Insertion of Molecular Oxygen in Transition‐Metal Hydride Bonds,Oxygen‐Bond Activation,and Unimolecular Dissociation of Metal Hydroperoxide Intermediates. Short Communication

Thermal activation of molecular oxygen is observed for the late‐transition‐metal cationic complexes [M(H)(OH)]⁺ with M=Fe, Co, and Ni. Most of the reactions proceed via insertion in a metal? hydride bond followed by the dissociation of the resulting metal hydroperoxide intermediate(s) upon losses of O, OH, and H₂O. As indicated by labeling studies, the processes for the Ni complex are very specific such that the O‐atoms of the neutrals expelled originate almost exclusively from the substrate O₂. In comparison to the [M(H)(OH)]⁺ cations, the ion? molecule reactions of the metal hydride systems [MH]⁺ (M=Fe, Co, Ni, Pd, and Pt) with dioxygen are rather inefficient, if they occur at all. However, for the solvated complexes [M(H)(H₂O)]⁺ (M=Fe, Co, Ni), the reaction with O₂ involving O? O bond activation show higher reactivity depending on the transition metal: 60% for the Ni, 16% for the Co, and only 4% for the Fe complex relative to the [Ni(H)(OH)]⁺/O₂ couple.     

Molecular structure and binding energies of monosubstituted hexacarbonyls of chromium,molybdenum, and tungsten: Relativistic density functional study

Relativistic density functional calculations have been carried out for the group VI transition metal carbonyls M(CO)₅L (M=Cr, Mo, W; L=OH₂, NH₃, PH₃, PMe₃, N₂, CO, OC (isocarbonyl), CS, CH₂, CF₂, CCl₂, NO⁺). The optimized molecular structures and M(SINGLE BOND)L bond dissociation energies, as well as the metal–carbonyl bond energy of the trans CO group, have been calculated. Besides the marked dependence of the trans M(SINGLE BOND)CO bond length on the type of ligand L, such an effect on the that bond energy is also observed. For the chromium compounds, the trans Cr(SINGLE BOND)CO bond length varies from 184 to 199 pm and its bond energy from 242 to 150 kJ/mol. For the molybdenum compounds, the range is 197 to 216 pm and 253 to 128 kJ/mol and, for tungsten, 198 to 214 pm and 293 to 159 kJ/mol. The observed trends can be explained with the π acceptor strength of the L ligand. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1985–1992, 1997     

Studies on the Reactivity of [Ge9]4− towards [Fe(cot)(CO)3]: Synthesis and Characterization of [Ge8Fe(CO)3]3− and of the Anionic Organometallic Species [Fe(cot)(CO)3]−

Reaction of cyclooctatetraene (COT) iron(II) tricarbonyl, [Fe(cot)(CO)₃], with one equivalent of K₄Ge₉ in ethylenediamine (en) yielded the cluster anion [Ge₈Fe(CO)₃]^3? which was crystallographically‐characterized as a [K(2,2,2‐crypt)]⁺ salt in [K(2,2,2‐crypt)]₃[Ge₈Fe(CO)₃]. The chemically‐reduced organometallic species [Fe(η³‐C₈H₈)(CO)₃]^? was also isolated as a side‐product from this reaction as [K(2,2,2‐crypt)][Fe(η³‐C₈H₈)(CO)₃]. Both species were further characterized by EPR and IR spectroscopy and electrospray mass spectrometry. The [Ge₈Fe(CO)₃]^3? cluster anion represents an unprecedented functionalized germanium Zintl anion in which the nine‐atom precursor cluster has lost a vertex, which has been replaced by a transition‐metal moiety.     

The implementation of analytical energy gradients based on a quasi-relativistic density functional method: The application to metal carbonyls

The capabilities of the quasi-relativistic scheme due to J. G. Snijders at al. [Mol. Phys, 38 , 1969 (1979) Ibid., J. Phys. Chem. 93 , 3050 (1989)] has been extended by deriving expressions for the energy gradients with respect to the total energy E^QR and implementing them into the ADF program system [B. to Velde and E. J. Baerends, Int. J. Quantum Chem. 33 , 87 (1988)]. This implementation enables automated geometry optimization at the relativistic level. The new scheme has been applied together with a self-consistent nonlocal density functional scheme, NL –SCF + QR , to the calculation of M? CO bond lengths and the first bond dissociation energy (FBDE ) in the binary transition metal carbonyls M(CO)₅ (M = Fe, Ru, Os) and M(CO)₆ (M = Cr, Mo, W). The calculated M? CO bond lengths are in good agreement with available experimental data with an error typically smaller than 0.01 Å. The calculated FBDES are 45.7 (Fe), 33.0 (Ru), 34.7 (Os), 46.2 (Cr), 39.7 (Mo), and 43.7 (W) kcal/mol, respectively. These values compare well with the available experimental estimates of 42 (Fe), 28 (Ru), 31 (Os), 37 (Cr), 41 (Mo), and 46 (W), respectively. The relativistic effects are found to contract M? CO bonds by between 0.07 and 0.16 A and strengthen the FBDEs by 5-11 kcal/mol for third-row compounds. The relativistic stabilization of the FBDES among the 5d elements makes, in general, the M? CO bond of the 4d element weakest within a triad. © 1995 John Wiley & Sons, Inc.     

Stereochemie der Metall—Metall-Bindung Die Strukturen der Verbindungen (CO)4Cr[μ-PMe2]2Ni(CO)2 und (CO)3Fe[μ-PMe2, μ-I]Fe(CO)3 mit je zwei verschiedenen Komplexhälften

Die Kristallstrukturen der Titelkomplexe, deren einer zwei verschiedene Carbonylmetall-Einheiten, deren anderer zwei verschiedene Brückenliganden besitzt, wurden bestimmt. Die Stereochemie des Cr? Ni-Komplexes entspricht der Erwartung, seine Metall—Metall-Bindung ist jedoch kürzer als der Durchschnittswert aus den entsprechenden Cr₂- bzw. Ni₂-Verbindungen. Bei dem Fe₂-Komplex ist die Gesamt-Molekülgeometrie ebenfalls normal, doch der Metall—Metall-Abstand ist deutlich kürzer als erwartet. Die Verkürzung der Metall—Metall-Bindungen steht bei beiden Komplexen in Zusammenhang mit der Minimisierung der intramolekularen sterischen Hinderung. Stereochemistry of the Metal—Metal Bond. Structures of the Compounds (CO)₄Cr[μ-PMe₂]₂Ni(CO)₂ and (CO)₃Fe[μ-PMe₂, μ-I]Fe(CO)₃. Each with Two Different Complex Halves The crystal structures of the title complexes, one of which has two different carbonylmetal units and the other has two different bridging ligands, were determined. The stereochemistry of the Cr? Ni complex is as expected, its metal—metal bond however is shorter than the average value of the corresponding Cr₂ and Ni₂ compounds. For the Fe₂ complex the overall molecular geometry is also normal, but the metal—metal distance is considerably shorter than expected. The shortening of the metal—metal bonds is in both complexes correlated with the minimization of intramolecular steric strain.     

Novel Transition‐Metal (M=Cr,Mo, W,Fe) Carbonyl Complexes with Bis(guanidinato)silicon(II) Ligands

The donor‐stabilized silylene 2 (the first bis(guanidinato)silicon(II ) complex) reacts with the transition‐metal carbonyl complexes [M(CO)₆] (M=Cr, Mo, W) to form the respective silylene complexes 7 – 10 . In the reactions with [M(CO)₆] (M=Cr, Mo, W), the bis(guanidinato)silicon(II ) complex 2 behaves totally different compared with the analogous bis(amidinato)silicon(II ) complex 1 , which reacts with [M(CO)₆] as a nucleophile to replace only one of the six carbonyl groups. In contrast, the reaction of 2 leads to the novel spirocyclic compounds 7 – 9 that contain a four‐membered SiN₂C ring and a five‐membered MSiN₂C ring with a M?Si and M?N bond (nucleophilic substitution of two carbonyl groups). Compounds 7 – 10 were characterized by elemental analyses (C, H, N), crystal structure analyses, and NMR spectroscopic studies in the solid state and in solution.     

Synthesis and Characterization of the products from reaction of Metal Carbonyls [M(CO)6 (M Cr,Mo, W), Re(CO)5Br,Mn(CO)3Cp] with Salicylaldehyde Methanesulfonylhydrazone

Five new complexes, [M(CO)₅(salmsh)] (M?=?Cr;?1,?Mo;?2,?W;?3), [Re(CO)₄Br(salmsh)], 4, and [Mn(CO)₃ (salmsh)], 5, have been synthesized by the photochemical reaction of metal carbonyls with salicylaldehyde methanesulfonylhydrazone (salmsh). The complexes have been characterized by elemental analyses, EI mass spectrometry, FT-IR and ¹H NMR spectroscopy. The spectroscopic studies show that salmsh behaves as a monodentate ligand coordinating via the imine N donor atom in 1–4 and as a tridentate ligand in 5.     

Why are the Homoleptic Diyl Complexes M(InR)4 with M = Ni and Pt Stable Compounds while only Ni(CO)4 but not Pt(CO)4 can become Isolated? A Theoretical Study of M(EMe)44 and M(CO)4 (M = Ni,Pd, Pt; E = B,Al, Ga,In, Tl)

The equilibrium geometries and first bond dissociation energies of the homoleptic complexes M(EMe)₄ and M(CO)₄ with M = Ni, Pd, Pt and E = B, Al, Ga, In, Tl have been calculated at the gradient corrected DFT level using the BP86 functionals. The electronic structure of the metal‐ligand bonds has been examined with the topologial analysis of the electron density distribution. The nature of the bonding is revealed by partitioning the metal‐ligand interaction energies into contributions by electrostatic attraction, covalent bonding and Pauli repulsion. The calculated data show that the M‐CO and M‐EMe bonding is very similar. However, the M‐EMe bonds of the lighter elements E are much stronger than the M‐CO bonds. The bond energies of the latter are as low or even lower than the M‐TlMe bonds. The main reason why Pd(CO)₄ and Pt(CO)₄ are unstable at room temperature in a condensed phase can be traced back to the already rather weak bond energy of the Ni‐CO bond. The Pd‐L bond energies of the complexes with L = CO and L = EMe are always 10 — 20 kcal/mol lower than the Ni‐L bond energies. The calculated bond energy of Ni(CO)₄ is only D_o = 27 kcal/mol. Thus, the bond energy of Pd(CO)₄ is only D_o = 12 kcal/mol. The first bond dissociation energy of Pt(CO)₄ is low because the relaxation energy of the Pt(CO)₃ fragment is rather high. The low bond energies of the M‐CO bonds are mainly caused by the relatively weak electrostatic attraction and by the comparatively large Pauli repulsion. The σ and π contributions to the covalent M‐CO interactions have about the same strength. The π bonding in the M‐EMe bonds is less than in the M‐CO bonds but it remains an important part of the bond energy. The trends of the electrostatic and covalent contributions to the bond energies and the σ and π bonding in the metal‐ligand bonds are discussed.     

Structure of Mn2(CO)10 and Mn2(CO)9: Insights from ab initio calculations

Optimization of the Mn–Mn distance in Mn₂(CO)₁₀ with various basis sets of at least doublezeta quality results in Mn–Mn bond lengths in the range of 3.07–3.15 Å, 0.2–0.25 Å longer than the experimental value of 2.895 Å. Incrementing the basis set with diffuse p functions (exponent 0.0332) on the carbon atoms improves the calculated bond length to a value of 2.876 Å at the CI level, as a consequence of a charge transfer between each Mn atom and the equatorial carbonyls of the other Mn atom. For Mn₂(CO)₉ four structures have been studied at the SCF and CI levels with assumed geometries. The structure with a symmetric bridging carbonyl turns to be much higher in energy at the SCF level. The two structures which are purely metal–metal bonded [corresponding to the departure of an axial or equatorial carbonyl from Mn₂(CO)₁₀] are nearly degenerate in energy and more stable than the structure with a semibridging carbonyl by 5 kcal/mol at the SCF level and 10–11 kcal/mol at the CI level (seemingly at variance with the conclusions of matrix experiments that favor the semibridging structure).     

Homoleptic mononuclear and binuclear osmium carbonyls Os(CO)n(n = 3-5) and Os2(CO)n (n = 8, 9): comparison with the iron analogues

The structures and energetics of the experimentally known Os(CO)n ( n = 3-5), Os2(CO)9, and Os2(CO)8 have been investigated using density functional theory. For Os(CO)5, the lowest-energy structure is the singlet D(3h) trigonal bipyramid. However, the C(4v) square pyramid for Os(CO)5 lies only approximately 1.5 kcal/mol higher in energy, suggesting extraordinary fluxionality. For the coordinatively unsaturated Os(CO)4 and Os(CO)3, a D(2d) strongly distorted tetrahedral structure and a Cs bent T-shaped structure are the lowest-energy structures, respectively. For Os2(CO)9, the experimentally observed singly bridged Os2(CO)8(mu-CO) structure is the lowest-energy structure. A triply bridged Os2(CO)6(mu-CO)3 structure analogous to the known Fe2(CO)9 structure is a transition state rather than a true minimum and collapses to the singly bridged global minimum structure upon following the corresponding normal mode. An unbridged (OC)5Os --> Os(CO)4 structure with a formal Os --> Os dative bond analogous to known stable complexes of the type (R3P)2(OC)3Os --> W(CO)5 is also found for Os2(CO)9 within 8 kcal/mol of the global minimum. The global minimum for the coordinatively unsaturated Os2(CO)8 is a singly bridged (OC)4Os(mu-CO)Os(CO)3 structure derived from the Os2(CO)9 global minimum by loss of a terminal carbonyl group. However, the unbridged structure for Os2(CO)8 observed in low-temperature matrix experiments lies only approximately 1 kcal/mol above this global minimum. In all cases, the triplet structures for these osmium carbonyls have significantly higher energies than the corresponding singlet structures.     

A Deeper Insight in Solutions Containing the Hypothetical Labile Complex Species “Fe(CO)4THF”

In the literature it was proposed that the treatment of [Fe₂(CO)₉] in THF resulted, during dissolution, in deep red solutions which should presumably contain labile complexes “Fe(CO)₄THF”. This was supported by the fact that such solutions afforded, in the presence of N‐donor ligands like pyridine (py) or pyrazine (pz), metal carbonyl complexes of the formula [Fe(CO)₄(py)] and [Fe(CO)₄(pz)], respectively. Herein we describe how the true nature of these solutions can be better explained by a valence‐disproportionation reaction of the diiron nonacarbonyl, induced by the donor solvent THF, resulting in the compound [Fe(THF)₆][Fe₃(CO)₁₁]. The formation of the undecacarbonyl‐triferrate(2–) in such solutions was unambiguously confirmed by IR spectroscopy and by the isolation and crystallization of the corresponding salt (PPN)₂[Fe₃(CO)₁₁]; its molecular structure was determined, however, already described in the literature.     

Coordination chemistry of organometallic polydentate ligand Reactive chemistry of the tridentate ligand trans‐Fe(Ph2PQu‐P)2‐(CO)3 [PhzPQu=2‐diphenyl‐phosphino‐4‐methylquinoline] and molecular structure of [Fe(CO)3(μ‐Ph2PQu)2HgI]+ [HgI3]

Reaction of a new type of bidentate ligand PhPQu [PhPQu = 2‐diphenylphosphino‐4‐methylquinoline] with Fe(CO)₅ in butanol gave trans‐Fe(FpPQu‐P)(CO)₃ (1). Compound 1, which can act as a neutral tridentate organometallic ligand, was reacted with I B, II B metal compounds and a rhodium complex to give six binuclear complexes with Fe? M bonds, Fe(CO)₃ (μ‐Ph₂PQu)MX_n (2–7) [M= Zn(II), Cd(II), Hg(II), Cu(I), Ag(I), Rh(I)], and an ion‐pair complex [Fe(CO)₃ (μ‐Ph₂PQu)₂HgI][HgI₃]^? (8). The structure of 8 was determined by X‐ray crystallography. Complex 8 crystallizes in the space group P‐1 with a = 1.0758(3), b = 1.6210(4), c=1.7155(4)nm; a=75.60(2), β=71.81(2), γ=81.78(2)° and Z = 2 and its structure was refined to give agreement factors of R=0.050 and R_w = 0.057. The Fe‐Hg bond distance is 0.2536nm.     

O−O Bond Formation and Liberation of Dioxygen Mediated by N5‐Coordinate Non‐Heme Iron(IV) Complexes

Formation of the O?O bond is considered the critical step in oxidative water cleavage to produce dioxygen. High‐valent metal complexes with terminal oxo (oxido) ligands are commonly regarded as instrumental for oxygen evolution, but direct experimental evidence is lacking. Herein, we describe the formation of the O?O bond in solution, from non‐heme, N₅‐coordinate oxoiron(IV) species. Oxygen evolution from oxoiron(IV) is instantaneous once meta‐chloroperbenzoic acid is administered in excess. Oxygen‐isotope labeling reveals two sources of dioxygen, pointing to mechanistic branching between HAT (hydrogen atom transfer)‐initiated free‐radical pathways of the peroxides, which are typical of catalase‐like reactivity, and iron‐borne O?O coupling, which is unprecedented for non‐heme/peroxide systems. Interpretation in terms of [Fe^IV(O)] and [Fe^V(O)] being the resting and active principles of the O?O coupling, respectively, concurs with fundamental mechanistic ideas of (electro‐) chemical O?O coupling in water oxidation catalysis (WOC), indicating that central mechanistic motifs of WOC can be mimicked in a catalase/peroxidase setting.     

Polymere Thiolatokomplexe [M(SPh)3]∞ der Metalle Molybdän,Wolfram, Eisen und Ruthenium mit linearen Metallketten. Synthese und Struktur von (OC)3Fe(SPh)3Fe(SPh)3Fe(CO)3 · 2(CH3)2CO

Polymeric Thiolato Complexes [M(SPh)₃]∞ of the Metals Mo, W, Fe, and Ru with Linear Metal Chains. Synthesis and Crystal Structure of (OC)₃Fe(SPh)₃Fe(SPh)₃Fe(CO)₃ · 2(CH₃)₂CO At high temperature the reaction of the metal carbonyls Mo(CO)₆, W(CO)₆ and Fe(CO)₅ with S₂Ph₂ (Ph = C₆H₅) yields the polymeric complexes [M(SPh)₃]∞. Similarly [Ru(SPh)₃]∞ can be obtained from ruthenium(III) acetylacetonate and HSPh. At room temperature under UV-irradiation Fe(CO)₅ reacts with S₂Ph₂ to form the oligomeric complex (OC)₃Fe(SPh)₃Fe(SPh)₃Fe(CO)₃. The polymeric complexes [M(SPh)₃]∞ (M = Mo, W, Fe, Ru) are composed of linear chains with bridging SPh-ligands between the metal atoms. Of these complexes [Fe(SPh)₃]∞ is paramagnetic, whereas the others exhibit antiferromagnetic behaviour. The spin coupling is presumably connected with the formation of metal pairs, resulting in alternating shortened and extended distances in the metal chain. The oligomeric complex (OC)₃Fe(SPh)₃Fe(SPh)₃Fe(CO)₃ crystallizes triclinic in the space group P1 with z = 2. It has almost the symmetry D_3d with a linear arrangement of the Fe atoms. The paramagnetism of Fe₃(CO)₆(SPh)₆ can be explained by a d⁶ high spin configuration of the central atom and low spin behaviour of the two other Fe atoms, which are bonded to CO.     

Gas chromatographic separation of PF3 substituted group 6 metal carbonyl complexes using serially-coupled capillary columns

The retention of group 6 metal trifluorophosphine carbonyl compounds in serially-coupled gas capillary columns has been studied as a function of different column configurations. For the trifluorophosphine-substituted Mo, W, and Cr carbonyls, as well as the analogous Fe compounds, it was observed that the maximum resolution achievable by the coupled column technique was dependent on the order in which the nonpolar (DB-1) and moderately polar (DB-1701) columns were connected. The optimum configuration was different, however, for each series M(PF₃)_x(CO)_6?x(M = Cr, Mo, or W) or Fe(PF₃)_x(CO)_5?x. It was also observed that the use of coupled columns of dissimilar polarity can, in some cases, actually decrease resolution relative to that obtained by coupled identical columns (i. e. DB-1 + DB-1, or DB-1701 + DB-1701).     

A comparative study of O2, CO,and NO binding to iron–porphyrin

Minimum-energy structures of O₂, CO, and NO iron–porphyrin (FeP) complexes, computed with the Car–Parrinello molecular dynamics, agree well with the available experimental data for synthetic heme models. The diatomic molecule induces a 0.3–0.4 Å displacement of the Fe atom out of the porphyrin nitrogen (N_p) plane and a doming of the overall porphyrin ring. The energy of the iron–diatomic bond increases in the order Fe(SINGLE BOND)O₂ (9 kcal/mol) < Fe(SINGLE BOND)CO (26 kcal/mol) < Fe(SINGLE BOND)NO (35 kcal/mol). The presence of an imidazole axial ligand increases the strength of the Fe(SINGLE BOND)O₂ and Fe(SINGLE BOND)CO bonds (15 and 35 kcal/mol, respectively), with few structural changes with respect to the FeP(CO) and FeP(O₂) complexes. In contrast, the imidazole ligand does not affect the energy of the Fe(SINGLE BOND)NO bond, but induces significant structural changes with respect to the FeP(NO) complex. Similar variations in the iron–imidazole bond with respect to the addition of CO, O₂, and NO are also discussed. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 31–35, 1998     

The π‐Bonding Trend in VIB M(CO)6 Observed by NMR Spectroscopy — A Natural Bond Orbital View

Analysis of carbonyl's 2π orbital populations, [2π], obtained by NMR relaxation time experiments of VIB M(CO)(?⁶‐C₆H₆) reveals the 3d < 4d < 5d trend for M r? CO back‐donation, as reported values of [2π] for VIB M(CO)₅(quinuclidine). The same analysis performed on Mn(CO)₃(?⁵C₅H₅) and Re(CO)₃(?⁵‐C₅H₅) also gives 3d < 5d order of back‐donation. The distinctive 3d ～ 5d > 4d trend reported for VIB M(CO)₆ has been investigated by second‐order perturbation theory analysis within the natural bond orbital (NBO) scheme to search for orbital‐based explanations. Besides the conventional d_π r? 2π donor‐acceptor (DA) interaction in the trend 3d < 4d < 5d, the other DA interaction arising from three‐center‐hyperbond (3CHB) hyperconjugation has been found in the trend 3d >> 5d ～ 4d. Within the VIB M(CO)₆ family, this 3CHB hyperconjugation is so much higher in Cr(CO)₆ than in W(CO)₆ as to render the overall 2π populations exhibiting the 3d ～ 5d > 4d trend.     

Binuclear homoleptic manganese carbonyls: Mn2(CO)x (x = 10, 9, 8, 7)

The unsaturated homoleptic manganese carbonyls Mn(2)(CO)(n)() (n = 7, 8, 9) are characterized by their equilibrium geometries, thermochemistry, and vibrational frequencies using methods from density functional theory (DFT). The computed metal-metal distances for global minima range from 3.01 A for the unbridged Mn(2)(CO)(10) with a Mn-Mn single bond to 2.14 A for a monobridged Mn(2)(CO)(7) formulated with a metal-metal quadruple bond. The global minimum for Mn(2)(CO)(9) has a four-electron bridging mu-eta(2)-CO group and a 2.96 A Mn-Mn distance suggestive of the single bond required for 18-electron configurations for both metal atoms. This structure is closely related to an experimentally realized structure for the isolated and structurally characterized stable phosphine complex [R(2)PCH(2)PR(2)](2)Mn(2)(CO)(4)(mu-eta(2)-CO). An unbridged (OC)(4)Mn-Mn(CO)(5) structure for Mn(2)(CO)(9) has only slightly (<6 kcal/mol) higher energy with a somewhat shorter metal-metal distance of 2.77 A. For Mn(2)(CO)(8) the lowest energy structure is a D(2)(d)() unbridged structure with a 2.36 A metal-metal distance suggesting the triple bond required for the favored 18-electron configuration for both metal atoms. However, the unbridged unsymmetrical (CO)(3)Mn-Mn(CO)(5) structure with a metal-metal bond distance of 2.40 A lies only 1 to 3 kcal/mol above this global minimum. The lowest energy structure of Mn(2)(CO)(7) is an unbridged C(s)() structure with a short metal-metal distance of 2.26 A. This is followed energetically by another C(s)() unbridged Mn(2)(CO)(7) structure with a somewhat longer metal-metal distance of 2.38 A.     

Syntheses,toxicity and biodistribution of CO‐releasing molecules containing M(CO)5 (M = Mo,W and Cr)

A series of CO‐releasing molecules M(CO)₅ L (M = Mo, W and Cr), ( 1 , 2 , 3 , L = glycine methyl ester; 4 , 5 , 6 , N‐methylimidazole; 7 , 8 , 9 , 2‐aminopyridine; 10 , 11 , 12 , 3‐aminopyridine; 13 , 14 , 15 , 4‐aminopyridine), were synthesized. All complexes have been characterized by NMR, IR and electrospray ionization mass spectroscopy; the octahedral structures of 14 and 15 were also established by X‐ray crystallography. Furthermore, all complexes were evaluated for toxicity, pharmacokinetics and metabolic processes. Cytotoxic effects on the proliferation of fibroblast cell line were assayed by MTT. Among the complexes, Mo complex 1 showed the lowest cytotoxicity (IC₅₀ = 597 µmol l^?1) and W complex 2 showed a remarkable toxic effect, with IC₅₀ = 52 µmol l^?1. With the same ligand, the toxic effects of the complexes increase in the order of metal element W < Cr < Mo. For the same central metal element, the complexes containing imidazole showed lower toxic effects than those containing amino acid ester or aminopyridine. In accordance with the results from cytotoxicity, the complexes also showed corresponding toxic effects in animal models. The biodistributions of the complexes were established by inductively coupled plasma–atomic emission spectroscopy, measuring metal in tissues and organs. The results show that the complexes were gradually absorbed and unevenly distributed in vivo. The complexes containing imidazole entered tissues and organs faster than those containing amino acid ester. The complexes containing W atom were absorbed and distributed more slowly than those containing Mo or Cr atoms. Copyright © 2014 John Wiley & Sons, Ltd.     

Addition of CCl4 to unsaturated compounds catalyzed by M3(CO)12 (M=Fe, Ru, Os)

The addition of CCl₄ to hex-1-ene and to the methyl ester ofN-(trans-cinnamoyl)-l-proline (2) catalyzed by M₃(CO)₁₂ or by the M₃(CO)₁₂+DMF system (M=Fe, Ru, Os) was studied. The use of ruthenium and osmium dodecacarbonyls in combination with DMF increases the yields of adducts CCl₃CH₂CHClC₄H₉ (4) and PhCHClCH(CCl₃)C(O)R′ (3) over those obtained in reactions catalyzed by the same carbonyls without DMF. In addition to adduct3, salts [M(CO₃)Cl₃]⁻[Me₂NH₂]⁺ were isolated from the products of the reaction between CCl₄ and1 in the presence of M₃(CO)₁₂+DMF (M=Ru, Os). These salts do not catalyze this reaction and apparently result from chain termination. Experimental results in favor of a coordination mechanism of the addition of CCl₄ to olefins in the presence of Ru₃(CO)₁₂ and Os₃(CO)₁₂ were obtained. Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 6, pp. 1174–1179, June, 1997.