New calсium β-diketonate complexes: The monomeric complexes [Ca(PhCOCHCOCF3)2(15-crown-5)], [Ca(AdCOCHCOCF3)2(15-crown-5)] and the binuclear hydrated complex [{Ca(adtfa)(18-crown-6)(H2O)}{Ca(adtfa)3(H2O)}(EtOH)]. Synthesis, characterization and crystal structure

The preparation of the Ca-β-diketonate complexes with crown-ethers, [Ca(btfa)₂(15-crown-5)] (1), [Ca(adtfa)₂(15-crown-5)] (2), [Ca(adtfa)₂(15-crown-5)](C₆H₅CH₃)_0.5 (3) and [{Ca(adtfa)(18-crown-6)(H₂O)}{Ca(adtfa)₃(H₂O)}(EtOH)] (4) (btfa = 1,1,1-trifluoro-4-phenyl-butanedionato-2,4; adtfa = 1,1,1-trifluoro-4-(1-adamantyl)butanedionato-2,4; 15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane; 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), is described. Complex 1 has been prepared from the reaction of metallic Ca with 2 eq. of Hbtfa and 1 eq. of 15-crown-5 in toluene; complex 2 has been prepared from the reaction of metallic Ca with 2 eq. of Hadtfa and 1 eq. of 15-crown-5 in ethanol. The solvated complex 3 was obtained by cooling of a toluene-hexane solution of 2. The hydrated complex 4 was prepared from the reaction of metallic Ca with 2 eq. of Hadtfa and 1 eq. of 18-crown-6, followed by addition of excess H₂O to the resulting reaction mixture. The all complexes were characterized by elemental analyses, IR-spectroscopy, NMR-spectroscopy, single-crystal X-ray diffraction methods, DSC and TGA. A single-crystal X-ray study of 1 and 3 has show that complexes 1 and 3 are monomeric and contain the calcium atom bonded with two β-diketonate ligands and one molecule of crown-ether. Complex 4, as shown by X-ray analyses, is an ion-paired solvated adduct, containing the cation {Ca(adtfa)(18-crown-6)(H₂O)}⁺ and the anion {Ca(adtfa)₃(H₂O)}⁻. The monomeric complexes 1-3 are volatile and thermally stable in the temperature range 100-260 °C. Complex 4 undergoes decomposition above 110 °C with consecutive loss of ethanol, H₂O, 18-crown-6 and some evaporization of 4.     

Synthesis and characterization of heterometallic Rh/Ru complexes supported by 1,2-dichalcogenolato-o-carborane ligands

The 16-electron half-sandwich complexes Cp^∗Rh[E₂C₂(B₁₀H₁₀)] (E = S, 1a; Se, 1b) react with [Ru(COD)Cl₂]_x under different conditions to give different types of heterometallic complexes. When the reactions were carried out in THF for 24 h, the binuclear Rh/Ru complexes [Cp^∗Rh(μ-Cl)₂(COD)Ru][E₂C₂(B₁₀H₁₀)] (E = S, 2a; Se, 2b) bridged by two Cl atoms and the binuclear Rh/Rh complexes (Cp^∗Rh)₂[E₂C₂(B₁₀H₁₀)] (E = S, 3a; Se, 3b) with direct Rh-Rh bond can be isolated in moderate yields. [Ru(COD)Cl₂] fragments in 2a and 2b have inserted into the Rh-E bond. If the [Ru(COD)Cl₂]_x was reacted with 1a in the presence of K₂CO₃ in methanol solution, the product [Cp^∗Rh(COD)]Ru[S₂C₂(B₁₀H₁₀]] (4a), K[(μ-Cl)(μ-OCH₃)Ru(COD)]₄ (5a) and 3a were obtained. The B(3)-H activation in complex 4a was found. However, when the reaction between 1b and [Ru(COD)Cl₂]_x was carried out in excessive NaHCO₃, the carborane cage opened products {Cp^∗Rh[S₂C₂(B₉H₁₀)]}Ru(COD) (6b), {Cp^∗Rh[S₂C₂(B₉H₉)]}Ru(COD)(OCH₃) (7b) and 3b were obtained. All complexes were fully characterized by their IR, ¹H NMR and elemental analyses. The molecular structures of 2a, 2b, 3b, 4a, 5a, and 7b have been determined by X-ray crystallography.     

Di(1H,1H,2H,2H-perfluorooctyl)-dibenzo-18-crown-6: A “light fluorous” recyclable phase transfer catalyst

A series of dibenzo-18-crown-6 lariat ethers containing two C₇H₁₅ (11), (CH₂)₂C₆F₁₃ (14), (CH₂)₂C₈F₁₇ (15), NHC₇H₁₅ (18) and NHCH₂C₆F₁₃ (19) sidearms were prepared and the single crystal X-ray structure of cis-4,4′-di(1H,1H,2H,2H-perfluorodecyl)-dibenzo-18-crown-6 (15a) is reported. The “light fluorous” dibenzo-18-crown-6 ether (14) has emerged as a stable and robust PTC catalyst, which can be recycled efficiently by fluorous solid-phase extraction, and gives better PTC catalytic activity compared to the parent, non-fluorinated PTC catalyst, dibenzo-18-crown-6, and the alkylated derivative (11) in aliphatic and aromatic nucleophilic substitutions.     

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.     

Coordinating properties of [M(CO)5(CN)] [M=Cr; Mo; W] ligands: formation of ion pairs or dinuclear cyanide-bridged complexes, spectroscopic and X-ray diffraction studies

The reaction of sodium cyanopentacarbonylmetalates Na[M(CO)₅(CN)] (M=Cr; Mo; W) with cationic Fe(II) complexes [Cp(CO)(L)Fe(thf)][O₃SCF₃], [L=PPh₃ (1a), CN-Benzyl (1b), CN-2,6-Me₂C₆H₃ (1c); CN-Bu^t (1d), P(OMe)₃ (1e), P(Me)₂Ph (1f)] in acetonitrile solution, yielded the metathesis products [Cp(CO)(L)Fe(NCCH₃)][NCM(CO)₅] [M=W, L=PPh₃ (2a), CN-Benzyl (2b), CN-2,6-Me₂C₆H₃ (2c); CN-Bu^t (2d), P(OMe)₃ (2e), P(Me)₂Ph (2f); M=Cr, L=(PPh₃) (3a), CN-2,6-Me₂C₆H₃ (3c); M=Mo, L=(PPh₃) (4a), CN-2,6-Me₂C₆H₃ (4c)]. The ionic nature of such complexes was suggested by conductivity measurements and their main structural features were determined by X-ray diffraction studies. Well-resolved signals relative to the [M(CO)₅(CN)] moieties could be distinguished only when ¹³C NMR experiments were performed at low temperature (from −30 to −50 °C), as in the case of [Cp(CO)(PPh₃)Fe(NCCH₃)][NCW(CO)₅] (2a) and [Cp(CO)(Benzyl-NC)Fe(NCCH₃)][NCW(CO)₅] (2b). When the same reaction was carried out in dichloromethane solution, neutral cyanide-bridged dinuclear complexes [Cp(CO)(L)FeNCM(CO)₅] [M=W, L=PPh₃ (5a), CN-Benzyl (5b); M=Cr, L=(PPh₃) (6a), CN-2,6-Me₂C₆H₃ (6c), CO (6g); M=Mo, L=CN-2,6-Me₂C₆H₃ (7c), CO (7g)] were obtained and characterized by infrared and NMR spectroscopy. In all cases, the room temperature ¹³C NMR measurements showed no broadening of cyano pentacarbonyl signals and, relative to tungsten complexes [Cp(CO)(PPh₃)FeNCW(CO)₅] (5a) and [Cp(CO)(CN-Benzyl)FeNCW(CO)₅] (5b), the presence of ¹⁸³W satellites of the ¹³CN resonances (J_CW ∼ 95 Hz) at room temperature confirmed the formation of stable neutral species. The main ¹³C NMR spectroscopic properties of the latter compounds were compared to those of the linkage isomers [Cp(CO)(PPh₃)FeCNW(CO)₅] (8a) and [Cp(CO)(CN-Benzyl)FeCNW(CO)₅] (8b). The characterization of the isomeric couples 5a-8a and 5b-8b was completed by the analyses of their main IR spectroscopic properties. The crystal structures determined for 2a, 5a, 8a and 8b allowed to investigate the geometrical and electronic differences between such complexes. Finally, the study was completed by extended Hückel calculations of the charge distribution among the relevant atoms for complexes 2a, 5a and 8a.     

Activation of C-H and C-Br bonds in cyclopalladation reactions of Schiff base ligands: Influence of the benzylidene ring substituents

Reaction of Pd(AcO)₂ with the Schiff base ligands 2-Br-4,5-(OCH₂O)C₆H₂C(H)N(Cy) (a) and 4,5-(OCH₂CH₂)C₆H₃C(H)N(Cy) (b) leads to the cyclometallated compounds [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)N(Cy)-C6,N}(μ-O₂CMe)]₂ (1a) and [Pd{4,5-(OCH₂CH₂)C₆H₂C(H)N(Cy)-C6,N}(μ-O₂CMe)]₂ (1b), respectively, via C-H activation. Treatment of a with Pd₂(dba)₃ gave [Pd{4,5-(OCH₂O)C₆H₂C(H)N(Cy)-C2,N}(μ-Br)]₂ (6a), via C-Br activation. The metathesis reaction of 1a and 1b with aqueous sodium chloride gave the corresponding cyclopalladated dimers with bridging chloride ligands, 2a and 2b, respectively. Treatment of the halogen-bridged compounds with tertiary tri- and diphosphines in the appropriate molar ratio gave the mono and dinuclear compounds 3a-5a, 7a-9a and 3b-5b. The structure of compounds 3a, 4a, 5a, 8a, 2b, 3b and 5b has been determined by X-ray diffraction analysis.     

Barium bis(5,5-dimethyl-1,1,1-trifluorohexane-2,4-dionate)(crown-ether) complexes: Synthesis,characterization and crystal structure

The preparation of the barium β-diketonate complexes with crown-ethers [Ba(pta)₂(18-crown-6)] (1), [Ba(pta)₂(18-crown-6)] (THF) (2), [Ba(pta)₂(18-dibenzocrown-6)](C₆H₅CH₃) (3), [Ba(pta)₂(18-dibenzocrown-6)] (4) (pta = 1,1,1-trifluoro-5,5-dimethylhexanedionato-2,4; 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; 18-dibenzocrown-6 = 6,7,9,10,17,18,20,21-octahydrodibenzo[b,k][1,4,7,10,13,16]-hexaoxacyclooctadecane) is described. The complexes 1 and 2 have been synthesized from reaction of metallic barium with 2 molar equiv. of Hpta and 1 molar equiv. of 18-crown-6 in toluene; the complexes 3 and 4 from reaction of Ba(OH)₂·8H₂O with 1 molar equiv. 18-dibenzocrown-6 and 2 molar equiv. Hpta. The complexes were characterized by elemental analyses, IR-spectroscopy, ¹H NMR spectroscopy. The crystal structures of 2 and 3 were determined by means of single-crystal X-ray diffraction methods. A single-crystal X-ray study of 2 and 3 has shown it be monomeric. The coordination number of Barium cation in 2 and 3 is nine owing to nine oxygen atoms from two pta ligands and crown-ether molecule.     

Synthesis and characterization of hetero-binuclear Co-Rh complexes [CpCoS2C2(B9H10)][Rh(COD)] and [CpCoSe2C2(B10H10)][Rh(COD)]

Two hetero-binuclear complexes [Cp^∗CoS₂C₂(B₉H₁₀)][Rh(COD)] (2a) and [Cp^∗CoSe₂C₂(B₁₀H₁₀)][Rh(COD)] (2b) [Cp^∗ = η⁵-pentamethylcyclopentadienyl, COD = cyclo-octa-1,5-diene (C₈H₁₂)] were synthesized by the reactions of half-sandwich complexes [Cp^∗CoE₂C₂(B₁₀H₁₀)] [E = S (1a), Se (1b)] with low valent transition metal complexes [Rh(COD)(OEt)]₂ and [Rh(COD)(OMe)]₂. Although the reaction conditions are the same, the structures of two products for dithiolato carborane and diselenolato carborane are different. The cage of the carborane in 2a was opened; However, the carborane cage in 2b was intact. Complexes 2a and 2b have been fully characterized by ¹H, ¹¹B NMR and IR spectroscopy, as well as by elemental analyses. The molecular structures of 2a and 2b have been determined by single-crystal X-ray diffraction analyses and strong metal-metal interactions between cobalt and rhodium atoms (2.6260 Å (2a) and 2.7057 Å (2b)) are existent.     

Yttrium thiocyanate-based supramolecular architectures: Synthesis, crystal structures, and thermal properties

The reaction of [Y(H₂O)₅(NCS)₃]·H₂O (1) with crown ether (18-crown-6) and KNCS in methanol afforded the complexes [Y(H₂O)₄(NCS)₃]·1.5(18-crown-6) (2) and [K(18-crown-6)(H₂O)_1.25]_2n{[K(18-crown-6)]₂[Y(NCS)₆]}_n·n(NCS) (3). In mononuclear complex 1, yttrium has a coordination number 8 and forms the coordination unit YO₅N₃. Complexes 1 are linked by hydrogen bonds to form a framework. The crystal structure of 2 contains the centrosymmetric ensembles [Y(H₂O)₄(NCS)₃]₂(18-crown-6)₃ formed via hydrogen bonds. In the crystal structure of 3, the [Y(NCS)₆]³⁻ anions and the [K(18-crown-6)]⁺ cations form one-dimensional polymeric chains (-Y-NCS-K-)_n. The thermal behavior of compounds 1 and 2 was investigated. It was shown that the supramolecular assembly has an effect on the temperature range for the removal of coordinated water molecules from the thiocyanate complex. The oxidative decomposition of the acido ligands in 1 and 2 occurs in a similar way to give Y₂O₂SO₄ as the final product (700 °С).     

Ferrocene bridged and substituted tetramethylcyclopentadienyl (or indenyl) carbonyl complexes of iron, ruthenium, and molybdenum

Reactions of ferrocene bridged and substituted tetramethylcyclopentadiene ligands 1,1′-Fc(C₅Me₄H)₂ (1) (Fc = 1,1′-ferrocenediyl) and (C₅H₅FeC₅H₄)C₅Me₄H (5) with Ru₃(CO)₁₂, Fe(CO)₅, and Mo(CO)₃(CH₃CN)₃ in refluxing xylene gave the corresponding trinuclear and tetranuclear complexes Fc[(C₅Me₄)M(CO)]₂(μ-CO)]₂ [M = Ru (2), Fe (3)], Fc[(C₅Me₄)Mo(CO)₃]₂ (4) and [(C₅H₅ FeC₅H₄)C₅Me₄M(CO)]₂(μ-CO)₂ [M = Ru (6), Fe (7)], [(C₅H₅FeC₅H₄)C₅Me₄Mo(CO)₃]₂ (8). Reactions of (3-indenyl)ferrocene (9) with Ru₃(CO)₁₂ or Fe(CO)₅ in refluxing xylene or heptane, also gave the corresponding tetranuclear metal complexes [(C₅H₅FeC₅H₄)C₉H₆M(CO)]₂(μ-CO)₂ [M = Ru (10), Fe (11)]. The molecular structures of 2 and 3 were determined by X-ray diffraction analysis.     

Synthesis and properties of new Mo(II) complexes with N-heterocyclic and ferrocenyl ligands

New Mo(II) complexes with 2,2′-dipyridylamine (L1), [Mo(CH₃CN)(η³-C₃H₅)(CO)₂(L1)]OTf (C1a) and [{MoBr(η³-C₃H₅)(CO)₂(L1)}₂(4,4′-bipy)](PF₆)₂ (C1b), with {[bis(2-pyridyl)amino]carbonyl}ferrocene (L2), [MoBr(η³-C₃H₅)(CO)₂(L2)] (C2), and with the new ligand N,N-bis(ferrocenecarbonyl)-2-aminopyridine (L3), [MoBr(η³-C₃H₅)(CO)₂(L3)] (C3), were prepared and characterized by FTIR and ¹H and ¹³C NMR spectroscopy. C1a, C1b, L3, and C2 were also structurally characterized by single crystal X-ray diffraction. The Mo(II) coordination sphere in all complexes features the facial arrangement of allyl and carbonyl ligands, with the axial isomer present in C1a and C2, and the equatorial in the binuclear C1b. In both C1a and C1b complexes, the L1 ligand is bonded to Mo(II) through the nitrogen atoms and the NH group is involved in hydrogen bonds. The X-ray single crystal structure of C2 shows that L2 is coordinated in a κ²-N,N-bidentate chelating fashion. Complex C3 was characterized as [MoBr(η³-C₃H₅)(CO)₂(L3)] with L3 acting as a κ²-N,O-bidentate ligand, based on the spectroscopic data, complemented by DFT calculations.The electrochemical behavior of the monoferrocenyl and diferrocenyl ligands L2 and L3 has been studied together with that of their Mo(II) complexes C2 and C3. As much as possible, the nature of the different redox changes has been confirmed by spectrophotometric measurements. The nature of the frontier orbitals, namely the localization of the HOMO in Mo for both in C2 and C3, was determined by DFT studies.     

Mono- and bimetallic platinum(II) and palladium(II) complexes containing fluorinated benzothiolates

The new mononuclear palladium(II) and platinum(II) [M(p-SC₆F₄(CF₃))₂(dppe)] complexes M = Pd 1a, Pt 2a; [M(o-SC₆H₄(CF₃))₂(dppe)] M = Pd 1d, Pt 2d as well as the previously known [M(SC₆F₅)₂(dppe)] M = Pd 1b, Pt 2b and [M(p-SC₆HF₄)₂(dppe)] M = Pd 1c, Pt 2c, have been used as metalloligands for the preparation of the heteroleptic bimetallic complexes [M₂(μ-SRf)₂(dppe)₂](SO₃CF₃)₂ M = Pd, Rf = p-C₆F₄(CF₃) 3a, C₆F₅3b, p-C₆HF₄3c, o-C₆H₄(CF₃) 3d; M = Pt, Rf = p-C₆F₄(CF₃) 4a, C₆F₅4b, p-C₆HF₄4c and o-C₆H₄(CF₃) 4d. Variable temperature ¹⁹F NMR experiments show that the fluorothiolate bridged bimetallic compounds are fluxional in solution whereas mononuclear complexes are not. The solid state X-ray diffraction structures of [Pd(p-SC₆HF₄)₂(dppe)] (1c), [Pt(SC₆F₅)₂(dppe)] (2b) and [Pt(o-SC₆H₄(CF₃))₂(dppe)] (2d) show square-planar coordination around the metal centers. The solid state molecular structure of the compound [Pt₂(μ-o-SC₆H₄(CF₃))₂(dppe)₂](SO₃CF₃)₂ (4d), exhibit a planar [Pt₂(μ-S)₂] ring with the sulfur substituents in an anti configuration.     

Dppm-substituted ruthenium clusters with capping sulfido and selenido ligands derived from thiourea, tetramethylthiourea and elemental selenium

Treatment of [Ru₃(CO)₁₀(μ-dppm)] (4) [dppm = bis(diphenylphosphido)methane] with tetramethylthiourea at 66 °C gave the previously reported dihydrido triruthenium cluster [Ru₃(μ-H)₂(μ₃-S)(CO)₇(μ-dppm)] (5) and the new compounds [Ru₃(μ₃-S)₂(CO)₇(μ-dppm)] (6), [Ru₃(μ₃-S)(CO)₇(μ₃-CO)(μ-dppm)] (7) and [Ru₃(μ₃-S){η¹-C(NMe₂)₂}(CO)₆(μ₃-CO)(μ-dppm)] (8) in 6%, 10%, 32% and 9% yields, respectively. Treatment of 4 with thiourea at the same temperature gave 5 and 7 in 30% and 10% yields, respectively. Compound 7 reacts further with tetramethylthiourea at 66 °C to yield 6 (30%) and a new compound [Ru₃(μ₃-S)₂{η¹-C(NMe₂)₂}(CO)₆(μ-dppm)] (9) (8%). Thermolysis of 8 in refluxing THF yields 7 in 55% yield. The reaction of 4 with selenium at 66 °C yields the new compounds [Ru₃(μ₃-Se)(CO)₇(μ₃-CO)(μ-dppm)] (10) and [Ru₃(μ₃-Se)(μ₃-η³-PhPCH₂PPh(C₆H₄)}(CO)₆(μ-CO)] (11) and the known compounds [Ru₃(μ-H)₂(μ₃-Se)(CO)₇(μ-dppm)] (12) and [Ru₄(μ₃-Se)₄(CO)₁₀(μ-dppm)] (13) in 29%, 5%, 2% and 5% yields, respectively. Treatment of 10 with tetramethylthiourea at 66 °C gives the mixed sulfur-selenium compounds [Ru₃(μ₃-S)(μ₃-Se)(CO)₇(μ-dppm)] (14) and [Ru₃(μ₃-S)(μ₃-Se){η¹-C(NMe₂)₂}(CO)₆(μ-dppm)] (15) in 38% and 10% yields, respectively. The single-crystal XRD structures of 6, 7, 8, 10, 14 and 15 are reported.     

Synthesis and characterization of triosmium and triruthenium pyrene clusters

The reaction between 1-pyrenecarboxaldehyde (C₁₆H₉CHO) and the labile triosmium cluster [Os₃(CO)₁₀(CH₃CN)₂] gives rise to the formation of two new compounds by competitive oxidative addition between the aldehydic group and an arene C-H bond, to afford the acyl complex [Os₃(CO)₁₀(μ-H)(μ-COC₁₆H₉)] (1) and the compound [Os₃(CO)₁₀(μ-H) (C₁₆H₈CHO)] (2), respectively. Thermolysis of [Os₃(CO)₁₀(μ-H)(μ-C₁₆H₉CO)] (1) in n-octane affords two new complexes in good yields, [Os₃(CO)₉(μ-H)₂(μ-COC₁₆H₈)] (3) and the pyryne complex [Os₃(CO)₉(μ-H)₂(μ₃-η¹:η¹:η²-C₁₆H₈)] (4).In contrast, when 1-pyrenecarboxaldehyde reacts with [Ru₃(CO)₁₂] only one product is obtained, [Ru₃(CO)₉(μ-H)₂(μ₃-η¹:η¹:η²-C₁₆H₈)] (5), a nonacarbonyl cluster bearing a pyrene ligand. All compounds were characterized by analytical and spectroscopic data, and crystal structures for 1, 2, 4 and 5 were obtained.     

Orthopalladation of phosphorus ylides in endo position with bidentate ligands

The ortho-metallated complexes [Pd₂{κ²(C,C)-C₆H₄(PPh₂CHC(O)C₆H₅R}₂(μ-Cl)₂] (R = Ph (1a), NO₂ (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph₃PCHC(O)C₆H₅R, (R = Ph, NO₂, Br) and Pd(OAc)₂ in MeOH, followed by an excess of NaCl. The dinuclear complexes (1a-1c) react with silver trifluoromethylsulfonate and bidentate ligands [L = bipy (2,2′-bipyridine), phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), dppp (bis(diphenylphosphino)propane)] giving the mononuclear stabilized orthopalladated complexes in endo position [Pd{κ²(C,C)-C₆H₄(PPh₂CHC(O)R}L](OTf) [R = Ph, L = phen (2a), bipy (3a), dppe (4a), dppp (5a); R = NO₂, L = phen (2b), bipy (3b), dppe (4b), dppp (5b); R = Br, L = phen (2c), bipy (3c), dppe (4c), dppp (5c); OTf = trifluoromethylsulfonate anion]. Orthometalation and ylidic C-coordination are demonstrated by an X-ray diffraction study of 2c and 3c. In the structures, the palladium atom shows a slightly distorted square-planar coordination geometry.     

Versatility in the mode of coordination {(N), (N,O), (C,N) or (C,N,O)} of [(η-C5H5)Fe{(η-C5H4)-CHN-(C6H4-2OH)}] to palladium(II)

The study of the reactivity of the ferrocenyliminoalcohol [(η⁵-C₅H₅)Fe{(η⁵-C₅H₄)-CHN-(C₆H₄-2OH)}] (1b) with Na₂[PdCl₄] or Pd(OAc)₂ has allowed the isolation and characterization of the heterotrimetallic complexes: trans-[Pd{(η⁵-C₅H₅)Fe[(η⁵-C₅H₄)-CHN-(C₆H₄-2OH)]}₂Cl₂] (2b), [Pd{[(η⁵-C₅H₃)-CHN-(C₆H₄-2O)]Fe(η⁵-C₅H₅)}{(η⁵-C₅H₅)Fe[(η⁵-C₅H₄)-CHN-(C₆H₄-2OH)]}] (3b) and trans-[Pd{(η⁵-C₅H₅)Fe[(η⁵-C₅H₄)-CHN-(C₆H₄-2O)]}₂] (4b). Ligand 1b acts as a (N) (in 2b) or a (N,O)⁻ (in 4b) ligand; while in 3b the two units of the iminoalcohol exhibit simultaneously different modes of binding {(N) and [C(sp², ferrocene),N,O]²⁻}. The crystal structures of 2b · 3H₂O and 3b · 1/2CHCl₃ are also reported and confirm the mode of binding of the ligand in these compounds. The relative importance of the factors affecting the preferential formation of products (2b-4b) is also discussed. The study of the reactivity of 3b with PPh₃ has enabled the obtention of the cyclopalladated complexes [Pd{[(η⁵-C₅H₃)-CHN-(C₆H₄-2O)]Fe(η⁵- C₅H₅)}(PPh₃)] (6b) and [Pd{[(η⁵-C₅H₃)-CHN-(C₆H₄-2OH)]Fe(η⁵-C₅H₅)}Cl(PPh₃)] (7b), in which 1b behaves as a [C(sp², ferrocene),N,O]²⁻ (in 6b) or [C(sp², ferrocene),N]⁻ (in 7b) ligand. Treatment of 3b with MeO₂C-CC-CO₂Me produces [Pd{[(MeO₂C-CC-CO₂Me)₂(η⁵-C₅H₃)-CHN-(C₆H₄-2O)]Fe(η⁵-C₅H₅)}] (8b), that arises from the bis(insertion) of the alkyne into the σ[Pd-C(sp², ferrocene)] bond. The comparison of the results obtained for 1b and [C₆H₅-CHN-(C₆H₄-2OH)] (1a) has allowed to establish the influence of the substituents on the imine carbon on their reactivity in front of palladium(II) as well as on the lability of the Pd-ligands bond. ⁵⁷Fe Mössbauer studies of 2b-4b and 6b provide conclusive evidence of the effect induced by the mode of binding of 1b on the environment of the iron(II).     

New N-heterocyclic carbene silver(I) and mercury(II) 2-D supramolecular layers by the π-π stacking interactions

The precursor 1-(9-anthracenylmethyl)-3-alkylbenzimidazolium chlorides (1a, alkyl = C₄H₉, 1b, alkyl = C₆H₁₃) and their three new NHC silver(I) and mercury(II) complexes {[1-(9-anthracylmethyl)-3-alkylbimy]MCl}₂ (2a, alkyl = C₄H₉, M = Ag; 2b, alkyl = C₆H₁₃, M = Ag; 3a, alkyl = C₄H₉, M = Hg; bimy = benzimidazol-2-ylidene) have been prepared and characterized. The crystal structures of 2a, 2b and 3a showed that 2-D supramolecular layers are formed by both benzimidazole ring head to tail π-π stacking interactions and anthracene ring face-to-face π-π stacking interactions.     

Biferrocene NCN pincer metal-d complexes: Synthesis, reaction chemistry and cyclovoltammetric studies

The synthesis of biferrocene-bridged NCN pincer palladium and platinum complexes (NCN = [1-C₆H₂(CH₂NMe₂)₂-3,5]⁻) is discussed. Sonogashira cross-coupling of [(η⁵-C₅H₄)Fe(η⁵-C₅H₄CCH)]₂ (1) with I-1-NCN-4-X (2a, X = H; 2b, X = Br) produces [(η⁵-C₅H₄)Fe(η⁵-C₅H₄CC-1-NCN-4-X)]₂ (3a, X = H; 3b, X = Br). Homobimetallic 3b further reacts with [Pd₂(dba)₃ · CHCl₃] (4) or [Pt(tol)₂(SEt₂)]₂ (5) (dba = dibenzylidene acetone, tol = 4-tolyl), respectively, to give tetrametallic [(η⁵-C₅H₄)Fe(η⁵-C₅H₄CC-4-NCN-1-MBr)]₂ (6, M = Pd; 7, M = Pt) in which NCN-MBr fragments are connected by a biferrocene unit. Cyclovoltammetric studies show that the ferrocene moieties can independently be oxidized. The difference of the Fe(II)/Fe(III) redox couples amounts to ca. 300 mV and is not affected by the nature of the NCN pincer metal moities.