Unsaturated Anion Research Articles

The role of ionic liquid additives in enhancing the tribological performance of plastic-derived oils

Improper disposal of waste plastic contributes significantly to environmental pollution. A promising solution to address this issue involves converting such plastics into valuable lubricating oils. This study investigated the tribological performance of both an aromatic-lean industrial plastic oil (PO) and aromatic-rich lab-scale plastic oils (LPO) using a ball-on-disk setup. The results revealed that PO exhibited considerably higher coefficients of friction (COF) and specific wear rates compared to LPO. To enhance the lubrication performance, a bio-based ionic liquid (IL: trihexyltetradecyl phosphonium saccharinate) with an unsaturated anion was incorporated. The COF and wear rates were further reduced with an IL blend in both PO and LPO. The IL additive promoted increased film thickness, beneficial micelle formation, facilitated adsorption film formation, and provided a phosphorus-rich tribofilm. These mechanisms collectively contributed to the notable improvement in tribological performance. Overall, this research demonstrates the potential of IL additives to enhance the tribological performance of both PO and LPO, thereby mitigating waste plastic pollution, and fostering a sustainable future.

Titan's ionospheric chemistry, fullerenes, oxygen, galactic cosmic rays and the formation of exobiological molecules on and within its surfaces and lakes

We discuss the formation of aerosols within Titan's thermosphere-ionosphere and the different chemical pathways. Negative ion measurements by the Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS) give evidence for formation of unsaturated anion carbon chains, while positive ion measurements of the Cassini Ion Neutral Mass Spectrometer (INMS) indicate formation of more aromatic cation hydrocarbons. There is presently no direct observational evidence for large neutral molecule growth in Titan's thermosphere-ionosphere. The hydrocarbon cations are expected to form Polycyclic Aromatic Hydrocarbons (PAH), those with the addition of nitrogen being called PAHNs. We theorize anion carbon chains can eventually become long enough to fold into fullerene C60,70 carbon shells, of various charge states. Based on laboratory data the fullerenes can trap incoming O+ magnetospheric ions that have relatively high energy collisions with the fullerenes and, once trapped, protect the oxygen atom from Titan's reducing thermosphere-ionosphere. The fullerenes can form into larger onion fullerenes and condense into larger embryo aerosols (i.e., m/q > 10,000 amu/q anions as observed by CAPS/ELS) eventually falling onto Titan's surface and precipitating to the bottom of its hydrocarbon lakes. Molecule production composed of H, C, N is known to occur in Titan's atmosphere with energy input from the magnetosphere, solar UV, and deep-penetrating irradiation from galactic cosmic rays (GCR). Space radiation effects by GCR irradiation of Titan's surface and lakes can lead to the manufacture of exobiological molecules with oxygen as the new ingredient. We have developed a model of galactic cosmic ray irradiation of Titan's atmosphere, surface, subsurface and bottoms of Titan lakes. GCR would provide further energy for processing of the aerosols into more complex organic forms such as tholins and precursor molecules for amino acids. A second process called hydrolysis then converts the precursor molecules into amino acids. Hydrolysis is provided via meteor impacts with size >10 km and cryovolcanism both which can produce liquid water on Titan's surface for episodic periods > several 100 to 1000 years. Our model shows that GCR secondary particles can penetrate ~ 100 m below the ice surface (including the bottom of Titan's less dense hydrocarbon lakes ~ 150 m depths) and produce chemically significant dosages over very long timescales ~ 450 Myrs. The GCR model is combined with laboratory data from experiments in which dry methyl ices were irradiated to doses producing prebiotic amino acids such as glycine. The model calculations show glycine can form to ~ 2.5 ppb levels near the surface after ~ 450 Myrs of GCR proton irradiation and potentially to 5 ppb if heavy-ion GCRs up through Fe are included. If such molecules were detected, this would not only confirm this model but indicate that life forms different from ours may not be required.

Structural and Chemical Effects of the PtBu2 Bridge at Unsaturated Dimolybdenum Complexes Having Hydride and Hydrocarbyl Ligands.

A high-yield synthetic route for the preparation of the unsaturated anion [Mo2Cp2(μ-PtBu2)(μ-CO)2]- (2) was implemented, via two-electron reduction of the chloride complex [Mo2Cp2(μ-Cl)(μ-PtBu2)(CO)2] (1). Reaction of 2 with [NH4][PF6] led to the formation of the 30-electron complex [Mo2Cp2(H)(μ-PtBu2)(CO)2] (3), in which the hydride ligand adopts an uncommon terminal disposition. DFT analysis of the electronic structure of 3 gave support to the presence of a M≡M triple bond in this complex following from a σ2δ2δ2 configuration, a view also supported by the high electron density accumulated at the corresponding Mo-Mo bond critical point. In contrast, reactions of 2 with IMe or ClCH2Ph gave the alkyl-bridged complexes [Mo2Cp2(μ-κ1:η2-CH2R)(μ-PtBu2)(CO)2] (R = H (4a), Ph (4b)), which in solution display agostic Mo-H-C interactions. Decarbonylation of 4a took place rapidly under photochemical conditions to give the 30-electron complex [Mo2Cp2(μ-κ1:η2-CH3)(μ-PtBu2)(μ-CO)] (7), with a stronger agostic coordination of its methyl ligand. In contrast, irradiation of 4b led to the formation of the benzylidyne derivative [Mo2Cp2(μ-CPh)(μ-PtBu2)(μ-CO)] (9), following from fast decarbonylation and dehydrogenation of the bridging benzyl ligand. Low-temperature photochemistry allowed for the NMR characterization of an intermediate preceding the hydrogen elimination, identified as the carbene hydride [Mo2Cp2(H)(μ-CHPh)(μ-PtBu2)(CO)] (10), a product which evolves slowly by H2 elimination to the benzylidyne derivative. Analogous dehydrogenation of the methyl ligand in 7 could be accomplished upon moderate heating, to yield the corresponding methylidyne derivative [Mo2Cp2(μ-CH)(μ-PtBu2)(μ-CO)] (9). A complete reaction mechanism accounting for these photochemical reactions was elaborated, based on the reaction intermediates identified experimentally and on extensive DFT calculations. Surprisingly, for both systems the C-H bond activation steps are relatively easy thermal processes occurring with modest activation energies after photochemical ejection of CO, with a rate-determining step involving the formation of agostic carbenes requiring also a strong structural reorganization of the central Mo2PC rings of these molecules.

SYNTHESIS AND CHARACTERIZATION OF SOME HYDRAZINEDERIVATIVES WITH Α, Β UNSATURATED ACIDS

Metal cinnamate monohydrazinates of the formula M(cin)2N2H4, where M= Co or Zn, nickel crotante monohydrazinate monohydrate Ni(crot)2N2H4.H2O, metal cinnamate and crotonate dihydrazinates M(cin)2(N2H4)2 Where M = Co, Ni, Zn or Cd , M(crot)2(N2H4)2 Where M = Co or Ni and cadmium crotante dihydrazinate monohydrate Cd(crot)2(N2H4)2.H2O have been prepared and characterized by spectral, thermal and X-ray diffraction studies. Electronic spectra indicate that the cobalt and nickel complexes are high-spin octahedral complexes. The IR data show that the binding of hydrazine and the unsaturated carboxylate anion to the metal ion is bidentate. TG-DTA studies show that metal complexes undergo decomposition through metal carboxylate intermediate to give respective metal oxide as the final product. Xray powder diffraction patterns of the complexes indicate isomorphism among them.

Low-Temperature N–O Bond Cleavage and Reversible N–P Bond Formation Processes in the Reactions of the Unsaturated Anions [M2(η5-C5H5)2(μ-PCy2)(μ-CO)2]− (M = Mo, W) with the Nitrosyl Complex [Re(η5-C5H4Me)(CO)2(NO)]+

The unsaturated anion [Mo2Cp2(μ-PCy2)(μ-CO)2](-) (Na(+) salt) reacted rapidly with [ReCp'(CO)2(NO)]BF4 in a dichloromethane solution at 253 K to give the oxo nitride tetracarbonyl complex [Mo2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(CO)4] as the major product (Cp = η(5)-C5H5; Cp' = η(5)-C5H4Me). This complex underwent spontaneous decarbonylation at room temperature to give the unsaturated tricarbonyl derivative [Mo2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(CO)3], a very dioxygen-sensitive molecule rapidly evolving upon manipulation to give the dioxo nitride dicarbonyl complex [Mo2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(O)(CO)2] in modest yield. The latter product was obtained as a mixture of isomers, with the major ones differing in the relative arrangement (cis and trans) of their MoCp moieties [Mo-Mo = 2.7707(8) Å in the cis isomer]. The ditungsten anion [W2Cp2(μ-PCy2)(μ-CO)2](-) (Na(+) salt) also reacted rapidly with [ReCp'(CO)2(NO)]BF4 in a dichloromethane solution at 253 K to give an analogous oxo nitride complex, [W2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(CO)4], but instead of releasing CO, this complex undergoes at room temperature a reversible insertion of the nitride ligand into a W-PCy2 bond, to reach an equilibrium with its phosphinoimido-bridged isomer [W2ReCp2Cp'(μ3-N:N:P-NPCy2)(O)(CO)4], which displays a V-shaped metal core [W-W = 3.0564(7) Å; W-Re = 2.9021(6) Å]. Decarbonylation of this mixture in a refluxing toluene solution led to partial degradation and condensation of these heterometallic species, to give [ReCp'(CO)3] and the pentanuclear oxo nitride complex [W4ReCp4Cp'(μ2-N)(μ3-N)(μ-O)(O)(μ-PCy2)2(CO)3], a very air-sensitive molecule displaying both linear and trigonal nitride ligands bound to rather unsaturated ditungsten centers [W-W = 2.7246(6) and 2.7900(6) Å].

Reactivity of the Anionic Diphosphorus Complex [Mo2Cp2(μ-PCy2)(CO)2(μ-κ2:κ2-P2)]− Toward ER3X Electrophiles (E = C to Pb): Insights into the Multisite Donor Ability and Dynamics of the P2 Ligand

The Li(+) salt of the unsaturated anion [Mo(2)Cp(2)(μ-PCy(2))(μ-CO)(2)](-) reacted with P(4) in tetrahydrofuran at room temperature to give the title complex. This fluxional anion reacted with MeI and ClCH(2)Ph to give the diphosphenyl complexes [Mo(2)Cp(2)(μ-κ(2):κ(2)-P(2)CH(2)R)(μ-PCy(2))(CO)(2)] (R = H, Ph), with the incoming electrophile being attached at the basal P atom of the Mo(2)P(2) tetrahedron via the lone electron pair (P-P-CH(3) = 122.8(1)(o)). In contrast, reactions with ClER(3) (ER(3) = GePh(3), SnPh(3), PbMe(3), PbPh(3)) gave neutral complexes [Mo(2)Cp(2)(μ-κ(2):κ(2)-P(2)ER(3))(μ-PCy(2))(CO)(2)] having the incoming electrophile attached at the basal P atom but defining an acute P-P-E angle close to 90° with elongated P-P lengths of ca. 2.20 Å. These complexes undergo an easy fluxional process involving an exchange of the ER(3) group between the P atoms that could be properly modeled through DFT calculations, and some of them displayed minor isomers in solution. Their structure could be rationalized as derived from the interaction of the electrophile with high-energy orbitals of the anion having both σ(Mo-P) and π(P-P) bonding character. Reaction with BrSiMe(3) gave instead the agostic phosphenyl complex [Mo(2)Cp(2)(μ-κ(2):κ(1),η(2)-HP(2))(μ-PCy(2))(CO)(2)], formally derived from the attachment of a proton to a basal Mo-P edge of the anion (computed length 2.810 Å) and displaying an unusually low P-H coupling of 4 Hz. A similar structure, with the agostic H atom replaced with SnH(3), was found to be a satisfactory model for the minor isomer of the tin compound and represents a third and unprecedented coordination mode of the diphosphorus ligand. The agostic complex undergoes a fluxional process involving the intermediacy of the nonagostic isomer [Mo(2)Cp(2)(μ-κ(2):κ(2)-P(2)H)(μ-PCy(2))(CO)(2)], which was computed to display a geometry comparable to the major isomers of the ER(3) compounds (P-P = 2.183 Å; P-P-H = 81.7°).

Formal oxidation potentials of actinide couples in K10P2W17O61 solutions

The formal oxidation potentials of the M(VI)/M(V), M(V)/M(IV), and M(IV)/M(III) couples for actinides from U to No and of the M(IV)/M(III) couples for some actinides in 1 M H+ or 1 M Na+ (pH ∼5–5.5) solutions containing K10P2W17O61 were calculated from the data on stability of complexes of f element ions with the unsaturated heteropolytungstate anion P2W17O 61 10− . In some cases, the previously accepted values were subjected to major revision, especially the potentials of the An(V)/An(IV) couples. Problems arising in measuring the potentials of the couples involving Np(III) and Pu(III) which react with the heteropolyanion to form a heteropoly blue are discussed. The potentials of some M(III)/M(II) couples are estimated.

A Novel Zirconium Polyoxometalate Complex that Contains Both a Coordinated Saturated Anion [PMo12O40]3‐, and a Coordinated Unsaturated Anion, [PMo11O39]7‐.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An intramolecular N-H...(mu-H)Re2 dihydrogen bond and a novel mu 3-eta 2 coordination mode of the pyrazolate anion on a triangular cluster face.

The quantitative addition of pyrazole (Hpz) to the 44 valence-electron, triangular cluster anion [Re3(mu 3-H)-(mu-H)3(CO)9]- gives the novel unsaturated anion [Re3(mu-H)4(CO)9(Hpz)]- (1, 46 valence electrons), which contains a pyrazole molecule that is terminally coordinated on a cluster vertex. Solidstate X-ray and IR analyses reveal a rather weak hydrogen-bonding interaction between the NH proton and one of the hydrides bridging the opposite triangular cluster edge (delta H degree = -3.1 kcal mol-1 from the Iogansen equation). Both IR and NMR data indicate that such a proton-hydride interaction is maintained in the major conformer present in CD2Cl2, but also provide evidence of the presence of minor conformers of 1 in which the NH proton is involved in an intermolecular hydrogen bond with the solvent. The mu-H...HN bond length evaluated in solution through the T1 minimum value (2.07 A) and that determined in the solid state by X-ray diffraction (2.05 A) are in good agreement. NMR experiments show that, in acetone, intermolecular N-H...solvent interactions replace the intramolecular dihydrogen bond. At room temperature in CH2Cl2, the pyrazole ligand in 1 is labile and 1 slowly "disproportionates" to [Re3(mu 3-H)-(mu-H)3(CO)9]- and [Re3(mu-H)3(CO)9-(mu-eta 2-pz)(Hpz)]-, with H2 evolution. Slow H2 evolution also leads to the formation of the anion [Re3(mu-H)3-(CO)9(pz)]- (5), in which the pyrazolate anion adopts a novel mu 3-eta 2-coordination mode, as revealed by a single-crystal X-ray analysis. The analysis of the bond lengths indicates that the pyrazolate anion in 5 acts as a six-electron donor, with loss of the aromaticity. The formation of 5 from 1 is much faster in solvents with a high dielectric constant, such as acetone or DMF. Anion 5 was also obtained from the reaction of pyrazole with [Re3(mu-H)3(CO)9(mu 3-CH3)]- through the intermediate formation of two isomeric addition derivatives and following CH4 evolution.

Synthesis, Solid-State Structure and Solution Behavior of Hydrido-Bridged Adducts between the Group 11 [M(PPh3)]+Cations and the Triangular Cluster Anion [Re3(μ-H)4(CO)9(PPh3)]-

The reactions of the unsaturated anion [Re3(μ-H)4(CO)9(PPh3)]- (1) with the metallic Lewis acids [M(PPh3)]+ (M = Cu, Ag, Au) afford the addition derivatives [Re3{μ-M(PPh3)}(μ3-H)(μ-H)3(CO)9(PPh3)], which have been characterized in solution and in the solid state, by X-ray analysis. The copper derivative is obtained also by reaction of [Re3(μ-H)3(μ3-H)(CO)9]- (as the [Re(CO)3(Me2CO)3]+ salt) with [Cu(PPh3)2NO3]. Treatment with PPh3 extrudes the [M(PPh3)]+ groups, restoring the starting anion 1. Solid-state structures of the adducts show a butterfly Re3M metal skeleton with one hydride bridging the Re2M face and three hydrides spanning the three Re−Re edges. The interaction of the [M(PPh3)]+ cation with 1 leads only to a minor structural perturbation of the unsaturated Re2(μ-H)2 moiety. The solid-state structure is maintained in nondonor solvents, while in acetone partial (Au, Ag) or complete (Cu) reversible ionic dissociation of the adducts is observed, affording 1 and solvated [M(PPh3)]+ cations. Experime...

Reactions of Pyrazole with Unsaturated Triangular Clusters of Rhenium. Solid-State and Solution Characterization of an Intramolecular N−H···π Hydrogen Bond

The reaction of the unsaturated anion [Re3(μ-H)4(CO)10]- with pyrazole (used as solvent at 80 °C) proceeds in a stepwise manner, at first giving the [Re3(μ-H)3(μ-η2-pz)(CO)10]- anion (2, pz = pyrazolate), with H2 evolution. Spectroscopic characterization has shown that 2 contains a pz ligand bridging through the two N atoms, one edge of the triangular cluster. At longer times, CO is evolved and 2 transforms into the novel species [Re3(μ-H)3(μ-η2-pz)(CO)9(Hpz)]- (3), containing one pz ligand bridging a cluster edge and a second pyrazole molecule terminally bonded on the third vertex of the triangle, replacing an axial carbonyl of 2. The treatment with CO (atmospheric pressure, room temperature) slowly restores 2. A single-crystal X-ray analysis of 3 has revealed the syn coordination of the two heterocycles with respect to the metal triangle plane and an intramolecular hydrogen bond between the N−H proton of the pyrazole ligand and the aromatic π-electrons of the bridging pyrazolate. There is NMR evidence t...

Infrared Spectroelectrochemical Investigation of Carbon Dioxide Reduction Mediated by the Anion [Ru(SnPh3)(Co)2(iPr-DAB)]- (iPr-DAB = N,N'-Diisopropyl-1,4-diaza-1,3-butadiene)

Carbon dioxide was found to react slowly with the coordinatively unsaturated anion [Ru(SnPh3)(CO)2(iPr-DAB)]- electrogenerated in an IR OTTLE cell via bielectronic reduction of [Ru(Cl)(SnPh3)(CO)2(iPr-DAB)]. This reaction produced free CO, CO32-, O2CH- and other two unidentified carboxylato species. The overall process is not catalytic in nature since the anion cannot be recovered after the attack of CO2 due to its conversion into a stable complex tentatively assigned as {Ru0(CO)2(iPr-DAB)}2. Although limited, the inherent reactivity of [Ru(SnPh3)(CO)2(iPr-DAB)]- towards CO2 demonstrated that the strong π-bonding within the (Sn)Ru(iPr-DAB) metallacycle, stabilizing the five-coordinate structure, is slightly less delocalized in comparison with the closely related, but totally inert anions [Mn(CO)3(α-diimine)]- (α-diimine = bpy, iPr-DAB).

Transformation of a coordinated carbon monoxide into an oxyethyl bridging group in a hydrido-carbonyl rhenium cluster. Synthesis and crystal structure of the anion [Re 3(μ-H) 3(CO) 9{μ 3-η 2-C(H)(Me)O}] 2−

The reaction of the unsaturated anion [Re 3(μ-H) 4(CO) 10 − with LiMe at low temperature gives the unsaturated acyl derivative [Re 3(μ-H) 4(CO) 9{C(Me)O}] 2−, which is slowly converted, as the temperature is raised, into a saturated species in which a hydride ligand has migrated from the cluster to the acylic carbon atom to give [Re 3(μ-H) 3(CO) 9{μ 3-γ 2-C(H)(Me)O}] 2−. Variable temperature 1H-NMR spectroscopy has shown the existence of an unexpected equilibrium between the two anions.

Coordination and reduction of isocyanide ligands in hydrido-carbonyl rhenium cluster chemistry. Synthesis and characterization of the anion [Re 3(μ-H) 4(CO) 9(CNR)] − and of the formimidoyl derivative [Re 3(μ-H) 3(CO) 9(μ-η 2-C(H)NR)(PMe 2Ph)] − (R = C 6H 11)

The reaction of the unsaturated anion [Re 3(μ-H) 4(CO) 9(NCMe)] − with cyclohexylisocyanide gives the novel unsaturated anion [Re 3(μ-H) 4(CO) 9(CNC 6H 11) −. By reaction of this species with dimethylphenylphosphine a saturated compound is obtained, [Re 3(μ-H) 3(CO) 9(μ-η 2-C(H)NC 6H 11)-(PMe 2Ph)] −, containing a bridging formimidoyl ligand. Two isomers of this anion have been identified and the structure of one of them has been elucidated by X-ray analysis. The anion contains an isosceles triangle of Re atoms with two longer hydrogen-bridged edges [mean 3.255 Å] and one shorter edge [3.164(1) Å], doubly bridged by the formimidoyl ligand and the third hydride. The phosphine ligand is coordinated in the axial direction with respect to the Re 3 plane, with a ReP bond length of 2.454(7) Å.

Reduction of unsaturated organic molecules by hydridocarbonyl cluster compounds of rhenium. Reaction of the anion [Re 3(μ-H) 4(CO) 10] − with acetone: crystal structure of [NEt 4][Re 3(μ-H) 3(μ-OCHMe 2)(CO) 10

The reaction of the unsaturated anion [Re 3(μ-H) 4(CO) 10] − in acetone affords the two saturated species [Re 3(μ-H) 3(μ-OCHMe 2)(CO) 10] − and [Re 3(μ-H) 3(μ 3-OC-HMe 2)(CO) 9] − as a result of the attack of a hydride ligand of the parent anion on the ketonic carbon atom to give an isopropylate group. The structure of the former anion, as its (NEt 4) + salt, has been investigated by X-ray analysis. The crystals are monoclinic, space group P2 1/ c, with a 8.767(4), b 25.913(6), c 13.175(4) Å, β 91.80(4)° and Z = 4. The refinements performed by full-matrix least-squares methods, on the basis of 2847 independent significant reflections, with I > 3σ( I), gave final values of the conventional agreement indices R and R w of 0.041 and 0.052, respectively. The anion contains an isosceles triangle of Re atoms, with two longer hydrogen-bridged ReRe edges (mean 3.211 Å), and one shorter edge (2.930(1) Å) doubly bridged by a hydride and the isopropylate ligand. The mean value of the ReO(alkoxy) bonds is 2.153 Å.

ChemInform Abstract: 13C NMR Study of the Properties of the Unsaturated Anion (Re3(μ‐H)4(CO)9(NCMe))‐ at Low Temperature.

ChemInformVolume 18, Issue 48 Physical Organic Chemistry ChemInform Abstract: 13C NMR Study of the Properties of the Unsaturated Anion (Re3(μ-H)4(CO)9(NCMe))- at Low Temperature. T. BERINGHELLI, T. BERINGHELLI Dep. Chem., Univ. Leicester, Leicester LE1 7RH, UKSearch for more papers by this authorG. D'ALFONSO, G. D'ALFONSO Dep. Chem., Univ. Leicester, Leicester LE1 7RH, UKSearch for more papers by this authorH. MOLINARI, H. MOLINARI Dep. Chem., Univ. Leicester, Leicester LE1 7RH, UKSearch for more papers by this author T. BERINGHELLI, T. BERINGHELLI Dep. Chem., Univ. Leicester, Leicester LE1 7RH, UKSearch for more papers by this authorG. D'ALFONSO, G. D'ALFONSO Dep. Chem., Univ. Leicester, Leicester LE1 7RH, UKSearch for more papers by this authorH. MOLINARI, H. MOLINARI Dep. Chem., Univ. Leicester, Leicester LE1 7RH, UKSearch for more papers by this author First published: December 1, 1987 https://doi.org/10.1002/chin.198748044AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue48December 1, 1987 RelatedInformation

A novel unsaturated tetrahedral hydrido-carbonyl cluster anion of rhenium. Synthesis and X-ray characterization of [Re4(µ-H)3(µ3-H)2(CO)12]–

The reaction of the anion [Re4(µ-H)6(CO)12]2– with acids affords the unsaturated (58 valence electron) anion [Re4H5(CO)12]–, which contains a distorted tetrahedral cluster, with Re–Re bond lengths in the range 2.857(1)–3.251(1)Å, bearing three edge-bridging and two face-capping hydride ligands, completely fluxional in solution down to –90 °C.

Reactions of the unsaturated anion [Re 3(μ-H) 4(CO) 10] − with phosphines. Synthesis of the anions [Re 3(μ-H) 2(CO) 10(PR 3) 2] −, and crystal structure of [NEt 4][Re 3(μ-H) 2(CO) 10(PPh 3) 2

The reaction of the unsaturated cluster anion [Re 3(μ-H) 4(CO) 10] − with tertiary phosphines at room temperature results in the substitution of two hydride ligands (eliminated as H 2) by two PR 3 ligands, leading to saturated [Re 3(μ-H) 2(CO) 10-(PR 3) 2] − compounds. A single crystal X-ray diffraction study of the PPh 3 derivative revealed that the two phosphines occupy non-equivalent equatorial coordination sites on the triangular cluster. The rate of the reaction greatly increases with increase of the basicity of the phosphine.

An unusual species from the reaction of the unsaturated anion [Re 3(μ-H) 4(CO) 10] − with Me 3NO. Synthesis and spectroscopic characterization of the adduct anion [Re 3(μ-H) 3(CO) 9(μ 3-O⋯H⋯NMe 3)] −, and crustal and molecular structure of its tetraethylammonium salt

The reactions of the unsaturated cluster anion [Re 3(μ-H) 4(CO) 10] − with Me 3NO, in a solvent of low donor ability, such as acetone or tetrahydrofuran, give three products, in a ratio which depends on the reaction conditions: two of them, the unsaturated [Re 3(μ-H) 4(CO) 9(NMe 3)] − and [Re 3(μ-H) 4(CO) 9(ONMe 3)] − species, have been characterized spectroscopically. The third has been isolated and characterized by X-ray single crystal analysis as an adduct formed by hydrogen bonding between Me 3N and the triangular cluster anion [Re 3(μ-H) 3(CO) 9(μ 3-OH)] −. The crystals are monoclinic, space group P2 1/ m, with a 8.576(3), b 20.442(4), c 8.748(3) Å, β 108.08(4)°; Z = 2. The structure was solved by Patterson and Fourier methods by use of 2085 unique reflections and refined to a final R value of 0.026. The mean ReRe and ReO(OH) bond lengths are 2.979 and 2.126 Å, respectively. The O · H · N hydrogen bond is short and almost linear (O ⋯ N 2.502(10) Å). Various experiments have demonstrated that the triply bridging OH group can, according to the reaction conditions, come either from a water molecule (present in the commercial amine oxide) or by attack of a hydridic ligand on the oxygen of a coordinated amine oxide molecule. The same adduct has been obtained starting from the dianion [Re 3(μ-H) 3(CO) 9(μ 3-O)] 2−, directly by reaction with Me 3NHCl or in a two step sequence of protonation to [Re 3(μ-H) 3(CO) 9(μ 3-OH)] − and subsequent treatment with Me 3N.

Reactions of the unsaturated anion [Re 3H 4(CO) 10] − with car☐ylic acids and x-ray characterization of the anions [Re 3H 3(CO) 10(μ-O 2CR)] − (R = H, CF 3)

The novel anions [Re 3H 3(CO) 10(μ-O 2CR)] − (R = H, CH 3, CF 3), obtained by reaction of [Re 3H 4(CO) 10] − with the corresponding car☐ylic acids, have been characterized by IR and NMR spectra and by X-ray analysis of the formate and trifluoroacetate derivatives. They contain a triangle of rhenium atoms, with the car☐ylate group diaxially bridging on the shorter Re Re edge.