Synthesis and crystal structure of the double cluster [Cp3Fe4(CO)4(C5H4)]2(p-C6H4)

[Cp₄Fe₄(CO)₄] (1) reacts with p-BrC₆H₄Li and MeOH in sequence to afford the functionalized cluster [Cp₃Fe₄(CO)₄(C₅H₄-p-C₆H₄Br)] (2), while the reaction of 2 with n-BuLi and MeOH produces [Cp₂Fe₄(CO)₄(C₅H₄Bu)(C₅H₄-p-C₆H₄Br)] (3). The double cluster [Cp₃Fe₄(CO)₄(C₅H₄)]₂(p-C₆H₄) (4) has been prepared by treatment of [Cp₄Fe₄(CO)₄] with p-C₆H₄Li₂ and MeOH in sequence. The electrochemistry of 2 and 4, as well as the crystal structure of 4 have been investigated.     

Synthesis and reactivity of [N(C6H4Br)3][B(C6F5)4]: the X-ray crystal structure of [Fe(C5H5)2][B(C6F5)4]

A new chemical oxidant [N(4-C₆H₄Br)₃][B(C₆F₅)₄], was prepared and used to synthesize [Fe(C₅H₅)₂][B(C₆F₅)₄]. The crystal structure of [Fe(C₅H₅)₂][B(C₆F₅)₄] was determined.     

Synthesis and crystal structure of Ir(C2H4)2(C5H7O2)

We report a new synthesis and characterization of Ir(C₂H₄)₂(C₅H₇O₂) [(acetylacetonato)-bis(η²-ethene)iridium(I)], prepared from (NH₄)₃IrCl₆ · H₂O in a yield of about 45%. The compound has been characterized by X-ray diffraction crystallography, infrared, Raman, and NMR spectroscopies and calculations at the level of density functional theory. Ir(C₂H₄)₂(C₅H₇O₂) is isostructural with Rh(C₂H₄)₂(C₅H₇O₂), but there is a substantial difference in the ethylene binding energies, with Ir-ethylene having a stronger interaction than Rh-ethylene; two ethylenes are bound to Ir with a binding energy of 94 kcal/mol and to Rh with a binding energy of 70 kcal/mol.     

Heat capacity of molecular chromium sandwich compounds: chromocene Cr(C5H5)2 and dibenzene chromium Cr(C6H6)2

Heat-capacity measurements have been made in the temperature range 110 to 300 K. In the range 160 to 240 K the chromocene curve shows an anomaly related to an order-disorder phase transition in the solid. On the other hand the dibenzene chromium curve indicates no phase transition and is in accordance with an ordered structure at room temperature.     

The crystal and molecular structure of tetraethylammonium hydrotris(3,5-dimethylpyrazolyl)boratotricarbonylmolybdenum(0), [NEt4][Mo(CO)3HB(C5H7N2)3]

The crystal and molecular structure of tetraethylammonium hydrotris(3,5-dimethylpyrazolyl)boratotricarbonylmolybdenum(0), [N(C₂H₅)₄][Mo(CO)_3^? HB(3,5-Me₂pz)₃] has been determined from intensity data collected using counter methods. The salt crystallizes in space group Pna2₁ with parameters a = 18.038(6), b = 9.956(3), c = 16.881(3) Å, V = 3031.4(20) ų, Z = 4, d_calc = 1.33 g/ml and d_obs = 1.33 g/ml. Final convergence yielded a conventional R = 0.042 and a “goodness of fit” of 2.07. The steric pocket formed by the 3-methyl hydrogens of the pyrazolyl moiety is discussed.     

The crystal structure of tetrakis(methyldiphenylphosphine)iridium(I) tetrafluoroborate with cyclohexane of solvation: Ir[P(C6H5)2CH3]4BF4 - C6H12

The crystal structure of tetrakis(methyldiphenylphosphine)iridium(I) tetrafluoroborate with cyclohexane of solvation, [Ir(PPh₂Me)₄]BF₄·C₆H₁₂, has been determined from a three-dimensional X-ray analysis. The compound has been analysed in space group C₂/c of the monoclinic system. There are twelve molecules (i.e. 1.5 molecules per asymmetric unit) in a cell of dimensions a = 36.804(8), b = 22.93(2), c = 21.676(4) Å, β = 121.41(1)°. Block-diagonal least-squares refinement has given a final R-factor of 0.060 for 7905 reflections having I > 3σ(I).The structure consists of two crystallographically distinct, but structurally similar molecules, one on a general position and one on a crystallographic two-fold axis. The phosphine ligands around the iridium atoms are in a very distorted square-planar arrangement. The reactions of the cation axe discussed in terms of this structure.     

Synthesis and reactions of a nucleophilic bis(μ-dimethylphosphido)dicobalt complex. The crystal and molecular structure of [C5H5Co(μ-PMe2)]2 and [(C5H5Co)2(μ-H)(μ-PMe2)2]BPh4

The bis(μ-dimethylphosphido)dicobalt complex [C₅H₅Co(μ-PMe₂)]₂ (II) has been prepared from Co(C₅H₅ and PMe₂H on almost quantitative yield. It has also been made by reduction of [C₅H₅Co(PMe₂H)₃]I₂ (IV) with NaH and from the reaction of [C₅H₅(PMe₃)Co(μ-CO)₂Mn(CO)C₅H₄Me] with PMe₂H. Protonation of II with CF₃CO₃H in the presence of NH₄PF₆ produces the PF₆^? salt of the (μ-hydrido)dicobalt cation [(C₅H₅Co)₂(μ-H)(μ-PMe₂)₂]⁺ (V) which reacts with aqueous NaOH to give II. Similar treatment of [C₅H₅Co(μ-SMe]₂ with CF₃CO₂H/NH₄PF₆ leads to the formation of [(C₅H₅Co)₂(μ-SMe)₃]PF₆ (VI). The nucleophilic character of complex II has also been demonstrated in the reaction with SO₂, which gives [(C₅H₅Co)₂ (μ-PMe₂)₂(μ-SO₂)] (VII). The crystal and molecular structures of II, the corresponding bis(μ-diphenylphosphido) compound [C₅H₅Co(μ-PPh₂)]₂ (III) and the BPh₄^? salt of V have been determined. In both neutral complexes the Co₂P₂ cores are similarly puckered, as reflected in the dihedral angle between the CoP₂ and P₂Co′ planes of 108.1 and 105.0° for R = Me and Ph, respectively. The CoCo bond length and the PP interatomic separations are essentially identical for both dimers. The CoCo bond length in V, 2.517(1) Å, is lower than that in II, 2.542(2) Å. The only obvious structural variation between the unprotonated and the protonated species is the large difference in the degree of canting of the C₅H₅ rings with respect to each other. The angles between the C₅(ring)-centroid and the CoCo line are ca. 150 and 167° in II and V, respectively, which reflects the influence of the bridging hydride ligand in the cationic complex.     

Synthesis of palladium and platinum donor complexes and study of their participation in self-assembly reactions. X-ray crystal structure of [Pt(C6H4CCC5H4N)2(dppp)] (dppp = 1,3-bis(diphenylphosphino)propane)

Novel square-planar compounds [M(NC₅H₄CCH)₂(dppp)](OTf)₂ (M = Pd (1), Pt (2)), [Pt(CCC₆H₄CN)₂(dppp)] (3) and [Pt(C₆H₄CCC₅H₄N)₂(dppp)] (4) (dppp = 1,3-bis(diphenylphosphino)propane) were prepared and characterised. Their potential as building blocks in the generation of heterobimetallic squares was studied. The reaction of 4 and the ditopic acceptor species [Pd(H₂O)₂(dppf)](OTf)₂ enabled a tetrametallic metallocycle containing two platinum and two palladium atoms to be obtained. The crystal X-ray structure of 4 shows that the Pt?N vectors are nearly perpendicular, and confirm the suitability of the compound to act as a corner unit for the construction of molecular squares.     

The molecular structure of benzoylmethylidynetricobalt nonacarbonyl,C6H5C(O)CCo3(CO)9

The molecular structure of benzoylmethylidynetricobalt nonacarbonyl, C₆H₅C(O)CCo₃(CO)₉, has been determined by single crystal X-ray crystallography. The sample crystallized from heptane forms as monoclinic prisms of spae group P2₁/c, with a = 8.836(2), b = 14.097(10), c = 16.514(3), β = 103.37(6) and z = 2. The final R value was 0.053. The structure is regular and normal but does not aid in explaining the interesting properties of this cluster.     

Hetero- and homo-nuclear bimetallic ruthenol complexes by dehydrogenative metallacyclization of Ru(CO)3(bi-1,7-cyclooctadienyl), preparation and x-ray structure of Fe(CO)3(C16H22), RuFe(CO)6(C16H22) and Ru2(CO)6(C16H20)

The reaction of M₃(CO)₁₂ (M = Ru, Fe) with excess bi-2,7-cyclooctadienyl (C₁₆H₂₂) 1 gave a mononuclear complex M(CO)₃(1,2,1′-2′-η⁴-C₁₆H₂₂), 2a (M = Ru) or 3a (M = Fe), in good yield. Treatment of 2a with Fe₃(CO)₁₂ or reaction of 3a with Ru₃(CO)₁₂ gave the heterobimetallic complex RuFe(CO)₆(C₁₀H₂₂) consisting of a ruthenacyclopentadiene unit coordinated to an Fe(CO)₃ fragment, as confirmed by ¹H NMR and X-ray studies. The corresponding homobimetallic complex Ru₂(CO)₆(C₁₆H₂₂) was obtained from the 1:1 reaction of 2a with Ru₃(CO)₁₂, while the direct reaction of 1 with Ru₃(CO)₁₂ gave Ru₂(CO)₆(C₁₆H₂₀) preferentially with a loss of two hydrogen atoms. The pathway for formation of these bimetallic complexes was interpreted as a dehydrogenative metallacyclization followed by hydrogen transfer.     

Reactions of methyl and ethyl halides with the complexes Ni[P(C2H5)3]4 and Ni(X)[P(C2H5)3]3

The rates of the thermal reaction of the nickel(0) complex Ni[P(C₂H₅)₃]₄ with the alkyl halides CH₃Br, CH₃I in toluene have been compared with those of the reactions of the nickel(I) complexes Ni(X)[P(C₂H₅)₃]₃ (X  Br,I). The organic products from CH₃X are methane and ethane, and those from C₂H₅I are ethane and ethylene. The reactivity of the nickel(I) complexes is 10–20 times less than that of the nickel(0) complex. The result suggest that the first step of the reaction of nickel(0) with CH₃I is the expected oxidative addition of the halide to the metal substrate. The intermediate thus formed decomposes to produce ethane (and small amounts of methane) without further reaction with the organic halide. This mechanism is supported by deuterium-labeling experiments.     

Die thermische reaktion von C5H5(CO)2FeNa mit benzimidchloriden C6H5(Cl)CNR

η⁵-C₅H₅(CO)₂FeNa reacts with the benzimide chlorides C₆H₅(Cl)CNR (R  CH(CH₃)₂, C₆H₅) in boiling THF to give the η¹-iminoacyl complexes η⁵-C₅H₅ (CO)₂Fe[η¹-C(C₆H₅)NR]. Alternatively, the new Fe complexes [η⁵-C₅H₅(CO)Fe$\text{C(C}{}_6\text{H}{}_5\text{)N(CH}{}_3\text{)C(C}{}_6\text{H}{}_5\text{)N}$CH₃PF₆ (IV) and [η⁵-C₅H₅(CO)₂FeC(C₆H₅)N(CH₃)C(C₆H₅)NCH₃]PF₆ (V) are formed under the same conditions, if R  CH₃. Hudrolysis of the CN single bond of the ligand in V, not stabilized by a chelate effects as in IV, results in the formation of [η⁵-C₅H₅(CO)₂FeC(C₆H₅)NHCH₃]PF₆ (VII). Reaction of η⁵-C₅H₅(CO)₂ with N-benyzylbenzimido chloride yields η⁵-C₅H₅(CO)₂FeCH₂C₆H₅ as the only isolated product.     

Synthesis and crystal structure of [Re2Cl2(CO)6(S e)]

The dinuclear complex [Re₂Cl₂(CO)₆S e] has been prepared and characterized in the solid state by X-ray crystallography. Proton NMR spectroscopy has shown the structure to be stereochemically rigid in solution.     

Photochemistry of (η5)-C5H5)Mn(CO)2[C(C6H5)2]. Generation of the diphenylcarbene radical anion

The electronic absorption spectrum of (η⁵-C₅H₅)Mn(CO)₂[C(C₆H₅)₂]shows an intense maximum which is assigned to a MLCT transition in which the empty p_π orbital on the carbene carbon is populated. Upon irradiation of this band, the complex undergoes a decomposition with a disappearance quantum yield Φ = 0.10 ± 0.01 independent of solvent. In the CT excited state, the complex can be roughly described as containing d⁵ Mn^II and a diphenylcarbene radical anion ligand C(C₆H₅)₂^?. Due to the kinetic lability, the complex decomposes producing a Mn^II species and the free carbene radical anion, which then undergoes secondary reactions. In addition, small amounts of substitution product are observed. It is proposed that prior to total decomposition of the excited state, a radical pair (η⁵-C₅H₅)Mn(CO)₂S⁺/C(C₆H₅)₂^?forms (S = solvent). A back electron transfer from C(C₆H₅)₂^?to the labile cation competes with decomposition to produce the substituted complex and free carbene.     

Crystal and molecular structure of triclinic [C5H5(CO)2Mol2(μ,η2-CNC6H5) and comparison with its monoclinic form

The crystal and molecular structure of [C₅H₅(CO)₂Mol]₂(μ,η₂-CNC₆H₅) were determined for a new polymorphic form in which the substance crystallizes in the triclinic system, as opposed to the monoclinic form previously described. The space group is P$\text{1}$ and the lattice constants are a 9.795(2), b 10.219(3), c 11.505(3) Å, α 81.53(2), β 70.83(2) and γ 66.91(2)°, V 997.70 ų and D(Z = 2) = 1.788 g cm^?3 The Niggli matrix rules out the possibility that the triclinic cell is a sub-cell of the monoclinic one previously described. Detailed comparison of bond lengths, angles, torsional angles and superposition of the two molecules through the BMFIT program show that the two determinations yield very close but not identical results, and that the largest deviations are associated with those groups (Cp and phenyl), which are able to respond readily to differences in packing forces. It is clear, however, that the general conformation of the molecules is not dictated by such forces, which merely modify the intramolecular forces controlling conformation and configuration.     

Kristall- und molekülstruktur von hexaphenyldistannylselenid (C6H5)3SnSeSn(C6H5)3

The crystal and molecular structure of hexaphenylditin selenide (C₆H₅)₃SnSeSn(G₆H₅)₃ was determined by X-ray diffraction data and was refined to R  0.055. The compound is monoclinic, space group P2₁, with a  9.950(4), b  18.650(7), c  18.066(6) Å, β  106.81(4)°, Z  4. The two molecules in the asymmetric unit differ slightly in their conformations, both having approximate C₂ symmetry. Bond lengths and angles are: SnSe 2.526 (2.521(3) ? 2.538(3)) Å; SnC 2.138 (2.107(16)?2.168(19)) Å; SnSeSn 103.4(1)°, 105.2(1)°. There are only slight angular distortions at the SnSeC₃ tetrahedra (SeSnC angles: 104.3(5)?114.8(4)°). The bond data indicate essentially single bonds around the Sn atoms.     

Bond energies and thermal decomposition of [Pt(X)(CH3)(P(C2H5)3)2] complexes

The thermal decomposition of the complexes trans-[Pt(X)(CH₃)L₂] (L  P(C₂H₅)₃; X  Cl, Br, I, CN) in decalin at 170 and 200°C affords methane platinum metal and [Pt(X)₂L₂]. The kinetics of the decomposition of the complexes were determined by monitoring the appearance of methane by GLC. The observed first-order rate constant was found to be independent on the nature of the ligand X. The thermal decomposition of the trideuteriomethyl complexes [Pt(X)(CD₃)L₂] (X  I, CN) in decalin-d₁₈ at 170 and 200°C was studied by GLC/MS. The thermolysis affords CD₃H and CD₄ in ratios which are independent of the nature of X and of the temperature used. The mass spectra of the complexes were also examined. A relative scale of platinum-to-methyl bond dissociation energies has been established by measuring the appearance potential of the fragment ion [Pt(X)L₂]⁺ and the ionization energies in the series [Pt(X)(CH₃)L₂]. Ionization potentials and PtCH₃ bond energies show a clear dependence on the nature of X which is not reflected in corresponding changes in the decomposition rates.     

Synthesis and crystal structure of [CODRh(SC6F5)]2

The metathetical reaction of Pb(SC₆F₅)₂ with the halogen bridged compounds [L RhCl]₂ where L are chelating dienes, afforded the chalcogen bridged analogs. Subsequent reactions with a variety of ligands including phosphines, arsines, sulfides and selenides, have shown important differences between sulphur and halogen bridged complexes, attributable to the fluorinated moiety. Some of these reactions will be discussed and the crystal structure of [COD Rh(SC₆F₅)]₂ will be described.     

Kristall-und molekülstrukturen zweier modifikationen de hexaphenyldigermylsulfids (C6H5)3GeSGe(C6H5)3

en Two differnt crystal modifications of hexaphenyldigermanium sulfide (C₆H₅GeSGe(C₆H₅)₃ (I and II were obtained by crystallization from hot benzene/methanol or form ethanol at 20°C. Single crystal X-ray structural analyses for both I (low temperature data at ?130°C) and II (at 20°C) (I, R = 0.046; II, R = 0.048) were performed. I is monoclinic, P2¹/c, with a = 11.020(3), b = 15.473(3), c 18.606(3) »,π = 106.92(2)°, Z = 4; II is orthorhombic, P2₁2₁2₁, with a = 2.617(2), b = 17.345(3), c = 18.408(3) », Z = 4.The molecules have different conformeric structures with respect to a rotation of the (C₆H₆)₃Ge groups around the Ge bonds with very similar bond lenghts and angles. Bond data for I(II) are: GeS 2.212(1) and 2.261(1) » (2.227(2) and 2.240(2) »); GeC 1.933(4) ? 1.971(4), mean 1.945(5) » (1.931(7)?1.954(7), mean 1.943(4) »); GeSGe 111.2(1)° (110.7(1)°). The Ge bond lenghts are comparable to those in thiogermanates and do not indicate significant π-bond contributions.     

Synthesis and crystal structures of (C8h8)Nd(C5H9C5H4) (THF)2 and [(C8H8)Gd(C5H9C4H4(THF)][(C8H8)GD(C5H9C5H4(THF)2]

LnCl₃ (Ln=Nd, Gd) reacts with C₅H₉C₅H₄Na (or K₂C₈H₈) in THF (C₅H₉C₅H₄ = cyclopentylcyclopentadienyl) in the ratio of 1 : to give (C₅H₉C₅H₄)LnCl₂(THF)_n (orC₈H₈)LnCl₂(THF)_n], which further reacts with K₂C₈H₈ (or C₅H₉C₅H₄Na) in THF to form the litle complexes. If Ln=Nd the complex (C₈H₈)Nd(C₅H₉C₅H₄)(THF)₂ (a) was obtained: when Ln=Gd the 1 : 1 complex [(C₈H₈)Gd(C_%H₉)(THF)][(C₈H₈)Gd(C₅H₉H₄)(THF)₂] (b) was obtained in crystalline form.

The crystal structure analysis shows that in (C₈H₈)Ln(C₅H₉C₅H₄)(THF)₂ (Ln=Nd or Gd), the Cyclopentylcyclopentadieny (η⁵), cyclooctatetraenyl (η⁸) and two oxygen atoms from THF are coordinated to Nd³⁺ (or Gd³⁺) with coordination number 10.

The centroid of the cyclopentadienyl ring (Cp′) in C₅H₉C₅H₄ group, cyclooctatetraenyl centroid (COTL) and two oxygens (THF) form a twisted tetrahedron around Nd³⁺ (or Gd³⁺). In (C₈H₈)Gd(C₅H₉C₅H₄)(THF), the cyclopentyl-cyclopentadienyl (η⁵), cyclooctatetraenyl (η⁸) and one oxygen atom are coordinated to Gd³⁺ with the coordination number of 9 and Cp′, COT and oxygen atom form a triangular plane around Gd³⁺, which is almost in the plane (dev. -0.0144 Å).