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.     

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.     

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 synthesis and 1H NMR study of vinyl organometallic monomers: (η5-C5H4CHCH2)M(CO)2(NO) (M = Cr,Mo, W) and (η5-C5H4CHCH2)M(CO)2 (M = Co,Rh, Ir)

A reaction between 6-methylfulvene and lithium diisopropylamide in THF solution produces vinylcyclopentadienyllithium in yields of 85–95%. The ¹H NMR spectrum of this air-sensitive organlithium reagent has been recorded in THF-d₈. Reactions of vinylcyclopentadienyllithium with Group VIB metal hexacarbonyls followed by treatment with N-methyl-N-nitroso-p-toluenesulfonamide afford the new vinyl organometallic monomers (η⁵-C₅H₄CHCH₂)M(CO)₂(NO) (M = Mo, W). Vinylcyclopentadienyllithium also serves as a convenient precursor to a series of (η⁵-vinylcyclopentadienyl)dicarbonylmetal monomers of cobalt, rhodium, and iridium. The ¹H NMR spectra of these vinylcyclopentadienylmetal derivatives have been compared as a function of the metal.     

Preparation and properties of the formamidino complexes [M(π-C5H5){HC(NR)2}(CO)2] (M = molybdenum or tungsten; R = aryl or alkyl)

The preparation and properties of the complexes [M(π-C₅H₅){HC(NR)₂}CO)₂] (M = Mo, W; R = aryl or alkyl) are reported. The complex [Mo(π-C₅H₅){HC(N-p-tolyl)₂}(CO)₂] could be prepared by (a) reaction of MoCp(CO)₃Cl with M′{HC(N-p-tolyl)₂} (M′ = K, Ag or Cu); (b) irradiation of MoCp(CO)₃Cl with HC(HN-p-tolyl)N-p-tolyl); and (c) reaction of [MoCp(CO)₃]₂ with M′{HC(N-p-tolyl)₂} (M′ = Ag or Cu). The several routes to this complex give indications of the mechanisms of formation. The structure of these complexes and the bonding nature of the metal with the formamidino group is discussed on basis of the ¹H and ¹³C NMR and IR spectra.Reaction of N,N′-dimethyl formamidine with MCp(CO)₃Cl gave the complex [M(π-C₅H₅){HC(NMe)N(CO)Me}(CO)₂], containing a carbonyl inserted between the metal and the formamidino group. Irradiation of this carbamoyl complex caused decarbonylation, yielding the complex [M(π-C₅H₅){HC(NMe)₂}CO)₂].     

Cumulated double bond systems as ligands : V. Dialkylsulfurdiimine compounds M(CO)4(RNSNR) (M = Cr,Mo, W) and M(CO)5(RNSNR) (M = Cr,W); structural,spectroscopic and fluxional properties.

The preparation and properties are reported of M(CO)₄(RNSNR) (M = Cr, Mo, W; R = i-Pr, t-Bu), in which the ligand is bidentate and in the trans,trans configuration, and of M(CO)₅(RNSNR) (M = CR, W; R = Et, i-Pr) in which the sulfurdiimine is monodentate and in the cis,trans configuration. In both cases the ligand is linked to the metal atom via the N-atom(s). With M(CO)₅(MeNSNMe) a second isomer is found in which the sulfurdiimine is probably bonded via the S-atom to the metal. All the pentacarbonyl compounds are fluxional; this is attributed to a gliding movement of the metal atom along the NSN system.Both W(CO)₄(t-BuNSN-tBu) and W(CO)₅(MeNSNMe) show vibronic coupling of metal to ligand charge transfer transitions with sulfurdiimine vibrations, as shown with Resonance Raman, but only for W(CO)₅(MeNSNMe) also with the symmetric mode of the equatorial carbonyl groups. The metalsulfurdiimine bond appears to be weak for M(CO)₅(RNSNR), but strong for M(CO)₄(RNSNR).     

A variable temperature H NMR study of stereochemical non-rigidity in group VI metal pentacarbonyl complexes of 1,3,5,7-Tetrathian; [M(CO)5( H2)] (M=Cr OR W)

Stereochemical non-rigidity in the complexes [M(CO)₅( H₂)] (M = Cr or W) has been studied by dynamic nuclear magnetic resonance spectroscopy. In the temperature range ca. −100 to 120°C two intramolecular processes were observed, namely pyramidal atomic inversion about sulphur atoms, and a commutation of the M(CO)₅ moiety between coordination sites on different sulphur atoms. Accurate energy barriers for both processes have been obtained by detailed computer simulations of the static and the dynamic spectra. The magnitudes of ΔG≠ (298.15 K) are compared with those reported for related complexes. The exact nature of the M(CO)₅ shift cannot be unambiguously assigned from the observed spectral line-shape changes. Two possible mechanisms are proposed and discussed.     

Ligandeneigenschaften von Fe3(CO)9(μ3-S)(μ3-ER) (R = alkyl,aryl; E = P,As)

The clusters Fe₃(CO)₉(μ₃-S)(μ₃-ER) (E = P, As; R = Alkyl, Aryl) react with (CO)₅M · THF (M = Cr, W) to give the violet crystalline adducts Fe₃(CO)₉(μ₃-SM(CO)₅)(μ₃-ER). Spectroscopic data and X-ray structure analyses show that adduct formation occurs via the triply bridging sulfur (SCr 242.8(5), SW 254.7(6) pm).     

Synthesis of the pentacarbonyl(chalcocarbonyl)chromium(0) complexes,Cr(CO)5(CX) (X = S,Se)

The arene complexes, (η⁶-C₆H₆)Cr(CO)₂(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60° C to produce the Cr(CO)₅(CX) complexes in high yield. The IR and NMR (¹³C and ¹⁷O) spectra of these complexes are in complete accord with the expected C_4v molecular symmetry. Like the analogous W(CO)₅(CS) complex, both compounds react with cyclohexylamine to give Cr(CO)₅(CNC₆H₁₁). However, while W(CO)₅(CS) undergoes stereospecific CO substitution with halide ions (Y^? to form trans-[W(CO)₄(CS)Y]^?, the two chromium chalcocarbonyl complexes apparently undergo both CO and CX substitution to afford mixtures of [Cr(CO)₅Y]^? and trans-[Cr(CO)₄(CX)Y]^?.     

Neutron scattering study of the reorientational motions in Cr(CO)3(η6C6H6) and Mn(CO)3(η5C5H5)

Incoherent quasi-eleastic neutron scattering experiments: using different resolutions and a wide Q range, have been performed on polycrystalline samples of Cr(CO)₃(η⁶C₆H₆) and Mn(CO)₃(η⁵C₅H₅) in the 280–320 K temperature range. It is shown that aromatic rings are involved into a reorientational process characterized by an activation energy of ≈ 16 kJ mol^?1 and by correlation times of the order of 2 × 10^?11 s and 5 × 10^?11 s at 300 K for C₆H₆ and C₅H₅ rings respectively. Experimental elastic incoherent structure factors are in agreement with the 2π/6 and 2π/5 jump models and the fitted spectra confirm these models. From a comparison with heat-capacity results we conclude that M(CO)₃ groups are fixed during the reorientational process. Finally a comparison with literature data is presented.     

Bidentate amines as bridges between M(CO)2Cl (M = Rh OR Ir) units

The preparation and characterization by elemental analysis, electronic and infrared spectroscopy are reported for the monomeric complexes cis-(amine)-M(CO)₂Cl (M = Ir or Rh, amine = 1,8-naphthyridine or pyridazine; M = Ir, amine = o-phenylenediamine) and the binuclear species (1,8-naphthyridine)Rh₂(CO)₄Cl₂, (1,8-naphthyridine)IrRh(CO)₄Cl₂, (pyrazine)Rh₂(CO)₄Cl₂ and (1,3-di-4-pyridylpropane)Rh₂(CO)₄Cl₂.     

Field desorption mass spectra of [M(CO)3(η-arene)]X (MMn,Re; XBF4, PF6) salts

Field desorption mass spectra are reported for a range of [M(CO)₃(η-arene)]X (MMn or Re, XBF₄ or PF₆) salts. In most cases the spectra are simple, being dominated by molecular, [M]^+·, [M + 1]⁺, and [MCO]⁺ ions for the cationic part of their structure. However, with the π-chloroarene complexes [Mn(CO)₃(η-ClC₆H₅)]PF₆ and [Mn(CO)₃(η-1-Cl, 4-MeC₆H₄)]PF₆, facile loss of the chloro substituent and further fragmentation leads to unusually complex spectra, which include strong peaks arising from recombination of fragment species. Cluster ions are also noted in several cases, allowing identification of the anion.     

Synthesis, structure and some reactions of (C5Me4hex)2Ru2(CO)4

The synthesis of the new cyclopentadiene, C₅Me₄(hex)H is described and its reaction with Ru₃(CO)₁₂ to yield (C₅Me₄hex)₂Ru₂(CO)₄ (hex = n-hexyl) is reported. The X-ray crystal structure of the dimer confirms the structure with bridging and terminal CO groups. Reactions of the dimer to yield (C₅Me₄hex)Ru(CO)₂X (X = Cl, Br, I) are reported. IR, NMR and mass spectra are reported for all new compounds. The solubility of the dimer is found to be 10 times greater than that for (C₅Me₅)₂Ru₂(CO)₄.     

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.     

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 Mössbauer spectroscopic studies on M(CO)5(azaferrocene) complexes (M = Cr, Mo, W). The crystal structures of W(CO)5(azaferrocene) and W(CO)5(2,5-dimethylazaferrocene)

⁵⁷Fe Mössbauer spectroscopic studies on M(CO)₅(azaferrocene) complexes (M = Cr, Mo, W) as well as the crystal structures of W(CO)₅(azaferrocene) and W(CO)₅(2,5-dimethylazaferrocene) are reported. The complexation of azaferrocene to the M(CO)₅ moiety brings about only a small change in the quadrupole splitting. The structures of both tungsten complexes reveal a significant shortening of the W-C bonds trans to the nitrogen. These data indicate that azaferrocene behaves as a relatively strong σ-donor and there is no evidence for any π-acceptor properties.     

Kinetic studies of the reactions of the carbene complex W(CO)5[C(SCH3)2] with phosphines to form phosphorane complexes W(CO)5[(CH3S)2C-PR3] and the synthesis of some cyclic phosphorane complexes

The dithiocarbene complex W(CO)₅[C(SCH₃)₂ reacts with tertiary phosphines, PPh₂CH₃, PPh(CH₃)₂, P(C₂H₅)₃ and P(OCH₃)₃ to form the phosphorane complexes W(CO)₅[CH₃S)₂C-PR₃] and with HPPh₂ to form the phosphine complex W(CO)₅[PPh₂[CH(SCH₃)₂]. Kinetic studies of both types of reactions show that their rates are first order each in W(CO)₅[C(SCH₃)₂] and in the phosphorus ligand. A mechanism involving rate determining phosphorus attack at the carbene carbon followed by rapid rearrangement to the product is consistent with this rate law. Rate constants for the reactions increase with increasing nucleophilicities of the phosphines: P(OCH₃)₃ < PPh₂H < PPh₂C_H3 ? PPh(CH₃)₂ < P(C₂H₅)₃. The ΔH values decrease (P(OCH₃)₃ > PPh₂H > PPh₂(CH₃) > PPh(CH₃)₂ > P(C₂H₅)₃) as the nucleophilicities of the phosphines increase. The ΔS values (≈-30 e.u.) remain essentially constant for all the reactions. The cyclic dithiorcarbenes W(CO)₅[CS(CH₂)_nS], wheren- 3 or 4, react with PPh₂(CH₃) to form the cyclic phosphorane complexes, W(CO)₅[S(CH₂)_nSC-PPh₂(CH₃)]. The 6- and 7- membered cyclic dithiocarbenes also react with PPh₂H to form the phosphine complexes, W(CO)₅ {PPh₂- [CS(CH₂)_nS(H)]}.     

The enthalpies of formation of CH3Mn(CO)5 and of CH3Re(CO)5, and the strengths of the CH3Mn and CH3Re bonds

From measurements of the heats of iodination of CH₃Mn(CO)₅ and CH₃Re(CO)₅ at elevated temperatures using the ‘drop’ microcalorimeter method, values were determined for the standard enthalpies of formation at 25° of the crystalline compounds: ΔH^o_f[CH₃Mn(CO)₅, c] = ?189.0 ± 2 kcal mol^?1 (?790.8 ± 8 kJ mol^?1), ΔH^o_f[Ch₃Re(CO)₅,c] = ?198.0 ± kcal mol^?1 (?828.4 ± 8 kJ mo^?1). In conjunction with available enthalpies of sublimation, and with literature values for the dissociation energies of MnMn and ReRe bonds in Mn₂(CO)₁₀ and Re₂(CO)₁₀, values are derived for the dissociation energies: D(CH₃Mn(CO)₅) = 27.9 ± 2.3 or 30.9 ± 2.3 kcal mol^?1 and D(CH₃Re(CO)₅) = 53.2 ± 2.5 kcal mol^?1. In general, irrespective of the value accepted for D(MM) in M₂(CO)₁₀, the present results require that, D(CH₃Mn) = $\text{1}\text{2}$D(MnMn) + 18.5 kcal mol^?1 and D(CH₃Re) = $\text{1}\text{2}$D(ReRe) + 30.8 kcal mol^?1.     

Germylene complexes of tungsten pentacarbonyls W(CO)5GeCl2 and W(CO)5GeW(CO)5: Electrochemical synthesis and quantum-chemical computations

Convenient synthetic route to prepare the germylene complexes of tungsten pentacarbonyls, W(CO)₅GeCl₂ and W(CO)₅GeW(CO)₅, electrochemically is developed. Combined quantum-chemical/IR spectroscopic approach is used for identification of the synthesized compounds. Good agreement between theoretical and experimental spectra can be regarded as one of the proofs of their supposed structures.     

Octahedral metal carbonyls LXXII. Volumes of activation for solvent displacement in (solvent)M(CO)5 transients (M = Cr,Mo, W) generated from M(CO)6 via pulsed laser flash photolysis

Pulsed laser flash photolysis of M(CO)₆ (M = Cr, Mo, W) in aliphatic and aromatic hydrocarbon solutions (solvent = n-C₇H₁₆ and C₆H₅X (X = F, Cl, H, CH₃)) produces (solvent)M(CO)₅ transients, which then react with Lewis bases (L; 1-hexene, piperidine, 2-picoline, pyridine) to afford LM(CO)₅ products. The solvent-displacement process has been studied at variable pressures to 150 MPa, and volumes of activation for this process have been determined. These volumes of activation are sensitive to the identity of the coordinated solvent and suggest that bonding of chlorobenzene to Cr takes place via a lone pair of electrons on Cl, but through an isolated olefinic linkage for benzene, fluorobenzene and toluene. Observed volumes of activation also are consistent with the accessibility of an interchange mechanism for solvent displacement of n-heptane and with a dissociative solvent displacement mechanism for the arenes and support an increasing contribution from the solvent interchange process vs. reversible solvent dissociation in the order of the increasing size of the metal atom, Cr<Mo ⋍ W. The observed ability of “[M(CO)₅]” to discriminate among various nucleophiles arises in part from the accessibility of these two competitive mechanisms.