Reactions of Propargyl Compounds Containing a Cyclobutyl Group Induced by a Ruthenium Complex

Reactions of [Ru]Cl ([Ru]={Cp(PPh₃)₂Ru}; Cp=cyclopentadienyl) with three alkynyl compounds, 1 , 5 , and 8 , each containing a cyclobutyl group, are explored. For 1 , the reaction gives the vinylidene complex 2 , with a cyclobutylidene group, through dehydration at C_δH and C_γOH. With an additional methylene group, compound 5 reacts with [Ru]Cl to afford the cyclic oxacarbene complex 6 . The reaction proceeds via a vinylidene intermediate followed by an intramolecular cyclization reaction through nucleophilic addition of the hydroxy group onto C_α of the vinylidene ligand. Deprotonation of 2 with NaOMe produces the acetylide complex 3 and alkylations of 3 by allyl iodide, methyl iodide, and ethyl iodoacetate generate 4 a – c , respectively, each with a stable cyclobutyl group. Dehydration of 1 is catalyzed by the cationic ruthenium acetonitrile complex at 70 °C to form the 1,3‐enyne 7 . The epoxidation reaction of the double bond of 7 yields oxirane 8 . Ring expansion of the cyclobutyl group of 8 is readily induced by the acidic salt NH₄PF₆ to afford the 2‐ethynyl‐substituted cyclopentanone 9 . The same ring expansion is also seen in the reaction of [Ru]Cl with 8 in CH₂Cl₂, affording the vinylidene complex 10 , which can also be obtained from 9 and [Ru]Cl. However, in MeOH, the same reaction of [Ru]Cl with 8 affords the bicyclic oxacarbene complex 12 a through an additional cyclization reaction. Transformation of 10 into 12 a is readily achieved in MeOH/HBF₄, but, in MeOH alone, acetylide complex 11 is produced from 10 . In the absence of MeOH, cyclization of 10 , induced by HBF₄, is followed by fluorination to afford complex 13 . Crystal structures of 6 and 12 a ′ were determined by single‐crystal diffraction analysis.     

Reactions of Ruthenium Complexes Containing Pentatetraenylidene Ligand

Two ruthenium acetylide complexes [Ru]?C≡C?C≡C?C(OR)(C₃H₅)₂ ( 2 , R=H and 2 a , R=CH₃; [Ru]=Cp(PPh₃)₂Ru) each with two cyclopropyl rings were synthesized from TMS?C≡C?C≡C?C(OH)(C₃H₅)₂ ( 1 ; TMS=trimethylsilyl). Treatments of 2 and 2 a with allyl halide in the presence of KPF₆ afforded the vinylidene complexes 3 and 3 a , respectively. When NH₄PF₆ was used, instead of KPF₆, additional ring‐opening reaction took place on one of the three‐membered ring. Treatment of [Ru]Cl with 1,3‐butadiyne ( 6 ), bearing an epoxide ring, afforded acetylide complex 7 with a furyl ring. Treatment of 2 a with Ph₃CPF₆ presumably afforded pentatetraenylidene complex {[Ru]=C=C=C=C=C(C₃H₅)₂}[PF₆] ( 10 ), which was not isolated. Additions of various alcohols in a solution of 10 generated a number of disubstituted allenylidene complexes {[Ru]=C=C=C(OR)?C=C(C₃H₅)₂}[PF₆] ( 11 ). Treatment of 11 with K₂CO₃ afforded the acetylide complex 12 bearing a carbonyl group, characterized by single X‐ray diffraction analysis. Addition of a primary amine to 10 caused cleavage of the farthermost C=C bond and several allenylidene complexes {[Ru]=C=C=C(Me)(NHR)}[PF₆] ( 18 ) were isolated.     

Cyclization Reactions of Aryl Propargyl Acetates with Tethered Epoxide Induced by Ruthenium Complex

Reactions of the ruthenium complex [Ru]Cl ([Ru]=Cp(PPh₃)₂Ru; Cp=η⁵‐C₅H₅) with several aryl propargyl acetates, each with an ortho ‐substituted chain of various length containing an epoxide on the aromatic ring and with or without methyl substitutents on the epoxide ring, bring about novel cyclizations. The cyclization reactions of HC≡CCH(OAc)(C₆H₄)CH₂(RC₂H₂O) (R=H, 6 a ; R=CH₃, 6 b , where RC₂H₂O is an epoxide ring) in MeOH give the vinylidene complexes 5 a – b , respectively, each with the Cβ integrated into a tetrahydro‐5H ‐benzo[7]annulen‐6‐ol ring. A C−C bond formation takes place between the propargyl acetate and the less substituted carbon of the epoxide ring. Further cyclizations of 5 a – b induced by HBF₄ give the corresponding vinylidene complexes 8 a – b each with a new 8‐oxabicyclo‐[3.2.1]octane ring by removal of a methanol molecule in high yield. For similar aryl propargyl acetates with a shorter epoxide chain, the cyclization gives a mixture of a vinylidene complex with a tetrahydronaphthalen‐1‐ol ring and a carbene complex with a tricyclic indeno‐furan ring. For the cyclization of 18 , with a longer epoxide chain, opening of the epoxide is required to afford the vicinal bromohydrin 22 , then tandem cyclization occurs in one pot. Products are characterized by spectroscopic methods as well as by XRD analysis.     

Oxygenation of Ruthenium Carbene Complexes Containing Naphthothiophene or Naphthofuran: Spectroscopic and DFT Studies

The aryl propargylic alcohol 1‐[2‐(thiophen‐3‐yl)phenyl]prop‐2‐yn‐1‐ol ( 1a ) is readily prepared from 2‐(thiophen‐3‐yl)benzaldehyde. In the presence of visible light, treatment of 1a with one‐half mole equivalent of [Ru]Cl ([Ru]?Cp(dppe)Ru) (dppe=1,2‐bis(diphenylphosphino)ethane) and NH₄PF₆ in O₂ affords the naphtha[2,1‐b]thiophene‐4‐carbaldehyde ( 4a ) in high yields. The cyclization reaction of 1a proceeds through the formation of the carbene complex 2a that contains the naphtha[2,1‐b]thiophene ring, which is isolated in a 1:1 stoichiometric reaction. The C? C bond formation between the inner carbon of the terminal triple bond and the heterocyclic ring is confirmed by structure determination of 2a using single‐crystal X‐ray diffraction analysis. Facile oxygenation of 2a by O₂ yields the aldehyde product 4a accompanied by the formation of phosphine oxide of dppe. Oxygen is most likely activated by coordination to the ruthenium center when one PPh₂ unit of the dppe ligand dissociates. This dissociated PPh₂ unit then reacts with the coordinated oxygen nearby to generate half‐oxidized dppe ligand and an unobserved oxo–carbene intermediate. Coupling of the oxo/carbene ligands followed by demetalation then yields 4a . Presumably the resulting complex with the half‐oxidized dppe ligand continuously promotes cyclization/oxygenation of 1a to yield the second aldehyde molecule. In alcohol such as MeOH or EtOH, the oxygenation reaction affords a mixture of 4a and the corresponding esters 5a or 5a' . Four other aryl propargylic alcohols 1b , 1c , 1d , 1e , which contain thiophen‐2‐yl, isopropenyl, fur‐3‐yl, and fur‐2‐yl, respectively, on the aryl ring are also prepared. Analogous aldehydes 4b , 4c , 4d , 4e are similarly prepared from 1b , 1c , 1d , 1e , respectively. For oxygenations of 1b , 1d , and 1e in alcohol, mixtures of aldehyde 4 , ester 5 , and acetal 8 are obtained. The carbene complex 2b obtained from 1b was also characterized by single‐crystal X‐ray diffraction analysis. The UV/Vis spectra of 2a and 2b consist of absorption bands with a high extinction coefficient. From DFT calculations on 2a and 2b , the visible light is found to populate the LUMO antibonding orbital of mainly Ru?C bonds, thereby weakening the Ru?C bond and promoting the oxygenation/demetalation reactions of 2 .     

A trichloro‐bridged binuclear ruthenium complex with 1,1,1‐tris(diphenylphosphinomethyl)ethane

The tri­chloro‐bridged dinuclear Ru^II complex tri‐μ‐chloro‐bis{[1,1,1‐tris­(di­phenyl­phosphino­methyl)­ethane‐κ³P,P′,P′′]ruthenium(II)} hexa­fluoro­phosphate ethanol solvate, [Ru₂Cl₃(tripod)₂]PF₆·C₂H₆O, containing the tripod [1,1,1‐tris­(di­phenyl­phosphino­methyl)­ethane, C₄₁H₃₉P₃] ligand, was unexpectedly obtained from the reaction of [Ru^IIICl₃(tripod)] with 1,4‐bis­(di­phenyl­phosphino)­butane (dppb), followed by pre­cipitation with NH₄PF₆. The magnetic moment of the compound at room temperature indicates that the dinuclear [Ru₂(μ‐Cl)₃(tripod)₂]⁺ cation is diamagnetic. A single‐crystal X‐ray structure determination revealed that the two Ru atoms are bridged by the three Cl atoms. The coordination sphere of each Ru atom is completed by the three P atoms of a tripod ligand. The two P₃Ru units are exactly eclipsed, while the bridging Cl atoms are staggered with respect to the six P atoms. The Ru⋯Ru distance is 3.3997 (7) Å and the mean Cl—Ru—Cl bond angle is 77.7°.     

Study of the Bonding Modes of Di‐2‐pyridyl ketoxime Ligand towards Ruthenium,Rhodium and Iridium Half Sandwich Complexes

The bonding modes of the ligand di‐2‐pyridyl ketoxime towards half‐sandwich arene ruthenium, Cp*Rh and Cp*Ir complexes were investigated. Di‐2‐pyridyl ketoxime {pyC(py)NOH} react with metal precursor [Cp*IrCl₂]₂ to give cationic oxime complexes of the general formula [Cp*Ir{pyC(py)NOH}Cl]PF₆ ( 1a ) and [Cp*Ir{pyC(py)NOH}Cl]PF₆ ( 1b ), for which two coordination isomers were observed by NMR spectroscopy. The molecular structures of the complexes revealed that in the major isomer the oxime nitrogen and one of the pyridine nitrogen atoms are coordinated to the central iridium atom forming a five membered metallocycle, whereas in the minor isomer both the pyridine nitrogen atoms are coordinated to the iridium atom forming a six membered metallacyclic ring. Di‐2‐pyridyl ketoxime react with [(arene)MCl₂]₂ to form complexes bearing formula [(p‐cymene)Ru{pyC(py)NOH}Cl]PF₆ ( 2 ); [(benzene)Ru{pyC(py)NOH}Cl]PF₆ ( 3 ), and [Cp*Rh{pyC(py)NOH}Cl]PF₆ ( 4 ). In case of complex 3 the ligand coordinates to the metal by using oxime nitrogen and one of the pyridine nitrogen atoms, whereas in complex 4 both the pyridine nitrogen atoms are coordinated to the metal ion. The complexes were fully characterized by spectroscopic techniques.     

Reactions of Ruthenium–Allenylidene Complexes Tethering a Cyclopropyl Group

Two cyclopropyl allenylidene complexes [Ru]=CCC(R)(C₃H₅) ([Ru]=[RuCp(PPh₃)₂], Cp=Cyclopentadienyl; R=thiophene ( 2a ) and R=Ph ( 2b )) are prepared from the reactions of [Ru]Cl with the corresponding 1‐cyclopropyl‐2‐propyn‐1‐ol in the presence of KPF₆. Thermal treatment, halide‐anion addition, and palladium‐catalyzed reactions of 2a and 2b all lead to a ring expansion of the cyclopropyl group, giving the vinylidene complexes 4a and 4b , respectively, each with a five‐membered ring. This ring expansion proceeds by C C bond formation between Cβ of the cumulative double bond and a methylene group of the cyclopropyl ring. In the reaction of 2a with pyrrole, consecutive formation of two C C bonds, one between C‐2 of pyrrole and Cγ of 2a and the other between C‐3 of pyrrole and Cα, results in the formation of 6a . The reaction proceeds by addition of pyrrole and 1,3‐proton shifts. The hydrogenation of 2a by NaBH₄ is carried out in different solvents. The cumulative double bonds are reduced regioselectively to give a mixture of 7a and 8a . Interestingly, use of different solvents leads to different ratios of 7a and 8a . Presence of a protic solvent like methanol in dichloromethane or chloroform solution increases the yield of 8a , thus revealing that both the rates of hydroboration and deboronation increase. The structures of two new complexes 4a and 6a have been firmly established by X‐ray diffraction analysis.     

Synthesis and Structural Characterization of the Tetrakis(methimazolyl)borates Li[Bmt4] and [Ru(p‐cymene)(Bmt4)][PF6]

The lithium tetrakis(methimazolyl)borate, Li[Bmt₄], is accessible from the reaction of Li[BH₄] with four equivalents of methimazole. The crystal structure of Li[Bmt₄] supported by four water molecules is described. Reaction of Li[Bmt₄] with [Ru(p‐cymene)Cl₂]₂ and subsequent treatment with NH₄PF₆ in CH₃CN results in the formation of the complex [Ru(p‐cymene)(Bmt₄)][PF₆]. In addition, we report the result of the X‐ray structure analysis of the chiral Ru complex [Ru(p‐cymene)(Bmt₄)][PF₆].     

Basische metalle : XX. Synthese und reaktivität von C6Me6Ru(CO)PMe3. Ein stabiler aromaten-ruthenium(0)-carbonyl-komplex

Treatment of [C₆Me₆RuCl₂]₂ with carbon monoxide gives C₆Me₆Ru(CO)Cl₂ (II) which reacts with PMe₃ in the presence of NH₄PF₆ to form [C₆Me₆Ru(CO)(PMe₃)Cl]PF₆ (III). Reduction of the cation of III with NaC₁₀H₈ in THF yields C₆Me₆Ru(CO)PMe₃ (IV) which is the first stable mononuclear areneruthenium(0) carbonyl complex. IV reacts with CF₃COOH/NH₄PF₆ and MeI/NH₄PF₆ to give the stable salts [C₆Me₆RuH(CO)PMe₃]PF₄ (V) and [C₆Me₆RuCH₃(CO)PMe₃]PF₆ (VI).     

Cyclopentadienyl-ruthenium and -osmium chemistry. Syntheses and deprotonation of some vinylidene-ruthenium complexes.

Reactions between 1-alkynes and RuCl(PPh₃)₂(η-C₅H₅) in the presence of NH₄PF₆ afford the cationic vinylidene complexes [Ru(C:CHR)(PPh₃)₂(η-C₅H₅)]PF₆; these are readily deprotonated by base to give the η¹-alkynyl derivatives Ru(CCR)(PPh₃)₂(η-C₅H₅). The latter may be protonated to reform the monosubstituted vinylidene complexes.     

Triazole‐Functionalized N‐Heterocyclic Carbene Complexes of Palladium and Platinum and Efficient Aqueous Suzuki–Miyaura Coupling Reaction

Imidazolium salts bearing triazole groups are synthesized via a copper catalyzed click reaction, and the silver, palladium, and platinum complexes of their N‐heterocyclic carbenes are studied. [Ag₄(L1)₄](PF₆)₄, [Pd(L1)Cl](PF₆), [Pt(L1)Cl](PF₆) (L1=3‐((1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl)‐1‐(pyrimidin‐2‐yl)‐1H‐imidazolylidene), [Pd₂(L2)₂Cl₂](PF₆)₂, and [Pd(L2)₂](PF₆)₂ (L2=1‐butyl‐3‐((1‐(pyridin‐2‐yl)‐1H‐1,2,3‐triazol‐4‐yl)methyl)imidazolylidene) have been synthesized and fully characterized by NMR, elemental analysis, and X‐ray crystallography. The silver complex [Ag₄(L1)₄](PF₆)₄ consists of a Ag₄ zigzag chain. The complexes [Pd(L1)Cl](PF₆) and [Pt(L1)Cl](PF₆), containing a nonsymmetrical NCN ′ pincer ligand, are square planar with a chloride trans to the carbene donor. [Pd₂(L2)₂Cl₂](PF₆)₂ consists of two palladium centers with CN₂Cl coordination mode, whereas the palladium in [Pd(L2)₂](PF₆)₂ is surrounded by two carbene and two triazole groups with two uncoordinated pyridines. The palladium compounds are highly active for Suzuki–Miyaura cross coupling reactions of aryl bromides and 1,1‐dibromo‐1‐alkenes in neat water under an air atmosphere.     

Synthesen und Strukturen von Bis(4,4′‐t‐butyl‐2,2′‐bipyridin)‐Ruthenium(II)‐Komplexen mit funktionellen Derivaten des Tetramethyl‐bibenzimidazols

Syntheses and Structures of Bis(4,4′‐t‐butyl‐2,2′‐bipyridine) Ruthenium(II) Complexes with functional Derivatives of Tetramethyl‐bibenzimidazole [(tbbpy)₂RuCl₂] reacts with dinitro‐tetramethylbibenzimidazole ( A ) in DMF to form the complex [(tbbpy)₂Ru( A )](PF₆)₂ ( 1a ) (tbbpy: bis(4,4′‐t‐butyl)‐2,2′bipyridine). Exchange of the two PF₆^? anions by a mixture of tetrafluor‐terephthalat/tetrafluor‐terephthalic acid results in the formation of 1b in which an extended hydrogen‐bonded network is formed. According to the ¹H NMR spectra and X‐ray analyses of both 1a and 1b , the two nitro groups of the bibenzimidazole ligand are situated at the periphery of the complex in cis position to each other. Reduction of the nitro groups in 1a with SnCl₂/HCl results in the corresponding diamino complex 2 which is a useful starting product for further functionalization reactions. Substitution of the two amino groups in 2 by bromide or iodide via Sandmeyer reaction results in the crystalline complexes [(tbbpy)₂Ru( C )](PF₆)₂ and [(tbbpy)₂Ru( D )](PF₆)₂ ( C : dibromo‐tetrabibenzimidazole, D : diiodo‐tetrabibenzimidazole). Furthermore, 2 readily reacts with 4‐t‐butyl‐salicylaldehyde or pyridine‐2‐carbaldehyde under formation of the corresponding Schiff base Ru^II complexes 5 and 6 . ¹H NMR spectra show that the substituents (NH₂, Br, I, azomethines) in 2 ‐ 6 are also situated in peripheral positions, cis to each other. The solid state structure of both 2 , and 3 , determined by X‐ray analyses confirm this structure. In addition, the X‐ray diffraction analyses of single crystals of the complexes [(tri‐t‐butyl‐terpy)(Cl)Ru( A )] ( 7 ) and [( A )PtCl₂] ( 8 ) display also that the nitro groups in these complexes are in a cis‐arrangement.     

Renewable Surface Sol‐Gel Derived Carbon Ceramic Electrode Modified with [Ru(NH3)5Cl](PF6)2 Complex : Application to Amperometric Detection of Chlorate

A novel modified carbon ceramic electrode (CCE ) containing [Ru(NH₃)₅ Cl](PF₆)₂ complex was fabricated by sol‐gel technique. The cyclic voltammograms of the modified electrodes show a well defined redox couple due to Ru(III)/Ru(II) system with surface confined characteristics. The stability of the modified CCE modified with ruthenium complex was checked over several days, obtaining reproducible results. Chlorate has been chosen as a model to elucidate the electrocatalytic ability of modified CCE. The modified electrode showed excellent electrocatalytic activity toward chlorate electroreduction in acidic medium. Chlorate was determined amperometrically at the surface of this modified electrode in pH 2 solution. Under the optimized conditions the calibration curve is linear in the concentration range 10 μM?5 mM chlorate. The detection limit and sensitivity are 1 μM and 0.43 nA/μM respectively. The advantages of the modified CCE is its good stability and reproducibility of surface renewal by simple polishing, excellent catalytic activity and simplicity of preparation. This sensor can be used as an amperometric detector in flow systems. or chromatographic instruments.     

Mononuclear Complexes of Platinum Group Metals Containing η6‐ and η5‐Cyclic Π‐Perimeter Hydrocarbon and Pyridylpyrazolyl Derivatives: Syntheses and Structural Studies

Piano‐stool‐shaped platinum group metal compounds, stable in the solid state and in solution, which are based on 2‐(5‐phenyl‐1H‐pyrazol‐3‐yl)pyridine ( L ) with the formulas [(η⁶‐arene)Ru( L )Cl]PF₆ {arene = C₆H₆ ( 1 ), p‐cymene ( 2 ), and C₆Me₆, ( 3 )}, [(η⁶‐C₅Me₅)M( L )Cl]PF₆ {M = Rh ( 4 ), Ir ( 5 )}, and [(η⁵‐C₅H₅)Ru(PPh₃)( L )]PF₆ ( 6 ), [(η⁵‐C₅H₅)Os(PPh₃)( L )]PF₆ ( 7 ), [(η⁵‐C₅Me₅)Ru(PPh₃)( L )]PF₆ ( 8 ), and [(η⁵‐C₉H₇)Ru(PPh₃)( L )]PF₆ ( 9 ) were prepared by a general method and characterized by NMR and IR spectroscopy and mass spectrometry. The molecular structures of compounds 4 and 5 were established by single‐crystal X‐ray diffraction. In each compound the metal is connected to N1 and N11 in a k² manner.     

Syntheses,spectroscopic and structural studies of indenyl ruthenium complexes incorporating amine and nitrile ligands: molecular structures of [(η5-C9H7) Ru(η2-dppe)(CH3CN)]PF6 and [(η5-C9H7)Ru(η2-dppe)(NH3)]PF6

The reaction of [(η⁵-C₉H₇)Ru(η²-dppe)Cl] (1) with monodentate nitriles, (L) in the presence of NH₄PF₆ afforded the complexes [(η⁵-C₉H₇)Ru(η²-dppe)(L)]PF₆, with L?=?CH₃CN (2a), CH₃CH=CHCN (2b), NCC₆H₄CN (2c), C₆H₅CH₂CN (2d), respectively. However, reaction of 1 with NH₄PF₆ in methanol yielded an amine complex of the type [(η⁵-C₉H₇) Ru(η²-dppe)(NH₃)]PF₆ (3a). The complexes were fully characterized by spectroscopy and analytical data. The molecular structures of the complexes [(η⁵-C₉H₇)Ru(η²-dppe) (CH₃CN)]PF₆ (2a) and [(η⁵-C₉H₇)Ru(η²-dppe)(NH₃)]PF₆ (3a) have been determined by single crystal X-ray analyses.     

Syntheses,Structures, and Properties of Phosphorescent Iridium(III) Complexes Containing N‐Heterocyclic Carbene Ligands

The organic salts 1‐(2‐pyridylmethyl)‐3‐alkylbenzimidazolium halide (pm‐RbH ⁺X⁻) and 1‐(2‐pyridylmethyl)‐3‐alkylimidazolium halide (pm‐R′iH ⁺X′⁻) were prepared (where R = 4‐, 3‐, 2‐fluorobenzyl ( 4f , 3f , and 2f , respectively), 4‐, 3‐, 2‐chlorobenzyl ( 4c , 3c , and 2c , respectively); 4‐methoxybenzyl (4mo); 2,3,4,5,6‐pentafluorobenzyl (f₅); benzyl (b); and methyl (m)); X = Cl and Br; R′ = benzyl (b) and methyl (m); and X′ = Cl and I. From these salts, heteroleptic Ir(III ) complexes containing one N ‐heterocyclic carbene (NHC ) ligand [Ir(κ²‐ppy)₂(κ²‐(pm‐Rb))]PF₆ (R = 4f, 1 (PF₆ ); 3f, 2 (PF₆ ); 2f, 3 (PF₆ ); f₅b, 4 (PF₆ ); 4c, 5 (PF₆ ); 3c, 6 (PF₆ ); 2c, 7 (PF₆ ); 4mo, 8 (PF₆ ); b, 9 (PF₆ ); m, 10 (PF₆ )) and [Ir(κ²‐ppy)₂(κ²‐(pm‐R′i))]PF₆ (R = b, 11 (PF₆ ); m, 12 (PF₆ )), were synthesized, and the crystal structures of 1 (PF₆ ), 2 (PF₆ ), 3 (PF₆ ), 5 (PF₆ ), 6 (PF₆ ), 7 (PF₆ ), 9 (PF₆ ), 10 (PF₆ ), and 12 (PF₆ ) were determined by X‐ray diffraction. The neutral NHC ligands 1‐(2‐pyridylmethyl)‐3‐alkylbenzimidazolin‐2‐ylidene (pm‐Rb) and 1‐(2‐pyridylmethyl)‐3‐alkylimidazolin‐2‐ylidene (pm‐R′i) of all cations were found to be involved in the intermolecular π−π stacking interactions with the surrounding cations in the solid state, thereby probably influencing the photophysical behavior in the solid state and in solution. The absorption and emission properties of all the complexes show only small variations.     

Reactivity Studies of η5‐ Indenyl and η5‐Cp* Ruthenium(II) Complexes towards some Polypyridyl Ligands

The reaction of [(η⁵‐L³)Ru(PPh₃)₂Cl], where; L³ = C₉H₇ ( 1 ), C₅Me₅ (Cp*) ( 2 ) with acetonitrile in the presence of [NH₄][PF₆] yielded cationic complexes [(η⁵‐L³)Ru(PPh₃)₂(CH₃CN)][PF₆]; L³= C₉H₇ ([3]PF₆) and L³ = C₅Me₅ ([4]PF₆), respectively. Complexes [3]PF₆ and [4]PF₆ reacts with some polypyridyl ligands viz, 2,3‐bis (α‐pyridyl) pyrazine (bpp), 2,3‐bis (α‐pyridyl) quinoxaline (bpq) yielding the complexes of the formulation [(η⁵‐L³)Ru(PPh₃)(L²)]PF₆ where; L³ = C₉H₇, L² = bpp, ([5]PF₆), L³ = C₉H₇, L² = bpq, ([6]PF₆); L³ = C₅Me₅, L² = bpp, ([7]PF₆) and bpq, ([8]PF₆), respectively. However reaction of [(η⁵‐C₉H₇)Ru(PPh₃)₂(CH₃CN)][PF₆] ([3]PF₆) with the sterically demanding polypyridyl ligands, viz. 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine (tptz) or tetra‐2‐pyridyl‐1,4‐pyrazine (tppz) leads to the formation of unexpected complexes [Ru(PPh₃)₂(L²)(CH₃CN)][PF₆]₂; L² = tppz ([9](PF₆)₂), tptz ([11](PF₆)₂) and [Ru(PPh₃)₂(L²)Cl][PF₆]; L² = tppz ([10]PF₆), tptz ([12]PF₆). The complexes were isolated as their hexafluorophosphate salts. They have been characterized on the basis of micro analytical and spectroscopic data. The crystal structures of the representative complexes were established by X‐ray crystallography.     

Stereospecific synthesis and redox properties of ruthenium(II) carbonyl complexes bearing a redox-active 1,8-naphthyridine unit

Two stereoisomers of cis-[Ru(bpy)(pynp)(CO)Cl]PF₆ (bpy = 2,2′-bipyridine, pynp = 2-(2-pyridyl)-1,8-naphthyridine) were selectively prepared. The pyridyl rings of the pynp ligand in [Ru(bpy)(pynp)(CO)Cl]⁺ are situated trans and cis, respectively, to the CO ligand. The corresponding CH₃CN complex ([Ru(bpy)(pynp)(CO)(CH₃CN)]²⁺) was also prepared by replacement reactions of the chlorido ligand in CH₃CN. Using these complexes, ligand-centered redox behavior was studied by electrochemical and spectroelectrochemical techniques. The molecular structures of pynp-containing complexes (two stereoisomers of [Ru(bpy)(pynp)(CO)Cl]PF₆ and [Ru(pynp)₂(CO)Cl]PF₆) were determined by X-ray structure analyses.     

Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push–Pull Effects and Bite Angle Optimization: A Comprehensive Experimental and Theoretical Study

The synergy of push–pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the ¹MLCT absorption and the ³MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the ³MLCT excited‐state lifetime. In these complexes, that is, [Ru(ddpd)(EtOOC‐tpy)][PF₆]₂, [Ru(ddpd‐NH₂)(EtOOC‐tpy)][PF₆]₂, [Ru(ddpd){(MeOOC)₃‐tpy}][PF₆]₂, and [Ru(ddpd‐NH₂){(EtOOC)₃‐tpy}][PF₆]₂ the combination of the electron‐accepting 2,2′;6′,2′′‐terpyridine (tpy) ligand equipped with one or three COOR substituents with the electron‐donating N,N′‐dimethyl‐N,N′‐dipyridin‐2‐ylpyridine‐2,6‐diamine (ddpd) ligand decorated with none or one NH₂ group enforces spatially separated and orthogonal frontier orbitals with a small HOMO–LUMO gap resulting in low‐energy ¹MLCT and ³MLCT states. The extended bite angle of the ddpd ligand increases the ligand field splitting and pushes the deactivating ³MC state to higher energy. The properties of the new isomerically pure mixed ligand complexes have been studied by using electrochemistry, UV/Vis absorption spectroscopy, static and time‐resolved luminescence spectroscopy, and transient absorption spectroscopy. The experimental data were rationalized by using density functional calculations on differently charged species (charge n=0–4) and on triplet excited states (³MLCT and ³MC) as well as by time‐dependent density functional calculations (excited singlet states).     

Syntheses of 3‐arm and 4‐arm star‐branched polystyrene Ru(II) complexes by the click‐to‐chelate approach

Metal template synthesis is a useful methodology to make sophisticated macromolecular architectures because of the variety of metal ion coordination. To use metal template methodology, chelating functionalities should be introduced to macromolecules before complexation. In this article, we demonstrate the click‐to‐chelate approach to install chelating functionality to polystyrene (PS) and complexation with Ru(II) ions to form 3‐arm and 4‐arm star‐branched PS Ru(II) complexes. Azide‐terminated PS (PS‐N₃) was readily prepared by atom transfer radical polymerization using 1‐bromoethylbenzene as an initiator followed by substitution of bromine by an azide group. The Cu(I)‐catalyzed 1,3‐dipolar cycloaddition of PS‐N₃ with 2‐ethynylpyridine or 2,6‐diethynylpyridine affords 2‐(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐tapy) or 2,6‐bis(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐bitapy) ligands bearing one or two PS chains at the first‐position of the triazole rings. Ru(II) complexes of PS‐tapy and PS‐bitapy were prepared by conventional procedure. The number‐averaged molecular weights (M_ns) of these complexes were determined to be 6740 and 10,400, respectively, by size exclusion chromatography using PS standards. These M_n values indicated the formation of 3‐arm and 4‐arm star‐branched PS Ru(II) complexes [Ru(PS‐tapy)₃](PF₆)₂ and [Ru(PS‐bitapy)₂](PF₆)₂ on the basis of the M_n values of PS‐tapy (2090) and PS‐bitapy (4970). The structures of these complexes were also confirmed by UV–vis spectroscopy and X‐ray crystallography of the Ru(II) complexes [Ru(Bn‐tapy)₃](PF₆)₂ and [Ru(Bn‐bitapy)₂](PF₆)₂, which bear a benzyl group instead of a PS chain. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011