Synthesis of arene ruthenium triazolato complexes by cycloaddition of the corresponding arene ruthenium azido complexes with activated alkynes or with fumaronitrile

The neutral arene ruthenium azido complexes [(η⁶-p-cymene)Ru(LL)(N₃)], [LL = acetylacetonato (acac) (4), benzoylacetonato (bzac) (5) diphenylbenzoyl methane (dbzm) (6)] undergo [3+2] cycloaddition reaction with a series of activated alkynes and fumaronitrile to produce the arene ruthenium triazolato complexes: [(η⁶-p-cymene)Ru(LL){N₃C₂(CO₂R)₂}] [LL = (acac), R = Me (7); LL = (bzac), R = Me (8); LL = (dbzm), R = Me (9); LL = (acac), R = Et (10); LL = (bzac), R = Et (11); LL = (dbzm), R = Et (12) and [(η⁶-p-cymene)Ru(LL)(N₃C₂HCN)]; LL = acac (13), bzac (14); dbzm (15). However, cationic azido complexes, [(η⁶-p-cymene)Ru(dppe)(N₃)]⁺ and [(η⁶-p-cymene)Ru(dppm)(N₃)]⁺ do not undergo such cycloaddition reactions. The complexes were characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. Crystal structures of representative complexes were determined by single crystal X-ray diffraction.     

Structures, preparation and catalytic activity of ruthenium cyclopentadienyl complexes based on pyridyl-phosphine ligand

Ruthenium complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) and [(η⁵-C₅H₅)Ru(κ²-P-N-PPh₂Py)(PPh₃)]⁺ (1a) containing diphenyl-2-pyridylphosphine (PPh₂Py) are reported. Coordinated PPh₂Py in the complex [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) exhibits monodentate behavior. In presence of NH₄PF₆ in methanol at room temperature it afforded chelated complex [(η⁵-C₅H₅)Ru(κ²-P,N-PPh₂Py)(PPh₃)]⁺ (1a). Further, 1 reacted with various species viz., CH₃CN, NaCN, NH₄SCN and NaN₃ to afford cationic and neutral complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L]⁺ and [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L] [L = CH₃CN (1b); CN⁻ (1c); N₃⁻ (1d) and SCN⁻ (1e)] and it’s reaction with N,N-donor chelating ligands dimethylglyoxime (H₂dmg) and 1,2-phenylenediamine (pda) gave cationic complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(κ²-N-N)]PF₆ [κ²-N-N = dmg (1f) and pda (1g)]. The complexes 1-1g have been characterized by physicochemical techniques and crystal structures of 1, 1a, 1c, 1e and 1f have been determined by single crystal X-ray analyses. Catalytic potential of the complex 1 has been evaluated in water under aerobic conditions. It was observed that the complex 1 selectively catalyzes reduction of aldehyde into alcohol.     

Planar chiral alkenylferrocene phosphanes: Preparation, structural characterisation and catalytic use in asymmetric allylic alkylation

Planar chiral alkenylferrocene phosphanes, viz. (S_p)-[Fe(η⁵-C₅H₃-1-PPh₂-2-CHCR₂)(η⁵-C₅H₅)] (R = H, (S_p)-2; Ph, (S_p)-5) and (S_p)-[Fe(η⁵-C₅H₃-1-PPh₂-2-(E)-CHCHR)(η⁵-C₅H₅)] (R = Ph, (S_p)-3; C(O)CH₃, (S_p)-6; and CO₂CH₂CH₃, (S_p)-7) have been prepared by alkenylation of (S_p)-2-(diphenylphosphanyl)ferrocenecarboxaldehyde and tested as ligands for enantioselective palladium-catalysed allylic alkylation of 1,3-diphenyprop-2-en-1-yl acetate with dimethyl malonate. All phosphanylalkenes formed active catalysts. However, the induced enantioselectivity was only poor to moderate [12-43% ee after 20 h at room temperature], with the ee’s and configuration of the preferred product strongly depending on the ligand structure. The catalytic results have been related to solution properties (NMR, ESI MS) and the solid-state structural data (X-ray diffraction) of [Pd(η³-1,3-Ph₂C₃H₃){(S_p)-2-η²:κP}]ClO₄ ((S_p)-12), which represent a model of the plausible reaction intermediate.     

Half sandwich complexes of Ru(II) and complexes of Pd(II) and Pt(II) with seleno and thio derivatives of pyrrolidine: Synthesis, structure and applications as catalysts for organic reactions

The reactions of PhSe⁻, PhS⁻ and Se²⁻ with N-{2-(chloroethyl)}pyrrolidine result in N-{2-(phenylseleno)ethyl}pyrrolidine (L1), N-{2-(phenylthio)ethyl}pyrrolidine (L2), and bis{2-pyrrolidene-N-yl)ethyl selenide (L3), respectively, which have been explored as ligands. The complexes [PdCl₂(L1/L2)] (1/7), [PtCl₂(L1/L2)] (2/8), [RuCl(η⁶-C₆H₆)(L1/L2)][PF₆] (3/9), [RuCl(η⁶-p-cymene)(L1/L2)][PF₆] (4/10), [RuCl(η⁶-p-cymene)(NH₃)₂][PF₆] (5) and [Ru(η⁶-p-cymene)(L1)(CH₃CN)][PF₆]₂·CH₃CN (6) have been synthesized. The L1-L3 and complexes were found to give characteristic NMR (Proton, Carbon-13 and Se-77). The crystal structures of complexes 1, 3-6, 9 and 10 have been solved. The Pd-Se and Ru-Se bond lengths have been found to be 2.353(2) and 2.480(11)/2.4918(9)/2.4770(5) Å, respectively. The complexes 1 and 7 have been explored for catalytic Heck and Suzuki-Miyaura coupling reactions. The value of TON has been found up to 85 000 with the advantage of catalyst’s stability under ambient conditions. The efficiency of 1 is marginally better than 7. The Ru-complexes 3 and 9 are good for catalytic oxidation of primary and secondary alcohols in CH₂Cl₂ in the presence of N-methylmorpholine-N-oxide (NMO). The TON value varies between 8.0 × 10⁴ and 9.7 × 10⁴ for this oxidation. The 3 is somewhat more efficient catalyst than 9.     

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.     

Coordination compounds of N,N′-olefin functionalized imidazolin-2-ylidenes

N-Heterocyclic carbene ligands (NHC) were metalated with Pd(OAc)₂ or [Ni(CH₃CN)₆](BF₄)₂ by in situ deprotonation of imidazolium salts to give the N-olefin functionalized biscarbene complexes [MX₂(NHC)₂] 3-7 (3: M = Pd, X = Br, NHC = 1,3-di(3-butenyl)imidazolin-2-ylidene; 4: M = Pd, X = Br, NHC = 1,3-di(4-pentenyl)imidazolin-2-ylidene; 5: M = Pd, X = I, NHC = 1,3-diallylimidazolin-2-ylidene; 6: M = Ni, X = I, NHC = 1,3-diallylimidazolin-2-ylidene; 7: M = Ni, X = I, NHC = 1-methyl-3-allylimidazolin-2-ylidene). Molecular structure determinations for 4-7 revealed that square-planar complexes with cis (5) or trans (4, 6, 7) coordination geometry at the metal center had been obtained. Reaction of nickelocene with imidazolium bromides afforded the η⁵-cyclopentadienyl (η⁵-Cp) monocarbene nickel complexes [NiBr(η⁵-Cp)(NHC)] 8 and 9 (8: NHC = 1-methyl-3-allylimidazolin-2-ylidene; 9: NHC = 1,3-diallylimidazolin-2-ylidene). The bromine abstraction in complexes 8 and 9 with silver tetrafluoroborate gave complexes [NiBr(η⁵-Cp)(η³-NHC)] 10 and 11. The X-ray structure analysis of 10 and 11 showed a trigonal-pyramidal coordination geometry at the nickel(II) center and coordination of one N-allyl substituent.     

Hydride addition at μ-vinyliminium ligand obtained from disubstituted alkynes

New μ-vinylalkylidene complexes cis-[Fe₂{μ-η¹:η³-C_γ(R′)C_β(R″)C_αHN(Me)(R)}(μ-CO)(CO)(Cp)₂] (R = Me, R′ = R″ = Me, 3a; R = Me, R′ = R″ = Et, 3b; R = Me, R′ = R″ = Ph, 3c; R = CH₂Ph, R′ = R″ = Me, 3d; R = CH₂Ph, R′ = R″ = COOMe, 3e; R = CH₂ Ph, R′ = SiMe₃, R″ = Me, 3f) have been obtained b yreacting the corresponding vinyliminium complexes [Fe₂{μ-η¹:η³-C_γ(R′)C_β(R″)C_αN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (2a-f) with NaBH₄. The formation of 3a-f occurs via selective hydride addition at the iminium carbon (C_α) of the precursors 2a-f. By contrast, the vinyliminium cis-[Fe₂{μ-η¹:η³-C_γ (R′) = C_β(R″)C_α = N(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R′ = R″ = COOMe, 4a; R′ = R″ = Me, 4b; R′ = Prⁿ, R″ = Me, 4c; Prⁿ = CH₂CH₂CH₃, Xyl = 2,6-Me₂C₆H₃) undergo H⁻ addition at the adjacent C_β, affording the bis-alkylidene complexes cis-[Fe₂{μ-η¹:η²-C(R′)C(H)(R″)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂], (5a-c). The cis and trans isomers of [Fe₂{μ-η¹:η³-C_γ(Et)C_β(Et)C_αN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (4d) react differently with NaBH₄: the former reacts at C_α yielding cis-[Fe₂{μ-η¹:η³-C_γ(Et)C_β(Et)C_αHN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂], 6a, whereas the hydride attack occurs at C_β of the latter, leading to the formation of the bis alkylidene trans-[Fe₂{μ-η¹:η²-C(Et)C(H)(Et)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (5d). The structure of 5d has been determined by an X-ray diffraction study. Other μ-vinylalkylidene complexes cis-[Fe₂{μ-η¹:η³-C_γ(R′)C_β(R″)C_αHN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂], (R′ = R″ = Ph, 6b; R′ = R″ = Me, 6c) have been prepared, and the structure of 6c has been determined by X-ray diffraction. Compound 6b results from treatment of cis-[Fe₂{μ-η¹:η³-C_γ(Ph)C_β(Ph)C_αN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (4e) with NaBH₄, whereas 6c has been obtained by reacting 4b with LiHBEt₃. Both cis-4d and trans-4d react with LiHBEt₃ affording cis-6a.     

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.     

Syntheses and characterization of η-cyclopentadienyl and η-indenyl ruthenium(II) complexes of arylazoimidazoles: The molecular structure of the complex [(η-C5H5)Ru(PPh3)(C6H5-NN-C3H3N2)]

The complex [(η⁵-C₅H₅)Ru(PPh₃)₂Cl] (1) reacts with several arylazoimidazole (RaaiR′) ligands, viz., 2-(phenylazo)imidazole (Phai-H), 1-methyl-2-(phenylazo)imidazole (Phai-Me), 1-ethyl-2-(phenylazo)imidazole (Phai-Et), 2-(tolylazo)imidazole (Tai-H), 1-methyl-2-(tolylazo)imidazole (Tai-Me) and 1-ethyl-2-(tolylazo)imidazole (Tai-Et), gave complexes of the type [(η⁵-C₅H₅)Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (2), R = H, R′ = CH₃ (3), R = H, R′ = C₂H₅ (4), R = CH₃, R′ = H (5), R, R′ = CH₃ (6), R = CH₃, R′ = C₂H₅ (7)}. The complex [(η⁵-C₉H₇)Ru(PPh₃)₂(CH₃CN)]⁺ (8) undergoes reactions with a series of N,N-donor azo ligands in methanol yielding complexes of the type [(η⁵-C₉H₇) Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (9), R = H, R′ = CH₃ (10), R = CH₃, R′ = H (11), R = CH₃, R′ = C₂H₅ (12)}, respectively. These complexes were characterized by FT IR and FT NMR spectroscopy as well as by analytical data. The molecular structure of the complex [(η⁵-C₅H₅)Ru(PPh₃)(C₆H₅-NN-C₃H₃N₂)]⁺ (2) was established by single crystal X-ray diffraction study.     

Syntheses and characterization of [(η-C6Me6)Ru(μ-N3)(X)]2 (X = N3 and Cl) complexes and their reactions towards mono- and bidentate ligands

The reaction of the complex [{(η⁶-C₆Me₆)Ru(μ-Cl)Cl}₂] 1 with sodium azide ligand gave two new dimers of the composition [{(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)}₂] 2 and [{(η⁶-C₆Me₆)Ru(μ-N₃)Cl}₂] 3, depending upon the reaction conditions. Complex 3 with excess of sodium azide in ethanol yielded complex 2. These complexes undergo substitution reactions with monodentate ligands to yield monomeric complexes of the type [(η⁶-C₆Me₆)Ru(X)(N₃)(L)] {X = N₃, Cl, L = PPh₃ (4a, 9a); PMe₂Ph (4b, 9b); AsPh₃ (4c, 9c); X = N₃, L = pyrazole (Hpz) (5a); 3-methylpyrazole (3-Hmpz) (5b) and 3,5-dimethyl-pyrazole (3,5-Hdmpz) (5c)}. Complexes 2 and 3 also react with bidentate ligands to give bridging complexes of the type [{(η⁶-C₆Me₆)Ru(N₃)(X)]₂(μ-L)} {X = N₃, Cl, L = 1,2-bis(diphenylphosphino)methane (dppm) (6, 10); 1,2-bis(diphenylphosphino)ethane (dppe) (7, 11); 1,2-bis(diphenylphosphino)propane (dppp) (8, 12); X = Cl, L = 4,4-bipyridine (4,4′-bipy) (13)}. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as by analytical data.The molecular structures of the representative complexes [{(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)}₂] 2, [{(η⁶-C₆Me₆)Ru(μ-N₃)Cl}₂] 3,[(η⁶-C₆Me₆)Ru(N₃)₂(PPh₃)] 4a and [{(η⁶-C₆Me₆)Ru(N₃)₂}₂ (μ-dppm)] 6 were established by single crystal X-ray diffraction studies.     

Mono and dinuclear half-sandwich platinum group metal complexes bearing pyrazolyl-pyrimidine ligands: Syntheses and structural studies

Reactions of 0.5 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = η⁶-C₆H₆, η⁶-p-ⁱPrC₆H₄Me) and [(Cp∗)M(μ-Cl)Cl]₂ (M = Rh, Ir; Cp∗ = η⁵-C₅Me₅) with 4,6-disubstituted pyrazolyl-pyrimidine ligands (L) viz. 4,6-bis(pyrazolyl)pyrimidine (L1), 4,6-bis(3-methyl-pyrazolyl)pyrimidine (L2), 4,6-bis(3,5-dimethyl-pyrazolyl)pyrimidine (L3) lead to the formation of the cationic mononuclear complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ (L = L1, 1; L2, 2; L3, 3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ (L = L1, 4; L2, 5; L3, 6), [(Cp∗)Rh(L)Cl]⁺ (L = L1, 7; L2, 8; L3, 9) and [(Cp∗)Ir(L)Cl]⁺ (L = L1, 10; L2, 11; L3, 12), while reactions with 1.0 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ and [(Cp∗)M(μ-Cl)Cl]₂ give rise to the dicationic dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(L)]²⁺ (L = L1, 13; L2, 14; L3, 15), [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(L)]²⁺ (L = L1, 16; L2, 17; L3, 18), [{(Cp∗)RhCl}₂(L)]²⁺ (L = L1, 19; L2, 20; L3, 21) and [{(Cp∗)IrCl}₂(L)]²⁺ (L = L1 22; L2, 23; L3 24). The molecular structures of [3]PF₆, [6]PF₆, [7]PF₆ and [18](PF₆)₂ have been established by single crystal X-ray structure analysis.     

1-Methyl-4-ferrocenylmethyl-3,5-diphenylpyrazole: A versatile ligand for palladium(II) and platinum(II)

The syntheses and characterization of two novel ferrocene derivatives containing 3,5-diphenylpyrazole units of general formula [1-R-3,5-Ph₂-(C₃N₂)-CH₂-Fc] {Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄) and R = H (2) or Me (3)} together with a study of their reactivity with palladium(II) and platinum(II) salts or complexes under different experimental conditions is described. These studies have allowed us to isolate and characterize trans-[Pd{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}₂Cl₂] (4a) and three different types of heterodimetallic complexes: cis-[M{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}Cl₂(dmso)] {M = Pd (5a) or Pt (5b)}, the cyclometallated products [M{κ²-C,N-[3-(C₆H₄)-1-Me-5-Ph-(C₃N₂)]-CH₂-Fc}Cl(L)] with L = PPh₃ and M = Pd (6a) or Pt (6b) or L = dmso and M = Pt (8b) and the trans-isomer of [Pt{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}Cl₂(dmso)] (7b). In compounds 4a, 5a, 5b and 7b, the ligand behaves as a neutral N-donor group; while in 6a, 6b and 8b it acts as a bidentate [C(sp²,phenyl),N(pyrazole)]⁻ group. A comparative study of the spectroscopic properties of the compounds, based on NMR, IR and UV-Visible experiments, is also reported.     

Palladium complexes of 8-(di-tert-butylphosphinooxy) quinoline

The preparation of the new ligand 8-(di-tert-butylphosphinooxy)quinoline (1) and the palladium derivatives [PdCl₂(1)] (2), [Pd(η³-all)(1)]⁺ [all = C₃H₅ (3a), 1-PhC₃H₄ (3b) and 1,3-Ph₂C₃H₃ (3c)] and [Pd(η²-ol)(1)] [ol = dimethyl fumarate (4a) and fumaronitrile (4b)] is reported. The cationic species 3a-3c have been isolated as salts. The complex 3a(BF₄) is obtained either from the reaction of 1 with [Pd(μ-Cl)(η³-C₃H₅)]₂ or from the reaction of ClP(CMe₃)₂ with [Pd(η³-C₃H₅)(8-oxyquinoline)], followed in both cases by chloride abstraction with NaBF₄. In the complexes, the ligand 1 is P,N chelated to the central metal, as shown by the X-ray structural analysis of 3a(BF₄). At 25 °C in solution, 3a(BF₄) and 3b(BF₄) undergo a fast η³−η¹−η³ dynamic process which brings about a syn-anti exchange only for the allylic protons cis to phosphorus, while for 4a and 4b a slow rotation of the olefin around its bond axis to palladium takes place. The complexes 2 and 3a(BF₄) are efficient catalyst precursors in the coupling of the phenylboronic acid with aryl bromides and chlorides.     

Cyclopalladation of N-phenyl-4-ferrocenylmethylpyrazoles: Crystal structure of [Pd{κ-C,N-C6H4-1-[(3,5-Me2-C3N2)-CH2-(η-C5H4)Fe(η-C5H5)]}Cl(PPh3)] · CH2Cl2

The synthesis and characterization of pyrazole derivatives of general formula [C₆H₄-4-R-1-{(3,5-Me₂-C₃N₂)-CH₂-(η⁵-C₅H₄)Fe(η⁵-C₅H₅)}] [R = OMe (1a) or H (1b)] with a ferrocenylmethyl substituent are described.The study of the reactivity of compounds 1 with palladium(II) acetate has allowed the isolation of complexes (μ-AcO)₂[Pd{κ²-C,N-C₆H₃-4-R-1-[(3,5-Me₂-C₃N₂)-CH₂-(η⁵-C₅H₄)Fe(η⁵-C₅H₅)]}]₂ (2) [R = OMe (2a) or H (2b)] that contain a bidentate [C(sp², phenyl), N]⁻ ligand and a central “Pd(μ-AcO)₂Pd” unit.Furthermore, treatment of 2 with LiCl produced complexes (μ-Cl)₂[Pd{κ²-C,N-C₆H₃-4-R-1-[(3,5-Me₂-C₃N₂)-CH₂-(η⁵-C₅H₄)Fe(η⁵-C₅H₅)]}]₂ (3) [R = OMe (3a) or H (3b)] that arise from the replacement of the acetato ligands by the Cl⁻.Compounds 2 and 3 also react with PPh₃ giving the monomeric complexes [Pd{κ²-C,N-C₆H₃-4-R-1-[(3,5-Me₂-C₃N₂)-CH₂-(η⁵-C₅H₄)Fe(η⁵-C₅H₅)]}X(PPh₃)] {X⁻ = AcO⁻ and R = OMe (5a) or H (5b) or X⁻ = Cl⁻ and R = OMe (6a) or H (6b)}, where the phosphine is in a cis-arrangement to the metallated carbon atom. Treatment of 3 with thallium(I) acetylacetonate produced [Pd{κ²-C,N-C₆H₃-4-R-1-[(3,5-Me₂-C₃N₂)-CH₂-(η⁵-C₅H₄)Fe(η⁵-C₅H₅)]}(acac)] (7) [R = OMe (7a) or H (7b)]. Electrochemical studies of the free ligands and the cyclopalladated complexes are also reported. The dimeric complexes 3 also react with MeO₂C-CC-CO₂Me (in a 1:4 molar ratio) giving [Pd{(MeO₂C-CC-CO₂Me)₂C₆H₃-4-R-1-[(3,5-Me₂-C₃N₂)-CH₂-(η⁵-C₅H₄)Fe(η⁵-C₅H₅)]}Cl] (8) [R = OMe (8a) or H (8b)], which arise from the bis(insertion) of the alkyne into the σ{Pd-C(sp², phenyl)} bond of 3.     

Synthesis, characterization and molecular structure of the [(η-C6Me6)Ru(μ-N3)(N3)]2 complex and its reactions with some monodentate ligands

The reaction of complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂ (1) with sodium azide yielded complexes of the composition [(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)]₂ (2) and [(η⁶-C₆Me₆)Ru(μ-N₃)(Cl)]₂ (3), depending upon the reaction conditions. Complex 3 with excess of sodium azide in ethanol yielded complex 2. Complexes 2 and 3 undergo substitution reactions with monodentate ligands such as PPh₃, PMe₂Ph and AsPh₃ to yield monomeric complexes. The structure of complex 2 was determined by X-ray crystallography. All these complexes were characterized by micro analytical data and by FT-IR and FT-NMR spectroscopy. Complex 2 crystallizes in the monoclinic space group P2₁/n with a = 8.5370(11) Å, b = 16.192(2) Å, c = 10.4535(13) Å and β = 110.877(2)°.     

Trimethylstannyl (diphenylphosphino)acetate: a source of (diphenylphosphino)acetate ligand in the synthesis of coordination compounds

Trimethylstannyl (diphenylphosphino)acetate (1), which is readily accessible from potassium (diphenylphosphino)acetate and trimethylstannyl chloride, may serve as the source of (diphenylphosphino)acetate anion in the preparation of coordination compounds. Thus, the reactions between [M(cod)Cl₂] (M = Pd and Pt; cod = η²:η²-cycloocta-1,5-diene) and two equivalents of 1 give [M(Ph₂PCH₂CO₂-κ²O,P)₂] (2 and 3), while the reaction of [{Pd(μ-Cl)Cl(PFur₃)}₂] (4; Fur = 2-furyl) with one equivalent of 1 yields [SP-4-3]-[PdCl(Ph₂PCH₂CO₂-κ²O,P)(PFur₃)] (5). The reactions of 1 with the dimers [{Rh(η⁵-C₅Me₅)Cl(μ-Cl)}₂] and [{Ru(η⁶-1,4-MeC₆H₄(CHMe₂))Cl(μ-Cl)}₂] (at 1-to-metal ratio 1:1) produce O,P-chelated complexes as well, albeit as stable adducts with the liberated Me₃SnCl: [RhCl(η⁵-C₅Me₅)(Ph₂PCH₂CO₂-κ²O,P)] · Me₃SnCl (6) and[RuCl(η⁶-1,4-MeC₆H₄(CHMe₂))(Ph₂PCH₂CO₂-κ²O,P)] · Me₃SnCl (8). The related complexes with P-monodentate (diphenylphosphino)acetic acid, [RhCl₂(η⁵-C₅Me₅)(Ph₂PCH₂CO₂H-κ,P)] (7) and [RuCl₂(η⁶-1,4-MeC₆H₄(CHMe₂))(Ph₂PCH₂CO₂H-κP)] (9), were obtained by bridge splitting in the dimers with the phosphinocarboxylic ligand. All new compounds were characterized by spectral methods and combustion analyses, and the structures of 2 · 3CH₂Cl₂, 3, 4, 5, 6 and 8 were determined by X-ray crystallography.     

Cytotoxic half-sandwich rhodium(III) complexes: Polypyridyl ligand influence on their DNA binding properties and cellular uptake

The DNA binding of polypyridyl (pp) (η⁵-C₅Me₅)Rh^III complexes of the types [(η⁵-C₅Me₅)RhCl(pp)](CF₃SO₃) (2-6) (pp = bpy, phen, dpq, dppz, dppn), [(η⁵-C₅Me₅)Rh{(Me₂N)₂CS}(pp)](CF₃SO₃)₂ (7-9) (pp = dpq, dppz, dppn) and [(η⁵-C₅Me₅)Rh(L)(pp)](CF₃SO₃) (10) (L = C₆H₅S⁻) and (11) (L = C₁₀H₇S⁻) has been studied by UV/Vis spectroscopy, circular dichroismus and viscosity measurements. Complexes 3-11 are cytotoxic towards the human MCF-7 breast and HT-29 colon cancer cell lines and exhibit IC₅₀ values in the range 0.56-10.7 μM. Stable intercalative binding into CT-DNA is indicated for the dpq and dppz complexes by large increases ΔT_m of 6-12 °C in the DNA thermal denaturation temperature for r = [complex]/[DNA] = 0.1 and by induced CD bands and large viscosity increases. In contrast, significant DNA lengthening is not observed after incubation of the biopolymer with the dppn complexes 2 and 9 at molar ratios of r < 0.08. Pronounced hypochromic shifts for the π-π^∗ transitions of the dppn ligands in the range 320-425 nm indicate the possible presence of surface stacking. The in vitro cytotoxicities of the chloro complexes 4-6 and the (Me₂N)₂CS complexes 7-9 are dependent on the size of the polypyridyl ligand with IC₅₀ values decreasing in the order dpq > dppz > dppn. For instance, IC₅₀ values of 5.3, 1.5 and 0.91 μM were determined for 7-9 against MCF-7 cells. Rapid Cl⁻/H₂O exchange leads the formation of aqua dications for 4-6, whose levels of cellular uptake and cytotoxicities are similar to those established for 7-9. Intramolecular interactions between the aromatic thiolate and dppz ligands of 10 and 11 prevent significant DNA intercalation. X-ray structural determinations have been performed for 2-7 and 11.     

Anticancer activity of new organo-ruthenium, rhodium and iridium complexes containing the 2-(pyridine-2-yl)thiazole N,N-chelating ligand

The dinuclear dichloro complexes [(η⁶-arene)₂Ru₂(μ-Cl)₂Cl₂] and [(η⁵-C₅Me₅)₂M₂(μ-Cl)₂Cl₂] react with 2-(pyridine-2-yl)thiazole (pyTz) to afford the cationic complexes [(η⁶-arene)Ru(pyTz)Cl]⁺ (arene = C₆H₆1, p-ⁱPrC₆H₄Me 2 or C₆Me₆3) and [(η⁵-C₅Me₅)M(pyTz)Cl]⁺ (M = Rh 4 or Ir 5), isolated as the chloride salts. The reaction of 2 and 3 with SnCl₂ leads to the dinuclear heterometallic trichlorostannyl derivatives [(η⁶-p-ⁱPrC₆H₄Me)Ru(pyTz)(SnCl₃)]⁺ (6) and [(η⁶-C₆Me₆)Ru(pyTz)(SnCl₃)]⁺ (7), respectively, also isolated as the chloride salts. The molecular structures of 4, 5 and 7 have been established by single-crystal X-ray structure analyses of the corresponding hexafluorophosphate salts. The in vitro anticancer activities of the metal complexes on human ovarian cancer cell lines A2780 and A2780cisR (cisplatin-resistant), as well as their interactions with plasmid DNA and the model protein ubiquitin, have been investigated.     

Catalytic efficacy of Schiff-base copper(II) complexes: Synthesis,X-ray structure and olefin oxidation

Three copper(II) Schiff-base complexes, [Cu(L¹)(H₂O)](ClO₄) (1), [Cu(L²)] (2) and [Cu(L³)] (3) have been synthesized and characterized [where HL¹ = 1-(N-ortho-hydroxy-acetophenimine)-2-methyl-pyridine], H₂L² = N,N′-(2-hydroxy-propane-1,3-diyl)-bis-salicylideneimine and H₂L³ = N,N′-(2,2-dimethyl-propane-1,3-diyl)-bis-salicylideneimine]. The structure of complex 1 has been determined by single crystal X-ray diffraction analysis. In complex 1, the copper(II) ion is coordinated to one oxygen atom and two nitrogen atoms of the tridentate Schiff-base ligand, HL¹. The fourth coordination site of the central metal ion is occupied by the oxygen atom from a water molecule. All the complexes exhibit high catalytic activity in the oxidation reactions of a variety of olefins with tert-butyl-hydroperoxide in acetonitrile. The catalytic efficacy of the copper(II) complexes towards olefin oxidation reactions has been studied in different solvent media.     

Reactions of [η:σ-Me2C(C5H4)(C2B10H10)]Ru(COD) with Lewis bases: Synthesis, structure, and electrochemistry of ruthenium amine, nitrile, carbene, phosphite and phosphine complexes

Treatment of [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(COD) (1) with phosphites, phosphines, amines or N-heterocyclic carbene in THF afforded the COD displacement complexes [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[P(OEt)₃]₂ (2), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[PPh₂(OEt)]₂ (3), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[NH₂CH₂CH₂Prⁱ]₂ (4), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NH₂Prⁿ)₂ (5), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru (η²-NH₂CH₂CH₂NH₂) (6), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[η²-NH(CH₃)CH₂CH₂NH(CH₃)] (7) or [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru[NHC]₂ (8, NHC = 1,3,4,5-tetramethylimidazol-2-yilidene), respectively. Ruthenium-amine complexes were much more labile than 1. Upon exposure to moisture, 5 was converted into [{η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)}Ru(μ-H₂O)]₂ (9). Reactions of 5 with PR₃ (R = PPh₃, Cy), TMEDA (TMEDA = N,N,N′,N′-tetramethylethylenediamine) and CH₃CN afforded the corresponding amine replacement products[η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NH₂Prⁿ)(PPh₃) (10), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NH₂Prⁿ)(PCy₃) (11), [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(TMEDA) (12) and [η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)]Ru(NCCH₃)₂ (13). These results indicated that the steric factor dominated these substitution reactions. The electrochemical studies showed that the electron richness of the Ru atom decreased in the order L₂Ru(NHC)₂ > L₂Ru(amine)₂ > L₂Ru(NCMe)₂ > L₂Ru(P)₂. All of these complexes were fully characterized by various spectroscopic techniques and elemental analyses. The molecular structures of 2, 3, 5-10, 12 and 13 were further confirmed by single-crystal X-ray analyses.