Ag[Fe(CO)5]2+: A Bare Silver Complex with Fe(CO)5 as a Ligand

Attempts to prepare Fe(CO)₅⁺ from Ag[Al(OR^F)₄] (R^F=C(CF₃)₃) and Fe(CO)₅ in CH₂Cl₂ yielded the first complex of a neutral metal carbonyl bound to a simple metal cation. The Ag[Fe(CO)₅]₂⁺ cation consists of two Fe(CO)₅ molecules coordinating Ag⁺ in an almost linear fashion. The ν(CO) modes are blue‐shifted compared to Fe(CO)₅, with one band above 2143 cm^?1 indicating that back‐bonding is heavily decreased in the Ag[Fe(CO)₅]₂⁺ cation.     

New Iron–Mercury Clusters: [Hg7{Fe(CO)4}5(StBu)3Cl], [Hg14Fe12{Fe(CO)4}6S6(StBu)8Br18], and [Hg39Fe8{Fe(CO)4}18S8(StBu)14Br28]

Three new chalcogen-bridged mercury–iron clusters with 7, 14, and 39 mercury centers were obtained from the reaction of tBuSSiMe₃ with [Fe(CO)₄(HgX)₂] (X= Cl, Br). The compounds were isolated in the form of orange crystals that were characterized by X-ray crystallography. The picture on the right shows the structure of the heavy-atom skeleton of [Hg₁₄Fe₁₂{Fe(CO)₄}₆S₆(StBu)₈Br₁₈] (Hg, Fe, Br, and S are black, diagonally striped, white, and horizontally striped, respectively).     

Mapping the Transformation [{RuII(CO)3Cl2}2]→[RuI2(CO)4]2+: Implications in Binuclear Water–Gas Shift Chemistry

The complete sequence of reactions in the base‐promoted reduction of [{Ru^II(CO)₃Cl₂}₂] to [Ru^I₂(CO)₄]²⁺ has been unraveled. Several μ‐OH, μ:κ²‐CO₂H‐bridged diruthenium(II) complexes have been synthesized; they are the direct results of the nucleophilic activation of metal‐coordinated carbonyls by hydroxides. The isolated compounds are [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐OH)(NP^F‐Am)₂][PF₆] ( 1 ; NP^F‐Am=2‐amino‐5,7‐trifluoromethyl‐1,8‐naphthyridine) and [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)(μ‐OH)(NP‐Me₂)₂][BF₄]₂ ( 2 ), secured by the applications of naphthyridine derivatives. In the absence of any capping ligand, a tetranuclear complex [Ru₄(CO)₈(H₂O)₂(μ³‐OH)₂(μ:κ²‐C,O‐CO₂H)₄][CF₃SO₃]₂ ( 3 ) is isolated. The bridging hydroxido ligand in 1 is readily replaced by a π‐donor chlorido ligand, which results in [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐Cl)(NP‐PhOMe)₂][BF₄] ( 4 ). The production of [Ru₂(CO)₄]²⁺ has been attributed to the thermally induced decarboxylation of a bis(hydroxycarbonyl)–diruthenium(II) complex to a dihydrido–diruthenium(II) species, followed by dinuclear reductive elimination of molecular hydrogen with the concomitant formation of the Ru^I? Ru^I single bond. This work was originally instituted to find a reliable synthetic protocol for the [Ru₂(CO)₄(CH₃CN)₆]²⁺ precursor. It is herein prescribed that at least four equivalents of base, complete removal of chlorido ligands by Tl^I salts, and heating at reflux in acetonitrile for a period of four hours are the conditions for the optimal conversion. Premature quenching of the reaction resulted in the isolation of a trinuclear Ru^I₂Ru^II complex [{Ru(NP‐Am)₂(CO)}{Ru₂(NP‐Am)₂(CO)₂(μ‐CO)₂}(μ₃:κ³‐C,O,O′‐CO₂)][BF₄]₂ ( 6 ). These unprecedented diruthenium compounds are the dinuclear congeners of the water–gas shift (WGS) intermediates. The possibility of a dinuclear pathway eliminates the inherent contradiction of pH demands in the WGS catalytic cycle in an alkaline medium. A cooperative binuclear elimination could be a viable route for hydrogen production in WGS chemistry.     

{Sn10[Si(SiMe3)3]4}2−: A Highly Reactive Metalloid Tin Cluster with an Open Ligand Shell

The reaction of a Sn^ICl solution with LiSi(SiMe₃)₃ gave the anionic metalloid tin cluster {Sn₁₀[Si(SiMe₃)₃]₄}^2? ( 7 ) in good yield. The arrangement of the ten tin atoms in the cluster core can be described as a distorted centaur polyhedron. Quantum chemical calculations suggest that there are 26 bonding electrons in the cluster core, which may be described as an arachno cluster in agreement with Wade’s rules. NMR and mass spectrometric investigations showed that 7 is highly reactive, which may be due to the open ligand shell. The easily available tin atoms in 7 thereby open the door to further subsequent reactions, in which 7 may act as a building block to larger cluster aggregates.     

Chemical Bonding in Homoleptic Carbonyl Cations [M{Fe(CO)5}2]+ (M=Cu,Ag, Au)

Syntheses of the copper and gold complexes [Cu{Fe(CO)₅}₂][SbF₆] and [Au{Fe(CO)₅}₂][HOB{3,5-(CF₃)₂C₆H₃}₃] containing the homoleptic carbonyl cations [M{Fe(CO)₅}₂]⁺ (M=Cu, Au) are reported. Structural data of the rare, trimetallic Cu₂Fe, Ag₂Fe and Au₂Fe complexes [Cu{Fe(CO)₅}₂][SbF₆], [Ag{Fe(CO)₅}₂][SbF₆] and [Au{Fe(CO)₅}₂][HOB{3,5-(CF₃)₂C₆H₃}₃] are also given. The silver and gold cations [M{Fe(CO)₅}₂]⁺ (M=Ag, Au) possess a nearly linear Fe-M-Fe’ moiety but the Fe-Cu-Fe’ in [Cu{Fe(CO)₅}₂][SbF₆] exhibits a significant bending angle of 147° due to the strong interaction with the [SbF₆]⁻ anion. The Fe(CO)₅ ligands adopt a distorted square-pyramidal geometry in the cations [M{Fe(CO)₅}₂]⁺, with the basal CO groups inclined towards M. The geometry optimization with DFT methods of the cations [M{Fe(CO)₅}₂]⁺ (M=Cu, Ag, Au) gives equilibrium structures with linear Fe-M-Fe’ fragments and D₂ symmetry for the copper and silver cations and D_4d symmetry for the gold cation. There is nearly free rotation of the Fe(CO)₅ ligands around the Fe-M-Fe’ axis. The calculated bond dissociation energies for the loss of both Fe(CO)₅ ligands from the cations [M{Fe(CO)₅}₂]⁺ show the order M=Au (D_e=137.2 kcal mol⁻¹)>Cu (D_e=109.0 kcal mol⁻¹)>Ag (D_e=92.4 kcal mol⁻¹). The QTAIM analysis shows bond paths and bond critical points for the M−Fe linkage but not between M and the CO ligands. The EDA-NOCV calculations suggest that the [Fe(CO)₅]→M⁺←[Fe(CO)₅] donation is significantly stronger than the [Fe(CO)₅]←M⁺→[Fe(CO)₅] backdonation. Inspection of the pairwise orbital interactions identifies four contributions for the charge donation of the Fe(CO)₅ ligands into the vacant (n)s and (n)p AOs of M⁺ and five components for the backdonation from the occupied (n-1)d AOs of M⁺ into vacant ligand orbitals.     

Syntheses and Crystal Structures of Two New Iron-sulfur Carbonyl Complexes: [Fe2(SC6H4Cl)2(CO)6]·0.5(Et2O) and [Fe3(SC6H4NH2)6(CO)6]·2(MeOH)

Two new iron-sulfur carbonyl complexes, [Fe2(SC6H4Cl)2(CO)6]·0.5(Et2O) 1 and [Fe3(SC6H4NH2)6(CO)6]·2(MeOH) 2, have been prepared and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. Crystal data for 1: monoclinic, C2/c, a = 18.4439(8), b = 11.0999(5), c = 25.1830(10)(A), β = 97.0370(10)o, V = 5116.8(4)(A)3, Z = 8, C20H13Cl2Fe2O6.50S2, Mr = 604.02, Dc = 1.568 g/cm3, μ = 1.540 mm-1, F(000) = 2424, the final R = 0.0545 and wR = 0.1454 for 3443 observed reflections with I > 2σ(I); 2: monoclinic, P21/n, a = 12.350, b = 26.3050(11), c = 16.057(A),β = 97.891(3)°, V = 5166.9(2)(A)3, Z = 4, C44H44Fe3N6O8S6, Mr = 1144.76, Dc = 1.472 g/cm3, μ = 1.128 mm-1, F(000) = 2352, the final R = 0.0442 and wR = 0.1197 for 7978 observed reflections with I > 2σ(I). Complex 1 contains one iron dimer, in which two tricarbonyliron(I) fragments are bridged together by two 4-chlorophenylthiolate ligands, whereas complex 2 contains a linear tri-iron cluster, in which two terminal tricarbonyliron(II) fragments and the central Fe(II) atom are linked together by six 4-aminophenylthiolate bridging ligands.     

Mn(bipyridyl)(CO)(3) Br]: An Abundant Metal Carbonyl Complex as Efficient Electrocatalyst for CO(2) Reduction

Manganese at work: Carbonyl bipyridyl complexes based on manganese, a non-noble abundant and inexpensive metal, have been proved to be excellent molecular catalysts for the selective electrochemical reduction of CO(2) to CO under mild conditions. Another advantage of manganese complexes over rhenium complexes is that these catalysts operate at markedly less overpotential (0.40?V gain).     

[(Te2)3{Mn(CO)3}2{Mn(CO)4}3]– – A Novel Tellurium‐­Manganese Carbonyl with Ufosane‐like Structure

By reacting Mn₂(CO)₁₀ and TeI₄ in the ionic liquid[BMIm][OTf] (1‐butyl‐3‐methylimidazolium trifluromethanesulfonate), brick‐red crystals of [BMIm][(Te₂)₃{Mn(CO)₃}₂{Mn(CO)₄}₃]are obtained. The title compound contains the carbonyl anion[(Te₂)₃{Mn(CO)₃}₂{Mn(CO)₄}₃]^–. Herein, three formal Te₂^2– units and two formal Mn(CO)₃⁺ fragments establish a distorted heterocubane‐like Te₆Mn₂ structure. Three edges of this heterocubane are furthermore capped by Mn(CO)₄⁺ fragments. The resulting Te₆Mn₅ building unit, moreover, looks very similar to the P₁₁^3– anion – the so‐called ufosane. The mean distances Te–Te and Te–Mn are observed with 277.6 and 264.7 pm, respectively. In addition to single‐crystal structure analysis, the title compound is characterized by infrared spectroscopy (FT‐IR), thermogravimetry (TG) and energy‐dispersive X‐ray (EDX) analysis.     

Copper halide-bridged ruthenium telluride carbonyl complexes: discovery of the semiconducting cluster chain polymer {[PPh4]2[Te2Ru4(CO)10Cu4Br2Cl2].THF}infinity

A new series of Te-Ru-Cu carbonyl complexes was prepared by the reaction of K(2)TeO(3) with [Ru(3)(CO)(12)] in MeOH followed by treatment with PPh(4)X (X=Br, Cl) and [Cu(MeCN)(4)]BF(4) or CuX (X=Br, Cl) in MeCN. When the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was first treated with PPh(4)X followed by the addition of [Cu(MeCN)(4)]BF(4), doubly CuX-bridged Te(2)Ru(4)-based octahedral clusters [PPh(4)](2)[Te(2)Ru(4)(CO)(10)Cu(2)X(2)] (X=Br, [PPh(4)](2)[1]; X=Cl, [PPh(4)](2)[2]) were obtained. When the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was treated with PPh(4)X (X=Br, Cl) followed by the addition of CuX (X=Br, Cl), three different types of CuX-bridged Te-Ru carbonyl clusters were obtained. While the addition of PPh(4)Br or PPh(4)Cl followed by CuBr produced the doubly CuBr-bridged cluster 1, the addition of PPh(4)Cl followed by CuCl led to the formation of the Cu(4)Cl(2)-bridged bis-TeRu(5)-based octahedral cluster compound [PPh(4)](2)[{TeRu(5)(CO)(14)}(2)Cu(4)Cl(2)] ([PPh(4)](2)[3]). On the other hand, when the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was treated with PPh(4)Br followed by the addition of CuCl, the Cu(Br)CuCl-bridged Te(2)Ru(4)-based octahedral cluster chain polymer {[PPh(4)](2)(Te(2)Ru(4)(CO)(10)Cu(4)Br(2)Cl(2)).THF}(infinity) ({[PPh(4)](2)[4].THF}(infinity)) was produced. The chain polymer {[PPh(4)](2)[4].THF}(infinity) is the first ternary Te-Ru-Cu cluster and shows semiconducting behavior with a small energy gap of about 0.37 eV. It can be rationalized as resulting from aggregation of doubly CuX-bridged clusters 1 and 2 with two equivalents of CuCl or CuBr, respectively. The nature of clusters 1-4 and the formation and semiconducting properties of the polymer of 4 were further examined by molecular orbital calculations at the B3LYP level of density functional theory.     

Synthesis, Chemical Characterization, and Molecular Structure of Au8{Fe(CO)4}4(dppe)2 and Au6Cu2{Fe(CO)4}4(dppe)2

The new Au₈{Fe(CO)₄}₄(P^P)₂ and Au₆Cu₂{Fe(CO)₄}₄(P^P)₂ (P^P=dppm, dppe) neutral cluster compounds were isolated in good yields by condensation of the [Au₃{Fe(CO)₄}₂(P^P)]^- anions with Au(SEt₂)Cl and CuCl, respectively, and have been characterized by IR, NMR and microanalyses. The molecular structures of Au₈{Fe(CO)₄}₄(dppe)₂ and Au₆Cu₂{Fe(CO)₄}₄(dppe)₂ have been determined by X-ray diffraction studies. Both molecules adopt a stereogeometry of the heavy atoms consisting of a triangulated and corrugated ribbon twisted around the elongation direction. Contrary to the expectations the latter displays the two copper atoms in the sites of highest connectivity. This implies that site exchange between copper and gold occurs during the synthesis.     

[Cu12(NPEt3)8]4+ and [Ag12(NPEt3)8]4+: Cubane Structures

Unusual, highly symmetrical cubes are formed by the dodecameric cationic phosphoraneiminato complexes of copper(I ) and silver(I ) [M₁₂(NPEt₃)₈]⁴⁺, in which the metal atoms occupy the edges and the N atoms of NPEt ³⁻₃ groups the corners of the cube (see figure). The structures can be understood as molecular sections of the Cu₃N structure, which is inverse to the ReO₃‐type structure.