Syntheses and Structures of trans-bis(Alkenylacetylide) Ruthenium Complexes

A series of ruthenium alkenylacetylide complexes trans-[Ru{C≡CC(=CH₂)R}Cl(dppe)₂] (R=Ph ( 1 a ), ^cC₄H₃S ( 1 b ), 4-MeS-C₆H₄ ( 1 c ), 3,3-dimethyl-2,3-dihydrobenzo[b]thiophene (DMBT) ( 1 d )) or trans-[Ru{C≡C-^cC₆H₉}Cl(dppe)₂] ( 1 e ) were allowed to react with the corresponding propargylic alcohol HC≡CC(Me)R(OH) (R=Ph ( A ), ^cC₄H₃S ( B ), 4-MeS-C₆H₄ ( C ), DMBT ( D ) or HC≡C-^cC₆H₁₀(OH) ( E ) in the presence of TlBF₄ and DBU to presumably give alkenylacetylide/allenylidene intermediates trans-[Ru{C≡CC(=CH₂)R}{C=C=C(Me)}(dppe)₂]PF₆ ([ 2 ]PF₆). These complexes were not isolated but deprotonated to give the isolable bis(alkenylacetylide) complexes trans-[Ru{C≡CC(=CH₂)R}₂(dppe)₂] (R=Ph ( 3 a ), ^cC₄H₃S ( 3 b ), 4-MeS-C₆H₄ ( 3 c ), DMBT ( 3 d )) and trans-[Ru{C≡C-^cC₆H₉}₂(dppe)₂] ( 3 e ). Analogous reactions of trans-[Ru(CH₃)₂(dmpe)₂], featuring the more electron-donating 1,2-bis(dimethylphosphino)ethane (dmpe) ancillary ligands, with the propargylic alcohols A or C and NH₄PF₆ in methanol allowed isolation of the intermediate mixed alkenylacetylide/allenylidene complexes trans-[Ru{C≡CC(=CH₂)R}{C=C=C(Me)}(dmpe)₂]PF₆ (R=Ph ([ 4 a ]PF₆), 4-MeS-C₆H₄ ([ 4 c ]PF₆). Deprotonation of [ 4 a ]PF₆ or [ 4 c ]PF₆ gave the symmetric bis(alkenylacetylide) complexes trans-[Ru{C≡CC(=CH₂)R}₂(dmpe)₂] (R=Ph ( 5 a ), 4-MeS-C₆H₄ ( 5 c )), the first of their kind containing the dmpe ancillary ligand sphere. Attempts to isolate bis(allenylidene) complexes [Ru{C=C=C(Me)R}₂(PP)₂]²⁺ (PP=dppe, dmpe) from treatment of the bis(alkenylacetylide) species 3 or 5 with HBF₄ ⋅ Et₂O were ultimately unsuccessful.     

Areneruthenium(II) Complexes with Functionalized Phosphines Coordinating as Mono‐, Bi‐ or Tridentate Ligands

Areneruthenium(II) compounds [Ru(p‐cym)Cl₂{κ‐P‐ⁱPrP(CH₂CH₂OMe)₂}], 3 , and [Ru(arene)Cl₂{κ‐P‐RP(CH₂CO₂Me)₂}] 4 – 7 (arene=p‐cym (=1‐methyl‐4‐isopropylbenzene), mes (=1,3,5‐trimethylbenzene); R=ⁱPr, ^tBu) were prepared from the dimers [Ru(arene)Cl₂]₂ and the corresponding functionalized phosphine. Treatment of 6 and 7 with 1 equiv. of AgPF₆ affords the monocationic complexes [Ru(mes)Cl{κ²‐P,O‐RP(CH₂C(O)OMe)(CH₂CO₂Me)}]PF₆, 10 and 11 , while the related reaction of 5 – 7 with 2 equiv. of AgPF₆ produces the dicationic compounds [Ru(p‐cym){κ³‐P,O,O‐^tBuP(CH₂C(O)OMe)₂}](PF₆)₂ ( 12 ) and [Ru(mes){κ³‐P,O,O‐RP(CH₂C(O)OMe)₂}](PF₆)₂, 13 and 14 . Partial hydrolysis of one hexafluorophosphate anion of 12 – 14 leads to the formation of [Ru(arene){κ²‐P,O‐RP(CH₂C(O)OMe)(CH₂CO₂Me)}(κ‐O‐O₂PF₂)]PF₆, 15 – 17 , of which 17 (arene=mes; R=^tBu) has been characterized by X‐ray crystallography. Compounds 13 and 14 react with 2 equiv. of KO^tBu in ^tBuOH/toluene to give the unsymmetrical complexes [Ru(mes){κ³‐P,C,O‐RP(CHCO₂Me)(CH=C(O)OMe)}], 18 and 19 , containing both a five‐membered phosphinoenolate and a three‐membered phosphinomethanide ring. The molecular structure of compound 18 has been determined by X‐ray structure analysis. The neutral bis(carboxylate)phosphanidoruthenium(II) complexes [Ru(arene){κ³‐P,O,O‐RP(CH₂C(O)O)₂}], 20 – 23 are obtained either by hydrolysis of 18 and 19 , or by stepwise treatment of 4 and 5 with KO^tBu and basic Al₂O₃. Novel tripodal chelating systems are generated via insertion reactions of 19 with PhNCO and PhNCS.     

Stereochemical investigation of the reaction of cyclopentadienyl(diphosphine)methoxycarbeneruthenium(II) complexes with LiAlH4

[(η-C₅H₅)Ru{Ph₂PCHRCHR′PPh₂}({C(OCH₃)CH₂C₆H₅})]PF₆ (where R, R′ = H or CH₃) reacts with LiAlH₄ in THF at ?80° C to give the corresponding 2-phenylethyl complexes, which have an antiperiplanar conformation around the H₂CCH₂ bond in solution; the reaction takes place with retention of configuration at the ruthenium atom.     

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.     

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.     

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.     

The synthesis,spectroscopic properties and electrochemistry of (8-quinolinolato)-bis-{1-alkyl-2- (arylazoimidazole)}ruthenium(ii) hexafluorophosphate: single crystal X-ray structure of [ru(q)(meaaime)2](PF6)·CH2Cl2 [Q = 8-quinolinolate,meaaime = 1-methyl-2-( p-tolylazoimidazole)]

The reaction of [Ru(OH₂)₂(RaaiR′)₂]²⁺ [RaaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R–C₆H₄–N=N–C₃H₂–NN(1)–R′, R=H (1), Me (2), Cl (3); R′ = Me (a), Et (b), CH₂Ph (c)] with 8-quinolinol (HQ) in acetone solution followed by the addition of NH₄PF₆ afforded violet, mixed ligand complexes of composition [Ru(Q)(RaaiR′)₂](PF₆). The structure of [Ru(Q)(MeaaiMe)₂](PF₆) (2a) has been confirmed by X-ray diffraction studies. Solution electronic spectra exhibit a strong MLCT band at 560–580?nm in MeCN. Cyclic voltammogrames show a Ru(III)/Ru(II) couple at 1.0–1.1?V versus SCE along with three successive ligand reductions. The electronic properties are correlated with EHMO results.     

“Living” radical polymerization of styrene catalyzed by cyclometalated ruthenium(II) complexes bearing nonlabile ligands

Cationic substitutionally inert cyclometalated ruthenium (II) and osmium (II) complexes, ([Mt(o‐C₆H₄‐2‐py)(LL)₂]PF₆), where LL‐1,10‐phenanthroline (phen) or 2,2′‐bipyridine (bipy), were used for radical polymerization of styrene. Gradual modification of the complexes within the series allowed comparison of the catalytic activity and the redox properties. There was no correlation between the reducing powers of the complexes and their catalytic activities. The osmium compound of the lowest reduction potential was not active. All the ruthenium complexes catalyzed the polymerization of styrene in a controlled manner; but the level of control and the catalytic activity were different under the same polymerization conditions. [Ru(o‐C₆H₄‐2‐py)(phen)₂]PF₆ demonstrated the best catalytic performance though its redox potential was the highest. It catalyzed the “living” polymerization with a reasonable rate at a catalyst‐to‐initiator ratio of 0.1. 1 equiv. of Al(OiPr)₃ accelerated the polymerization and improved the control, but higher amount of Al(OiPr)₃ did not speed up the polymerization and moved the process into the uncontrollable regime. Under the most optimal conditions, the controlled polymerization occurs fast without any additive and the catalyst degradation. Added free ligands inhibited the polymerization suggesting that the catalytically active ruthenium intermediates are generated via the reversible dechelation of bidentate phen or bipy ligands. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3814–3828, 2009     

Thermal isomerization of ruthenium hydride compounds containing asymmetric bidentate pyrrole‐imine ligands

A series of ruthenium hydride compounds containing substituted bidentate pyrrole‐imine ligands were synthesized and characterized. Reacting RuHCl(CO)(PPh₃)₃ with one equivalent of [C₄H₃NH(2‐CH=NR)] in ethanol in the presence of KOH gave compounds {RuH(CO)(PPh₃)₂[C₄H₃N(2‐CH=NR)]} where trans‐Py‐Ru‐H 1, R = CH₂CH₂C₆H₉; cis‐Py‐Ru‐H 2, R = Ph‐2‐Me; and cis‐Py‐Ru‐H 3, R = C₆H₁₁. Heating trans‐Py‐Ru‐H 1 in toluene at 70°C for 12 hr resulted a thermal conversion of the trans‐Py‐Ru‐H 1 into its cis form, {RuH(CO)(PPh₃)₂[C₄H₃N(2‐CH=NCH₂CH₂C₆H₉)]} (cis‐Py‐Ru‐H 1) in very high yield. The ¹H NMR spectra of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 2, cis‐Py‐Ru‐H 3, and cis‐Py‐Ru‐H 1 all show a typical triplet at ca. δ–11 for the hydride. The trans and cis form indicate the relative positions of pyrrole ring and hydride. The geometries of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 1, and cis‐Py‐Ru‐H 3 are relatively similar showing typical octahedral geometries with two PPh₃ fragments arranged in trans positions.     

η4‐HBCC‐σ,π‐Borataallyl Complexes of Ruthenium Comprising an Agostic Interaction

Thermolysis of [Cp*Ru(PPh₂(CH₂)PPh₂)BH₂(L₂)] 1 (Cp*=η⁵‐C₅Me₅; L=C₇H₄NS₂), with terminal alkynes led to the formation of η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)B{R‐C=CH₂}(L)₂] ( 2 a – c ) and η²‐vinylborane complexes [Cp*Ru(R‐C=CH₂)BH(L)₂] ( 3 a – c ) ( 2 a , 3 a : R=Ph; 2 b , 3 b : R=COOCH₃; 2 c , 3 c : R=p‐CH₃‐C₆H₄; L=C₇H₄NS₂) through hydroboration reaction. Ruthenium and the HBCC unit of the vinylborane moiety in 2 a – c are linked by a unique η⁴‐interaction. Conversions of 1 into 3 a – c proceed through the formation of intermediates 2 a – c . Furthermore, in an attempt to expand the library of these novel complexes, chemistry of σ‐borane complex [Cp*RuCO(μ‐H)BH₂L] 4 (L=C₇H₄NS₂) was investigated with both internal and terminal alkynes. Interestingly, under photolytic conditions, 4 reacts with methyl propiolate to generate the η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)BH{R‐C=CH₂}(L)] 5 and [Cp*Ru(μ‐H)BH{HC=CH‐R}(L)] 6 (R=COOCH₃; L=C₇H₄NS₂) by Markovnikov and anti‐Markovnikov hydroboration. In an extension, photolysis of 4 in the presence of dimethyl acetylenedicarboxylate yielded η⁴‐σ,π‐borataallyl complex [Cp*Ru(μ‐H)BH{R‐C=CH‐R}(L)] 7 (R=COOCH₃; L=C₇H₄NS₂). An agostic interaction was also found to be present in 2 a – c and 5 – 7 , which is rare among the borataallyl complexes. All the new compounds have been characterized in solution by IR, ¹H, ¹¹B, ¹³C NMR spectroscopy, mass spectrometry and the structural types were unequivocally established by crystallographic analysis of 2 b , 3 a – c and 5 – 7 . DFT calculations were performed to evaluate possible bonding and electronic structures of the new compounds.     

Reactions of transition metal σ-acetylide complexes: IX. Preparation and properties of some cycloheptatrienylvinylidene complexes

Addition of [C₇H₇][PF₆] to iron, ruthenium or osmium alkynyl complexes has given eight cationic cycloheptatrienylvinylidene derivatives [M{C C(C₇H₇)R}(L)₂ (η-C₅H₅)][PF₆] (M = Fe, Ru or Os; R = Me, Pr, Ph or C₆F₅; L = PPh₃, L₂ = dppm or dppe; but not all combinations). With Fe(C₂Ph)(CO)₂(η-C₅H₅), only [Fe(CO)₂(thf)(η-C₅H₅)][PF₆] was obtained. Reactions of the new complexes are characterised by loss of the C₇H₇ group. The NMR spectra and FAB mass spectra are described in detail.     

Selenoquinones Stabilized by Ruthenium(II) Arene Complexes: Synthesis,Structure, and Cytotoxicity

A new series of monoselenoquinone and diselenoquinone π complexes, [(η⁶‐p‐cymene)Ru(η⁴‐C₆R₄SeE)] (R=H, E=Se ( 6 ); R=CH₃, E=Se ( 7 ); R=H, E=O ( 8 )), as well as selenolate π complexes [(η⁶‐p‐cymene)Ru(η⁵‐C₆H₃R₂Se)][SbF₆] (R=H ( 9 ); R=CH₃ ( 10 )), stabilized by arene ruthenium moieties were prepared in good yields through nucleophilic substitution reactions from dichlorinated‐arene and hydroxymonochlorinated‐arene ruthenium complexes [(η⁶‐p‐cymene)Ru(C₆R₄XCl)][SbF₆]₂ (R=H, X=Cl ( 1 ); R=CH₃, X=Cl ( 2 ); R=H, X=OH ( 3 )) as well as the monochlorinated π complexes [(η⁶‐p‐cymene)Ru(η⁵‐C₆H₃R₂Cl)][SbF₆]₂ (R=H ( 4 ); R=CH₃ ( 5 )). The X‐ray crystallographic structures of two of the compounds, [(η⁶‐p‐cymene)Ru(η⁴‐C₆Me₄Se₂)] ( 7 ) and [(η⁶‐p‐cymene)Ru(η⁴‐C₆H₄SeO)] ( 8 ), were determined. The structures confirm the identity of the target compounds and ascertain the coordination mode of these unprecedented ruthenium π complexes of selenoquinones. Furthermore, these new compounds display relevant cytotoxic properties towards human ovarian cancer cells.     

Further Studies of CoIII(TIM) Mono-Alkynyl and Bis-Alkynyl Complexes

A new series of mono- and bis-alkynyl Co^III(TIM) complexes (TIM=2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) is reported herein. The trans-[Co(TIM)(C₂R)Cl]⁺ complexes were prepared from the reaction between trans-[Co(TIM)Cl₂]PF₆ and HC₂R (R=tri(isopropyl)silyl or TIPS ( 1 ), -C₆H₄-4-^tBu ( 2 ), -C₆H₄-4-NO₂ ( 3 a ), and N-mesityl-1,8-naphthalimide or NAP^Mes ( 4 a )) in the presence of Et₃N. The intermediate complexes of the type trans-[Co(TIM)(C₂R)(NCMe)](PF₆)(OTf), 3 b and 4 b , were obtained by treating 3 a and 4 a , respectively, with AgOTf in CH₃CN. Furthermore, bis-alkynyl trans-[Co(TIM)(C₂R)₂]PF₆ complexes, 3 c and 4 c , were generated following a second dehydrohalogenation reaction between 3 b and 4 b , respectively, and the appropriate HC₂R in the presence of Et₃N. These new complexes have been characterized using X-ray diffraction ( 2 , 3 a , 4 a , and 4 c ), IR, ¹H NMR, UV/Vis spectroscopy, fluorescent spectroscopy ( 4 c ), and cyclic voltammetry.     

Further Evidence for ‘Extended’ Cumulene Complexes: Derivatives from Reactions with Halide Anions and Water

Reactions of [Ru{C=C(H)-1,4-C₆H₄C≡CH}(PPh₃)₂Cp]BF₄ ([ 1 a ]BF₄) with hydrohalic acids, HX, results in the formation of [Ru{C≡C-1,4-C₆H₄-C(X)=CH₂}(PPh₃)₂Cp] [X=Cl ( 2 a-Cl ), Br ( 2 a-Br )], arising from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C₆H₄=C=CH₂)(PPh₃)₂Cp]⁺. Similarly, [M{C=C(H)-1,4-C₆H₄-C≡CH}(LL)Cp ]BF₄ [M(LL)Cp’=Ru(PPh₃)₂Cp ([ 1 a ]BF₄); Ru(dppe)Cp* ([ 1 b ]BF₄); Fe(dppe)Cp ([ 1 c ]BF₄); Fe(dppe)Cp* ([ 1 d ]BF₄)] react with H⁺/H₂O to give the acyl-functionalised phenylacetylide complexes [M{C≡C-1,4-C₆H₄-C(=O)CH₃}(LL)Cp’] ( 3 a – d ) after workup. The Markovnikov addition of the nucleophile to the remote alkyne in the cations [ 1 a–d ]⁺ is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene complexes [M(=C=C=C₆H₄=C=CH₂)(LL)Cp’]⁺ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(C≡C-1,4-C₆H₄-C≡CH)(PPh₃)₂Cp] ( 4 a ) and [Ru(C≡C-1,4-C₆H₄-C≡CH)(dppe)Cp*] ( 4 b ) reacted with the relatively small electrophiles [CN]⁺ and [C₇H₇]⁺ at the β-carbon to give the expected vinylidene complexes, the bulky trityl ([CPh₃]⁺) electrophile reacted with [M(C≡C-1,4-C₆H₄-C≡CH)(LL)Cp’] [M(LL)Cp’=Ru(PPh₃)₂Cp ( 4 a ); Ru(dppe)Cp* ( 4 b ); Fe(dppe)Cp ( 4 c ); Fe(dppe)Cp* ( 4 d )] at the more exposed remote end of the carbon-rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C₆H₄=C=C(H)CPh₃}(LL)Cp’]⁺, which were isolated as the water adducts [M{C≡C-1,4-C₆H₄-C(=O)CH₂CPh₃}(LL)Cp’] ( 6 a–d ). Evincing the scope of the formation of such extended cumulenes from ethynyl-substituted arylvinylene precursors, the rather reactive half-sandwich (5-ethynyl-2-thienyl)vinylidene complexes [M{C=C(H)-2,5-^cC₄H₂S-C≡CH}(LL)Cp’]BF₄ ([ 7 a – d ]BF₄ add water readily to give [M{C≡C-2,5-^cC₄H₂S-C(=O)CH₃}(LL)Cp’] ( 8 a – d )].     

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.     

Reactions of nucleophiles with cyclopentadienyliron complexed halotoluenes

η⁶-o-Chlorotoluene-η⁵-cyclopentadienyliron hexafluorophosphate undergoes nucleophilic substitution of the chlorine atom with anions generated (K₂CO₃/DMF) from methyl thioglycolate, diethyl malonate, dimethyl malonate, methyl acetoacetate and 2,4-pentanedione. The compounds prepared were o-CH₃C₆H₄SCH₂CO₂CH₃FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(CO₂C₂H₅)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(CO₂CH₃)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(COCH₃)CO₂CH₃FeCp⁺PF₆⁻ and o-CH₃C₆H₄CH₂COCH₃FeCp⁺PF₆ . Similarly, the reaction of diethyl malonate, dimethyl malonate, methyl acetoacetate anions and methylamine with η⁶-2,6-dichlorotoluene-η⁵-cyclopentadienyliron hexafluorophosphate yielded monosubstitution of one of the chloro groups. The complexes prepared in this study were η⁶-diethyl(3-chloro-2-methyl) phenylmalonate- η⁵-cyclopentadienyliron hexafluorophosphate, η⁶-dimethyl(3-chloro-2-methyl)phenylmalonate-η⁵-cyclopentadienyliron hexafluorophosphate, η⁶-methyl(3-chloro-2-methyl)phenylacetoacetate-η⁵-cyclopentadienyliron hexafluorophosphate and η⁶-3-chloro(2-methyl-N-methyl)aniline-η⁵-cyclopentadienyliron hexafluorophosphate. Reaction of η⁶-2,6-dichlorotoluene-η⁵-cyclopentadienyliron hexafluorophosphate with excess methanol as well as methyl thioglycolate in the presence of K₂CO₃ resulted in disubstitution of both chloro groups to yield new complexes, η⁶-2,6-dimethoxytoluene-η⁵-cyclopentadienyliron hexafluorophosphate and η⁶-methyl[(2-methylphenyl)1,3-dithio] diacetate-η⁵5-cyclopentadienyliron hexafluorophosphate, respectively. Complexes o-CH₃C₆H₄CH(CO₂C₂H₅)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(CO₂CH₃)₂FeCp⁺PF₆⁻ and o-CH₃C₆H₄CH₂ COCH₃FeCp⁺ PF₆⁻ react with excess K₂CO₃ and benzyl bromide in refluxing methylene chloride to give 80–90% yields of complexes o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂CH₃)₂FeCp⁺PF₆⁻ and o-CH₃C₆H₄CH(CH₂C₆H₅)COCH₃FeCp⁺PF₆⁻, respectively. Reaction of complex, o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻ with one molar equivalent of t-BuOK followed by acidic work-up gives o-(C₂H₅CO₂CH₂)C₆H₄CH(CO₂C₂H₅)CH₂C₆H₅FeCp⁺PF₆⁻. Similarly, reactions of complexes o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻ and o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂CH₃)₂FeCp⁺PF₆⁻ with t-BuOK in THF followed by alkylation with methyl iodide gave the new complexes, o-(C₂H₅O₂C(CH₃)CH)C₆H₄CH(CH₂C₆H₅)CO₂C₂H₅FeCp⁺PF₆⁻ and o-(CH₃O₂C(CH₃)CH)C₆H₄CH(CH₂C₆H₅)CO₂CH₃FeCp⁺PF₆⁻, respectively. Vacuum sublimation of the new complexes, o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻ and o-(C₂H₅O₂CCH₂)C₆H₄CH(CH₂C₆H₅)CO₂C₂H₅FeCp⁺PF₆⁻ gives o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂ and O-(C₂H₅O₂CCH₂)C₆H₄CH(CH₂C₆H₅)CO₂C₂H₅, respectively.     

Synthesis reactivity and electrochemical properties of substituted cyclopentadienyl cobalt (III) complexes

Cyclopentadienyl cobalt complexes (η⁵‐C₅H₄R) CoLI₂ [L = CO,R=‐COOCH₂CH=CH₂ (3); L=PPh₃, R=‐COOCH₂‐CH=CH₂ (6); L=P(p‐C₆H₄O₃)₃, R = ‐COOC(CH₃) = CH₂ (7), ‐COOCH₂C₆H₅ (8), ‐COOCH₂CH = CH₂ (9)] were prepared and characterized by elemental analyses, ¹H NMR, ER and UV‐vis spectra. The reaction of complexes (η⁵‐C₅H₄R)CoLI₂ [L= CO, R= ‐COOC(CH₃) = CH₂ (1), ‐COOCH₂C₆H₅(2); L=PPh₃, R=‐COOC (CH₃) = CH₂ (4), ‐COOCH₂C₆H₅ (5)] with Na‐Hg resulted in the formation of their corresponding substituted cobaltocene (η⁵‐C₅H₄R)₂ Co[R=‐COOC(CH₃) = CH₂ (10), ‐COOCH₂C₆H₅ (11)]. The electrochemical properties of these complexes 1–11 were studied by cyclic voltammetry. It was found that as the ligand (L) of the cobalt (III) complexes changing from CO to PPh₃ and P(p‐tolyl)₃, their oxidation potentials increased gradually. The cyclic voltammetry of α,α′‐substituted cobaltocene showed reversible oxidation of one electron process.     

Heteroleptic ruthenium(II)/(III) 2,2′-bipyridine/1,10-phenanthroline complexes incorporating bidentate Schiff base N,O-ligands

Eight substituted bidentate Schiff base ligands HOC₆H₄CH=N-R (HL) (HL1: R = 4-ClC₆H₄, HL2: R = 2-ClC₆H₄, HL3: R = 4-NO₂C₆H₄, HL4: R = 4-MeC₆H₄, HL5: R = 2,6-Me₂C₆H₃, HL6: R = 2,46-Me₃C₆H₂, HL7: R = CH₂C₆H₅, and HL8: R = n-Pr) were synthesized by the typical condensation reaction. Interaction of cis-[Ru(bpy)₂Cl₂]?2H₂O (bpy = 2,2′-bipyridine) with one equivalent of HL ligand in the presence of KPF₆ afforded the cationic ruthenium(II) complexes of the type [Ru(bpy)₂(L)](PF₆) (1–8). The reaction of cis-[Ru(phen)₂Cl₂]?2H₂O (phen = 1,10-phenanthroline) and HL1 under similar condition gave complex [(phen)₂Ru(L)](PF₆) (1a). Treatment of cis-[Ru(phen)₂Cl₂]?2H₂O with two equivalents of HL in the presence of KPF₆ resulted in isolation of the cationic ruthenium(III) complexes of the type [Ru(phen)(L)₂](PF₆) (9-16). All complexes have been spectroscopically characterized. The structures of 1a?CH₂Cl₂, 2?½CH₂Cl₂, 3?CH₃CN, 5?½H₂O, 6, 12?½HOCH₂CH₂OH, 13?CH₃CN, 15?H₂O, and 16 have been determined by single-crystal X-ray diffraction.     

Optically active [(η-C5H5)Ru{(R)-Ph2PCH(CH3)CH2PPh2}(Olefin)]PF6 complexes: Influence of the stereogenic metal atom on the enantioface selection

The synthesis and characterization of optically active olefinic complexes of the type [(η-C₅H₅)Ru{Ph₂PCH(CH₃)CH₂PPh₂}(CH₂CHR″)]PF₆ (R″  H, CH₃, C₆H₅, COOCH₃), in which the metal is a stereogenic center, are reported. The enantioface discrimination of the prochiral olefin is influenced by the chiral ligand and by the stereogenic metal atom. The chiral center at the metal appears to be optically labile. The rates of the epimerization at the metal and of the olefin enantioface depend on the structure of the coordinated olefin.     

Coordination Chemistry of Highly Hemilabile Bidentate Sulfoxide N‐Heterocyclic Carbenes with Palladium(II)

Imidazolium salts, [RS(O)? CH₂(C₃H₃N₂)Mes]Cl (R=Me ( L1 a ), Ph ( L1 b )); Mes=mesityl), make convenient carbene precursors. Palladation of L1 a affords the monodentate dinuclear complex, [(PdCl₂{MeS(O)CH₂(C₃H₂N₂)Mes})₂] ( 2 a ), which is converted into trans‐[PdCl₂(NHC)₂] (trans‐ 4 a ; N‐heterocyclic carbene) with two rotamers in anti and syn configurations. Complex trans‐ 4 a can isomerize into cis‐ 4 a (anti) at reflux in acetonitrile. Abstraction of chlorides from 4 a or 4 b leads to the formation of a new dication: trans‐[Pd{RS(O)CH₂(C₃H₂N₂)Mes}₂](PF₆)₂ (R=Me ( 5 a ), Ph ( 5 b )). The X‐ray structure of 5 a provides evidence that the two bidentate SO? NHC ligands at palladium(II) are in square‐planar geometry. Two sulfoxides are sulfur‐ and oxygen‐bound, and constitute five‐ and six‐membered chelate rings with the metal center, respectively. In acetonitrile, complexes 5 a or 5 b spontaneously transform into cis‐[Pd(NHC)₂(NCMe)₂](PF₆)₂. Similar studies of thioether–NHCs have also been examined for comparison. The results indicate that sulfoxides are more labile than thioethers.