Rhenium Carbonyl Research Articles

X-ray structure, spectroscopic characterisation and DFT calculations of the [Re(CO) 3(dppt)Cl] complex

The reaction of the complex Re(CO) 5Cl with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) has been examined and the Re ( CO ) 3 + rhenium carbonyl – fac-[Re(CO) 3(dppt)Cl] – has been obtained. The compound has been studied by IR, UV–Vis spectroscopy and X-ray crystallography. The molecular orbital diagram of the tricarbonyl has been calculated with the density functional theory (DFT) method. The spin-allowed singlet–singlet electronic transitions of [Re(CO) 3(dppt)Cl] have been calculated with the time-dependent DFT method, and the UV–Vis spectrum of the title compound has been discussed on this basis.

A Re(CO)5Fragment Bonded to a Polyhedral Oligomeric Hydroxysilsesquioxane as a Model which Gives Further Evidence to the Existence of an Unexpected Re(CO)5Surface Species

Reaction of Re(CO)5O3SCF3 with (c-C6H11)7Si8O12O-Li+ at 273 K under a CO atmosphere affords the [Re(CO)5OR] (R = (c-C6H11)7Si8O12) derivative (1). 1 is the first example of a rhenium pentacarbonyl bearing an OR ligand (R = alkyl, aryl, or silyl) stable enough to be characterized, and it represents also the first molecular model of the surface [Re(CO)5OSi] species formed by reductive carbonylation of silica-supported [Re(CO)3OH]4. At room temperature, 1 loses one carbonyl ligand and dimerizes to afford {Re(CO)4[(mu-O)O12Si8(c-C6H11)7]}2 (2), which has been characterized by X-ray diffraction and is the first reported example of a rhenium tetracarbonyl mu-oxo-bridged dimer of the type [Re(CO)4(mu-OR)]2.

Water gas shift activity and kinetics of Pt/Re catalysts supported on ceria-zirconia oxides

UTRC has developed a stable, high activity water gas shift (WGS) catalysts for the removal of carbon monoxide from hydrogen containing reformate, generated from natural gas. Hydrogen streams that contain lower concentrations of carbon monoxide poison can extend the life of proton exchange membrane (PEM) fuel cell stacks. This study presents WGS reactivity and kinetics experiments performed comparing platinum and platinum/rhenium (T.H. Vanderspurt, F. Wijzen, X. Tang, M.P. Leffler, R.R. Willigan, C.A. Newman, R. Radhakrishnan, F. Feng, B.L. Laube, Z. Dardas, S.M. Opalka, Y. She, US Patent Application 0235526 A1 (2003)) supported on high surface area (∼200m2/g), nano-crystalline (∼4nm) large average pore size (∼5nm) ceria-zirconia under various reaction conditions. These represent gas compositions and temperatures that the catalysts see in fuel processing systems. It was found that rhenium enhanced the WGS activity of ceria-zirconia supported platinum catalysts and that rhenium carbonyl Re2(CO)10 was an optimal source for introducing rhenium to the platinum/ceria-zirconia catalysts. The optimal platinum to rhenium ratio for these catalysts was approximately 2:1 (Pt/Re) where the platinum loading was about 2wt.%. A simple kinetic model adequately represents the rhenium promotion effect sufficient to size the WGS reactors for a system. This model suggests that the enhancement in reaction rates was a function of a larger positive order dependency for H2O concentration with lower inhibitory orders for CO2 and H2 concentrations for the platinum/rhenium catalyst compared to the platinum only catalyst.

Synthesis and X-ray structures of rhenium(I) carbonyl aminoalkoxide and aminocarboxylate complexes

The complexes [Re{MeN(CH 2CH 2O)(CH 2CH 2OH)-κ 3 N, O, O}(CO) 3] ( 1), [Re{N(CH 2CH 2O)(CH 2CH 2OH) 2-κ 3 N, O, O}(CO) 3] ( 2), [Me 3NH] 2[(OC) 3Re{N(CH 2CO 2) 2-κ 3 N, O, O}CH 2CH 2{N(CH 2CO 2) 2-κ 3 N, O, O}Re(CO) 3] ( 3), [Me 3NH] 2[Re 2{μ 2-2,6-(O 2C) 2(C 5H 3N)-κ 3 N, O, O} 2(CO) 6] ( 4) and [Re 2{μ 2-2,6-(OCH 2)(C 5H 3N)(CH 2OH)-κ 2 N, O} 2(CO) 6] ( 5) were synthesized in high yields via the reactions of [Re 2(CO) 10] and Me 3NO with MeN(CH 2CH 2OH) 2, N(CH 2CH 2OH) 3, EDTA, pyridine-2,6-dicarboxylic acid and pyridine-2,6-dimethanol, respectively. Complexes 1– 5 were characterized by IR and 1H NMR spectroscopy, elemental analysis and X-ray crystallography.

A novel ruthenium(II) tris(bipyridine)–zinc porphyrin–rhenium carbonyl triad: synthesis and optical properties

A novel ruthenium(II) tris(bipyridine)–zinc porphyrin–rhenium carbonyl triads and its free base porphyrin derivative were synthesized and characterized by 1H, 13C NMR, UV–vis, mass-spectrometry and elemental analysis. The redox potentials of the two compounds were measured and compared to their corresponding reference complexes. The fluorescence and transient absorption spectra of the two complexes revealed the features of two different pathways for possible photoinduced intramolecular electron transfer or energy transfer in the triads.

Unusual, Bifurcated Photoreactivity of a Rhenium(I) Carbonyl Complex of Triethynylphosphine

Preparations of the first metal complexes of triethynylphosphine (TEP) are described. They are of the type fac-Re(bpy)(CO)(3)(TEP)(+) (1) and cis,trans-[Re(bpy)(CO)(2)(TEP)L](n)(+) (CH(3)CN, n = 1, complex 2; Cl, n = 0, complex 3), where bpy is 2,2'-bipyridine. Complex 1 displays unusual photochemical behavior compared to analogous fac-[Re(bpy)(CO)(3)(PR(3))](+) complexes in that it emits from a state that has pi-pi* character but undergoes competitive photosubstitution of both TEP and CO. Density functional theory (DFT)/time-dependent DFT calculations predict that the lowest emitting state should, in fact, have pi-pi* character.

Unconventional distribution of hydrides in hydrido rhenium carbonyl clusters

Unconventional distribution of hydrides in hydrido rhenium carbonyl clusters

Manganese(III) and rhenium(II) complexes with bulky 4,6-di- tert-butyl- N-(2,6-di- iso-propylphenyl)- o-iminobenzoquinonato ligands via carbonyls of corresponding metals

Four-coordinate complex Mn III(ISQ-Pr i )(AP-Pr i ) ( 1), where ISQ-Pr i = 4,6-di- tert-butyl- N-(2,6-di- iso-propylphenyl)- o-iminobenzosemiquinonate anion-radical, AP-Pr i = 4,6-di- tert-butyl- N-(2,6-di- iso-propylphenyl)- o-amidophenolate dianion, has been prepared by the reaction of Mn 2(CO) 10 with free 4,6-di- tert-butyl- N-(2,6-di- iso-propylphenyl)- o-iminobenzoquinone (IBQ-Pr i ) in the molar ratio 1:4 in toluene. In contrast to manganese, rhenium carbonyl reacts with o-iminobenzoquinone to form complex Re II(ISQ-Pr i ) 2(CO) 2 ( 2) with the retention of two carbonyls in coordination sphere of rhenium. The complexes have been characterized by IR, UV–Vis, and EPR spectroscopies. Molecular structures of compounds 1 and 2 have been determined by single-crystal X-ray crystallography. Compound 1 is centro-symmetric square-planar molecule with delocalized mixed valent state of AP-Pr i and ISQ-Pr i ligands. EPR spectrum of 1 in solid at 300–77 K is typical for manganese complexes with S = 3/2 state. The effective magnetic moment of 1 is 1.96 μ B at temperature 5 K as it was established by variable-temperature magnetic susceptibility measurements. Six-coordinate octahedral complex 2 possesses an S = 1/2 ground state, which is attained via strong intramolecular antiferromagnetic interaction between t 2g orbital unpaired electron of the low spin Re II ion and the unpaired electron on π-orbital of the radical ligand.

Rhenium carbonyl complexes with monodentate-coordinated diphosphines: activation of terminal phosphino groups towards amine-oxide oxidation

Terminal phosphino groups of [Re 2(CO) 9(η 1-P-P)] (P-P = diphosphines) are activated towards oxidation by Me 3NO. The respective reactions of Me 3NO with [Re 2(CO) 9{η 1-P( o-anisyl) 2(CH 2) 3PPh 2}], [Re 2(CO) 9{η 1-PPh 2(CH 2) 3P( o-anisyl) 2}] and [Re 2(CO) 9(η 1- trans-PPh 2CH CHPPh 2)] were studied to investigate the mechanism of this oxidation. The results are consistent with an intramolecular pathway involving a cyclic intermediate, without exchange of the coordinated and terminal phosphino groups. A mechanism which involves an interaction of the terminal phosphino group with a carbonyl ligand is proposed. In sharp contrast to eq-[Re 2(CO) 9(η 1-P-P)] (P-P = Ph 2P(CH 2) n PPh 2, n = 1–6), eq-[Re 2(CO) 9(η 1- trans-PPh 2CH CHPPh 2)] appears to be indefinitely stable towards equatorial → axial isomerization at room temperature, thus, allowing its crystal structure to be determined.

Intramolecular hydroamination of 6-aminohex-1-yne catalyzed by Lewis acidic rhenium(I) carbonyl complexes

With the aim to determine the effect of Lewis acidity of rhenium(I) carbonyl complexes on their catalytic properties, and to develop more efficient catalysts based on Re(I) carbonyl systems, a series of rhenium(I) carbonyl triflate complexes with various degrees of Lewis acidity was investigated. Pyridine-substituted bromo tricarbonyl rhenium(I) complexes of the type fac-[ReBr(CO) 3L 2] (L = py-Cl, py, py-Me and py-NMe 2) were synthesized from [ReBr(CO) 5] using trimethylamine N-oxide (TMNO) as decarbonylating agent. The complexes [ReBr(CO) 5] and fac-[ReBr(CO) 3L 2] were then reacted with silver triflate to yield the complexes [Re(CF 3SO 3)(CO) 5] and fac-[Re(CF 3SO 3)(CO) 3L 2]. The synthesis and characterization of these complexes and their application in the catalysis of the cyclization of 6-aminohex-1-yne are discussed. The crystal structure of [Re(CF 3SO 3)(CO) 3(py) 2] is also presented.

Surface organometallic chemistry — Carbonyl complexes of Re(I) with silanolates as models of silica anchored rhenium carbonyl species

Reaction of Me3SiONa with [Re(CO)5Cl] affords the new complex Na[Re2(CO)6(µ-OSiMe3)3], which could be generated via formation of [Re(CO)5OSiMe3] followed by immediate reaction with Me3SiO–. Substitution of some CO ligands by phosphines significantly decreases the electrophilicity of the Re(I) center, and therefore hinders further attack by Me3SiO–. Thus, fac-[Re(CO)3(Ph2PCH2CH2PPh2)OTf] (OTf is the triflate anion) reacts with Me3SiONa to give fac-[Re(CO)3(Ph2PCH2CH2PPh2)OSiMe3], a molecular model of silica anchored [Re(CO)5OSi≡]. However, substitution of only one CO by triphenylphosphine is not enough to avoid the formation of [Re2(CO)6(µ-OSiMe3)3]–. While fac-[Re(CO)3(Ph2PCH2CH2PPh2)OSiMe3] is stable towards hydrolysis, [Re2(CO)6(µ-OSiMe3)3]– is readily hydrolyzed to [Re2(CO)6(µ-OH)(µ-OSiMe3)2]–, a molecular model of silica anchored [Re2(CO)6(µ-OH)(µ-OSi≡)2]–, whose structure has been determined by single crystal X-ray diffraction. Key words: surface organometallic chemistry, rhenium, silica, silanolate, molecular model.

Deuterium Quadrupolar Coupling Constants of Deuteride Bridging Ligands: A Study on Rhenium Hydrido Carbonyl Clusters

Deuterium variable-temperature T1 measurements have been performed for a series of rhenium carbonyl clusters containing doubly and triply bridging deuterides, namely Re2(μ-D)2(CO)8 (1), Re3(μ-D)3(CO)12 (2), Re4(μ3-D)4(CO)12 (3), [NEt4][Re3(μ-D)4(CO)10] (4), [NEt4][Re3(μ-D)3(μ-Cl)(CO)10] (5), and [NEt4][Re3(μ-D)4(CO)9] (6). The deuterium quadrupolar coupling constants (DQCC) of the deuteride ligands have been evaluated for compounds 1−5, while the fluxionality of 6 hampered such a determination. The experimental DQCC of compound 3 (21.8 kHz) was, until now, the smallest found for organometallic compounds. Overall the DQCC values span a 4-fold range, and their fine-tuning depends on the bridging mode of the deuteride ligands (μ3 vs μ), the local unsaturation degree of the Re atoms bridged by the deuteride, and the presence of other bridging ligands. The experimental DQCC's of rhenium derivatives and those of bridging deuterides in Cr, W, and Os clusters linearly correlate with the respective metal−hydrogen ...

12 Manganese, technetium and rhenium

As would be expected research into the Group 7 elements has focused on manganese. Much of this research deals with polynuclear compounds and their ability to act as single molecular magnets (SMMs). Notable examples are a new synthetic route to {Mn12} complexes involving the reduction of Mn(VII) in alcohol/carboxylic acid media and the first example of an {Mn2} unit with SMM behaviour. Rhenium(I) carbonyl compounds continue to receive attention due their luminescent behaviour. Examples where the emission properties of the complex are altered upon formation of a pseudorotaxane or in the presence of anions are discussed.

Preparation and characterization of poly(amidoamine) dendrimers functionalized with a rhenium carbonyl complex and PEG as new IR probes for carbonyl metallo immunoassay

The first poly(amidoamine) (PAMAM) dendrimers tethered with both (η 5-cyclopentadienyl) rhenium tricarbonyl (CpRe(CO) 3) units and polyethylene glycol (PEG) chains were prepared and characterized by combining NMR spectroscopy and Fourier-transform IR spectroscopy. Grafting of CpRe(CO) 3 units was achieved by reductive amination of formyl-CpRe(CO) 3 with the peripheral amines of generation 3 and 4 PAMAMs to yield dendrimers labeled with a variable number of CpRe(CO) 3 units, ranging from 8 to 14 for PAMAM-G3 and 17–30 for PAMAM-G4. PEG chains of different lengths were then attached to some of the remaining peripheral amines, and their respective ability to improve the solubility of the metallodendrimers in aqueous buffered media was evaluated. These metallodendrimers represent new infrared probes designed to be coupled to immunological reagents for the amplification of the IR signal in carbonyl metallo immunoassay (CMIA).

Assessment of vapor pressure data of solid metal carbonyls

The vapor pressure data of solid metal carbonyls have been assessed and compiled using the “Oonk arc representation” (OAR), also called the “ln f representation”. A simple modification is proposed to the existing OAR called the “ modified Oonk arc representation” (MOAR), which aids in the visual representation of the vapor pressure data. The solid metal carbonyls chosen for these data assessment do not exhibit any disproportionation: chromium carbonyl (Cr(CO) 6), tungsten carbonyl (W(CO) 6), osmium carbonyl (Os 3(CO) 12), molybdenum carbonyl (Mo(CO) 6), rhenium carbonyl (Re 2(CO) 10), and manganese carbonyl (Mn(CO) 5) have been evaluated. The sublimation properties using the assessed data (Δ sub G ∘, Δ sub H ∘ and Δ sub C p , m ∘ ) of these compounds have been evaluated and a discussion on the mutual consistency of various data sets for each compound over a wide range of temperature is presented.

A vibrational spectroscopic study of the thermal behavior of Re2(CO)10 on zeolite Y

This work describes the thermal decomposition of Re2(CO)10 in zeolite Y, which generates the zeolite-supported complex Re0(CO)3(O-Z)3, where (O-Z) represents a framework oxygen. The adsorption and thermal decomposition of Re2(CO)10 was performed on dehydrated and hydrated zeolite NaY. The conversion to Re0(CO)3(O-Z)3 was not significantly affected by the presence of water within the supercages as the supported complex formed at around 200 °C no matter what the initial water content of the zeolite was. However, when the zeolite sample was treated at ≥200 °C for long periods, the adsorbed H2O became involved in the reactivity, playing a role as an oxidant. The subcarbonyl complex Re0(CO)3(O-Z)3 was oxidized, generating isolated Re2O7 or HReO4, or a mixture of both, which was dispersed inside the zeolite host. This result suggests that thermal decomposition of Re2(CO)10 on a hydrated zeolite under mild conditions can be a convenient route for preparation of zeolite-supported Re2O7 catalysts. Re0(CO)3(O-Z)3 was also formed in siliceous zeolite Y (SiY) upon heating. But it quickly decomposes into metal Re at around 200 °C, suggesting that the tricarbonyl species is destabilized in the almost natural zeolite framework. The present study also shows that FT-Raman spectroscopy is a useful technique for monitoring the behavior of the metal carbonyl species in zeolitic hosts.Key words: Raman spectroscopy, zeolite Y, rhenium carbonyl, rhenium oxide.

Dimeric Rhenium(I) Carbonyl Complexes with Thiosemicarbazone Backbone

AbstractDimeric, neutral rhenium(I) complexes of the composition [Re2(CO)6X(LR)] (X = Cl or Br) are formed when [NEt4]2[Re(CO)3Br3] or [Re(CO)3Cl(CH3CN)2] react with 2, 2′‐dipyridylketone thiosemicarbazones (HLR, R = H, Ph). The thiosemicarbazones deprotonate during the reaction and connect two tricarbonylrhenium(I) units as formally pentadentate bridging ligands. This results in an extremely rare coordination mode, in which the two nitrogen atoms of the hydrazone unit bind to each one of the rhenium atoms. The bond lengths inside the thiosemicarbazonato backbone reflect a large degree of delocalization of electron density.

Solvent Stabilization and Hydrogenation Catalysis of Trimethylphosphine-Substituted Carbonyl Rhenium Cations

A series of cationic complexes were designed as catalysts for imine hydrogenation processes, and it was anticipated that for this purpose naked 16e- cations or relatively labile solvent-coordinated ones possessing noncoordinating counterions would suffice. Solvento complexes [Re(CO)3(PMe3)2(S)][BArF] (4(PhCl) and 4(THF)) and [mer-Re(CO)2(PMe3)3(S)][BArF] (5(PhCl) and 5(THF)) (BArF = [B(3,5-(CF3)2C6H3)4]-; S = PhCl)) were obtained from their corresponding hydride complexes 1 and 2 after treatment with [Ph3C][BArF] in chlorobenzene. The five-coordinated cationic complex [Re(CO)(PMe3)4][BArF] (6) (BArF = [B(3,5-(CF3)2C6H3)4]-) was obtained by the reaction of ReH(CO)(PMe3)4 (3) with 1 equiv of [Ph3C][BArF] in chlorobenzene. Hydride abstraction also occurred except for 1 from 2 and 3 with B(C6F5)3, producing [Re(CO)2(PMe3)3(S)][BH(C6F5)3] and [Re(CO)(PMe3)4][BH(C6F5)] (S = PhCl, THF). Treatment of ReH(CO)3(PMe3)2 (1) and ReH(CO)2(PMe3)3(2) with 1 equiv of [isopropylisopropylideneiminium][BArF] in chlorobenzene...

A rhenium carbonyl bonded to highly dealuminated zeolite Y: structure determination by infrared and X-ray absorption spectroscopies

Rhenium carbonyls bonded to dealuminated Y zeolite (DAY) were synthesized from HRe(CO)5 and characterized by infrared and extended X-ray absorption fine structure spectroscopies. In the zeolite calcined at 573 K, a mixture of rhenium carbonyls was formed, but in the zeolite calcined at 773 K, a nearly unique rhenium carbonyl characterized by narrow infrared bands in the νCO region was formed, represented as Re(CO)3{OR42−}2{OR62−}, with rhenium bonded to three surface oxygen atoms at a T5 site located at an aluminum center in the zeolite (the braces signify sites on the zeolite surface and the subscript R4 refers to a surface oxygen atom bridging two four-ring sites and R6 refers to a surface oxygen atom bridging a four-ring and a six-ring site). The three surface oxygen atoms in the complex are not all equivalent, giving rise to a slightly distorted C3v symmetry, consistent with the observed infrared spectra. Two Re-support oxygen distances were found by EXAFS spectroscopy, 2.09 and 2.47 A. The Re–C and Re–carbonyl–oxygen distances were found to be 1.96 and 3.14 A, respectively. The data show that rhenium carbonyls are good probes of three-fold surface sites of zeolites and oxides.

Synthesis, Characterization, and Reactivity of a Rhenium Complex with a Corannulene-Based Ligand

A new rhenium carbonyl complex, exo-(η5-C20H17)Re(CO)3 (3), containing a corannulene-derived ligand has been synthesized in 12% yield. The X-ray structure determination of 3 shows that the rhenium center is bound to the exo face of the bowl-shaped ligand. The reaction of 3 with PPh3 in benzene at 70 °C produces trans,mer-Re(H)(PPh3)2(CO)3 and C20H16 (4), a bowl-shaped dibenzofulvene type molecule. The reaction of 3 with PPh3 proceeds via an η5-η3-η1 ring slip followed by a β-hydride elimination.