New Insights into the Stoichiometric and Catalytic Reactivity of Unsaturated Pd 3 (dppm) 3 CO n + Clusters ( n = 0, 1) Towards Halocarbons – First Evidence for Inorganic By‐Products

The title clusters, Pd 3 (dppm) 3 (CO) + and Pd 3 (dppm) 3 (CO) 0 can be electrochemically generated from the 1- and 2-electron reductions, respectively, of the Pd 3 (dppm) 3 (CO) 2 + cluster [dppm = bis(diphenylphosphanyl)methane; Pd 3 2 + ]. Pd 3 + reacts in a stoichiometric ratio with methyl iodide, MeI, and benzyl bromide, BzBr, in THF to provide the corresponding Pd 3 (X) + adducts (X = I, Br respectively) as inorganic products. Other products are Bz 2 and PhMe for BzBr but, for MeI, no organic product was observed (since they are too volatile). In the presence of the same substrates, Pd 3 0 also reacts in a stoichiometric ratio to form the same organics and the Pd 3 -(X) + adducts (X …

The first unpaired electron placed inside a C3-symmetry P-chirogenic cluster

The Pd(3)(dppm*)(3)(CO)(n+) enantiomers (n = 2 (2), 1 (3)) were prepared either from (R,R)- or (S,S)-P-chirogenic bis(phenyl-m-xylylphosphino)methane (dppm*; 1) and Pd(OAc)(2) in the presence of CF(3)CO(2)H, CO and water (n = 2), and then by reductive electrolysis (n = 1). The stable enantiomeric [Pd(3)((S,S)-dppm*)(3)(CO)](+)˙ (3), is the first C(3)-symmetry radical-cation M-M bonded cluster, therefore the odd electron is delocalized onto the Pd(3) frame within this symmetry. The novel chiral species have been characterized by circular dichroism (CD) of both enantiomers of the Pd(3)(dppm*)(3)(CO)(2+) clusters (2) and by EPR spectroscopy for the Pd(3)((S,S)-dppm*)(3)(CO)(+)˙ paramagnetic co…

Exploring the redox reactivity of magnesium porphine. Insight into the origins of electropolymerisation.

International audience; Magnesium(II) porphine, MgP (1), was synthesised according to the Lindsey procedure allowing to isolate and crystallise 1-formyldipyrromethane (2) as a synthetic intermediate. Unprecedented Xray diffraction studies revealed multiple intermolecular associations in the crystal between neighbouring units of 2, namely hydrogen bond and CH … π. The electrochemical behaviour of 1 was examined by means of cyclic voltammetry. In oxydation, two well-defined and distinct steps are assigned to macrocycle concerned electron transfers yielding initially the π-cation radical and π dication, respectively. The highly reactive dication condenses neutral magnesium porphine to form a d…

Thermodynamic and kinetic control over the oxidation mechanism of the natural vanadyl porphyrin series (DPEP)VO in methylene chloride: electrogeneration of an unusual dicationic species [(DPEP)VO]22+

The electrochemical behavior of the natural (DPEP)VO series (where DPEP is the dianion deoxophylloerythroetioporphyrinate) is studied in methylene chloride. The investigated compounds, which were extracted from oil shales of Tarfaya (Morocco), exhibit a typical electrochemical behavior as compared to that of related synthetic vanadyl porphyrins. The electro-oxidation of (DPEP)VO is characterized by a splitting of the peaks when carried out at a glassy carbon electrode. This can be explained by two possible paths (CE and EC mechanisms) which are characterized by a “square diagram” where the chemical step, C, corresponds to a dimerization (radical–radical or substrate–substrate reaction). The…

The Pd3(dppm)3(CO)2+ Cluster: An Efficient Electrochemically Assisted Lewis Acid Catalyst for the Fluorination and Alcoholysis of Acyl Chlorides.

The dicationic palladium cluster Pd3(dppm)3(CO)2+ (dppm = bis(diphenylphosphino)methane) reacts with acid chlorides RCOCl (R = n-C6H13, t-Bu, Ph) to afford quantitatively the chloride adduct Pd3(dppm)3(CO)(Cl)+ and the acyl cation RCO+ as the organic counterpart. The dicationic reactive cluster can be reformed by electrolyzing the chloride complex with a copper anode leaving CuCl as a byproduct. The combination of these two reactions provides an electrocatalytic way to form the acylium from the acid chloride. Indeed, in CH2Cl2, 0.2 M NBu4PF6, or NBu4BF4, the electrolysis of the acid chloride in the presence of a catalytic amount of the cluster (1%) gives in good yields the acid fluoride RCO…

Thermal and electrochemically assisted Pd-Cl bond cleavage in the d9-d9 Pd2dppm2Cl2 complex by Pd3 dppm3COn+ clusters (n = 2, 1, 0).

A new aspect of reactivity of the cluster [Pd3(dppm)3(micro3-CO)]n+, ([Pd3]n+, n = 2, 1, 0) with the low-valent metal-metal-bonded Pd2(dppm)2Cl2 dimer (Pd2Cl2) was observed using electrochemical techniques. The direct reaction between [Pd3]2+ and Pd2Cl2 in THF at room temperature leads to the known [Pd3(dppm)3(micro3-CO)(Cl)]+ ([Pd3(Cl)]+) adduct and the monocationic species Pd2(dppm)2Cl+ (very likely as Pd2(dppm)2(Cl)(THF)+, [Pd2Cl]+) as unambiguously demonstrated by UV-vis and 31P NMR spectroscopy. In this case, [Pd3]2+ acts as a strong Lewis acid toward the labile Cl- ion, which weakly dissociates from Pd2Cl2 (i.e., dissociative mechanism). Host-guest interactions between [Pd3]2+ and Pd2…

Investigation into the reactivity of oxoniobocene complexes [Cp*2Nb(O)R] (Cp*=η5-C5Me5; R=H, OH, OMe) towards heterocumulenes: formation of carbamato and thiocarbamato complexes and catalytic cyclization of PhNCO

Abstract The reaction of [Cp*2NbCl2] (Cp*=η5-C5Me5) with KOH or Ba(OH)2·8H2O in THF was investigated under slightly modified conditions. In addition to the known complex [Cp*2Nb(O)H] (1), the new compound [Cp*2Nb(O)OH] (2) was formed. The reaction of 2 with PhNCS gave yellow [Cp*2Nb(O){SC(O)NHPh}] (3), while PhNCO formed yellow [Cp*2Nb(O){OC(O)NHPh}] (4). Complexes 3 and 4 were analytically and spectroscopically characterized. X-ray diffraction analyses of both compounds show that they contain either η1-S-thiocarbamato (3) or η1-O-carbamato ligand (4) along with a terminal NbO group. The reaction of 1 with one equivalent of PhNCO mainly gave orange [Cp*2NbH{OC(O)NPh}] (5) along with so…

Generation, Characterization, and Electrochemical Behavior of the Palladium-Hydride Cluster [Pd3(dppm)3(3-CO)(3-H)]+ (dppm=Bis(diphenylphosphinomethane)

Addition of formate on the dicationic cluster [Pd(3)(dppm)(3)(mu(3)-CO)](2+) (dppm=bis(diphenylphosphinomethane) affords quantitatively the hydride cluster [Pd(3)(dppm)(3)(mu(3)-CO)(mu(3)-H)](+). This new palladium-hydride cluster has been characterised by (1)H NMR, (31)P NMR and UV/Vis spectroscopy and MALDI-TOF mass spectrometry. The unambiguous identification of the capping hydride was made from (2)H NMR spectroscopy by using DCO(2) (-) as starting material. The mechanism of the hydride complex formation was investigated by UV/Vis stopped-flow methods. The kinetic data are consistent with a two-step process involving: 1) host-guest interactions between HCO(2) (-) and [Pd(3)(dppm)(3)(mu(3…

Syntheses and reactivity of oxo niobocene complexes Cp*2Nb(O)X (X=H, OCH3) and crystal structures of [Cp*2Nb(OH)F]BF4 and Cp*2Nb(O)OC(O)H (Cp*=η5-C5Me5)

Abstract Reaction of Cp*2NbCl2 (Cp*=η5-C5Me5) with KOH or Ba(OH)2·8H2O in THF forms the complexes Cp*2Nb(O)X (X=Cl: 2, H: 3). The ratio of 2 and 3 depends on the stoichiometry. If NaOMe is added or MeOH in solution Cp*2Nb(O)OMe 4 is formed in good yields. Reactivity studies with 3 and 4 show that the NbO as well as the Nb–X unit behave as chemically active sites. Protonation of 3 or 4 with HBF4 is followed by an attack of fluoride (from BF4− anion) to give [Cp*2Nb(OH)F]BF4 6 and [Cp*2NbF2]BF4 7. In contrast the reaction of 3 or 4 with HCO2H results in an exchange of X− by formate to give Cp*2Nb(O)OC(O)H 8. The crystal structures of 6 and 8 are reported. Electrochemical investigations of…

Electron‐Sponge Behavior, Reactivity and Electronic Structures of Cobalt‐Centered Cubic Co 9 Te 6 (CO) 8 Clusters (Eur. J. Inorg. Chem. 12/2008)

The cover picture shows an organometallic electron sponge and an elephant-ear sponge in the background (photo by F. and J. Burek, National Marine Sanctuaries). The electronic flexibility of the cobalt-centered cubic [Co9Te6(CO)8]n cluster ([3]n) in the central circle is expressed by differently charged states (n = 1+ to 5–). Starting from the upper left corner of our graphic in a clockwise direction, neutral [Co9Te6(CO)4(PPh3)4], structurally diverse networks of [Ph3PNPPh3][3] and [Ph3PNPPh3]2[3] salts and the core of the [Co9Te3{ν5-Cp′2Nb(CO)Te}3(CO)8] cluster as a pseudo-protonated representative of the [3]3– anion are shown. Details of the structural, electrochemical and theoretical prop…

Synthesis, crystallographic and electrochemical study of ethynyl[2.2]paracyclophane derived cobalt metallatetrahedranes

Abstract A series of alkynyl cobalt complexes [Co2(μ-η2-HCC–PCP)(CO)6−nLn] [n = 0 (2); n = 2, L2 = dppa (3), dppm (4), dcpm (6), 2 P(OPh)3 (7)] and [Co2(CO)4L2]2(μ-η2:μ-η2-HCC–PCP–CCH)] (L2 = dppm (8), dcpm (9); (PCP = [2.2]paracyclophane) has been prepared and characterized. The molecular structures of 3 and 4, as well as that of [Co2(CO)4(μ-CO)2(μ2-dcpm)] (5), have been determined by X-ray diffraction. Electrochemical studies (Cyclic Voltammetry, Rotating Disk Electrode) and luminescence spectroscopy have been used to evaluate the extent of the electronic communication through the PCP motif using the “Co2C2” centres as a probe. No electronic coupling between the Co2(CO)n centres via the b…

The Pd3(dppm)3(CO)n clusters (n = 1-,2-); rare cases of anionic palladium species.

Two novel anionic palladium clusters, Pd(3)(dppm)(3)(CO)(n-) (Pd(3)(n); n = 1-,2-) were electrochemically generated from the dicationic cluster Pd(3)(2+) in 0.2 M THF/Bu(4)NPF(6)via two first consecutive reversible 1-electron reductions (Pd(3)(2+) + 1 e(-) ⇌ Pd(3)(+), -0.210, and Pd(3)(+) + 1 e(-) ⇌ Pd(3)(0), -0.470 V vs. SCE) followed by two others at -2.350 (Pd(3)(0) + 1 e(-) ⇌ Pd(3)(1-), reversible) and at -2.690 V vs. SCE (Pd(3)(1-) + 1 e(-) ⇌ Pd(3)(2-), irreversible). The chemical stability and instability, respectively, of the Pd(3)(dppm)(3)(CO)(n-) clusters (Pd(3)(n); n = 1-,2-) at the time scale of the electrochemical experiments were addressed by DFT computations. Indeed, geometry …

Structural Rearrangements in Triple-Decker-Like Complexes with Mixed Group 15/16 Ligands: Synthesis and Characterization of the Redox Couple [Cp2*Fe2As2Se2]/[Cp2*Fe2As2Se2]+ (Cp*=C5Me5)

The reaction of As4Se4 with stoichiometric amounts of [Cp*Fe2(CO)4] (Cp* = C5Me5) in boiling toluene forms [Cp2*Fe2As2Se2] (1) in good yield. X-ray crystallography shows 1 to have a triple-decker structure which comprises a tetraatomic mu,eta4:4-As2Se2 ligand. Density functional theory (DFT) and extended Huckel molecular orbital (EHMO) calculations confirm that the As2Se2 ligand behaves as a four-electron pi donor. Oxidation of 1 with equimolar amounts of [(C5H5)2Fe]PF6, Br2 and I2, respectively, gave compounds 2-4. According to X-ray crystallographic investigations that were carried out on 2 and 4, the oxidation state has a considerable influence on the structure of the Fe2As2Se2 core: sig…

Evidence of intramolecular electron transfer between two metallic atoms in a bimetallic complex by electrochemical methods

The electrochemical properties of the monomeric complex [(η5-C5H5)(μ-η5:η1-C5H4(CH2)2P(C6H5)2TiCl2] 1 and the heterobimetallic complex [(η5-C5H5)(μ-η5:η1-C5H4(CH2)2P(C6H5)2TiCl2][RuCl2(C6H4(CH3)(C3H7))] 2 have been studied by cyclic voltammetry, controlled potential electrolysis and rotating disk electrode voltammetry. An unexpected electron transfer between the two heterobimetallic atoms has been observed. This transfer takes place via an intramolecular interaction, hence via a chloride bridge. Electrochemical simulation has been carried out to verify experimental results and to obtain the kinetic constant of the proposed square scheme.

Electrochemical and chemical reduction of niobocene dichlorides in the presence of carbon dioxide

Abstract The chemical and electrochemical reduction of the niobocene dichlorides [Nb(η5-C5H4SiMe3)2Cl2]1, [Nb(η5-C5Me5)2Cl2] 2 and [Nb(η5-C5Me4Et)2Cl2] 3, in the presence of carbon dioxide has been investigated. Formation of compounds of the type [Cp2Nb(CO2)] and [Cp2(∗)NbCl(CO2))] 1 has been established by means of IR, ESR and/or NMR spectroscopy. They contain a labile η2-CO2. The order of stability increases with the degree of substitution the Cp. Less stable intermediates in the reduction of the system [Cp2NbCl2]/CO2 are discussed on the basis of cyclovoltammetric and coulometric data.

On the mechanistic behavior of highly efficient palladium-tetraphosphine catalytic systems for cross-coupling reactions: first spectroscopic and electrochemical studies of oxidative addition on Pd(0)/multidentate ferrocenylpolyphosphine complexes

Electrochemical studies carried out in conjunction with 31P NMR spectroscopy on the palladium(II)/palladium(0) halogeno complexes of the tetraphosphine 1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di...

Synthesis, reactivity and structures of ruthenium carbonyl clusters with telluride and hydride ligands

The reaction of [Cp* 2 Nb(Te 2 H)] ( 1 ) (Cp*=C 5 Me 5 ) with [Ru 3 (CO) 12 ] in boiling toluene gave [Ru 3 (μ 2 -H) 2 (CO) 9 (μ 3 -Te)] ( 2 ), [Ru 6 (μ 3 -H)(CO) 15 (μ 3 -Te) 3 ][Cp* 2 Nb(CO) 2 ] ( 3 ) and [Ru 5 (μ 2 -H)(CO) 14 (μ 4 -Te)][Cp* 2 Nb(CO) 2 ] ( 4 ) along with already known [Ru 4 (CO) 11 (μ 4 -Te) 2 ] ( 5 ). Complexes 2 – 4 were analytically and spectroscopically characterized and X-ray diffraction analyses of 3 and 4 were carried out. The anion of 3 is built up of a triangular hexametallic core of C 3 v symmetry, in which the central Ru 3 triangle, being bridged by a μ 3 -H ligand, is composed of three corner-linked Ru 3 Te tetrahedra. The main structural feature of the anion …

Electron-Sponge Behavior and Electronic Structures in Cobalt-Centered Pentagonal Prismatic Co11Te7(CO)10 and Co11Te5(CO)15 Cluster Anions

The novel cluster anion [Co11Te5(CO)15]- ([3]-) has been isolated and structurally characterized as part of the salt [Cp*2Nb(CO)2][3] (Cp* = C5Me5). The cobalt-centered Co10 pentagonal prism is surrounded by a shell of two μ5-Te, three μ4-Te ligands, and 15 CO groups in terminal, symmetrical, and σ-semibridging bonding modes. The hybrid carbonyl-telluride character of the ligand shell is reflected in the solid state by a one-dimensional assembly of polyhedral prisms along a backbone of [Cp*2Nb(CO)2]+ cations. Electrochemical studies reveal the presence of four redox couples of [3]n (n = −1 to −5). The electronic structures of various metal-centered and empty pentagonal-prismatic (PP) M10 cl…

Preparative and Electrochemical Investigations on the Electron Sponge Behavior of Cobalt Telluride Clusters: CO Substitution in[Co11Te7(CO)10]n− Ions (n=1, 2) by PMe2Ph and Crystal Structure of[Co11Te7(CO)5(PMe2Ph)5]

The reaction of the cluster salts [Cp* 2 Nb(CO) 2 ] n [Co 1 1 Te 7 (CO) 1 0 ] (Cp* = C 5 Me 5 ; n = 1, 2) with excess PMe 2 Ph gave the neutral, dark brown clusters [Co 1 1 Te 7 (CO) 6 (PMe 2 Ph) 4 ] (5) and [Co 1 1 Te 7 (CO) 5 (PMe 2 Ph) 5 ] (6) with 147 metal valence electrons. The new compounds were characterized by IR spectroscopy, elemental analyses, and mass spectrometry. The molecular structure of 6 was determined by X+ray crystallography. Like its precursor anion, it consists of a pentagonal-prismatic [Co 1 1 Te 7 ] core, but with a ligand sphere composed of five CO and five PMe 2 Ph ligands. Detailed electrochemical studies of both reactions reveal that a stepwise substitution of C…

Syntheses, Properties and Structures of [{(C 5 Me 5 ) 2 Nb} 2 NiTe 4 ] and [( t BuC 5 H 4 Nb) 2 Ni 5 Te 7 (Ph 2 PCH 2 PPh 2 ) 2 ]: The Quest for Tetratelluronickelate Clusters

The reaction of [Ni(COD) 2 ] with [Cp* 2 NbTe 2 H] (1; Cp * = η-C 5 Me 5 ) in the presence of Ph 2 PCH 2 PPh 2 (dppm) in boiling toluene gives black-violet [(Cp * 2 Nb) 2 NiTe 4 ] (3). If [Cp' 2 NbTe 2 H] (2; Cp' = tBuC 5 H 4 ) is used under similar conditions dark-brown [(Cp'Nb)2Ni5Te7(dppm)2] (4) is formed. The structures of 3 and 4 have been determined crystallographically. Complex 3 contains a severely distorted NiTe 4 tetrahedron to which two niobocene groups are coordinated. Density functional analysis of the electronic structure of the NiTe 4 building block shows that it is best described as an [Ni(η 2 -Te 2 ) 2 ] 2- fragment. The structure of 4 reveals the presence of two Ni 5 and T…

Bis(η-tert-butylcyclopentadienyl)hydridoniobium Ditelluride, a Convenient Reagent for the Synthesis of Polynuclear Metal Telluride Complexes

Fragmentation reactions of realgar caused by early transition metal hydrides

Abstract The reaction of realgar with [Cp′2MH3] in boiling toluene gave [Cp′2M2As2S6] (Cp′ = t-BuC5H4; M = Nb: 1; Ta: 2), while [Cp2WH2] (Cp = C5H5) reacted with As4S4 to give [Cp2W(H)(η1-As5S2)] (6). The structures were determined by X-ray crystallography. Compounds 1 and 2 are dimers in which two Cp′M units are symmetrically bridged by a μ,η2:2-AsS3 ligand, a sulfide ligand and a heteroallylic μ,η2:2-AsS2 ligand. The structure of 6 belongs to the type of bent metallocenes in which tungsten is surrounded tetrahedrally by two Cp ligands, a crystallographically found hydride atom and the new As5S2 cage. The reaction of 1 with W(CO)5THF gave [Cp′2Nb2As2S6·W(CO)5] (3) and [Cp′2Nb2As2S6W(CO)3·W…

Metal Telluride Clusters Composed of Niobocene Carbonyl, Telluride, and Cobalt Carbonyl Units: Syntheses, Structures, and Reactivity

Abstract: The reaction of [Cp#2NbTe2H] (1#; Cp# = Cp* (C5Me5) or Cp(x) (C5Me4Et)) with two equivalents of [Co2(CO)8] gives a series of cobalt carbonyl telluride clusters that contain different types of niobocene carbonyl fragments. At 0 degrees C, [Cp#2NbTe2CO3(CO)7] (2#) and [Co4Te2(CO)10] (3) are formed which disappear at higher temperatures: in boiling toluene a mixture of [cat2][Co9Te6(CO)8] (5#) (cat= [Cp#2Nb(CO)2]+) and [cat2][Co11Te7(CO)10] (6#) is formed along with [cat][Co(CO)4] (4#). Complexes 6# transform into [cat][Co11Te7(CO)10] (7#) upon interaction with HPF6 or wet SiO2. The molecular structures of 2(Cp(x)), 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) have been determined by X-ray cr…

Optical, Electrochemical, and Catalytic Properties of the Unsaturated Host Pd3(dppm)3(CO)2+and Pd4(dppm)4(H)2+2Clusters: An Overview

This paper presents an overview of the optical, photophysical, and photochemical properties including UV-visible and luminescence spectra in solution at 298 and 77 K, along with electrochemical, and catalytic behavior under reduction conditions (for both thermally and electrochemically assisted systems) of the tri- and tetranuclear Pd3(dppm)3(CO)2+ and Pd4(dppm)4(H)2+ 2 clusters (dppm=bis(diphenylphosphino)methane). This review is also complemented with relevant information about their syntheses, molecular and electronic structures supported from computer modeling, EHMO and DFT calculations, and their host-guest behavior with anions and neutral molecules, in relation with their observed rea…

Investigation into the reaction of (t-BuC5H4)2Nb(η2-Te2)H with CH3Li: Hydride abstraction versus telluride methylation

Abstract The reaction of [ Cp 2 ′ Nb ( Te 2 ) H ] ( 1 ) (Cp′ =  t -BuC 5 H 4 ) with CH 3 Li in THF was examined by variable temperature 1 H NMR, ESR and mass spectroscopic means. From these methods it is evident that the diamagnetic compounds [ Cp 2 ′ NbH 2 ( TeCH 3 ) ] ( 2 ) and [ Cp 2 ′ Nb ( Te ) CH 3 ] ( 3 ) as well as the paramagnetic compound [ Cp 2 ′ Nb ( TeCH 3 ) 2 ] ( 4 ) form simultaneously. In the subsequent reaction of the intermediate solution with [Co 2 (CO) 8 ] compound 4 was consumed and the compound [ Cp 2 ′ Nb ( μ - TeCH 3 ) 2 Co(CO) 2 ] ( 5 ) formed in good yield. Complex 5 was characterized by IR and variable temperature 1 H NMR spectroscopies. Electrochemical two-electro…

Preparative, structural, and electrochemical investigations on peralkylated niobocene dichlorides and difluorides

CP(dagger)2NbCl2 (CP(dagger) = 175-C5Me4Et) (1b) was synthesized from NbCl5 and a slight excess of Cp(dagger)Li and NaBH4. Its electrochemical (2 e-, E1/2 = -1.6 V) and chemical reduction (2 equiv of Na/Hg) was studied showing that peralkylation of the Cp ligand facilitates two-electron reduction compared to less substituted CP2NbHal2 derivatives. The reduced solutions of CP*2NbCl2 (CP* = C5Me5) (1a) and of lb were shown by means of EPR spectroscopy to contain two new paramagnetic species 1A,B for which bent niobocene (A(Nb) = 100 G) and fulvene-like structures (A(Nb) = 55 G) are proposed. The high reduction potential of these species led in their reaction with HPF6 to the first stable difl…

Synthesis of μ-C2S44− Cobalt Complexes by Activation of the 1,3,4,6-tetrathiapentalene-2,5-dione, and Electrochemical Study of [(Cp*Co)2(μ-C2S4)]

The bimetallic complex [Cp(*)Co)2(μ-C2S4)] in which the two metal centres are linked by an ethylenetetrathiolate C2S44− unit, was synthesized in high yield by oxidative addition of 1,3,4,6 tetrathiapentalene-2,5-dione to [Cp(*)Co(CO)2]. The X-ray crystal structure of the intermediate product Cp*Co(dmid) (dmid2− = 4,5-disulfanyl-1,3-dithiol-2-onate) is presented. The electrochemical behaviour of the [(Cp*Co)2(μ-C2S4)] complex was studied in detail in the oxidative range. This study has shown that the nature of the product obtained after oxidation depends on the presence of complexing agent in the solution. The mechanism has been elucidated in a CH2Cl2 solution in the presence of P(OMe)3. In …

Synthesis and characterisation of [(C5Me4R)2NbS2]2M complexes (M = Fe, Co; R = Me, Et) : organometallic tetrathiometalates with niobocene ligands

Abstract Irradiation of Cp 2 ∗ Nb(η 2 S 2 )H (Cp ∗ = C 5 Me 5 ) 1a in the presence of Fe(CO) 5 gives the CO-free complex [Cp 2 ∗ NbS 2 ] 2 Fe 2a . The core of 2a contains an FeS 4 tetrahedron which is ligated by two niobocene ligands as shown by X-ray diffraction analysis. In the reaction of 1a or Cp 2 x Nb(η 2 S 2 )H (CP x = C 5 Me 4 Et) 1b with Co 2 (CO) 8 , compounds 3a and 3b of the same type are formed. Electrochemical studies of 2a and 3a,b show that they undergo three reversible 1e − steps. The oxidation of 3b exerts a considerable influence on its absorption spectrum. A qualitative EHMO analysis is in agreement with a strong delocalisation of electron density over the whole NbS 2 …

Syntheses and properties of tetrathio- and tetraseleno metalates [(C5Me4R)2NbE2]2M (E=S, Se; M=Cr, Mo; R=Me, Et) with peripheric niobocene ligands

Abstract Reactions of Cp*2Nb(η2-S2)H 1 (Cp*=C5Me5 (a), C5Me4Et (b)) and Cp*2Nb(η2-Se2H) 3 with 0.5 equivalents of M(CO)6 (M=Cr, Mo) in boiling toluene give the CO free complexes [Cp*2NbE2]2M 4–7. X-ray diffraction analyses have been carried out for the Mo complexes 5a (E=S) and 7a (E=Se) showing that the structures contain ME4 tetrahedral cores with two attached niobocene ligands thus forming a nearly linear trimetallic unit. Absorption spectra and electrochemical studies of complexes 4–7 are described. Characteristic of the novel CrSe4 chromophor are four reversible one electron redox steps. Chemical oxidation of 4a and 5a with [(C5H5)2Fe]PF6 gives the salts {[Cp*2NbS2]2M}PF6 (M=Cr, Mo) 10…

Electrochemical reduction properties of A-frame compounds and crystal structure of Pd2(dppm)2(Me)2(Br)+ dimer

Abstract Two series of A-frame complexes, [Pd2(dppm)2(R)2(μ-X)]+ (R = Me and X = Cl, Br, I, H; R = Mes and X = Br, I), were investigated by cyclic voltammetry (CV). The 2-electron reduction potentials for the first series increase from I (−1.10), Br (−1.17), Cl (−1.25) to H (−1.65 V versus SCE, in CHCl3), as well as in the second series; Br (−1.35) and I (−1.38 V versus SCE, in THF). The nature of the LUMO where the electron reduction takes place is qualitatively addressed by DFT on the corresponding model complexes [Pd2(H2PCH2PH2)2(R)2(μ-X)]+. The LUMO and (LUMO + 1) of the halide derivatives exhibit the presence of Pd d x 2 - y 2 atomic orbitals interacting in an anti-bonding fashion with…

Unexpected Reaction of the Unsaturated Cluster Host and Catalyst [Pd3(3-CO)(dppm)3]2+ with the Hydroxide Ion: Spectroscopic and Kinetic Evidence of an Inner-Sphere Mechanism

The title cluster, [Pd(3)(mu(3)-CO)(dppm)(3)](2+) (dppm=bis(diphenylphosphino)methane), reacts with one equivalent of hydroxide anions (OH(-)), from tetrabutylammonium hydroxide (Bu(4)NOH), to give the paramagnetic [Pd(3)(mu(3)-CO)(dppm)(3)](+) species. Reaction with another equivalent of OH(-) leads to the zero-valent compound [Pd(3)(mu(3)-CO)(dppm)(3)](0). From electron paramagnetic resonance analysis of the reaction medium using the spin-trap agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the 2-tetrahydrofuryl or methyl radicals, deriving from the tetrahydrofuran (THF) or dimethyl sulfoxide (DMSO) solvent, respectively, were detected. For both [Pd(3)(mu(3)-CO)(dppm)(3)](2+) and [Pd(3)(mu…

Electron-Sponge Behavior, Reactivity and Electronic Structures of Cobalt-Centered Cubic Co9Te6(CO)8 Clusters

Extended investigations of the reaction sequence [Cp′2Nb(Te2)H]/CH3Li/[Co2(CO)8] (Cp′ = tBuC5H4) led to the identification of Lin[3] {3 = [Co9Te6(CO)8]; n = 1, 2} salts through their transformation with [PPN]Cl into [PPN]n[3] (PPN = Ph3PNPPh3). These compounds form in the solid state columnar ([PPN][3]) or undulated 2D ([PPN]2[3]) supramolecular networks. Electrochemical studies of [Cp*2Nb(CO)2][3] (Cp* = C5Me5) or [Na(THF)6][3] revealed the presence of the redox couples [3]–/[3]2–/[3]3–/[3]4–/[3]5– regardless of the nature of the cation, whereas in the anodic part oxidative degradation of the cluster takes place. This behavior is in agreement with the observation that [3]– containing salts…