The reaction of ortho-halogenated aromatic aldazine ligands with Fe2(CO)9: symmetrical cleavage of the azine and carbon-halogen activation

Azine ligands derived from hydrazine and benzaldehyde derivatives bearing halogen substituents in ortho-position with respect to the carbonyl function upon treatment with Fe₂(CO)₉ show two typical reaction principles. One is the symmetrical cleavage of the N-N bond of the azine to yield either di- or trinuclear iron carbonyl compounds [Fe₂(CO)₆(μ₂-NCHR)₂] and [Fe₃(CO)₉(μ₂-NCHR)(μ₂-η²-NCHR)] each showing two arylidenimido moieties. In addition, a trinuclear iron carbonyl cluster compound exhibiting a tetrahedral Fe₃N cluster core is isolated. The cluster shows only one half of the former azine ligand. It is a ionic compound of the general formula [Fe₃(CO)₉(μ₃-η²-NCHR)]Na × H₂O. This trinuclear cluster compound is quantitatively converted into [Fe₃(CO)₉(μ₂-H)(μ₃-η²-NCHR)] upon treatment with phosphorous acid. Most interestingly, we were also able to isolate two types of compounds in which an activation of one of the carbon halogen bonds in ortho-position with respect to the imine functions of the azine has occured in terms of an ortho-metallation reaction. In the N-N bond of the azine is still preserved, whereas in [Fe₃(CO)₉(μ₃-η³-NCHR)] again only one half of the former azine ligand is coordinated in an arylidenimido fashion. In both types of compounds one additional iron carbon bond is present due to the activation of an aromatic carbon halogen bond. The reaction of iron carbonyls with 2,6-difluorobenzonitrile produces [Fe₃(CO)₉(μ₃-η²-NCR)] as the sole product. All new iron carbonyl compounds are characterized by means of X-ray crystallography.     

Synthesis and characterisation of the methylene-inserted mixed-chalcogenide compounds Fe2(CO)6(μ-SeCH2Te) and Fe2(CO)6(μ-SCH2Te)

The methylene-bridged, mixed-chalogen compounds Fe₂(CO)₆(μ-SeCH₂Te) (1) and Fe₂(CO)₆(μ-SCH₂Te) (3) have been synthesised from the room temperature reaction of diazomethane with Fe₂(CO)₆(μ-SeTe) and Fe₂(CO)₆(μ-STe), respectively. Compounds 1 and 3 have been characterised by IR, ¹H, ¹³C, ⁷⁷Se and ¹²⁵Te NMR spectroscopy. The structure of 1 has been elucidated by X-ray crystallography. The crystalsare monoclinic,space group P2₁/n, A = 6.695(2), B = 13.993(5), C = 14.007(4)Å, β = 103.03(2)°, V = 1278(7) ų, Z = 4, D_c = 2.599 g cm⁻³ and R = 0.030 (R_w = 0.047).     

Reactions of isonitriles with [Fe3(CO)12] and [Ru3(CO)12] monitored by electrospray mass spectrometry: structural characterisation of [Fe3(CO)10(CNPh)2] and [Ru4(CO)11(μ3-η-CNPh)2(CNPh)]

The reactions of [Fe₃(CO)₁₂] or [Ru₃(CO)₁₂] with RNC (R=Ph, C₆H₄OMe-p or CH₂SO₂C₆H₄Me-p) have been investigated using electrospray mass spectrometry. Species arising from substitution of up to six ligands were detected for [Fe₃(CO)₁₂], but the higher-substituted compounds were too unstable to be isolated. The crystal structure of [Fe₃(CO)₁₀(CNPh)₂] was determined at 150 and 298 K to show that both isonitrile ligands were trans to each other on the same Fe atom. For [Ru₃(CO)₁₂] substitution of up to three COs was found, together with the formation of higher-nuclearity clusters. [Ru₄(CO)₁₁(CNPh)₃] was structurally characterised and has a spiked-triangular Ru₄ core with two of the CNPh ligands coordinated in an unusual μ₃-η² mode.     

Efficient rearrangement of epoxides catalyzed by a mixed-valent iron trifluoroacetate [Fe3O(O2CCF3)6(H2O)3]

The mixed-valent oxo-centered triiron(III, III, II) trifluoroacetate complex [Fe₂^IIIFe^IIO(O₂CCF₃)₆(H₂O)₃] was prepared by reacting anhydrous iron(III) chloride with boiling trifluoroacetic acid under nitrogen. The non-hygroscopic and readily available mixed-valent triiron trifluoroacetate complex was found to be an efficient catalyst for the regioselective rearrangement of epoxides. A number of carbonyl compounds formed via the rearrangement of epoxides could be obtained by a simple filtration of the reaction mixture through a short plug of silica gel.     

Some additional aspects of versatile starting compounds for cationic organoiron complexes: molecular structure of the aqua complex [(η-C5Me4Et)Fe(CO)2(OH2)]BF4 and solution behavior of the THF complex [(η---C5R5)Fe(CO)2(THF)]BF4

The structures of the versatile starting compounds for organoiron complexes, the cationic aqua complex [(η⁵-C₅Me₄Et)Fe(CO)₂(OH₂)]BF₄ (1b) and the halide complexes (η⁵-C₅Me₅)Fe(CO)₂-I (2a), (η⁵-C₅Me₄Et)Fe(CO)₂-I (2b) and (η⁵-C₅Me₄Et)Fe(CO)₂-Cl (3b), are characterized by X-ray crystallography. Complex 1b [Fe---O: 2.022(8) Å and 2.043(9) Å, two independent molecules] is the first structurally characterized example of organoiron aqua complexes. Details of the synthetic procedures for the above complexes and the labile cationic THF complexes [η⁵-C₅R₅)Fe(CO)₂(THF)]BF₄ (4) are disclosed, and the dissociation equilibrium of 4 is confirmed by means of variable temperature ¹H-NMR as well as saturation transfer experiment.     

Synthesis and structure of the iron-substituted silylacetylene [(η-C5H5)Fe(CO)2SiMe2C]2 and its cobalt hexacarbonyl derivative [(η-C5H5)Fe(CO)2SiMe2C]2 · Co2(CO)6

A transition metal-substituted silylacetylene [(η⁵-C₅H₅)Fe(CO)₂SiMe₂C]₂, [FpMe₂SiC]₂ (I) was synthesized and characterized spectroscopically and structurally. I crystallized in the monoclinic space group P2₁/n, A = 13.011(3) Å B = 12.912(3) Å, C = 13.175(5) Å, β = 94.95(2). The acetylene linkage is reactive toward Co₂(CO)₈ to form I. Co₂(CO)₆ (II) which was also characterized spectroscopically and by single crystal X-ray diffraction. II crystallized in the orthorhombic space group Pbca, A = 17.64(2) Å, B = 14.225(10) Å, C = 24.49(2) Å.     

New Bimetallic Ni–Rh Carbonyl Clusters: Synthesis and X-ray Structure of the [Ni7Rh3(CO)18]3?, [Ni3Rh3(CO)13]3? and [NiRh8(CO)19]2? Cluster Anions

The reaction of the [Ni₆(CO)₁₂]²⁻ dianion with [Rh(COD)Cl]₂ (COD = cyclooctadiene) in acetone affords a mixture of bimetallic Ni–Rh clusters, mainly consisting of the new [Ni₇Rh₃(CO)₁₈]³⁻ and [Ni₈Rh(CO)₁₈]³⁻ trianions. A study of the reactivity of [Ni₇Rh₃(CO)₁₈]³⁻ led to isolation of the new [Ni₃Rh₃(CO)₁₃]³⁻ and [NiRh₈(CO)₁₉]²⁻ anions. All these new bimetallic Ni–Rh carbonyl clusters have been isolated in the solid state as tetrasubstituted ammonium salts and have been characterised by elemental analysis, X-ray diffraction studies, ESI-MS and electrochemistry. The unit cell of the [NEt₄]₃[Ni₇Rh₃(CO)₁₈] salt contains two orientationally-disordered ν₂-tetrahedral [Ni₇Rh₃(CO)₁₈]³⁻ trianions with occupancy factors of 0.75 and 0.25. Besides, their inner Ni₃Rh₃ octahedral moieties show two cis sites purely occupied by Rh atoms, two trans sites purely occupied by Ni atoms and the remaining two cis sites are disordered Ni and Rh sites with respective occupancy fraction of 0.5. At difference from the parent [Ni₇Rh₃(CO)₁₈]³⁻, the octahedral [Ni₃Rh₃(CO)₁₃]³⁻ displays an ordered distribution of Ni and Rh atoms in two staggered triangles. The [NiRh₈(CO)₁₉]²⁻ dianion adopts an isomeric metal frame with respect to that of the [PtRh₈(CO)₁₉]²⁻ congener. As a fallout of this work, new high-yield synthesis of the known [Ni₆Rh₃(CO)₁₇]³⁻ and [Ni₆Rh₅(CO)₂₁]³⁻, as well as other currently-investigated bimetallic Ni–Rh clusters have been obtained.     

Exchange of boryl ligand substituents in Os[B(OEt)2]Cl(CO)(PPh3)2

Reaction between Os[B(OEt)₂]Cl(CO)(PPh₃)₂ and 1,2-ethanediol in the presence of Me₃SiCl (1 equivalent) leads to the tethered boryl complex, Cl(CO)(PPh₃)₂ (1), in which one ethoxy substituent on the boryl ligand is exchanged with one hydroxy group of the 1,2-ethanediol leaving the other OH group available to coordinate to osmium, so giving a six coordinate complex. This formulation is confirmed by crystal structure determination. The same reactants, but with 2 equivalents of Me₃SiCl, lead to the yellow, coordinatively unsaturated complex, OsCl(CO)(PPh₃)₂ (2). Complex (2) adds CO to give OsCl(CO)₂ (PPh₃)₂ (3). Crystal structure determinations of 2 and 3 reveal a very marked difference in the Os-B distances found in the five coordinate complex 2 (2.043(4) Å) and the six coordinate complex 3 (2.179(7) Å). In a reaction similar to that used for forming 2 but with 1,3-propanediol replacing 1,2-ethanediol, the product is OsCl(CO)(PPh₃)₂ (4). The crystal structure for 4 is also reported.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Synthesis and Structural Characterization of Manganese Carbonyl Incorporated Polyoxomolybdate （n-Bu4N）2 [Mo6O16（OCH3）2 {HOCH2C（CH2O）3}2 {Mn（CO）3}2]

The polyoxoanion incorporated {Mn（CO）3^＋} complex, （n-Bu4N）2[Mo6O16（OCH3）2{HOCH2C（CH2O）3}2·{Mn（CO）3}2]（1）, has been synthesized by the reaction of （n-Bu4N）4[Mo8O26] with Mn（CO）5Br in methanol, in the presence of C（CH2OH）4. The complex 1 has been characterized by IR, UV-Vis, X-ray single crystal diffraction, and TG. Crystal data for the complex 1：C25H48MnMo3NO16 （1）, Triclinic Pi, a=0.9405（3） nm, b=1.3351（4） nm, c=1.5455（4） nm, α=103.206（5）°, β=102.165（5）°, γ=100.784（5）°, V=1.7896（9） nm^3, Z=2, R1=0.0703, wR2= 0.1495. The structure analysis of complex 1 shows that the complex consists of two tetrabutylammonium cations and a polyoxomolybdate anion that incorporates two fac-Mn（CO）3^＋ units. The anion of complex 1 can be considered as the dimer of two rhomb-like anions by sharing of two comers.     

Bidentate phosphines of heteroarenes: effective stabilization of the Co2(CO)6 fragment by 4,6-bis(diphenylphosphino) dibenzofuran

Reaction of Co₂(CO)₈ with 4,6-bis(diphenylphosphino)dibenzofuran (1) in diethylether gives the dinuclear complex 4,6-bis(diphenylphosphino)dibenzofurandicobalthexacarbonyl (2). The solid state structures of 1 and 2 have been established by X-ray crystallography. Low temperature ¹³C-NMR spectroscopy was used to analyse 2 in solution.     

The reactivity of Cp2V2(CO)5 towards alkynes

The chemistry of Cp₂V₂(CO)₅ (I) with alkynes is reported. In non-coordinating solvents, I reacts with large, electron-poor alkynes to give the cyclobutadiene complexes CpV(CO)₂(C₄R₄), which are not formed from photolysis of CpV(CO)₄ in the presence of alkyne. Smaller, more basic alkynes give simple monomeric adduct products of the type CpV(CO)₂(RCCR). This latter product is the only one obtained if coordinating solvents are employed. It is demonstrated that coupling to form the cyclobutadiene ligand occurs on the dimer. The dimeric intermediate, produced at low temperature and observed at low temperature by IR and NMR, is believed to have the formula Cp₂V₂(CO)₄(μ-RCCR) (X).Cp₂V₂(CO)₅ is active as a catalyst precursor in the photochemical hydrogenation of diphenyl acetylene to cis-stilbene. The mechanism appears to proceed through a Cp₂V₂(CO)₄(alkyne) intermediate.     

Supramolecular 2D structures in [M(NCS)2(bpe)2(H2O)2] (M = Mn, Fe) systems connected by hydrogen bonds

Here we report the synthesis and characterization by X-ray diffraction, FTIR, UV-Vis and EPR spectroscopies, and the magnetic measurements of two new compounds: [Mn(NCS)₂(bpe)₂(H₂O)₂] (1) and [Fe(NCS)₂(bpe)₂(H₂O)₂] (2) (bpe = 1,2-bis(4-pyridyl)ethylene). Single-crystal structure analyses reveals discrete octahedral metal units that are assembled into 2D sheets through O-Hw?N(bpe) and O-Hw?S(thiocyanate) hydrogen bonds. The intermetallic M?M distances are 6.90 and 6.87 Å for 1 and 2, respectively. Supramolecular architectures are obtained by connections through H-bonds. Slight interactions are observed for compound 2.     

Four isomers from the oxidative addition of Me3SnH to Os(CO)2(PPh3)3 and the crystal structure of Os(SnMeI2)I(CO)2(PPh3)2, in which the pairs of CO and PPh3 ligands are mutually trans

Reaction between Os(CO)₂(PPh₃)₃ and Me₃SnH produces Os(SnMe₃)H(CO)₂(PPh₃)₂ (1). Multinuclear NMR studies of solutions of 1 reveal the presence of four geometrical isomers, the major one being that with mutually cis triphenylphosphine ligands and mutually trans CO ligands. Os(SnMe₃)H(CO)₂(PPh₃)₂ undergoes a redistribution reaction, at the trimethylstannyl ligand, when treated with Me₂SnCl₂ giving Os(SnMe₂Cl)H(CO)₂(PPh₃)₂ (2). Solutions of 2 again show the presence of four isomers but now the major isomer is that with mutually trans triphenylphosphine ligands and mutually cis CO ligands. The redistribution reaction of 1 with SnI₄ produces Os(SnMeI₂)H(CO)₂(PPh₃)₂ (3) which exists in solution as only one isomer, that with mutually trans triphenylphosphine ligands and mutually trans CO ligands. Treatment of 3 with I₂ cleaves the Os-H bond with retention of geometry giving Os(SnMeI₂)I(CO)₂(PPh₃)₂ (4). The crystal structure of 4 has been determined. No isomerization of the trans dicarbonyl complex 4 occurs when 4 is heated, instead there is a formal loss of “MeSnI” and formation of OsI₂(CO)₂(PPh₃)₂ (5).     

Hydrothermal synthesis, structural characterization and magnetic studies of the new pillared microporous ammonium Fe(III) carboxyethylphosphonate: [NH4][Fe2(OH){O3P(CH2)2CO2}2]

The preparation by hydrothermal reaction and the crystal structure of the iron(III) carboxyethylphosphonate of formula [NH₄][Fe₂(OH){O₃P(CH₂)₂CO₂}₂] is reported. The green-yellow compound crystallizes in the monoclinic system, space group Pc(n.7), with the following unit-cell parameters: a=7.193(3) Å, b=9.776(3) Å, c=10.17(4) Å and β=94.3(2)°. It shows a typical layered hybrid organic-inorganic structure featuring an alternation of organic and inorganic layers along the a-axis of the unit cell. The bifunctional ligand [O₃P(CH₂)₂CO₂]³⁻ is deprotonated and acts as a linker between adjacent inorganic layers, to form pillars along the a-axis. The inorganic layers are made up of dinuclear Fe(III) units, formed by coordination of the metal ions with the oxygen atoms originating from the [O₃P−]²⁻ end of the carboxyethylphosphonate molecules, the oxygen atoms of the [−CO₂]⁻ end group of a ligand belonging to the adjacent layer and the oxygen atom of the bridged OH group. Each Fe(III) ion is six-coordinated in a very distorted octahedral environment. Within the dimer the Fe-Fe separation is found to be 3.5 Å, and the angle inside the [Fe(1)-O(11)-Fe(2)] dimers is ∼124°. The resulting 3D framework contains micropores delimited by four adjacent dimers in the (bc) planes of the unit cell. These holes develop along the a-direction as tunnel-like pores and [NH₄]⁺ cations are located there. The presence of the μ-hydroxo-bridged [Fe(1)-O(11)-Fe(2)] dimers in the lattice is also responsible for the magnetic behavior of the compound at low temperatures. The compound contains Fe³⁺ ions in the high-spin state and the two Fe(III) ions are antiferromagnetic coupled. The J/k value of −16.3 K is similar to those found for other μ-hydroxo-bridged Fe(III) dimeric systems having the same geometry.     

Mixed-metal cluster chemistry VI: Phosphine substitution at CpMoIr3(μ-CO)3(CO)8; X-ray crystal structure of CpMoIr3(μ-CO)3(CO)7(PPh3)

Reactions of CpMoIr₃(μ-CO)₃(CO)₈ (1) with stoichiometric amounts of phosphines afford the substitution products CpMoIr₃(μ-CO)₃(CO)_8−x (L)_x (L = PPh₃, x = 1 (2), 2 (3); L = PMe₃, x = 1 (4), 2 (5), 3 (6)) in fair to good yields (23–54%); the yields of both 3 and 6 are increased on reacting 1 with excess phosphine. Products 2–5 are fluxional in solution, with the interconverting isomers resolvable at low temperatures. A structural study of one isomer of 2 reveals that the three edges of an MoIr₂ face of the tetrahedral core are spanned by bridging carbonyls, and that the iridium-bound triphenyiphosphine ligates radially and the molybdenum-bound cyclopentadienyl coordinates axially with respect to this Molr₂ face. Information from this crystal structure, ³¹P NMR data (both solution and solid-state), and results with analogous tungsten—triiridium and tetrairidium clusters have been employed to suggest coordination geometries for the isomeric derivatives.     

Synthesis and reactivity of [(RRN)2PH]Fe(CO)4 complexes. X-ray crystal structure of [(Ph2N)2PH]Fe(CO)4

KHFe(CO)₄ reacts with tris(amino)phosphines by substitution at phosphorus leading to [bis(amino)phosphine]tetracarbonyliron complexes [(R¹R²N)₂PH]Fe(CO)₄. The X-ray structure has been determined for R¹=R²=Ph. Deprotonation of these complexes with KH affords stable potassium phosphidotetracarbonylferrates which can be alkylated or acylated at phosphorus.