted square-pyramidal environment.     

X-ray structure of Fe{C(CF3)2(OH)}(CO)2(η-C5H5), a complex containing a substituted hydroxymethyl ligand

An X-ray structure determination on Fe{C(CF₃)₂(OH)}(CO)₂(η-C₅H₅), obtained by protonating the product from Na[Fe(CO)₂(η-C₅H₅)] and (CF₃)₂CO, showed the crystal to contain discrete molecules. There are substantial intramolecular OH…FCF₂ bonds but only weak intermolecular OH…O interactions. Important distances are: FeC 2.060(6), CCF₃ 1.505(9), COH 1.435(7), CF…HO 2.131(6), 2.485(6) Å.