Thermal and spectroscopic investigation on N,N-dimethylbenzylamine based cyclopalladated compounds containing isonicotinamide

Synthesis, spectroscopic characterization and thermal analysis of the [Pd(dmba)(Cl)(iso)] (1), [Pd(dmba)(NCO)(iso)] (2), [Pd(dmba)(N₃)(iso)] (3) and [Pd(dmba)(Br)(iso)] (4) (dmba = N,N′-dimethylbenzylamine; iso = isonicotinamide) compounds are described in this work. The complexes were investigated by infrared spectroscopy (IR), differential thermal analysis (DTA) and thermogravimetry (TG) and the residues of the thermal decomposition were identified as Pd^o by X-ray powder diffraction. The thermal stability order of the complexes varied as [Pd(dmba)(Cl)(iso)] (1) > [Pd(dmba)(Br)(iso)] (4) > [Pd(dmba)(NCO)(iso)] (2) > [Pd(dmba)(N₃)(iso)] (3).     

Binuclear cyclopalladated compounds with antitubercular activity: synthesis and characterization of [{Pd(C2,N-dmba)(X)}2(μ-bpp)] (X = Cl,Br, NCO,N3; bpp = 1,3-bis(4-pyridyl)propane)

Reactions between [Pd(C²,N-dmba)(μ-X)]₂ (Hdmba?=?N,N-dimethylbenzylamine; X?=?Cl, Br, NCO, N₃) and 1,3-bis(4-pyridyl)propane (bpp) in 1?:?1 molar ratio at room temperature resulted in the binuclear compounds [{Pd(C²,N-dmba)(X)}₂(μ-bpp)] (X?=?Cl (1), Br (2), NCO (3), N₃ (4)), which were characterized by elemental analyses, infrared (IR), ¹H- and ¹³C{¹H}-NMR spectroscopies, and thermogravimetric analysis. The IR and NMR data of 1–4 were consistent with the presence of bridging bpp. The thermal stability order of the complexes was 4?>?3?>?2?>?1. Compounds 1–4 and bpp were tested against Mycobacterium tuberculosis and their MIC values were determined.     

Thermal and Spectroscopy Investigation of Cyclopalladated Compounds of the Type [Pd(C13H10N)(μ-X)]2, (X=H3CCOO,NCO, SCN,CN)

The dimeric compound [Pd(bzan)(μ-OOCCH₃)]₂ (1) (bzan=N-benzylideneaniline) reacts with KX, in methanol/acetone (2:1), affording the analogous dimeric pseudohalogen-bridged species [Pd(bzan)(μ-X)]₂ [X=NCO(2),SCN(3), CN(4)]. The compounds were characterized by elemental analysis, infrared spectroscopy, NMR and thermogravimetric analysis. IR data for 2–4 showed bands typical of coordinated pseudohalogen ligands clearly indicating the occurrence of the exchange reaction. Their thermal behaviour was investigated and suggested that their stability is influenced by the bridging ligand. The thermal stability decreased in the order[Pd(bzan)(μ-CN)]₂>[Pd(bzan)(μ-SCN)]₂>[Pd(bzan)(μ-OOCCH₃)]₂>[Pd(bzan)(μ-NCO)]₂. X-ray results showed the formation of Pd° as final decomposition product. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal study of cyclopalladated complexes of the type [Pd<Subscript>2</Subscript>(dmba)<Subscript>2</Subscript>X<Subscript>2</Subscript>(bpe)]

The synthesis, characterization and thermal analysis of the novel cyclometallated compounds [Pd₂(dmba)₂Cl₂(μ-bpe)] (1), [Pd₂(dmba)₂(N₃)₂(μ-bpe)] (2), [Pd₂(dmba)₂(NCO)₂(μ-bpe)] (3), [Pd₂(dmba)₂(SCN)₂(μ-bpe)] (4), [Pd₂(dmba)₂(NO₃)₂(μ-bpe)] (5) (bpe=trans-1,2-bis(4-pyridyl)ethylene; dmba=N,N-dimethylbenzylamine) are described. The thermal stability of [Pd₂(dmba)₂X₂(μ-bpe)] complexes varies in the sequence 1>4>3>2>5. The final residues of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Cleavage of the dimeric cyclopalladated [Pd(N,C-dmba)(μ-X)]2, (dmba = N,N-dimethylbenzylamine; X = SCN and NCO) by diphosphines. Palladium(II) compounds with distinct structures in the solid-state and in solution

The reactions of the pseudohalide-bridged dimer [Pd(N,C-dmba)(-SCN)]₂ (1) (dmba = N,N-dimethylbenzylamine) with cis-Ph₂PCH=CHPPh₂ (cis-dppet) (1:1 molar ratio) and of [Pd(N,C-dmba)(-NCO)]₂ (2) with Ph₂PCH₂CH₂PPh₂ (dppe) (1:2 molar ratio) gave mononuclear [Pd(C-dmba)(SCN)(cis-dppet)]·H₂O (1a) and [Pd(C-dmba)(NCO)(dppe)] (2a), respectively, with the diphosphines acting as chelating ligands. Reaction of (2) with Fe(C₅H₄PPh₂)₂ (dppf) (1:1 molar ratio) yielded [{Pd(N,C-dmba)(NCO)}₂(-dppf)] (2b), a bimetallic species containing two palladium atoms bridged by the diphosphine, whereas reaction in a 1:2 molar ratio gave the mononuclear [Pd(N,C-dmba)(dppf)][NCO]·CH₂Cl₂ (2c), with the diphosphine acting as a chelating ligand. The compounds have been characterized by elemental analysis, i.r., ³¹P{¹H}, ¹³C- and ¹H-n.m.r. spectroscopies. Conductivity measurements together with spectroscopic data showed that (1a) and (2a) do not have the same structure in the solid state and in MeCl solution, whereas for compounds (2b) and (2c) no structural changes were observed when the solids were dissolved in MeCl.     

Synthesis, Characterization, and Fluxional Behaviour of Binuclear Palladium Complexes with a Half-A-Frame Structure

 Partial removal of chloride anions from the dimer [Pd(η³-2-CH₃*C₃H₄)(μ-Cl)]₂ with AgTf(Tf = CF₃SO₃) followed by addition of dppm affords [Pd₂(η³-Me*C₃H₄)₂(μ-Cl)(μ-dppm)]Tf (1). The substitution of Cl⁻ by X⁻ (X = pz, SC₆F₅, S _py ) using the appropriate salts yields the new derivatives [Pd₂(η³-Me*C₃H₄)₂(μ-X)(μ-dppm)]Tf (2–4). All complexes exhibit a dinuclear half-A-frame structure with two isomers present in solution. The isomers differ in the relative orientation of the two allyl groups (cis or trans). The isomer interconversion was studied by variable temperature ¹H NMR spectroscopy. The molecular structures of 2 and 4 were solved by X-ray diffraction studies. A distorted boat conformation of the seven- or six-membered metallacycle was found in both cases.     

Mono- and dinuclear palladium(II) compounds containing nitrogen ligands. Crystal and molecular structure of [Pd(N,C-dmba)(NCO)(2,3-lut)] and [Pd(H2CCOMe)Cl(2,2′-bipy)]

The cyanate-bridged cyclopalladated compound [Pd(N,C-dmba)(-NCO)]₂ (1)(dmba = PhCH₂NMe₂) reacts in CH₂Cl₂ with 2,3-lutidine (2,3-lut), 3,4-lutidine (3,4-lut), 2,2-bipyridine (2,2-bipy) and 4,4-bipyridine (4,4-bipy), to give [Pd(N,C-dmba)(NCO)(2,3-lut)](2), [Pd(N,C-dmba)(NCO)(3,4-lut)](3), [{Pd(N,C-dmba)(NCO)}₂(-2,2-bipy)]· CH₂Cl₂ (4) and [{Pd(N,C-dmba)(NCO)}₂(-4,4-bipy)]· CH₂Cl₂ (5), respectively. The compounds were characterized by elemental analysis, i.r. and n.m.r. spectroscopy and also by t.g.a. The i.r. spectra of (2–5) display typical bands of monodentate N-bonded cyanate groups, whereas the n.m.r. data of (4) are consistent with the presence of a bridging 2,2-bipyridine ligand. Complex (4) decomposes slowly in acetone. One of the products formed, [Pd(H₂CCOMe)Cl(2,2-bipy)](6), was characterized by X-ray diffraction. As inferred from the t.g.a., the thermal stability decreases in the order:[{Pd(N,C-dmba)(NCO)}₂(-4,4-bipy)].CH₂Cl₂ (5) > [Pd(N,C-dmba)(2,3-lut)(NCO)](2)=[Pd(N,C-dmba)(3,4-lut)(NCO)](3) > [{Pd(N,C-dmba)(NCO)}₂(-2,2-bipy)]· CH₂Cl₂ (4). According to thermal analysis and X-ray diffraction patterns compounds (2–3) decompose into metallic palladium Pd(0), whereas (4–5) decompose with the formation of PdO. The X-ray crystal and molecular structure of [Pd(N,C-dmba)(NCO)(2,3-lut)](2) was determined. The lutidine unit is perpendicular to the coordination plane.     

Thermal study of mononuclear Pd(II) complexes of the type [Pd(X)<Subscript>2</Subscript>(Rtu)(PPh<Subscript>3</Subscript>)] (X = Cl,SCN; Rtu = <Emphasis Type="Italic">N</Emphasis>-methylthiourea, <Emphasis Type="Italic">N</Emphasis>-phenylthiourea)

The synthesis, spectroscopic characterization, and thermal analysis of the compounds [Pd(X)₂(mtu)(PPh₃)] (X = Cl⁻ (1), SCN⁻ (2); mtu = N-methylthiourea; PPh₃ = triphenylphosphine) and [Pd(X)₂(phtu)(PPh₃)] (X = Cl⁻ (3), SCN⁻ (4); phtu = N-phenylthiourea) are described. The thermal decomposition of the compounds occurs in two, three, or four stages and the final decomposition products were identified as Pd⁰ by X-ray powder diffraction. The thermal stability order of the complexes is 4 > 3>2 > 1.     

Synthesis, Characterization, and Fluxional Behaviour of Binuclear Palladium Complexes with a Half-A-Frame Structure

Summary.  Partial removal of chloride anions from the dimer [Pd(η³-2-CH₃*C₃H₄)(μ-Cl)]₂ with AgTf(Tf = CF₃SO₃) followed by addition of dppm affords [Pd₂(η³-Me*C₃H₄)₂(μ-Cl)(μ-dppm)]Tf (1). The substitution of Cl⁻ by X⁻ (X = pz, SC₆F₅, S _py ) using the appropriate salts yields the new derivatives [Pd₂(η³-Me*C₃H₄)₂(μ-X)(μ-dppm)]Tf (2–4). All complexes exhibit a dinuclear half-A-frame structure with two isomers present in solution. The isomers differ in the relative orientation of the two allyl groups (cis or trans). The isomer interconversion was studied by variable temperature ¹H NMR spectroscopy. The molecular structures of 2 and 4 were solved by X-ray diffraction studies. A distorted boat conformation of the seven- or six-membered metallacycle was found in both cases. Received June 7, 2000. Accepted June 20, 2000     

Reaction of Sulfur and Oxygen-Bridged 8-Quinolinolato Trinuclear Molybdenum Cluster [Mo<Subscript>3</Subscript>OS<Subscript>3</Subscript>(qn)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>3</Subscript>]<Superscript>+</Superscript> with Acetylene Carboxylic Acids

The reaction of a sulfur and oxygen-bridged 8-quinolinolato trinuclear molybdenum cluster [Mo₃OS₃(qn)₃(H₂O)₃]⁺ (3; Hqn = 8-quinolinol) with equimolar amounts of acetylene carboxylic acid, 4-pentynoic acid, 5-hexynoic acid, acetic acid, and pimelic acid gave clusters having μ-carboxylato groups, [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡CCOO)] (6), [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡C(CH₂)₂COO)] (7), [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡C(CH₂)₃COO)] (8), [Mo₃OS₃(qn)₃(H₂O)(μ-CH₃COO)] (4), and [{Mo₃OS₃(qn)₃(C₂H₅OH)}₂(μ-C₇H₁₀O₄)] (5), respectively. X-ray structural analyses, ¹H NMR, and electronic spectra of these clusters made clear that each of the COO⁻ groups of the reagents bridges two Mo atoms in each cluster and that no adduct formation occurred at the sulfurs in the clusters. The reaction of 3 with a large excess-molar amount (50 times) of acetylene carboxylic acid gave [Mo₃OS(μ₃-SCH=C(COOH)S)(qn)₃(H₂O)(μ-HC≡CCOO)] (9) with two molecules of acetylene carboxylic acid, one acting as a carboxylato bridge and the other in adduct formation, as supported by the electronic and ¹H NMR spectra. The corresponding aqua cluster [Mo₃OS₃(H₂O)₉]⁴⁺ (1), on the contrary, reacts with acetylene carboxylic acid to give adduct [Mo₃OS(μ₃-SCH=C(COOH)S)(H₂O)₉]⁴⁺ (2). Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The role of water molecules in formation of heterometallic palladium acetate complexes with cerium and neodymium

The reactions of palladium(II) acetate with neodymium(III) and cerium(III) acetates in acetic acid containing a specified amount of water have been studied. The following homo- and heterometallic complexes have been synthesized and characterized by X-ray diffraction: Nd₂(μ-OOCMe)₂(μ,η²-OOCMe)₂(η²-OOCMe)₂(HOOCMe)₂(OH₂)₂ · 4HOOCMe, [Pd(μ-OOCMe)₄Ce(OH₂)₂(μ,η²-OOCMe)]₂ · 2HOOCMe · 6H₂O, [Pd(μ-OOCMe)₄Ce(OH₂)₂(μ,η²-OOCMe)]₂ · 14H₂O, [Pd(μ-OOCMe)₄M(HOOCMe)₂(OH₂)₂]⁺ [Pd(μ-OOCMe)₄M(μ-OOCMe)₄Pd]⁻ · 2MeCOOH · 1.5H₂O (M = Nd, Ce), and {[Pd(μ-OOCMe)₄Ce(OOCMe)₄]₂ [Pd₄(μ-OOCMe)₄]₂(μ₄-O)₈CePd₄}(OH)₃ · 27H₂O. From kinetic and structural data and optical spectra of reaction solutions, the conclusion was drawn that hydrolytic processes play a decisive role in complexation reactions.     

Cyclopalladated complexes based on 2-phenylbenzothiazole and 1,4-(benzothiazol-2-yl)benzene with acetate ligands and ethylenediamine

Complexes [Pd(bt)En]ClO₄, [Pd(bt)(μ-OOCCH₃)]₂, [(PdEn)₂(μ-dbt)](CH₃COO)₂, and [Pd₂(μ-dbt)· (μ-OOCCH₃)₂]₂ (bt⁻ and dbt²⁻ are the mono- and bisdeprotonated forms of 2-phenylbenzothiazole and 1,4-bis-(benzthiazol-2-yl)benzene, En is ethylenediamine) are characterized by ¹H NMR, electron absorption spectroscopy, and voltammetry. The upfield shift of the signal of protons of heterocyclic ligands in complexes with acetate ligands is assigned to anisotropic effect of the ring current of the two fragments {Pd(bt)} and {Pd(dbt)} in the complexes. The red shift of the optical transition of the metal-ligand charge transfer as well as the anodic shift of the ligand-centered reduction of [(PdEn)₂(μ-dbt)](CH₃COO)₂ relative to [Pd(bt)En]ClO₄ is due to the decrease in the LUMO energy of the complexes. The cathodic shift of the oxidation potential and the long wavelength absorption in complexes with acetate ligands is assigned to variation in the HOMO nature due to the metal-metal bond formation.     

Reactivity of Pd3(dppm)3(CO)n+ and Pd3(dppm)3(CO)(RCCR)n+ (n?=?0, +1, +2) Towards F?. Evidence of Reactive Intermediates and X-Ray Structure of [Pd3(dppm)3(MeO2CC≡CCO2Me)(F)]PF6

Abstract  

The reactivity of the trinuclear palladium cluster [Pd₃(dppm)₃(CO)] ⁿ⁺ (dppm = bis(diphenylphosphinomethane); n = 2, 1) towards F⁻ was investigated by electrochemical and spectroscopic methods. The reaction depends on the charge of the cluster. The chemical reduction of the cluster dication is observed in the presence of F⁻ generating the paramagnetic monocationic cluster. Spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) provided evidence for the radical F^• as an intermediate. In a similar manner to the dication, the monocationic cluster [Pd₃(dppm)₃(CO)]⁺ is also reduced, but in a slower process, by the F⁻ ion to produce [Pd₃(dppm)₃(CO)]⁰. Additionally, the alkyne cluster adducts [Pd₃(dppm)₃(CO)(RCCR)] ⁿ⁺ (n = 2, 1; R = CO₂Me) are also reactive towards F⁻. Particularly, the dication adduct leads to a metastable fluoride adduct [Pd₃(dppm)₃(CO)(RCCR)(F)]⁺. The electroreductive behavior of this adduct involves electron-transfer steps and F⁻ exchange equilibriums, for which digital simulation enables the extraction of the thermodynamic parameters (standard potentials and equilibrium constants). Concurrently, the monocation adduct [Pd₃(dppm)₃(CO)(RCCR)]⁺ with F⁻, leads to a disproponation generating 0.5 equiv. of [Pd₃(dppm)₃(CO)(RCCR)(F)]⁺ and 0.5 equiv. of [Pd₃(dppm)₃(CO)(RCCR)]⁰. The former slowly evolves to [Pd₃(dppm)₃(RCCR)(F)]⁺, which was described by X-ray diffraction method.     

Synthesis and crystal structures of terephthalato-bridged macrocyclic nickel(II) complexes with <Emphasis Type="Italic">cis</Emphasis> configurations

Three dinuclear terephthalato-bridged nickel(II) complexes [Ni(rac-L)]₂(μ-TPA)(ClO₄)₂ (1), [Ni(RR-L)]₂(μ-TPA)(ClO₄)₂ (2), and [Ni(SS-L)]₂(μ-TPA)(ClO₄)₂ (3) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, TPA = terephthalic acid) have been synthesized and characterized. Single-crystal X-ray diffraction analyses revealed that the Ni(II) atoms have six-coordinated distorted octahedral environments, and the terephthalato ligand bridges two Ni(II) centres in a bis bidentate fashion to form dimers in all three complexes. The monomers of {[Ni(RR-L)]₂(μ-TPA)}²⁺ and {[Ni(SS-L)]₂(μ-TPA)}²⁺ are connected through intermolecular hydrogen bonds to generate 1D right-handed and left-handed helical chains, respectively. The racemic character of 1 and the homochiral natures of 2 and 3 are confirmed by the results of CD spectroscopy.     

Providing Support in Favor of the Existence of a PdII/PdIV Catalytic Cycle in a Heck‐Type Reaction

The complex [Pd(O,N,C‐L)(OAc)], in which L is a monoanionic pincer ligand derived from 2,6‐diacetylpyridine, reacts with 2‐iodobenzoic acid at room temperature to afford the very stable pair of Pd^IV complexes (OC‐6‐54)‐ and (OC‐6‐26)‐[Pd(O,N,C‐L)(O,C‐C₆H₄CO₂‐2)I] (1.5:1 molar ratio, at ?55 °C). These complexes and the Pd^II species [Pd(O,N,C‐L)(OX)] and [Pd(O,N,C‐L′)(NCMe)]ClO₄, (X=MeC(O) or ClO₃, L′=another monoanionic pincer ligand derived from 2,6‐diacetylpyridine), are precatalysts for the arylation of CH₂?CHR (R?CO₂Me, CO₂Et, Ph) using IC₆H₄CO₂H‐2 and AgClO₄. These catalytic reactions have been studied and a tentative mechanism is proposed. The presence of two Pd^IV complexes was detected by ESI(+)‐MS during the catalytic process. All the data obtained strongly support a Pd^II/Pd^IV catalytic cycle.     

Synthesis,characterization, and cytotoxicity of platinum(II)/palladium(II) complexes with 4-toluenesulfonyl-L-amino acid dianion and diimine/diamine

Eight new platinum(II)/palladium(II) complexes with 4-toluenesulfonyl-L-amino acid dianion and diimine/diamine ligands, [Pd(en)(Tsile)]·H₂O (1), [Pd(bipy)(Tsile)] (2), [Pd(bipy)(Tsthr)]·0.5H₂O (3), [Pd(phen)(Tsile)]·0.5H₂O (4), [Pd(phen)(Tsthr)]·H₂O (5), [Pd(bqu)(Tsthr)]·1.5H₂O (6), [Pt(en)(Tsser)] (7), and [Pt(en)(Tsphe)]·H₂O (8), have been synthesized and characterized by elemental analyses, ¹H NMR and mass spectrometry. The crystal structure of 7 has been determined by X-ray diffraction. Cytotoxicities were tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and sulforhodamine B assays. The complexes exert cytotoxicity against HL-60, Bel-7402, BGC-823, and KB cell lines with 4 having the best cytotoxicity against HL-60, Bel-7402, and BGC-823 cell lines; the compounds are less cytotoxic than cisplatin.     

Cationic palladium(II) complexes involving unprecedented O-coordination of acetylmethylenetriphenylphosphorane

Cationic pentafluorophenyl palladium(II) complexes of the type [Pd(C₆F₅)L₂(APPY)]ClO₄ (L = PPh₃, PBu₃ⁿ; L₂ = bipy and A acetylmethylenetriphenylphosphorane) have been prepared by addition of APPY to the perchlorato complexes [Pd(OClO₃)(C₆F₅)L₂]; the APPY ligand is O-coordinated, which is unprecedented in keto-stabilized ylide complexes of palladium.The neutral complex Pd(C₆F₅)(Cl)(tht)(APPY) has been made by addition of APPY to the binuclear complex Pd₂(μ-Cl)₂(C₆F₅)₂(tht)₂ (tht = tetrahydrothiophene); in which the APPY ligand shows the normal C-coordination.     

1-Selenolato-2-phenyl-o-carborane complexes of palladium(II) and platinum(II): Synthesis, spectroscopy and structures

The reactions of PhCb^oSeNa (Cb^o = o-C₂B₁₀H₁₀), prepared by reductive cleavage of Se-Se bond in (PhCb^oSe)₂ by NaBH₄ in methanol, with Na₂PdCl₄, MCl₂(PR₃)₂ and [M₂Cl₂(μ-Cl)₂(PR₃)₂] afforded a variety of complexes, viz., [Pd(SeCb^oPh)Cl] (1), [M(SeCb^oPh)₂(PR₃)₂], [M₂Cl₂(μ-SeCb^oPh)(μ-Cl)(PR₃)₂] (M = Pd, Pt) and [Pd₂Cl(SeCb⁰Ph)(μ-Cl)(μ-SeCb^oPh)(PEt₃)₂] (7) have been isolated. These complexes were characterized by elemental analyses and NMR (¹H, ³¹P, ⁷⁷Se, ¹⁹⁵Pt) spectroscopy. The structures of [Pd(SeCb^oPh)₂(PEt₃)₂] (2), [Pt(SeCb^oPh)₂(PMe₂Ph)₂] (3), [Pd₂Cl₂(μ-SeCb^oPh)(μ-Cl)(PMe₂Ph)₂] (5) and [Pd₂Cl(SeCb^oPh)(μ-Cl)(μ-SeCb^oPh)(PEt₃)₂] (7) were established by X-ray crystallography. The latter represents the first example of asymmetric coordination of selenolate ligands in binuclear bis chalcogenolate complexes of palladium and platinum. Thermolysis of [Pd(SeCb^oPh)₂(PEt₃)₂] (2) in HDA (hexadecylamine) at 330 °C gave nano-crystals of Pd₁₇Se₁₅.     

Cyclopalladated 2-phenyldihydrooxazole complexes with ethylenediamine, 2,2′-bipyridine,and bridging acetate ligands

The ¹H NMR, electronic absorption, and luminescence spectra, as well as voltammograms of the reduction and oxidation of the complexes [Pd(C∧N)(N∧N)]ClO₄ and [Pd(C∧N)(μ-OOCCH₃)]₂ [where (C∧N)⁻ is deprotonated 2-phenyl-4,5-dihydro-1,3-oxazole, and N∧N is ethylenediamine or 2,2′-bipyridine (bpy)] were compared. Magnetic nonequivalence of protons in the dihydrooxazole ring and upfield shift of the corresponding signals were observed as a result of anisotropic effect of the ring current in palladated phenyl substituents in the [Pd(C∧N)(μ-OOCCH₃)]₂ complex having a C ₂ symmetry. One-electron reduction wave of [Pd(C∧N)bpy]⁺ was assigned to ligand-centered electron transfer to the π* orbital of 2,2′-bipyridine, and two oxidation waves of [Pd(C∧N)(μ-OOCCH₃)]₂ were attributed to successive one-electron oxidations of the palladium centers. Low-temperature (77 K) phosphorescence of [Pd(C∧N)En]⁺ and [Pd(C∧N)bpy]⁺ was ascribed to optical transition localized on the metal-complex fragment {Pd(C∧N)} and to interligand charge transfer between the chelating and cyclopalladated ligands. The formation of metal-metal bond in the complex [Pd(C∧N)(μ-OOCCH3₎]₂ gives rise to radiative decay of photoexcitation energy from two electronically excited states, one of which is localized on the {Pd(C∧N)} fragment, and the second corresponds to the charge transfer metal-metal-cyclopalladated ligand.     

Reaction of cyclopentadienyllutetium anthracenide with azobenzene. Synthesis and molecular and crystal structure of the binuclear complex [C5H5(THF)Lu(μ−η2:η2−PhN—NPh)]2(THF)2 and its dynamic behavior in solution

The reaction of the cyclopentadienyllutetium anthracenide, C₅H₅Lu(C₁₄H₁₀)²⁻(THF)₂ (1), with azobenzene yielded the [C₅H₅(THF)Lu(μ−η²:η²−PhN—NPh)]₂(THF)₂ (2) binuclear complex. The structure of the reaction product was established by X-ray structural analysis. The dynamic behavior of complex2 in a THF-d₈ solution was studied by¹H NMR spectroscopy in the temperature range of 265–330 K. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1667–1671, September, 1997.