The reaction between [η5-C5H5M(CO)3]2, η5-C5H5M(CO)3I (M  Mo,W) and isonitriles

The reaction between η⁵-C₅H₅M(CO)₃I (M  Mo, W) and isonitriles, RNC, (RNC  PhCH₂NC, t-BuNC and 2,6-dimethylphenylisocyanide (XyNC)) is catalysed by the dimer [η⁵-C₅H₅M(CO)₃]₂ (M = Mo, W) to yield η⁵-C₅H₅M(CO)_3?n(RNC)_nI (n = 1–3) and [η⁵-C₅H₅Mo(RNC)₄]I. The complexes (η⁵-C₅H₅)₂Mo₂(CO)₆?n(RNC)_n (n = 1, RNC = MeNC, PhCH₂NC, XyNC, t-BuNC; n = 2, RNC = t-BuNC) have been prepared in moderate yield from the direct reaction between [η⁵-C₅H₅Mo(CO)₃]₂ and RNC, and also catalyse the above reaction. A reaction pathway involving a fast non-chain radical mechanism and a slower chain radical mechanism is proposed to account for the catalysed reaction.     

The heats of hydrogenation of the metal—metal bonded complexes [M(CO)3C5H5]2 (M = Cr,Mo, W)

Direct measurement of the enthalpy of decomposition of HCr(CO)₃C₅H₅ to [Cr(CO)₃C₅H₅]₂ and H₂ was made by differential scanning calorimetry. The heat of hydrogenation of 1,3-cyclohexadiene by HM(CO)₃C₅H₅ for M = Cr, Mo, and W was measured by solution calorimetry. The enthalpies of iodination of [M(CO)₃C₅H₅]₂ and HM(CO)₃C₅H₅ were measured for M = Mo and W. These data have been used to calculate the heats of hydrogenation for each of the metal—metal bonded dimers, [M(CO)₃C₅H₅]₂ (M = Cr, Mo, and W).C₅H₅(CO)₃M-M(CO)₃C₅H₅(s) + H₂(g) → 2HM(CO)₃C₅H₅(s)Addition of hydrogen has been found to be exothermic for M = Cr, W (?3.3 kcal/mol and ?1.5 kcal/mole, respectively) but endothermic for M = Mo (+6.3 kcal/mol). These results are consistent with the trend of increasing MH bond strengths upon descending Group VI. Addition of H₂ to [Cr(CO)₃C₅H₅]₂ is favored by the unusually weak chromium—chromium bond.     

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.     

Photochemical studies of M(CO)6 (M = Cr,Mo, W) at low temperature in solution. Infrared spectra of M(CO)5 (solvent) (solvent = methylcyclohexane,methylene chloride) and W(CO)5L (L = aromatic hydrocarbon)

The infrared spectra of M(CO)₅(MCH) (MCH = methylcyclohexane; M = Cr, Mo, W), formed by 366 nm irradiation of M(CO)₆ at ?78°C in rigorously purified methylcyclohexane, are reported. The previously reported spectrum of “W(CO)₅” at low temperature in methylcyclohexane/isopentane solution is attributed to W(CO)₅(impurity), where the impurity is probably an aromatic or olefinic hydrocarbon. Spectra in methylene chloride solution are also discussed. The photochemical reactions of W(CO)₆ with aromatic hydrocarbon ligands in methylcyclohexane solution were also studied at ?78°C in a low temperature infrared cell. Irradiation (366 nm) of W(CO)₆ at ?78°C in rigorously purified methylcyclohexane solution containing approximately 5% (v/v) toluene, benzene, mesitylene, biphenyl, or p-xylene initially produces the complex W(CO)_5? (MCH). In the presence of the aromatic hydrocarbon, this complex is unstable and it decomposes in a dark reaction to give a complex which has an infrared spectrum typical for a C_4v M(CO)₅X molecule. It is proposed that the product of the dark reaction is W(CO)₅(aromatic), formed by reaction of W(CO)₅(MCH) with the aromatic ligand in solution. The infrared spectra of the W(CO)_5? (aromatic) complexes are different from the spectra previously reported for these complexes. It is shown that the spectra previously reported for W(CO)_5? (aromatic) are actually attributable to W(CO)₅(hexane) (hexane was the solvent used in the previous study); these spectra were probably obtained before W(CO)₅(hexane) had time to react with the aromatic hydrocarbon.     

Substitution reactions of [MBr(π allyl)(CO)2(LL)] complexes (M = Mo,W; L-L = 2,2 -bipyridine 1,2-bis(diphenylphosphine)ethane) with xanthates and dithiocarbamates

The complexes [MBr(π-allyl)(CO)₂(bipy)] (M = Mo, W, bipy = 2,2′-bipyridine) react with alkylxanthates (M^IRxant), and N-alkyldithiocarbamates (M^IRHdtc) (M^I = Na or K), yielding complexes of general formula [M(S,S)- (π-allyl)(CO)₂(bipy)] (M = Mo, (S,S) = Rxant (R = Me, Et, t-Bu, Bz), RHdtc (R = Me, Et); M = W, (S,S) = Extant). A monodentate coordentate coordination of the (S,S) ligand was deduced from spectral data. The reaction of [MoBr(π-allyl)(CO)₂(bipy)] with MeHdtc and Mexant gives the same complexes whether pyridine is present or not. The complexes [Mo(S,S)(π-allyl)(CO)₂(bipy)] ((S,S) = MeHdtc, Mexant) do not react with an excess of (S,S) ligand and pyridine.No reaction products were isolated from reaction of [MoBr(π-allyl)(CO)₂(dppe)] with xanthates or N-alkyldithiocarbamates.     

The chemical oxidation and electronic spectra of the complexes trans-[M(CNR)2(Ph2PCH2CH2PPh2)2] (M = Mo or W)

Oxidation of the complexes $\text{trans}$-[M(CNR)₂(dppe)₂] (A) (M = Mo or W; R = Me, Bu^t or CH₃C₆H₄-$\text{4}$; dppe = Ph₂PCH₂CH₂PPh₂) with diiodine or silver (I) salts gives the paramagnetic cations $\text{trans}$-[M(CNR)₂(dppe)₂]⁺, (M = Mo, R = CH₃C₆H₄-$\text{4}$; M = W, R = Bu^t) and $\text{trans}$-[M(CNR)₂(dppe)₂]²⁺ (M = Mo, R = Me or CH₃C₆H₄-$\text{4}$; M = W, R = Me or Bu^t). Mixtures of products are generally produced when dichlorine or dibromine are the oxidising agents, however pure salts, the seven-coordinate complex cations [MX(CNC₆H₄CH₃-$\text{4}$)₂(dppe)₂]⁺ (B, X = Cl or Br) have been isolated. A simple molecular orbital scheme is proposed for complexes (A) and used to discuss their electronic spectra and their oxidation.     

Photoinduzierte und thermische reaktionen der übergangsmetallethylverbindungen CpM(CO)3Et (Cp = η5-cyclopentadienyl; Et = ethyl; M = Mo,W)

In the compounds CpM(CO)₃Et (M = Mo, W) the metal-ethyl σ-bond is photolabile. Upon irradiation of a solution of CpM(CO)₃Et with UV light mainly [CpM(CO)₃]₂, CpM(CO)₃H, ethane, and ethylene are produced. Formation of CpM(CO)₃H is indicative of a β-elimination pathway for the photo-induced degradation. In the presence of trimethylphosphane (L) UV-irradiation of a solution of CpM(CO)₃Et leads to the products Cp(CO)(L)₂MM-(CO)₃Cp, CpM(CO)₂(L)Et and CpM(CO)₂(L)H, while the thermal reaction produces the propionyl complexes CpM(CO)₂(L)(COEt).     

Fe–Hg Interactions and P Chemical Shifts in [Fe(CO)3 (PPh2R)2(HgCl2)] (R=pym, fur, py, thi)

In order to study the effects of R group on Fe–Hg interactions and 31P chemical shifts, the structures of mononuclear complexes Fe(CO)₃(PPh₂R)₂ (R=pym:1, fur: 2, py: 3,thi: 4; pym=pyrimidine, fur=furyl, py=pyridine, thi=thiazole) and binuclear complexes [Fe(CO)₃(PPh₂R)₂(HgCl₂)] (R=pym: 5, fur: 6, py: 7, thi: 8) were studied using the density functional theory (DFT) PBE0 method. The 31P chemical shifts were calculated by PBE0-GIAO method. Nature bond orbital (NBO) analyses were also performed to explain the nature of the Fe–Hg interactions. The conclusions can be drawn as follows: (1) The complexes with nitrogen donor atoms are more stable than those with O or S atoms. The more N atoms there are, the higher is the stabilility of the complex. (2) The Fe–Hg interactions play a dominant role in the stabilities of the complexes. In 5 or 6, thereisa σ-bond between Fe and Hg atoms. However, in 7 and 8, the Fe–Hg interactions act as σ_P–Fe→n_Hg and σ_C–Fe→n_Hg delocalization. (3) Through Fe→Hg interactions, there is charge transfer from R groups towards the P, Fe, and Hg atoms, which increases the electron density on P nucleus in binuclear complexes. As a result, compared with their mononuclear complexes, the 31P chemical shifts in binuclear complexes show some reduction.     

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 tricarbonylpyridine complexes (NN)(py)M(CO)3 (M = Mo, W; NN = 2,2′-bipyridine, 1,10-phenanthroline) with mercuric derivatives HgX2 (X = Cl, CN, SCN)

Treatment of mercury(II) halides and pseudohalides with complexes (NN)(L)M(CO)₃ (L = py; NN = 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen); M = Mo, W) gives new tricarbonyl complexes. In all cases elimination of the pyridine ligand occurs and in some cases there is partial displacement of halogen from the mercuric halide. Treatment of bipy(py)W(CO)₃ with mercuric chloride gives only an adduct. Conductivity, IR and electronic absorption are given, and possible formulations suggested.     

Reactions of the cycloheptatrienyl complexes [MX(CO)2(η-C7H7)] (M=Mo, X=Br; M=W, X=I) with CNBu: X-ray crystal structure of [WI(CO)2(CNBu)2(η-C7H7)]

Reaction of [MX(CO)₂(η⁷-C₇H₇)] (M=Mo, X=Br; M=W, X=I) with two equivalents of CNBu^t in toluene affords the trihapto-bonded cycloheptatrienyl complexes [MX(CO)₂(CNBu^t)₂(η³-C₇H₇)] (1, M=Mo, X=Br; 2, M=W, X=I). The X-ray crystal structure of 2 reveals a pseudo-octahedral molecular geometry with an asymmetric ligand arrangement at tungsten in which one CNBu^t is located trans to the η³-C₇H₇ ring. Treatment of 2 with tetracyanoethene results in 1,4-cycloaddition at the η³-C₇H₇ ring to give [WI(CO)₂(CNBu^t)₂{η³-C₉H₇(CN)₄}], 3. The principal reaction type of the molybdenum complex 1 is loss of carbonyl and bromide ligands to afford substituted products [MoBr(CNBu^t)₂(η⁷-C₇H₇)] 4 or [Mo(CO)(CNBu^t)₂(η⁷-C₇H₇)]Br. Reaction of [MoBr(CO)₂(η⁷-C₇H₇)] with one equivalent of CNBu^t in toluene at 60°C affords [MoBr(CO)(CNBu^t)(η⁷-C₇H₇)], 5, which is a precursor to [Mo(CO)(CNBu^t)(NCMe)(η⁷-C₇H₇)][BF₄], 6, by reaction with Ag[BF₄] in acetonitrile. In contrast with the parent dicarbonyl systems [MoX(CO)₂(η⁷-C₇H₇)], complexes of the Mo(CO)(CNBu^t)(η⁷-C₇H₇) auxiliary, 5 and 6, do not afford observable η³-C₇H₇ products by ligand addition at the molybdenum centre.     

The thermochemistry of M(CO)6−xLx (M = Cr,Mo, W; L = piperidine,pyridine, pyrazine,pyrazole, thiazole; x = 1, 2, 3)

A number of M(CO)_6?xL_x complexes (M = Cr, Mo, W; L = piperidine, pyridine, pyrazine, pyrazole, thiazole; x = 1, 2, 3) are shown to undergo both disproportionation and substitution in a CO atmosphere, when heated on a thermobalance. Using a DSC, reaction enthalpies have been determined from which enthalpies of formation were calculated. Combined with the sublimation enthalpies of these complexes, individual metal—ligand bond enthalpies were evaluated and discussed.     

Synthesis and characterisation of HRuRh3(CO)12. Crystal structures of HRuRh3(CO)12, HRuRh3(CO)10(PPh3)2 and HRuCo3(CO)10(PPh3)2

A new ruthenium-rhodium mixed-metal cluster HRuRh₃(CO)₁₂ and its derivatives HRuRh₃(CO)₁₀(PPh₃)₂ and HRuCo₃(CO)₁₀(PPh₃)₂ have been synthesized and characterized. The following crystal and molecular structures are reported: HRuRh₃(CO)₁₂: monoclinic, space group P2₁/c, a 9.230(4), b 11.790(5), c 17.124(9) Å, β 91.29(4)°, Z = 4; HRuRh₃(CO)₁₀(PPh₃)₂·C₆H₁₄: triclinic, space group P$\text{1}$, a 11.777(2), b 14.079(2), c 17.010(2) Å, α 86.99(1), β 76.91(1), γ 72.49(1)°, Z = 2; HRuCo₃(CO)₁₀(PPh₃)₂·CH₂Cl₂: triclinic, space group P$\text{1}$, a 11.577(7), b 13.729(7), c 16.777(10) Å, α 81.39(4), β 77.84(5), γ 65.56°, Z = 2. The reaction between Rh(CO)₄^? and (Ru(CO)₃Cl₂)₂ tetrahydrofuran followed by acid treatment yields HRuRh₃(CO)₁₂ in high yield. Its structural analysis was complicated by a 80–20% packing disorder. More detailed structural data were obtained from the fully ordered structure of HRuRh₃(CO)₁₀(PPh₃)₂, which is closely related to HRuCo₃(CO)₁₀(PPh₃)₂ and HFeCo₃(CO)₁₀(PPh₃)₂. The phosphines are axially coordinated.     

Photochemical reactions of M(CO)6 (M = Cr,Mo, W) with Ph2P(S)P(S)Ph2

New complexes {M(CO)₄[Ph₂P(S)P(S)Ph₂]} (M = Cr, Mo and W), (1a)–(3a), [(1a), M = Cr; (2a), M = Mo; (3a), M = W] and {M₂(CO)₁₀[-Ph₂P(S)P(S)Ph₂]} (M = Cr, Mo, W), [(1b)–(3b) [(1b), M = Cr; (2b), M = Mo; (3b), M = W]] have been prepared by the photochemical reaction of M(CO)₆ with Ph₂P(S)P(S)Ph₂ and characterized by elemental analyses, f.t.-i.r. and ³¹P-(¹H)-n.m.r. spectroscopy and by FAB-mass spectrometry. The spectra suggest cis-chelate bidentate coordination of the ligand in {M(CO)₄[Ph₂P(S)P(S)Ph₂]} and cis-bridging bidentate coordination of the ligand between two metals in (M = Cr, Mo and W).     

Sublimation enthalpies of the complexes W(CO)6-x(NCCH3)x (x=1,2,3) and Mo(CO)6-x(NCCH3x(x=1,3)

Vapour pressure measurements have been carried out on the complexes W(CO)_it6-x (NCCH₃x(x=1,2,3) and Mo(CO)_it6-x(NCCH₃x(x=1,3) employing the Knudsen effusion technique. The following enthalpies of sublimation, ΔH²⁹⁸_sub(kJ mole^?1), have been determined from vapour pressure data: W(CO)₅(NCCH₃)=98.1±2.0; W(CO) ₄ (NCCH₃)₂=131.0±6.0; W(CO)₃(NCCH₃₃=103.4±6.0; Mo(CO)₅(NCCH₃)=105.8± 5.6; and Mo(CO)₃(NCCH₃)₃=111.3±3.0.     

Darstellung von mehrkernkomplexen aus As2Co2(CO)6

By reaction of As₂Co₂(CO)₆ with M(CO)₅THF (M = Cr, Mo, W), the heteronuclear complexes (CO)₅M · As₂Co₂(CO)₆ of low stability were obtained. Phosphine substitution increased the basicity of the As₂Co₂ cluster, into which up to two PMe₃ ligands and up to four P(OMe)₃ ligands could be introduced. Subsequently, two M(CO)₅ units (M = Cr, Mo, or W) could be attached to As₂Co₂(CO)₅ · PMe₃, As₂Co₂(CO)₄L₂ (L = PMe₃, P(OMe)₃), and As₂Co₂(CO)₃[P(OMe)₃]₃. The crystal structure of [(CO)₅W]₂As₂Co₂(CO)₄[P(OMe)₃]₂ was determined.     

Electrochemical behaviour of [Ru(L)(CO)2Cl2] [Ru(L)(CO)Cl3][Me4N] and [Ru(L)(CO)2(CH3CN)2][CF3SO3]2 complexes (L = 2,2′- bipyridine or 4,4′-isopropoxycarbonyl-2,2′-bipyridine)

The clectrochemical behaviour of the complexes [Ru^II(L)(CO)₂Cl₂], [Ru^II(L)(CO)Cl₃][Me₄N] and [Ru^II(L)(CO)₂(CH₃CN)₂][CF₃SO₃]₂ (L = 2,2′-bipyridine or 4,4′-isopropoxycarbonyl-2,2′-bipyridine) has been investigated in CH₃CN. The oxidation of [Ru(L)(CO)₂Cl₂] produces new complexes [Ru^III(L)(CO)(CH₃CN)₂Cl]²⁺ as a consequence of the instability of the electrogenerated transient Ru^III species [Ru^III(L)(CO)₂Cl₂]⁺. In contrast, the oxidation of [Ru^II(L)(CO)Cl₃][Me₄N] produces the stable [Ru^III(L)(CO)Cl₃] complex. In contrast [Ru^II(L)(CO)₂(CH₃CN)₂][CF₃SO₃]₂ is not oxidized in the range up to the most positive potentials achievable. The reduction of [Ru^II(L)(CO)₂Cl₂] and [Ru^II(L)(CO)₂(CH₃CN)₂][CF₃SO₃]₂ results in the formation of identical dark blue strongly adherent electroactive films. These films exhibit the characteristics of a metal-metal bond dimer structure. No films are obtained on reduction of [Ru^II(L)(CO)Cl₃][Me₄N]. The effect of the substitution of the bipyridine ligand by electron-withdrawing carboxy ester groups on the electrochemical behaviour of all these complexes has also been investigated.     

Trivalent phosphorus derivatives of group via : IV. Infrared and pmr studies of the protonation of M(CO)6−n(PA3)n Complexes (M = Mo,W; A = CH3, OCH3; n = 2, 3, 4)

The action of trifluoroacetic acid on the series M(CO)_6?n(PA₃)_n (M = Mo, W; A = CH₃, OCH₃; n = 2, 3, 4) has shown that protonation occurs if n ? 3. For n = 3 the basicity of the ligand PA₃ plays a more important role in the stability of [HM(CO)₃(PA₃)₃]⁺complexes than for n = 4. Infrared and proton NMR give evidence of the stereochemical non-rigidity of the [HM(CO)_6?n(PA₃)_n]⁺ heptacoordinated cation.     

The thermochemistry of carbonyl complexes of Cr,Mo and W with pyridine and acetonitrile

Microcalorimetric measurements at elevated temperatures of the heats of thermal decomposition and of iodination of a number of [M(CO)_nL_6-n] complexes (M = Cr, Mo, W; n = 3, 4; L = py, MeCN) have led to values for the standard enthalpies of formation of the following crystalline compounds (values given in kJ mol^?) at 25°C: fac-[Mo(CO)₃py₃](275 ± 12), fac-[Mo(CO)₃(NCCH₃)₃]  (410 ± 12), fac-[W(CO)₃py₃](250 ± 12), fac-[W(CO)₃(NCCH₃)₃](405 ± 12) and cis-[Cr(CO)₄py₂](505 ± 20). From these and other data, including estimated heats of sublimation, the bond enthalpy contributions of the various metalligand bonds in the gaseous metal complexes were evaluated as follows (values in kJ mol^?): D(Crpy) 102, D(Mopy) 146, DWPy) 173, D(Mo7z.sbnd;NCMe) 135 and D(WNCMe) 169. For a given metal the bond enthalpy contribution decreased in the order D(MCO) > D(Mpy) > D(Mz.sbnd;NCMe). This order is related to the σ- and π-bonding character of the ligand.     

Darstellung von M2Mn4(CO)18(M=In,Ga) und M2Mn4(CO)18 · 2 D (M  In,D  Pyridin,Aceton; M  Ga,D  Pyridin)

Clusters of the type M₂Mn₄(CO)₁₈ with main Group III metals (M  In, Ga) have been synthesized for the first time by allowing the metals to react in a bomb tube with Mn₂(CO)₁₀, Hg[Mn(CO)₅]₂, or Hg and Mn₂(CO)₁₀; In₂Mn₄(CO)₁₈ also was formed by thermolysis of In[Mn(CO)₅]₃ in the presence of xylene. All M₂Mn₄(CO)₁₈ compounds were shown by X-ray analysis to be isomorphous (space group I4₁/a). They contain a planar bridged ring of 2M and 2 Mn atoms, in which 2 Mn(CO)₄ groups form the MnMn bond, each being connected with 2 [μ-MMn(CO)₅] units; the Mn(CO)₅ ligands at M have trans-positions with respect to the planar metal ring. The new clusters coordinate donor molecules such as pyridine or acetone at M (coordination number 3) to form complexes M₂Mn₄(CO)₁₈ · 2 D (M  In, D  pyridine, acetone; M  Ga, D  pyridine), with M having a coordination number of 4. In pyridine dissociation of Mn(CO)₅^? anions takes place without decomposition of the metal ring.Hg[Mn(CO)₅]₂ was prepared using a new method by reaction of Hg with Mn₂(CO)₁₀ in a bomb tube.