Perfluormethyl-Element-Liganden. XVIII. Darstellung und spektroskopische Untersuchung von M(CO)5L und M(CO)4L2-Komplexen [L = MenP(CF3)3−n; n = 0–3; M = Cr,Mo, W]

Perfluoromethyl-Element-Ligands. XVIII. Preparation and Spectroscopic Investigation of M(CO)₅L and M(CO)₄L₂ Complexes [L = Me_nP(CF₃)_3?n; n = 0–3; M = Cr, Mo, W] M(CO)₅L and cis-M(CO)₄L₂ complexes, respectively [M = Cr, Mo, W; L = Me_nP(CF₃)_3?n; n = 0–3] are prepared reacting M(CO)₅ · THF or M(CO)₄norbor with L at room temperature. The cis-compounds isomerize above 50°C yielding the trans-complexes; the rate of isomerization increases with increasing number of CF₃ groups. Thermal reaction of M(CO)₆ (M = Cr, Mo, W) with P(CF₃)₃ yields M(CO)₅P(CF₃)₃ and trans-M(CO)₄[P(CF₃)₃]₂. Introduction of three P(CF₃)₃ ligands by reaction with M(CO)₃(cycloheptatriene) (M = Cr, Mo) proves unsuccessful; besides little M(CO)₅P(CF₃)₃ trans-M(CO)₄[P(CF₃)₃]₂ is formed. The new compounds are characterized by analytical and spectroscopic (n.m.r., i.r., MS) methods.     

Darstellung und spektroskopische Untersuchungen von M(CO)4L2- und M(CO)3L3-Komplexen (M = Cr,Mo, W; L = Me3SiOCH2PMe2, Me2(CH2CH) SiOCH2PMe2)

Preparation and spectroscopical Investigations of M(CO)₄L₂ and M(CO)₃L₃ Complexes (M = Cr, Mo, W; L = Me₃SiOCH₂PMe₂, Me₂(CH₂?CH)SiOCH₂PMe₂ The coordinating properties of the ligands L¹ (?Me₃SiOCH₂PMe₂) and L² (?Me₂ViSiOCH₂PMe₂)¹) have been studied by synthesis and spectroscopic investigations (IR, NMR, MS) of their complexes M(CO)₄L₂ and M(CO)₃L₃(M = Cr, Mo, W). The complexes are obtained by replacement of norbornadiene (NBD) in M(CO)₄NBD or cycloheptatriene CHT in M(CO)₃CHT. Spectroscopic data (v(CO), δ δ) support the σ-donor/-π-acceptor model of the MP bonds.     

Reactions of the carbonyl complexes M(CO)3(L)3 (L = py,M = Mo,W; L = NH3, M = Mo) and M(CO)4(2-Mepy)2 (M = Mo,W) with HgX2 (X = Cl,CN, SCN)

The reactions of the substituted Group VI metal carbonyls of the type M(CO)₄(2-Mepy)₂ (M = Mo, w) and M(CO)₃(L)₃ (L = py, M = Mo, W; L = NH₃, M = Mo) with mercuric derivatives HgX₂ (X = Cl, CN, SCN) have given rise to three series of tricarbonyl complexes: M(CO)₃(py)HgCl₂ · 1/2HgCl₂ (M = Mo, W); 2[M(CO)₃(L)]Hg(CN)·nHg(CN)_x (L = py, M = Mo, W, n = $\text{1}\text{2}$, × = 2; L = 2- Mepy, × = 1; M = Mo, n = 3; M = W, n = 1); and [M(CO)₃(L)Hg(SCN)₂ · nHg(SCN)₂] (L = py, M = Mo,W, n = 0; L = 2-Mepy, M = Mo, W, n = $\text{1}\text{2}$; L = NH₃, M = Mo, n = 0) depending on which mercuric compound is employed. All the reactions with Hg(SCN)₂ give isolable products whereas those with Hg(CN)₂ and HgCl₂ did so far only the reactions with [M(CO)₄(2-Mepy)₂] and M(CO)₃(py)₃. The greater reactivity of Hg(SCN)₂ than of Hg(CN)₂ and HgCl₂ is consistent with the various acceptor capacities of the groups bonded to the mercury atom.The reactions studied always involve displacement of the N-donor ligand of the original complex and partial or total displacement of the halide or pseudohalide groups of the mercury compound to give in all cases compounds containing MHg bonds. In addition, elimination of a CO group in the tetracarbonyl complexes M(CO)₄(2-Mepy)₂occurs.     

A mass spectral study of intramolecular rearrangements in cis-M(CO)4(13CO)piperidine (M = Cr,W) derivatives

Low voltage mass spectra of cis-M(CO)₄(¹³CO)piperidine (M = Cr,W) show the initial loss of CO to proceed with complete scrabling of the label between axial and equatorial sites.     

Vapour pressure measurements on M(CO)5L (M = Cr,Mo, W; L = piperidine,pyridine, pyrazine,pyrazole, thiazole)

The vapour pressures and enthalpies of sublimation for a number of M(CO)₅L-complexes (M = Cr, Mo, W and L = piperidine, pyridine, pyrazine, pyrazole, thiazole) have been determined by the Knudsen effusion method. The results are compared with similar complexes and dipole moment measurements from the literature.     

Interesting synthetic routes from the reinvestigation of the reaction of the M(CO)6 (M=Cr,Mo and W) species with KOH

Summary Reinvestigation of the reaction of M(CO)₆ (M=Cr, Mo or W) with KOH has been found to provide a very convenient route to the K[M₂H(CO)₁₀] compounds (M=Cr, Mo or W). The reaction involving Cr(CO)₆ yields new potassium derivatives containing [Cr₂(CO)₁₀]^2– and [HCr(CO)₅]^– species; also K[Cr₂D(CO)₁₀] is produced from the Cr(CO)₆/KOD interaction in C₂D₅OD. The reaction involving two different group 6 metal carbonyls yields [MM(CO)₁₀(-H)]^– (MM=CrMo, CrW or WMo) species as their K⁺ and PPN⁺ [bis(triphenylphosphine)iminium] salts.     

Perfluormethyl-Element-Liganden. XXIX. Darstellung und spektroskopische Untersuchungen von M(CO)4L2-Komplexen (M = Cr,Mo, W; L = Me2PSMe,Me2PSeMe, (CF3)2PSMe, (CF3)2PSeMe)

Perfluoromethyl Element Ligands. XXIX. Preparation and Spectroscopic Investigation of M(CO)₄L₂ Complexes (M ? Cr, Mo, W; L ? Me₂PSMe, Me₂PSeMe, (CF₃)₂PSMe, (CF₃)₂PSMe) The complexes M(CO)₄L₂ (see Inhaltsübersicht) have been prepared by the reaction of tetracarbonyl norbornadiene metal compounds M(CO)₄NBD with L at room temperature or 35°C, respectively. The cis-complexes formed in the first step undergo rearrangement to trans-isomers at higher temperatures. New compounds have been characterized by analytical and spectroscopic (IR, NMR, MS) methods.     

Ge4Cl4[MCp(CO)3]4 (M = Cr,Mo, W): A Series of Transition Metal Substituted Four-membered Cyclogermanes

The reaction of GeCl₂ · dioxane with the sodium salts NaMCp(CO)₃ (M = Cr, Mo, W) leads to new four-membered ring compounds Ge₄Cl₄[MCp(CO)₃]₄, where the remaining chlorine atom cannot be substituted by another MCp(CO)₃ substituent. A large excess of the sodium salts only leads to some minor side-reactions. All Ge₄-compounds exhibit a non-planar four-membered Ge₄ ring, which can be traced back to electrostatic effects as shown by quantum chemical calculations. Furthermore, cluster build-up reactions might be possible due to the halide substituents in the new ring compounds of germanium, showing that GeCl₂ · dioxane is an excellent starting material for the synthesis of cluster compounds of germanium.     

Si(SiMe3)3]3Ge9M(CO)3(-) (M=Cr, Mo, W): coordination chemistry with metalloid clusters

Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-)1 can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. So the reaction of 1 with Cr(CO)(3)(CH(3)CN)(3) leads to a cluster enlargement where the chromium atom is incorporated into the cluster core. Here further applications of 1 as a flexible ligand in coordination chemistry are presented where the reaction of 1 with Mo(CO)(3)(EtCN)(3) and W(CO)(3)(CH(3)CN)(3) leads to [(CO)(3)MoGe(9)R(3)](-)4 and [(CO)(3)WGe(9)R(3)](-)5 respectively (R = Si(SiMe(3))(3)), showing that 1 can indeed be used as a flexible ligand in coordination chemistry. Structural and electronic properties of the Ge(9)M clusters 4 and 5 are discussed as well as mechanistic aspects of their formation.     

Synthesis of the new, cubane-like W3S4Co cluster core. Completion of the homologous series [(eta5-Cp')3M3S4Co(CO)] (M = Cr, Mo, W)

Reaction between the cluster salts [(eta(5)-Cp')(3)M(3)S(4)][pts] (M = Mo, W; Cp' = methylcyclopentadienyl; pts = p-toluenesulfonate) and [Co(2)(CO)(8)] yielded the electroneutral clusters [(eta(5)-Cp')(3)M(3)S(4)Co(CO)]. The molecular structure of [(eta(5)-Cp')(3)W(3)S(4)Co(CO)] was determined by single-crystal X-ray diffraction methods. The unprecedented 60 electron W(3)S(4)Co cluster completes a homologous series of heterobimetallic clusters, [(eta(5)-Cp')(3)M(3)S(4)Co(CO)] (M = Cr, Mo, W), containing a cubane-like core motif.     

Observation of resonance effects in the relative partial photoionization cross sections of the d bands of M(CO)6, M = Cr,Mo and W

Relative partial photoionization cross sections as a function of photon energy, over the range 20–110 eV, have been measured for the valence bands of Cr(CO)₆, Mo(CO)₆ and W(CO)₆. All three t_2g⁻¹ bands show a very pronounced increase in intensity at photon energies (hv) corresponding to np resonant absorption (Cr(CO)₆, hv = 52.5 eV, n = 3; Mo(CO)₆,hv = 48 eV, n = 4; W(CO)₆, hv = 44 and 53 eV, n = 5). The other valence bands show a small intensity increase at similar energies. Observation of such resonant photoemission provides an unambiguous method for assignment of nd bands in the photoelectron spectra of gas-phase molecules.     

Direct Electrochemical Investigations of 17-Electron Complexes of CpM(CO)(3)(*) (M = Mo, W, and Cr)

Photolysis of complexes of the type M(2)(CO)(6)(RC(5)H(4))(2) (where M = W, Mo, Cr and R = H (Cp) or CH(3) (Cp')) leads to the production of short lived 17-electron radicals. Direct electrochemical characterization of these intermediates has been achieved using a technique known as photomodulated voltammetry (PMV). The results from PMV analysis are in excellent agreement with literature estimates for CpMo(CO)(3)(*) and CpCr(CO)(3)(*). However, CpW(CO)(3)(*) is found to be shifted oxidatively 115 mV relative to previous literature estimates. The change in the value for the tungsten complex changes previous estimates to the bond dissociation energy for tungsten metal hydrides by 3.0 +/- 0.9 kcal/mol. Lifetime information on the radicals is also reported based on the phase shift of the electrochemical signal observed by PMV under limiting current conditions.     

Indenyl and fluorenyl transition metal complexes: XV.Reactions of 1,1-dimethylindene,spirocyclopropane-1,1-indene,and spirocyclopropane-9,9-fluorene with L3M(CO)3 (L = NH3, Py; M = Cr,Mo, W)

Reaction of indene, 1,1-dimethylindene, spirocyclopropane-1,1-indene, and spirocyclopropane-9,9-fluorene with Py₃M(CO)₃/BF₃ · OEt₂ (M = Cr, Mo, W) involves two competing processes: (i) the formation of the ₆-arene complexes (A) and (ii) the oxidative addition at the C(1)R and C(9)R bonds (R = alkyl) with the formation of chelated σ,π-complex (B). The reaction pathway (A or B) is determined both by the metal and the ligand.     

Darstellung und Eigenschaften von Komplexen des Typs cis-(RCN)3M(CO)3 (M = Cr,M, W)

Metal complexes of the type cis-(RCN)₃M(CO)₃ (M = Cr, Mo, W) have been prepared by different methods starting with M(CO)₆ or, more conveniently, with substituted derivatives of the metal hexacarbonyls. Infrared spectroscopic studies indicate that the strength of the nitrile-to-metal bond in cis-(RCN)₃M(CO)₃ is only sligthly influenced by the R group. The chromium compounds cis-(RCN)₃Cr(CO)₃ may be used as starting materials for the preparation of hexaalkylborazine-chromium-tricarbonyls.     

Ligand substitution kinetics in M(CO)4(η-norbornadiene) complexes (M=Cr, Mo, W): displacement of norbornadiene by bis(diphenylphosphino)alkanes

The thermal substitution kinetics of norbornadiene (NBD) by bis(diphenylphosphino)alkanes (PP), (C₆H₅)₂P(CH₂)_nP(C₆H₅)₂ (n=1, 2, 3) in M(CO)₄(η^2:2-NBD) complexes (M=Cr, Mo, W), were studied by quantitative FT-IR spectroscopy. The reaction rate exhibits first-order dependence on the concentration of the starting complex, and the observed rate constant depends on the concentration of the leaving NBD ligand and on the concentration and the nature of the entering PP ligand. In the proposed mechanism there are two competing initial steps: an associative reaction involving the attachment of the entering PP ligand to the transition metal center and a dissociative reaction involving the stepwise detachment of the diolefin ligand from the transition metal center. A rate law is derived from the proposed mechanism. The activation parameters are obtained from the evaluation of the kinetic data. It is found that at higher concentrations of the entering ligand, the associative path is dominant, while at lower concentrations the contribution of the dissociative path becomes significant. Both the observed rate constant and the activation parameters show noticeable variation with the chain length of the diphosphine ligand.