Arene ruthenium β-diketonato triazolato derivatives: Synthesis and spectral studies (β-diketones: 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one, acetylacetone derivatives)

Mononuclear neutral arene ruthenium(II) β-diketonato complexes of the general formula (η⁶-arene)Ru(LL)Cl [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C₆H₆ (1), p-ⁱPrC₆H₄Me (2), C₆Me₆ (3); arene = p-ⁱPrC₆H₄Me, LL = 1-benzoylacetone (L3) (8); arene = p-ⁱPrC₆H₄Me, LL = dibenzoylmethane (L4) (9)] have been synthesized and their subsequent substitution reactions with NaN₃ in alcohol at room temperature yielded the corresponding neutral terminal azido complexes (η⁶-arene)Ru(LL)N₃ [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C₆H₆ (4), p-ⁱPrC₆H₄Me (6), C₆Me₆ (7); arene = p-ⁱPrC₆H₄Me, LL = dibenzoylmethane (L4) (10)] as well as a cationic complex [(η⁶-p-ⁱPrC₆H₄Me)Ru(L4) (PPh₃)]BF₄ (12) with PPh₃. The [3 + 2] cycloaddition reaction of selective azido complexes with the activated alkynes dimethyl and diethyl acetylenedicarboxylates produced the arene triazolato complexes [(η⁶-arene)Ru(LL){N₃C₂(CO₂R)₂}] [arene = p-ⁱPrC₆H₄Me, LL = L1, R = Me (13); arene = C₆Me₆, LL = L1, R = Me (14); arene = C₆Me₆, LL = acetyl acetone (L2), R = Me (15); arene = C₆Me₆, LL = L3, R = Me (16); arene = p-ⁱPrC₆H₄Me, LL = L1, R = Et (17); arene = C₆Me₆, LL = L1, R = Et (18); arene = C₆Me₆, LL = L2, R = Et (19); arene = C₆Me₆, LL = L3, R = Et (20)]. With fumaronitrile the reaction yielded the triazoles [(η⁶-arene)Ru(LL)(N₃C₂HCN)] [arene = p-ⁱPrC₆H₄Me, LL = L1 (21), arene = C₆Me₆, LL = L1 (22), arene = C₆Me₆, LL = L2 (23), arene = C₆Me₆, LL = L3 (24)]. In the above triazolato complexes only N(2) isomer was obtained. The complexes were characterized on the basis of spectroscopic data. Crystal structure of representatives complexes were determined by single crystal X-ray diffraction.     

Mono and dinuclear arene ruthenium complexes containing 6,7-dimethyl-2,3-di(pyridine-2-yl)quinoxaline as chelating ligand: Synthesis and molecular structure

The mononuclear cations of the general formula [(η⁶-arene)RuCl(dpqMe₂)]⁺ (dpqMe₂ = 6,7-dimethyl-2,3-di(pyridine-2-yl)quinoxaline; arene = C₆H₆, 1; C₆H₅Me, 2; p-PrⁱC₆H₄Me, 3; C₆Me₆, 4) as well as the dinuclear dications [(η⁶-arene)₂Ru₂Cl₂(μ-dpqMe₂)]²⁺ (arene = C₆H₆, 5; C₆H₅Me, 6; p-PrⁱC₆H₄Me, 7; C₆Me₆, 8) have been synthesised from 6,7-dimethyl-2,3-di(pyridine-2-yl)quinoxaline (dpqMe₂) and the corresponding chloro complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂, [(η⁶-C₆H₅Me)Ru(μ-Cl)Cl]₂, [(η⁶-p-PrⁱC₆H₄Me)Ru(μ-Cl)Cl]₂ and [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂, respectively. The X-ray crystal structure analyses of [1][PF₆], [3][PF₆] and [6][PF₆]₂ reveal a typical piano-stool geometry around the metal centre; in the dinuclear complexes the two chloro ligands, with respect to each other, are found to be trans oriented.     

Linear homobimetallic palladium complexes

The oxidative addition of C₆H₄-1,4-I₂ (1) to Pd(PPh₃)₄ (2) gives mononuclear trans-(Ph₃P)₂Pd(C₆H₄-4-I)(I) (3), which can be converted to trans-(Ph₃P)₂Pd(C₆H₄-4-I)(OTf) (5) by its reaction with [AgOTf] (4). Complex 5 can be used in the high-yield preparation of a series of unique cationic mono- and dinuclear palladium complexes of structural type [trans-(Ph₃P)₂Pd(C₆H₄-4-I)(L)]⁺ (7, L = C₄H₄N₂; 9a, L = C₅H₄N-4-CN; 9b, L = NC-4-C₅H₄N) and [trans-(C₆H₄-4-I)(Ph₃P)₂Pd ← N^∩N → Pd(PPh₃)₂(C₆H₄-4-I)]²⁺ (14a, N^∩N = C₆H₄-1,4-(CN)₂; 14b, N^∩N = (C₆H₄-4-CN)₂; 14c, N^∩N = 4,4′-bipyridine (=bipy)). Complexes 7, 9 and 14 rearrange in solution to give [trans-(Ph₃P)₂Pd(C₆H₄-4-PPh₃)(L)]²⁺ (10, L = C₄H₄N₂; 12a, L = C₅H₄N-4-CN; 12b, L = NC-4-C₅H₄N) and [trans-(C₆H₄-4-PPh₃)(Ph₃P)₂Pd ← N^∩N → Pd(PPh₃)₂(C₆H₄-4-PPh₃)]⁴⁺ (15a, N^∩N = C₆H₄-1,4-(CN)₂; 15b, N^∩N = (C₆H₄-4-CN)₂) along with {[(Ph₃P)₂(Ph₃P-4-C₆H₄)Pd(μ-I)]₂}²⁺ (11).The solid state structures of 3, 9a, 10, 11 and 15b are reported. Most characteristic for all complexes is the square-planar coordination geometry of palladium with trans-positioned PPh₃ ligands. In 3 the iodide and the 4-iodo-benzene are linear oriented laying with the palladium atom on a crystallographic C₂ axes. In 9a this symmetry is broken by steric interactions of the PPh₃ ligands with the 4-cyanopyridine and 4-iodobenzene groups. Compound 11 contains two μ-bridging iodides with different Pd-I separations showing that the ligand induces a stronger trans-influence than PPh₃. In 15b, the Ph₃PC₆H₄Pd ← NCC₆H₄C₆H₄CN → PdC₆H₄PPh₃ building block is rigid-rod structured with the C₆H₄ units perpendicular oriented to the Pd coordination plane, while the biphenylene connecting moiety is in-plane bound.     

o-Phenylene-bridged Cp/amido titanium and zirconium complexes and their polymerization reactivity

o-Phenylene-bridged trimethylcyclopentadienyl/amido titanium complexes [(η⁵-2,3,5-Me₃C₅H)C₆H₄NR-κN]TiCl₂ (18, R = CH₃; 19, R = CH₂CH₃; 20, R = CH₂C(CH₃)₃; 21, R = CH₂(C₆H₁₁)) and zirconium complexes {[(η⁵-2,3,5-Me₃C₅H)C₆H₄NR-κN]ZrCl-μCl}₂ (22, R = CH₃; 23, R = CH₂CH₃; 24, R = CH₂C(CH₃)₃; 25, R = CH₂(C₆H₁₁); 26, R = C₆H₁₁; 27, R = CH(CH₂CH₃)₂) are prepared via a key step of the Suzuki-coupling reaction between 2-dihydroxyboryl-3-methyl-2-cyclopenten-1-one (2) and the corresponding bromoaniline compounds. The molecular structures of titanium complexes 18 and 19 and dinuclear zirconium complexes 24 and 26 were confirmed by X-ray crystallography. The Cp(centroid)-Ti-N and Cp(centroid)-Zr-N angles are smaller, respectively, than those observed for the Me₂Si-bridged complex [Me₂Si(η⁵-Me₄C₅)(N^tBu)]TiCl₂ and its Zr-analogue, indicating that the o-phenylene-bridged complexes are more constrained than the Me₂Si-bridged complex. Titanium complex 19 exhibits comparable activity and comonomer incorporation to the CGC ([Me₂Si(η⁵-Me₄C₅)(N^tBu)]TiCl₂) in ethylene/1-octene copolymerization. Complex 19 produces a higher molecular-weight polymer than CGC.     

Reactivity studies of cyclopentadienyl ruthenium(II), osmium(II) and pentamethylcyclopentadienyl iridium(III) complexes towards 2-(2′-pyridyl)imidazole derivatives

The reaction of [CpRu(PPh₃)₂Cl] and [CpOs(PPh₃)₂Br] with chelating 2-(2′-pyridyl)imidazole (N ∩ N) ligands and NH₄PF₆ yields cationic complexes of the type [CpM(N ∩ N)(PPh₃)]⁺ (1: M = Ru, N ∩ N = 2-(2′-pyridyl)imidazole; 2: M = Ru, N ∩ N = 2-(2′-pyridyl)benzimidazole; 3: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-dimethylimidazole; 4: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-diphenylimidazole; 5: M = Os, N ∩ N = 2-(2′-pyridyl)imidazole; 6: M = Os, N ∩ N = 2-(2′-pyridyl)benzimidazole). They have been isolated and characterized as their hexafluorophosphate salts. Similarly, in the presence of NH₄PF₆, [Cp∗Ir(μ-Cl)Cl]₂ reacts in dry methanol with N ∩ N chelating ligands to afford in excellent yield [Cp∗Ir(N ∩ N)Cl]PF₆ (7: N ∩ N = 2-(2′-pyridyl)imidazole; 8: N ∩ N = 2-(2′-pyridyl)benzimidazole). All the compounds have been characterized by infrared and NMR spectroscopy and the molecular structure of [1]PF₆, [2]PF₆ and [7]PF₆ by single-crystal X-ray structure analysis.     

Synthesis, structure and electrochemistry of cationic diruthenium complexes of the type [(N∩N)2Ru2(CO)2(μ-CO)2(μ-OOCFc)] containing a ferrocenecarboxylato bridge and two chelating aromatic diimine ligands

The dinuclear bis(ferrocenecarboxylato) complex Ru₂(CO)₄(μ-OOCFc)₂(py)₂ (Fc = ferrocenyl, py = pyridine) was found to react with aromatic diimines (2,2′-dipyridyl, 4,4′-dimethyl-2,2′-dipyridyl, 1,10-phenanthroline, 5-nitro-1,10-phenanthroline, and 5-amino-1,10-phenanthroline) in methanol to give the cationic diruthenium complexes [(N∩N)₂Ru₂(CO)₂(μ-CO)₂(μ-OOCFc)]⁺ (1: N∩N = 2,2′-dipyridyl, 2: N∩N = 4,4′-dimethyl-2,2′-dipyridyl, 3: N∩N = 1,10-phenanthroline, 4: N∩N = 5-nitro-1,10-phenanthroline, 5: N∩N = 5-amino-1,10-phenanthroline), which have been isolated as the hexafluorophosphate salts. The molecular structure of 3, solved by single-crystal X-ray analysis of the tetraphenylborate salt [3][BPh₄], shows a diruthenium backbone bridged by two carbonyl and by one ferrocenecarboxylato ligand, the two 1,10-phenanthroline ligands being in the axial positions. Cyclic voltammetry in dichloromethane reveals for all compounds two successive oxidations due to ferrocene/ferrocenium redox couple and oxidation of the diruthenium core.     

Styrene polymerization using nickel(II) complexes as catalysts

Styrene polymerization is investigated with neutral and cationic Ni(II) complexes, i.e. Ni(bipy)Me₂, 1, Ni(bipy)Br₂, 2, Ni(phen)Br₂, 3, or Ni(Me₂phen)Br₂, 4, Ni(acac)₂, 5, (bipy = 2,2′-bipyridine, phen = phenanthroline, Me₂phen = 2,9-dimethyl-1,10-phenanthroline, acac = acetylacetonate), activated by [NHMe₂Ph][B(C₆F₅)₄] or B(C₆F₅)₃ as cocatalysts, in the presence of AlMe₃. The influence on the polystyrene features and the reaction kinetics of the nickel complex and boron activator, the Al/Ni or B/Ni molar ratios as well as the monomer concentration are studied. Catalytic systems derived from 2, 3 or 5 and [NHMe₂Ph][B(C₆F₅)₄] at a Ni:B:Al ratio of 1:1:5 are the most efficient at room temperature.     

Insertion of alkynes into the heterocycle of (η-pentaalkyl-2,3-dihydro-1,3-diborolyl)(η-pentamethylcyclopentadienyl)ruthenium: Formation and characterization of 4-borataborepine ruthenium complexes

The violet ruthenium complex [(η⁵-C₅Me₅)Ru(η⁵-C₃B₂Me₄R¹)] (2a, R¹ = Me) reacts with terminal alkynes R²CCH to give yellow 4-borataborepine compounds [(η⁵-C₅Me₅)Ru{η⁷-(MeC)₃(R¹B)₂(R²C₂H)}] (4c, R¹ = Me, R² = Ph; 4d, R¹ = Me, R² = SiMe₃; 4e, R¹ = Me, R² = H). The insertion of alkynes into the folded C₃B₂ heterocycle of 2a causes some steric hindrance, which yields with elimination of the distant boranediyl group the corresponding boratabenzene complexes 5 as byproducts. The analogous reactions with internal alkynes R²CCR² proceed slowly and afford predominantly the boratabenzene complexes [(η⁵-C₅Me₅)Ru{η⁶-(MeC)₃(MeB)(R²C)₂}] (5f, R² = Et, 5g, R² = p-tolyl), respectively. In the latter case, three byproducts are formed: methylboronic acid and 1,2,3,4-tetra-p-tolyl-1,3-butadiene (9) due to hydrolysis of the postulated 2,3,4,5-tetra-p-tolyl-1-methylborole (10) and unexpectedly, the cationic triple-decker complex [{(η⁵-C₅Me₅)Ru}₂{μ,η⁷-(MeC)₃(MeB)₂(CH)₂}]Cl (11) having two separated CH groups. The new compounds were characterized by NMR, MS, and single-crystal X-ray studies of 4c, 5f, 9 and 11.     

Synthesis, characterization, and catalytic activity of divalent organolanthanide complexes with new tetrahydro-2H-pyranyl-functionlized indenyl ligands

Two series of new divalent organolanthanide complexes with the general formula [η⁵:η¹-{1-R-3-(C₅H₉OCH₂)C₉H₅}]₂Ln^II (R = H, Ln = Yb (3); R = Me₃Si, Ln = Yb (4); R = H, Ln = Eu (5); R = Me₃Si, Ln = Eu (6)) were prepared by reactions of 2 equiv. of 1-R-3-(C₅H₉OCH₂)C₉H₆ (R = H (1), R = Me₃Si (2)) with the lanthanide(III) amides [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃ (Ln = Yb, Eu) via a one-electron reductive elimination process. Recrystallization of 6 from n-hexane afforded [η⁵:η¹-(C₅H₉OCH₂C₉H₅SiMe₃)]₂Eu^II · (C₆H₁₄)_0.5 (7). All compounds were fully characterized by elemental analyses, and spectroscopic methods. The structures of complexes 4 and 7 were additionally determined by single-crystal X-ray analyses. The catalytic activity of the complexes on methyl methacrylate and ε-caprolactone polymerization was studied, and the temperatures, substituents on the indenyl ring, and solvents effects on the catalytic activity of the complexes were examined.     

(1,2,3,4,7-Pentamethylindenyl)rhodium complexes with arene ligands

The reaction of (η⁵-C₉H₂Me₅)Rh(1,5-C₈H₁₂) (1) with I₂ gives the iodide complex [(η⁵-C₉H₂Me₅)RhI₂]₂ (2). The solvate complex [(η⁵- C₉H₂Me₅)Rh(MeNO₂)₃]²⁺ (generated in situ by treatment of 2 with Ag⁺ in nitromethane) reacts with benzene and its derivatives giving the dicationic arene complexes [(η⁵-₉H₂Me₅)Rh(arene)]²⁺ [arene = C₆H₆ (3a), C₆Me₆ (3b), C₆H₅OMe (3c)]. Similar reaction with the borole sandwich compound CpRh(η⁵-C₄H₄BPh) results in the arene-type complex [CpRh(μ-η⁵:η⁶-C₄H₄BPh)Rh(η⁵-C₉H₂Me₅)]²⁺ (4). Treatment of 2 with CpTl in acetonitrile affords cation [(η⁵-C₉H₂Me₅)RhCp]⁺ (5). The structure of [3c](BF₄)₂ was determined by X-ray diffraction. The electrochemical behaviour of complexes prepared was studied. The rhodium-benzene bonding in series of the related complexes [(ring)Rh(C₆H₆)]²⁺ (ring = Cp, Cp^∗, C₉H₇, C₉H₂Me₅) was analyzed using energy and charge decomposition schemes.     

Homolysis of the Ln-N bond: Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with 2-pyridylmethyl and 3-pyridylmethyl-functionalized indenyl ligands

Two series of new organolanthanide(II) complexes with general formula {η⁵:η¹-[1-R-3-(2-C₅H₄NCH₂)C₉H₅]}₂Ln(II) (R = H-, Ln = Yb (3), Eu (4); R = Me₃Si-, Ln = Yb (5), Eu (6)), and {η⁵:η¹-[1-R-3-(3-C₅H₄NCH₂)C₉H₅]}₂Ln(II) (R = H-, Ln = Yb (9), Eu (10); R = Me₃Si-, Ln = Yb (11), Eu (12)) were synthesized by silylamine elimination with one-electron reductive reactions of lanthanide(III) amides [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃ (Ln = Yb, Eu) with 2 equiv. 1-R-3-(2-C₅H₄NCH₂)C₉H₆ (R = H (1), Me₃Si- (2)) or 1-R-3-(3-C₅H₄NCH₂)C₉H₆ (R = H (7), Me₃Si- (8)) in good yields. All the complexes were fully characterized by elemental analyses and spectroscopic methods. Complexes 3 and 5 were additionally characterized by single-crystal X-ray diffraction study. The catalytic activities of the complexes for MMA polymerization were examined. It was found that complexes with 3-pyridylmethyl substituent on the indenyl ligands could function as single-component MMA polymerization catalysts with good activities, while the complexes with 2-pyridylmethyl substituent on the indenyl ligands cannot catalyze MMA polymerization. The temperatures and solvents effect on the MMA polymerization have also been examined.     

Synthesis, structures, and catalytic properties for ethylene polymerization of bridged [η,η-C5H4CHPhArO]TiCl2 complexes

A number of bridged half-sandwich titanium complexes [η⁵:η¹-2-C₅H₄CHPh-4-R¹-6-R²C₆H₂O]TiCl₂ [R¹ = H (5), Me (6), ^tBu (7, 8); R² = H (6, 7), ^tBu (5, 8)] were synthesized from the reaction of their corresponding trimethylsilyl substituted ligand precursors 2-Me₃SiC₅H₄CHPh-4-R¹-6-R²C₆H₂OSiMe₃ [R¹ = H (1), Me (2), ^tBu (3, 4); R² = H (2, 3), ^tBu (1, 4)] with TiCl₄ in hexane. All new complexes were characterized by ¹H and ¹³C NMR spectroscopy. Molecular structures of complexes 5 and 8 were determined by single crystal X-ray diffraction analysis. Upon activation with AlⁱBu₃/Ph₃CB (C₆F₅)₄, complexes 5-8 exhibit reasonable catalytic activity for ethylene polymerization and copolymerization with 1-hexene, producing polyethylene and poly(ethylene-co-1-hexene) with moderate molecular weights.     

Substituted lithiumtrimethylsiloxysilanides LiSiRR′(OSiMe3) - Investigations of their synthesis, stability and reactivity

The reactions of the trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-h: R′ = Ph, 1a: R = H, 1b: R = Me, 1c: R = Et, 1d: R = ⁱPr, 1e: R = ^tBu, 1f: R = Ph, 1g: R = 2,4,6-Me₃C₆H₂ (Mes), 1h: R = 2,4,6-(Me₂CH)₃C₆H₂ (Tip); 1i: R = R′ = Mes) with lithium metal in tetrahydrofuran (THF) at −78 °C and in a mixture of THF/diethyl ether/n-pentane in a volume ratio 4:1:1 at −110 °C lead to mixtures of numerous compounds. Dependent on the substituents silyllithium derivatives (Me₃SiO)RR′SiLi (2b-i), Me₃SiO(RR′Si)₂Li (3a-g), Me₃SiRR′SiLi (4a-h), (LiO)RR′SiLi (12e, 12g-i), trisiloxanes (Me₃SiO)₂SiRR′ (5a-i) and trimethylsiloxydisilanes (6f^∗, 6h^∗, 6i^∗) are formed. All silyllithium compounds were trapped with Me₃SiCl or HMe₂SiCl resulting in the following products: (Me₃SiO)RR′SiSiMe₂R″ (6b-i: R″ = Me, 7c-i: R″ = H), Me₃SiO(RR′Si)₂SiMe₂R″ (8a-g: R″ = Me, 9a-g: R″ = H), Me₃SiRR′SiSiMe₂R″ (10a-h: R″ = Me, 11a-h: R″ = H) and (HMe₂SiO)RR′SiSiMe₂H (13e, 13g-i). The stability of trimethylsiloxysilyllithiums 2 depends on the substituents and on the temperature. (Me₃SiO)Mes₂SiLi (2i) is the most stable compound due to the high steric shielding of the silicon centre. The trimethylsiloxysilyllithiums 2a-g undergo partially self-condensation to afford the corresponding trimethylsiloxydisilanyllithiums Me₃SiO(RR′Si)₂Li (3a-g). (Me₃)Si-O bond cleavage was observed for 2e and 2g-i. The relatively stable trimethylsiloxysilyllithiums 2f, 2g and 2i react with n-butyllithium under nucleophilic butylation to give the n-butyl-substituted silyllithiums ⁿBuRR′SiLi (15g, 15f, 15i), which were trapped with Me₃SiCl. By reaction of 2g and 2i with 2,3-dimethylbuta-1,3-diene the corresponding 1,1-diarylsilacyclopentenes 17g and 17i are obtained.X-ray studies of 17g revealed a folded silacyclopentene ring with the silicon atom located 0.5 Å above the mean plane formed by the four carbon ring atoms.     

Palladium complexes of multidentate pyrazolylmethyl pyridine ligands: Synthesis,structures and phenylacetylene polymerization

The compounds, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (_MeNˆNˆN) (L1) and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (_tBuNˆNˆN) (L2), react with either [Pd(NCMe)₂Cl₂] or [Pd(COD)ClMe] to form the mononuclear palladium complexes [Pd(_MeNˆNˆN)Cl₂] (1), [Pd(_MeNˆNˆN)ClMe] (2), [Pd(_tBuNˆNˆN)Cl₂] (3) and [Pd(_tBuNˆNˆN)ClMe] (4). Reactions of 1, 2 and 4 with the halide abstractor, NaBAr₄ (Ar = 3,5-(CF₃)₂C₆H₃), led to the formation of stable tridentate cationic species [Pd(_MeNˆNˆN)Cl]⁺(5), [Pd(_MeNˆNˆN)Me]⁺ (6) and [Pd(_tBuNˆNˆN)Cl]⁺ (7) respectively. The analogous carbonyl linker cationic species [Pd{(3,5-Me₂pz-CO)₂-py}Cl]⁺ (9) and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl]⁺ (10), prepared by halide abstraction of the neutral complexes [Pd{(3,5-Me₂pz-CO)₂-py}Cl₂] and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl₂] by NaBAr₄, were however less stable with t_1/2 of 14 and 2 days respectively. Attempts to crystallize 1 and 3 from the mother liquor resulted in the isolation of the salts [Pd(_MeNˆNˆN)Cl]₂[Pd₂Cl₆] (11) and [Pd(_tBuNˆNˆN)Cl]₂[Pd₂Cl₆] (12). Although when complexes 1–4 were reacted with modified methylaluminoxane (MMAO) or NaBAr₄, no active catalysts for ethylene oligomerization or polymerization were formed, activation with silver triflate (AgOTf) produced active catalysts that oligomerized and polymerized phenylacetylene to a mixture of cis-transoidal and trans-cisoidal polyphenylacetylene.     

Diiron-aminocarbyne complexes with amine or imine ligands: C-N coupling between imine and aminocarbyne ligands promoted by tolylacetylide addition to [Fe2{μ-CN(Me)R}(μ-CO)(CO)(NHCPh2)(Cp)2][SO3CF3]

A terminally coordinated CO ligand in the complexes [Fe₂{μ-CN(Me)R}(μ-CO)(CO)₂(Cp)₂][SO₃CF₃] (R = Me, 1a; R = Xyl, 1b; Xyl = 2,6-Me₂C₆H₃), is readily displaced by primary and secondary amines (L), in the presence of Me₃NO, affording the complexes [Fe₂{μ-CN(Me)R}(μ-CO)(CO)(L)(Cp)₂][SO₃CF₃] (R = Me, L = NH₂Et, 4a; R = Xyl, L = NH₂Et, 4b; R = Me, L = NH₂Prⁱ, 5a; R = Xyl, L = NH₂Prⁱ, 5b; R = Xyl, L = NH₂C₆H₁₁, 6; R = Xyl, L = NH₂Ph, 7; R = Xyl, L = NH₃, 8; R = Me, L = NHMe₂, 9a; R = Xyl, L = NHMe₂, 9b; R = Xyl, = NH(CH₂)₅, 10). In the absence of Me₃NO, NH₂Et gives addition at the CO ligand of 1b, yielding [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(O)NHEt}(Cp)₂] (11). Carbonyl replacement is also observed in the reaction of 1a-b with pyridine and benzophenone imine, affording [Fe₂{μ-CN(Me)R}(μ-CO)(CO)(L)(Cp)₂][SO₃CF₃] (R = Me, L = Py, 12a; R = Xyl, L = Py, 12b; R = Me, L = HNCPh₂, 13a; R = Xyl, L = HNCPh₂, 13b). The imino complex 13b reacts with p-tolylacetylide leading to the formation of the μ-vinylidene-diaminocarbene compound [Fe₂{μ-η¹:η²- CC(Tol)C(Ph)₂N(H)CN(Me)(Xyl){(μ-CO)(CO)(Cp₂)] (15) which has been studied by X-ray diffraction.     

Diastereomeric half-sandwich Ru(II) cationic complexes containing amino amide ligands. Synthesis, solution properties, crystal structure and catalytic activity in transfer hydrogenation of acetophenone

The cationic complexes [(η⁶-arene)Ru(N,O-amino amide)X]Y (arene = p-cymene or indane; N,O-amino amide = (l)-proline amide or (l)-phenylalanine amide; X = Cl or I; Y = Cl, I or PF₆) have been synthesised and fully characterized by spectroscopic and analytical methods. In several cases (1a, 3a, 4a, 4b, 5) the metal configuration has been definitively established by X-ray analysis on single crystal. The lability of the metal center in solution has been studied by ¹H NMR and CD techniques. The highest configurational stability has been found in the complexes of the type [(η⁶-indane)Ru(N,O-proline amide)Cl]Y (4a,b). The complexes 1b, 2a-b, 3b, 4b and 5 are good precatalysts for the transfer hydrogenation of acetophenone in basic i-PrOH, with ee up to 76% at 30 °C. An ESI(+)-MS study of pre-catalytic solutions has provided useful information on the catalytic mechanism.     

Cationic half-sandwich complexes (Rh, Ir, Ru) containing 2-substituted-1,8-naphthyridine chelating ligands: Syntheses, X-ray structure analyses and spectroscopic studies

Reactions of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me) and [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh, Ir) with 2-substituted-1,8-naphthyridine ligands, 2-(2-pyridyl)-1,8-naphthyridine (pyNp), 2-(2-thiazolyl)-1,8-naphthyridine (tzNp) and 2-(2-furyl)-1,8-naphthyridine (fuNp), lead to the formation of the mononuclear cationic complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ {L = pyNp (1); tzNp (2); fuNp (3)}, [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ {L = pyNp (4); tzNp (5); fuNp (6)}, [(η⁵-C₅Me₅)Rh(L)Cl]⁺ {L = pyNp (7); tzNp (8); fuNp (9)} and [(η⁵-C₅Me₅)Ir(L)Cl]⁺ {L = pyNp (10); tzNp (11); fuNp (12)}. All these complexes are isolated as chloro or hexafluorophosphate salts and characterized by IR, NMR, mass spectrometry and UV/Vis spectroscopy. The molecular structures of [1]Cl, [2]PF₆, [4]PF₆, [5]PF₆ and [10]PF₆ have been established by single crystal X-ray structure analysis.     

Metal β-diketiminates revisited: ansa-CH2-bridged bis(β-diketiminate)s of lithium and aluminium having diverse structures

The metal β-diketiminato ligand-to-metal binding modes are briefly reviewed, with reference particularly to our previous work on metal complexes using the ligands [{N(R¹)C(R²)}₂CH] (R¹ = SiMe₃ = R and R² = Ph; or R¹ = C₆H₃Prⁱ₂-2,6 and R² = Me). The syntheses of the β-diketimines H[{N(R)C(Ar)}₂CH] 1 (Ar = Ph) and 2 (Ar = C₆H₄Me-4) and the ansa-CH₂-bridged bis(β-diketimine)s 3 (Ar = Ph) and 4 (Ar = C₆H₄Me-4) are reported. Thus, from the appropriate compound Li[{N(R)C(Ar)}₂CH] and H₂O, (CH₂Br)₂ or CH₂Br₂ the product was 2, 3 or 4. Compound 1 was prepared from K[{N(R)C(Ph)}₂CH] and (CH₂Br)₂. Each of 3 or 4 with LiBuⁿ surprisingly yielded the bicyclic dilithium compound 5 (Ar = Ph) or 6 (Ar = C₆H₄Me-4) in which each of the β-diketiminato fragments is an N,N′-bridge between the two lithium atoms and the CH₂ moiety joins the two ligands through their central carbon atoms. However, 4 with AlMe₃ yielded the expected ansa-CH₂-bridged-bis[(β-diketiminato)(dimethyl)alane] 7, which was also obtained from 6 and Al(Cl)Me₂. X-ray structures of the known compounds 2 and 3, and of 5, 6 and 7 are presented; the ¹H NMR spectra of 6 in toluene-d₈ show that there is restricted rotation about the NC-C₆H₄Me-4 bond.