Darstellung und Strukturen von (Et4N)2[Re(CO)3(NCS)3] und (Et4N)[Re(CO)2Br4]

Syntheses and Structures of (Et₄N)₂[Re(CO)₃(NCS)₃] and (Et₄N)[Re(CO)₂Br₄] Rhenium(I) and rhenium(III) carbonyl complexes can easily be prepared by ligand exchange reactions starting from (Et₄N)₂[Re(CO)₃Br₃]. Using nonoxidizing reagents the facial Re^I(CO)₃ unit remains and only the bromo ligands are exchanged. Following this procedure, (Et₄N)₂[Re(CO)₃(NCS)₃] can be obtained in high yield and purity using trimethylsilylisothiocyanate. The compound crystallizes in the monoclinic space group P2₁/n, a = 18.442(5), b = 17.724(3), c = 18.668(5) Å, β = 92.54(1)°, Z = 8. The NCS^? ligands are coordinated via nitrogen. The reaction of [Re(CO)₃Br₃]^2? with Br₂ yields the rhenium(III) anion [Re(CO)₂Br₄]^?. The tetraethylammonium salt of this complex crystallizes in the noncentrosymmetric, orthorhombic space group Cmc2₁, a = 8.311(1), b = 25.480(6), c = 8.624(1) Å, Z = 4. The carbonyl ligands are positioned in a cis arrangement. Their strong trans influence causes a lengthening of the Re? Br bond distances by at least 0.05 Å.     

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)₃L₂] (L = py-Cl, py, py-Me and py-NMe₂) were synthesized from [ReBr(CO)₅] using trimethylamine N-oxide (TMNO) as decarbonylating agent. The complexes [ReBr(CO)₅] and fac-[ReBr(CO)₃L₂] were then reacted with silver triflate to yield the complexes [Re(CF₃SO₃)(CO)₅] and fac-[Re(CF₃SO₃)(CO)₃L₂]. 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(CF₃SO₃)(CO)₃(py)₂] is also presented.     

Synthesis and reactivity of [ReBr2(NCCH3)2(CO)2]: A new precursor for bioorganometallic chemistry

We have synthesised (Et₄N)[ReBr₂(NCCH₃)₂(CO)₂] 1 in two steps from [ReBr₃(CO)₃]²⁻. Complex 1 is water and air stable and the two Br⁻ ligands are easily exchanged for coordinating solvent molecules such as water. The reactivity of 1 with several ligands such as imidazole (imz) and 2-picolinic acid (2-pic) are easily possible with substitution exclusively occurring in trans-position to the carbonyl groups. The resulting complexes [Re(imz)₂(NCCH₃)₂(CO)₂]⁺ and [Re(2-pic)(NCCH₃)₂(CO)₂] have been isolated and structurally characterised. The two acetonitrile ligands are strongly bound and are not substituted under any conditions. Complex 1 represents therefore the new moiety “trans,cis-[Re(NCCH₃)₂(CO)₂]⁺” which can be considered as a further building block in organometallic chemistry.     

Reactions of [Y(BDI)(I)2(THF)] [BDI = {HC(CMeNAr)2}−, Ar = 2,6-diisopropylphenyl] with Na[M(Cp)(CO)3] (M = Cr,W): X-ray crystal structures of [{Y(BDI)[Cr(Cp)(CO)3]2(THF)}2] and [W(Cp)(CO)3][Na(THF)2]

Reaction of [Y(BDI)(I)₂(THF)] (1) with two equivalents of Na[Cr(Cp)(CO)₃] affords the dimeric complex [{Y(BDI)[Cr(Cp)(CO)₃]₂(THF)}₂] (2). Complex 2 contains two yttrium-BDI units which are each linked by two isocarbonyl bridging [Cr(Cp)(CO)₃]^? anions; a terminal, isocarbonyl bound [Cr(Cp)(CO)₃]^? anion and THF molecule completes the coordination sphere at each yttrium. This results in formation of a centrosymmetric, 12-membered C₄O₄Cr₂Y₂ ring. Forcing conditions were required to produce carbonyl metallate derivatives such as 2, as exemplified by the isolation of crystals of [W(Cp)(CO)₃][Na(THF)₂] (3) from the analogous reaction between 1 and two equivalents of Na[W(Cp)(CO)₃]. Complex 3 loses coordinated THF very easily and all isolated samples exhibit spectra consistent with the known, un-solvated form of Na[W(Cp)(CO)₃]. The crystal structure of 3 shows dimeric sodium units bridged by two THF molecules and one isocarbonyl group. Each sodium centre is further coordinated by one THF molecule and two isocarbonyl ligands. There are two crystallographically distinct [W(Cp)(CO)₃]^? units; one exhibits two bridging isocarbonyl groups and the other exhibits three bridging isocarbonyl groups to different sodium dimer units. This results in a 2-dimensional polymeric sheet network in the solid state. Complex 2 was characterised by single crystal X-ray diffraction, NMR spectroscopy, FTIR spectroscopy and CHN microanalysis; complex 3 was characterised by single crystal X-ray diffraction only.     

Rhenium Complexes with p-Fluorophenylisocyanide

p-Fluorophenylisocyanide (CNPh^pF) reacts with [Re(CO)₅Br] under stepwise exchange of the carbonyl ligands depending on the conditions applied. The reaction stops with the formation of fac-[Re(CO)₃Br(CNPh^pF)₂] in boiling THF. An ongoing carbonyl exchange is observed at higher temperatures, e. g. in refluxing toluene, with the final formation of the [Re(CNPh^pF)₆]⁺ cation. The progress of the reactions has been studied by ¹⁹F NMR spectroscopy and the structures of [Re(CO)Br(CNPh^pF)₄] and [Re(CNPh^pF)₆](BPh₄) have been elucidated by X-ray diffraction.     

Zur kenntnis der chemie der metallcarbonyle und der cyanokomplexe in flüssigem ammoniak : XXXIII. Über die darstellung neuer carbamoylcarbonyl-komplexe aus bekannten und neuen kationischen carbonylverbindungen des mangans und rheniums

The covalent carbamoyl carbonyl compounds Re(CO)₅COHN₂, cis-M(CO)₄(L)CONH₂, M(CO)₃(L)₂CONH₂ and M(CO)₃(D)CONH₂ (M = Mn, Re; L = PPh₃, PEt₃; D = bipy, phen) are formed by reactions of the cationic complexes [Re(CO)₆]⁺, [M(CO)₅L]⁺, [M(CO)₄L₂]⁺ and [M(CO)₄D]⁺ (M = Mn, Re; L = PPh₃, PEt₃; D = bipy, phen) with liquid NH₃ with concomitant deprotonation: [M(CO)_6?nL_n]⁺ + 2 NH₃ → M(CO)_5?nL_nCONH₂ + NH₄⁺ (n = 0, 1, 2) and [M(CO)₄D]⁺ + 2 NH₃ → M(CO)₃(D)CONH₂ + NH₄⁺ The stability of the above-mentioned carbamoyl carbonyl complexes increases from the penta- to the tetra- to the tri-carbonyl derivatives. In all cases the rhenium compounds are much more stable than the corresponding manganese complexes. Whereas the carbamoyl compound Re(CO)₄(PEt₃)CONH₂ can be isolated by reaction of [Re(CO)₅PEt₃]⁺ with NH₃, the corresponding manganese complex undergoes Hofmann degradation of amides even at ?70°C to form HMn(CO)₄PEt₃ and NH₄NCO. The IR and some mass and ¹H NMR spectra of the new hexacoordinated carbamoyl carbonyl complexes are discussed and the reactions of these compounds with liquid NH₃, HCl and CH₃OH are described.     

The chemistry of metal carbonyl anions : III. Sodium-potassium alloy: An efficient reagent for the production of metal carbonyl anions

Reduction of several metal carbonyl dimers including Mn₂](CO)₁₀, [C₅H₅Fe(C0)₂]₂, Co₂(CO)₈, and [C₅H₅M(CO)₃]₂ (M = Cr, Mo and W) by sodium—potassium alloy (NaK) in tetrahydrofuran at room temperature provides a rapid and clean method for the production of the corresponding metal carbonyl anions in high yield. Isolation and characterization of [n-Bu₄N] [Fe(CO)₂C₅H₅] from the iron dimer reduction is described. Reductions of other carbonyls including M(CO)₆ (M = Cr, Mo and W) and Re₂(CO)₁₀ proceed more slowly than previously established methods and provide principally M₂(CO)₁₀^2? and Re(CO)₅₅^?. Methods for the preparation of Re(CO)₅^? are critically considered. The reaction of NaK with [C₅H₅NiCO]₂ is discussed in relation to previously reported results. Infrared solution spectra of a number of carbonyl anions in THF, obtained in a special infrared solution cell, are reported.     

Tricarbonylrhenium(I) and -technetium(I) complexes with bis(2-pyridyl)phenylphosphine and tris(2-pyridyl)phosphine

(NEt₄)₂[Re(CO)₃Br₃] or (NEt₄)₂[Tc(CO)₃Cl₃] react with bis(2-pyridyl)phenylphosphine (PPhpy₂) or tris(2-pyridyl)phosphine (Ppy₃) under formation of neutral tricarbonyl complexes of the composition [M(CO)₃X(L)] (M = Re, X = Br; M = Tc, X = Cl; L = PPhpy₂ or Ppy₃). In all isolated products, the ligands coordinate solely via two of their nitrogen atoms. All attempts to force a tripodal coordination of the phosphinopyridines failed. Removal of the bromo ligands from (NEt₄)₂[Re(CO)₃Br₃] by the addition of AgNO₃ in THF/water, and subsequent reaction of the resulting [Re(CO)₃(THF)₃](NO₃)with Ppy₃ yielded the complex [Re(CO)₃(NO₃)(Ppy₃-N,N′)] with a monodentate coordinated nitrato ligand. The products have been characterized spectroscopically and by X-ray structure analyses.     

Characterization of transient species and products in photochemical reactions of Re(dmb) (CO)3 Et with and without CO2

Transient FT-IR spectra of fac-Re(dmb)(CO)₃(Et) after laser excitation (355 nm) were investigated in THF under Ar and CO₂ atmospheres. The CO stretching bands of Re(dmb^⊙)(CO)₃(THF) grow (2008 and 1897 cm^?1) and those of Re(dmb)(CO)₃(Et) bleach (1987 and 1875 cm^?1) at times <1 μs, consistent with clean cleavage of the Re-Et bond. Under a CO₂ atmosphere, the long-lived radical (τ>100 ms) converts slowly to the formato complex Re(dmb)(CO)₃(OC(O)H) (2020, 1916, 1873 and 1630 cm^?1). When the solvent is slightly wet, the bicarbonato complex, Re(dmb)(CO)₃(OC(O)OH), is also observed after photolysis under CO₂.     

Structure,electrochemistry, spectroscopy,and magnetic resonance,including high-field EPR,of {(μ-abpy)[Re(CO)3X]2}o/•−, where abpy = 2,2′-azobispyridine and X = F,Cl, Br,I

Attempts to prepare and study the title complexes yielded the structurally characterized neutral compounds anti-{(μ-abpy)[Re(CO)₃X]₂}, X = Br (I4₁/a), I (C2/c), and two crystalline forms of anti-{(μ-abpy)[Re(CO)₃Cl]₂}. One of these forms (P2₁/c) has been reported before, the other (I4₁/a), obtained through crystallization in the presence of Zn, is isostructural to the form found for anti-{(μ-abpy)[Re(CO)₃Br]₂}. Syntheses of {(μ-abpy)[Re(CO)₃Cl]₂} at high or low temperatures yielded different compositions, the high temperature procedure led to partial formation of syn/anti mixtures and one-electron reduced species. The same was observed to a greater extent in the preparation of labile syn/anti-{(μ-abpy)[Re(CO)₃F]₂}^o/??. The identity of isolated species was investigated using ¹H NMR spectroscopy, variable frequency EPR spectroscopy, cyclic voltammetry, UV/Vis- and IR-spectroelectrochemistry. The effects of halide variation on structure, reduction potentials, isomerism and electronic situation are being discussed.     

Formamidino and carbamoyl-formamidino complexes of manganese and rhenium carbonyls

Lithio-1,3-diarylformamidines undergo reaction with the monomeric and dimeric carbonyl chlorides of manganese and rhenium, [M(CO)₅Cl] and [M(CO)₄Cl₂] to yield respectively the carbamoyl-formamidino [M(CO)₄-CON(R)CHNR] and the formamidino [M(CO)₄RNCHNR] types of complex. The carbamoyl complexes undergo decarbonylation to produce the formamidino complexes in low yield.     

Insertionen in Wolfram(0)Kohlenstoff- und Wolfram(0)Wasserstoff-Bindungen

Trans-dicarbonylmethylnitrosyl-bis(triisopropylphosphite)tungsten (1) reacts with CO or CO₂ to give (CO)₂(ON)[P(O-i-Pr)₃]₂WCOCH₃ (2) or (OC)(ON)[P(O-i-Pr)₃]₂W-η²-OOCCH₃ (3), respectively.The hydride complex (OC)₂(ON)[P(O-i-Pr)₃]₂WH (4a) undergoes insertion by CO₂ or by activated acetylenes such as propiolic aldehyde or methyl propiolate to give (OC)₂(ON)[P(O-i-Pr)₃]₂OC(O)H (5) or (OC)₂(ON)]P(O-i-Pr)₃]₂CHCHR (R  CHO, 6; R  COOCH₃, 7). 4a adds BH₃ to yield a (OC)₂(ON)[P(O-i-Pr)₃]₂WHBH₃ system 8. This in turn can react with CO to give 4a and a (OC)₃(ON)P(O-i-Pr)₃WH complex (4b).     

Reactions of nitrosonium ion with anionic carbonyl monomers and clusters. Crystal and molecular structure of FeCo2(μ3-NH)(CO)9

The reactions of several mono- and poly-nuclear carbonyl metallates with nitrosonium ion have been studied. Besides simple substitution of a carbon monoxide with NO⁺ some reactions yielded products containing other nitrogeneous ligands. When [CoRu₃(CO)₁₃]^? reacts with NO⁺, low yields of the new nitrido cluster CoRu₃N(CO)₁₂ are formed. Prior conversion of [CoRu₃(CO)₁₃]^? to the new hydrido cluster [H₂CoRu₃(CO)₁₂]^? under hydrogen, followed by nitrosylation, forms the new imido cluster H₂Ru₃(NH)(CO)₉ in very low yield. The reaction of [FeCO₃(CO)₁₂]^? with NO⁺ also generates an imido cluster, FeCo₂(NH)(CO)₉, in 15% yield. This cluster has been characterized by X-ray crystallography and was found to be similar to the tricobalt alkylidyne clusters. (Triclinic crystal system, P$\text{1}$ space group, Z=2, a 6.787(1), b 8.016(1), c 13.881(2) Å, α 95.50(1), β 100.77(1), γ 107.93(1)°. Modifications of the nitrosylations using NO⁺ were studied. In particular, the addition of triethylamine or N-t-butylbenzaldimine allowed the use of NO⁺ in THF without solvent decomposition. With [CpMo(CO)₃]^? and [CpFe(CO)₂]^? the N-nitrosoiminium species appears to form transient alkylmetals which further react to give the dimers [CpMo(CO)₃]₂ and [CpFe(CO)₂]₂.     

Reactivity of ytterbium in liquid ammonia

A solution of metallic ytterbium in liquid ammonia reacts readily with various carbonyl complexes of metals to form the corresponding lanthanide carbonylmetallates. The reaction of an excess of Yb in liquid NH₃ with [CpFe(CO)₂]₂ gave (THF)₄Yb[Fe(CO)₂Cp]₂ in 42% yield. It was suggested that the resulting complex contains two equivalent Yb−Fe bonds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1883–1885, October, 1997.     

Synthesis and reactivity of rhodium(I) complexes of the type Rh(L-L)(CO)[P(OPh)3] and Rh(L-L)[P(OPh)3]2

Summary The carbonyl ligands in the Rh¹ complexes Rh(L-L)(CO)₂ [L-L=anthranilate (AA) orN-phenylanthranilate(FA) ions] are replaced by P(OPh)₃ to form the mono-or disubstituted products, Rh(L-L)(CO)[P(OPh)₃] and Rh(L-L)[P(OPh)₃]₂ respectively depending on the [P(OPh)₃]/[Rh] molar ratio, at room temperature and in air. Under argon at [P(OPh)₃]/[Rh]4 theortho-metallated Rh¹ complex Rh[P(OPh)₃]₃[P(OC₆H₄)-OPh)₂] is formed. The new route forortho-metallated Rh¹ complex synthesis is described.The Rh(AA)(CO)₂ complex was used as a catalyst precursor in hydroformylation of olefins.     

Transient Raman detection of excited state electron,transfer to methyl viologen from photoexcited molecular reagents in fluid solution and anchored to SiO2

The lowest electronic excited state of the complexes [Ru(2,2′-bipyridine)₃]²⁺, fac-[ClRe (CO)₃(2,2′-bipyridine)], and fac-[(pyridine) Re (CO)₃(2,2′-bipyridine)]⁺ can be quenched by methyl viologen, MV²⁺, N,N′-dimethyl-4,4′-bipyridinium, in fluid solutions. The quenching obeys Stern—Volmer kinetics as deduced from plots of relative luminescence quantum yield vs [MV²⁺], and the data are consistent with a quenching process that is essentially diffusion controlled. Pulsed laser excitation (18 ns, 354.7 nm frequency tripled Nd: YAG) of the metal complexes in the presence of MV²⁺ shows that a detectable fraction of the quenching results in net electron transfer to form MV⁺. The MV⁺ is detectable by resonance Raman scattering from the trailing portion of the excitation pulse. Excited state electron transfer to MV²⁺ from a photo-excited complex anchored to SiO₂ has also been detected by transient Raman spectroscopy. High surface area SiO₂ was functionalized by reaction with 4-[2-(trimethoxysilyl)ethyl]pyridine to give [SiO₂]-SiEtpyr. Reaction of [SiO₂]-SiEtpyr with [(CH₃CN)Re(CO)₃(2,2′-bipyridine)]⁺ then yields [SiO₂]-[(SiEtpyr) Re (CO)₃ (2,2′-bipyridine)]⁺. Electron transfer quenching of the photo-excited immobilized Re complex occurs when suspended in CH₃CN solutions of MV²⁺ to yield MV⁺ as detected by resonance Raman scattering and by lifetime attenuation in the presence of MV²⁺.     

Studies on organometallic compounds with hetero multiple bridges : V. Crystal and molecular structure of the parent rhenium complex Re2Br2(CO)6(THF)2 and substituted products of tricarbonylrhenium(I) derived from it

Reactions of the tetrahydrofuran adduct Re₂Br₂(CO)₆(THF)₂ with some phosphorous- and nitrogen-containing donors under mild conditions are reported, which led to the formation of substituted products of tricarbonylrhenium(I). Bromide abstraction from the THF adduct by secondary amines and CS₂ produced the dithiocarbamato derivatives Re(S₂CNR₂)(CO)₃(HNR₂) whose behaviour in solution with CO was also investigated. Mass spectral data for some of the substituted products have been measured. The title compound crystallizes in the space group P2₁/n with cell constants a = 8.661(2), b = 11.251(3), c = 11.424(3) Å and β = 110.36(2)°, U = 1043.67 ų and D_calc = 2.686 g cm^?3, Z = 2. The molecule consists of a planar Re₂Br₂ moiety, as demanded by symmetry. The two THF groups are on opposite sides of this plane and the three CO groups around each rhenium atom are arranged in a fac arrangement. The unique ReBr distances are 2.642(5) and 2.644(4)Å, while the ReO distance is 2.129(31) Å. The ReBrRe and BrReBr angles are 97.3(2) and 82.7(1)°, respectively. The Re?Re nonbonding distance is 3.967(3) Å. The THF ligands consist of a nearly planar C₄ fragment (maximum deviation from planarity 0.06 Å), while the oxygen is 0.348 Å out of that plane, the angle defined by the C₄ plane and the COC fragment of the THF ligand being 24.99°. Final values of the discrepancy indices are R(F) = 0.074 and R_w(F) = 0.095.     

Dinuclear ReI complex based on 1,2,4,5-tetrakis(diphenylphosphino)- pyridine: synthesis and luminescence properties

The reaction of 1,2,4,5-tetrakis(diphenylphosphino)pyridine (L) with Re(CO)₅Br (in a molar ratio of 1:2) leads to the bis-chelated complex [Re₂(CO)₆(L)Br₂] in 95% yield. At ambient temperature, the solid complex exhibits green phosphorescence (λ_max = 535 nm) with a quantum yield of 12% and a lifetime of 90 μs.     

Synthesis and structure of some ruthenium-rhenium heterodinuclear complexes and their catalytic activity in the addition of carboxylic acids to phenylacetylene

The salt elimination reaction of Na[Re(CO)₅] with Cp*Ru(dppm)Cl, CpRu(dppm)Cl or CpRu(CO)₂Cl afforded the heterodinuclear species Cp*Ru(μ-CO)₂(μ-dppm)Re(CO)₃, Cp(CO)Ru(μ-dppm)Re(CO)₄, or Cp(CO)₂RuRe(CO)₅, respectively, in moderate yields. An orthometallated species, Cp*(CO)Ru(μ-H)[μ-PhP(C₆H₄)CH₂PPh₂]Re(CO)₃, was also obtained from the first reaction. All these heterodinuclear products have been characterised crystallographically. They also showed good catalytic activity for the addition of carboxylic acids to phenylacetylene to afford the anti-Markovnikov products selectively.     

Coordination of bidentate aniline derivatives to the fac-[Re(CO)3] core

A series of rhenium(I) tricarbonyl complexes, containing bidentate derivatives of aniline, was synthesized and structurally characterized. With 1,2-diaminobenzene (Hpda) the ‘2+1’ complex salt fac-[Re(CO)₃(Hpda)₂]Br was isolated. The neutral complex [Re(CO)₃(Hapa)Br] was formed with 2-aminodiphenylamine (Hapa) as ligand. 2-Aminophenol (Hopa) also produced the neutral ‘2+1’ complex [Re(CO)₃(opa)₂(Hopa)], but with 2-mercaptophenol (Hspo) the bridged dimer [Re₂(CO)₇(spo)₂] was found. In the complex [Re(CO)₃(Htpn)Br] (Htpn = N′-{(2-methylthio)benzylidene}benzene-1,2-diamine) the potentially tridentate ligand Htpn is coordinated via the methylthio sulfur and imino nitrogen atoms only, with a free amino group.