Reaktionen von Undecacarbonyl(acetonitril)trieisen mit Alkinethern

Reactions of Undecacarbonyl(acetonitrile)triiron with Alkyne Ethers (CO)₁₁(CH₃CN) 1 reacts with the alkyne ethers H₃C? C?C? OC₂H₅ 2a , H? C?C? OC₂H₅ 2b , H₃C? O? CH₂? C?C? CH₂? O? CH₃, 2c and H₃C? O? C(CH₃)H? C?C? C(CH₃)H? O? CH₃ 2d forming different cluster products depending on the substituents and the reaction conditions. The product obtained with 2a is the bisalkylidyne cluster Fe₃(CO)₉(m?₃-C? CH₃)(m?₃-C? OC₂H₅) 3 which results from the cleavage of the carbon carbon triple bond. The alkyne 2b however yields the vinylidene cluster Fe₃(CO)₁₀(m?₃-η²-C? C(H)OC₂H₅) 4 by 1,2 proton shift. The alkyne clusters Fe₃(CO)₁₀(m?₃-η²-C? C(H)OC₂H₅) 4 by 1,2 proton shift. The alkyne clusters Fe₃(CO)₁₀(m?₃-η²- H₃ C? O? CH₂? C?C? CH₂? O? CH₃) 6 and Fe₃(CO)₉(m?-η²-H₃C? O? CH₂? C?C? CH₂? O? CH₃) 7 are the isolated products obtained from 2c . Thermolysis of 7 results in the formation of the dinuclear butatrien complex Fe₂(CO)₆ (H₂C? C? C? CH₂) 8a . The analogous compound Fe₂(CO)₆[H(H₃C)C ? C ? C ? C(CH₃)H] 8b is the only product of 2d and 1 . The structures of 4, 5 , and 6 have been determined by crystal structure determinations.     

Iron(0), rhodium(I) and palladium(II) complexes with p‐(N,N‐dimethylaminophenyl) diphenylphosphine and the application of the palladium complex as a catalyst for the Suzuki–Miyaura cross‐coupling reaction

The reaction of p‐(N,N‐dimethylaminophenyl)diphenylphosphine [PPh₂(p‐C₆H₄NMe₂)] with [Fe₃(CO)₁₂], [Rh(CO)₂Cl]₂ and PdCl₂ resulted in three new mononuclear complexes, {Fe(CO)₄[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1a ), trans‐{Rh(CO)Cl[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 2 ) and trans‐{PdCl₂[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 3 ), respectively. A small amount of dinuclear nonmetal‐metal bonded complex, {Fe₂(CO)₈[µ‐(P,N)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1b ), was also isolated as a side product in the reaction of [Fe₃(CO)₁₂]. The complexes were characterized by elemental analyses, mass, IR, UV–vis, ¹H, ¹³C (except 1b) and ³¹P{¹H} NMR spectroscopy. The Pd complex 3 effectively catalyzes the Suzuki–Miyaura cross‐coupling reactions of aryl halides with arylboronic acids in water–isopropanol (1:1) at room temperature. Excellent yields (up to 99% isolated yield) were achieved. The effects of different solvents, bases, catalyst quantities were also evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

ON THE MECHANISM OF PHOTOCHEMICAL ALKYNE INSERTION INTO CYCLOPENTADIENYLIRONDICARBONYL DIMER: ALKYNE ADDITION TO A “TIED-BACK” Cp-Fe DIMER

Abstract

The photochemical insertion of phenylacetylene with the “tied-back” dinuclear complex [(η⁵-C₅H₄)₂SiMe₂]Fe₂(CO)₂(μ-CO)₂ (4) yields, by X-ray structural analysis, a dimetallacyclopentenone product entirely analogous to that obtained from the photochemical reaction of the alkyne with (η⁵ - C₅H₅)₂Fe₂(CO)₂(μ-CO)₂ (1). This result is interpreted as evidence for an alternative pathway for photochemical alkyne addition to 1. Attempts to identify the photochemical intermediates from 4 have been unsuccessful. A competition study between 1 and 4 indicates that photochemical alkyne insertion into 1 is preferred by approximate ratio of 2:1 over insertion into 4.     

Formation of Alkyne Bridged Multicobalt Carbonyl Complexes with Tris(2‐Thienyl)Phosphine or Bis(Trimethylsilylethynyl)Phenylphosphine Ligand

Treatment of Co₄(CO)₁₂ with an excess of trimethylsilylacetylene (TMSA) in the presence of tri(2‐thienyl)phosphine in THF at 25 °C for 2 hours yielded six compounds. Two pseudo‐octahedral, alkyne‐bridged tetracobalt clusters, [Co₄(μ₄‐η²‐HC≡CSiMe₃)(CO)₁₀(μ‐CO)₂] ( 4 ) and [Co₄(μ₄‐η²‐HC≡CSiMe³)‐(CO)₉(μ‐CO)₂{P(C₄H₄S)₃}] ( 6 ), along with an alkyne‐bridged dicobalt complex, [Co₂(CO)₅(μ‐HC≡CSiMe₃)‐{P(C₄H₄S)₃}] ( 5 ), were obtained as new compounds. The addition of the thienylphosphine ligand, in fact, facilitates the reaction rate. Reaction of an alkyne‐bridged dicobalt complex, [(η²‐H‐C≡C‐SiMe₃)Co₂(CO)₆] ( 3 ), with a bi‐functional ligand, PPh(‐C≡C‐SiMe₃)₂, yielded an unexpected six‐membered, cyclic compound, {(Ph)(Me₃Si‐C≡C)P‐[(η²‐C≡C‐SiMe₃)Co₂(CO)₅]}₂ ( 7 ). All of these new compounds were characterized by spectroscopic means; the solid‐state structures of ( 5 ), ( 6 ) and ( 7 ) have been established by X‐ray crystallography.     

Isolation of New Disilanylene-bridged Bis（cyclopentadienyl）tetracarbonyldiiron Complexes and Molecular Structure of [η^5, η^5-C5H4SiMe（SiMePh2）C5H4]Fe2（CO）2（μ-CO）2

1,2-Diphenyl-1,2-dimethyldisilanylene-bridged bis-cyclopentadienyl complex[η~5,η~5-C_5H_4PhMeSiSiMePh-C_5H_4]Fe_2(CO)_2(μ-CO)_2(1)was synthesized by a modified procedure,from which the trans-isomer 1b that was pre-viously difficult to obtain has been isolated for the first time.More interestingly,two new regio-isomers[η~5,η~5C_5H_4SiMe(SiMePh_2)C_5H_4]Fe_2(CO)_2(μ-CO)_2(2)and [η~5,η~5-C_5H_4Me_2SiSiPh_2C_5H_4]Fe_2(CO)_2(μ-CO)_2(3)were occa-sionally obtained during above process,the novel structures of which opened up new options for further study ofthis type of Si—Si bond-containing transition metal complexes.The molecular structure of 2 has been determinedby the X-ray diffraction method.     

High Yield Synthesis,Molecular Structure,and Reactions of the 16‐Electron Norbornadiene Complex, [WI2(CO)2(nbd)]

Reaction of equimolar amounts of [WI₂(CO)₃(NCMe)₂] and norbornadiene (nbd) in toluene at 95 °C for 3h gave the 16‐electron crystallographically characterised complex, [WI₂(CO)₂(nbd)] (1) in 96 % yield. The structure of 1 has a distorted octahedral geometry, with the two cis‐ iodo ligands opposite to the two alkene groups in the equatorial plane, with the carbonyl groups in the axial sites. Treatment of 1 with two equivalents of PhC₂Ph in CH₂Cl₂ at room temperature afforded the bis(alkyne) complex [WI₂(CO)₂(η²—PhC₂Ph)₂] (2) . Equimolar quantities of 1 and 4, 4′‐bipyridine react in CH₂Cl₂ at room temperature to yield the seven‐coordinate complex, [WI₂(CO)₂(4, 4′‐bipyridine)(nbd)] (3) .     

New Tetracobalt Cluster Compounds for Electrocatalytic Proton Reduction: Syntheses,Structures, and Reactivity

Reaction of Co₂(CO)₈ and 1,3‐propanedithiol in a 1:1 molar ratio in toluene affords a novel tetracobalt complex, [(μ₂‐pdt)₂(μ₃‐S)Co₄(CO)₆] (pdt=‐SCH₂CH₂CH₂S‐, 1 ), which possesses some of the structural features of the active site of [FeFe]‐hydrogenase. Carbonyl displacement reaction of complex 1 in the presence of mono‐ or diphosphine ligands leads to the formation of [(μ₂‐pdt)₂(μ₃‐S)Co₄(CO)₅(PCy₃)] ( 2 ) and [(μ₂‐pdt)₂(μ₃‐S)Co₄(CO)₄(L)] [L=Ph₂PCH?CHPPh₂, 3 ; Ph₂PCH₂N(Ph)CH₂PPh₂, 4 ; Ph₂PCH₂N(iPr)CH₂PPh₂, 5 ]. Complexes 1 – 5 have been fully characterized by spectroscopy and single‐crystal X‐ray diffraction studies. Cyclic voltammetry has revealed that complexes 1 – 5 show a reversible first reduction wave and are active for electrocatalytic proton reduction in the presence of CF₃COOH. Protonation reactions have been monitored by ³¹P and ¹H NMR and infrared spectroscopies, which revealed the formation of different protonated species. The mono‐reduced species of 1 – 5 have been spectroscopically characterized by EPR and spectro‐electro‐infrared techniques.     

Regiospecific substitution of carbonyl by phosphine ligands in hydrocarbyl-substituted carbonyl clusters. Synthesis and spectroscopic characterization of Fe3(CO)8(PPh3)(μ3-η2- ⊥ -EtC2Et) and (η5-C5H5)NiFe2(CO)5(PPh3)(η3-η2- ⊥-C2But)

The complexes Fe₃(CO)₈(PPh₃)(μ₃-η²- ⊥ -EtC₂Et) and (η⁵-C₅H₅)NiFe₂(CO)₅(PPh₃)(η₃-η²- ⊥-C₂Bu^t) have been obtained by treating Fe₃(CO)₉(C₂Et₂) or (Cp)NiFe₂(CO)₆(C₂Bu^t) with PPh₃ under mild conditions; the substituted clustes have been characterized spectroscopically. Structures are proposed in which the phosphine is on the unique metalatom σ-bonded to the alkyne or acetylide moiety. Replacement of CO by PPh₃ ligands rather than by addition, is observed for the formally unsaturated Fe₃(CO)₉(C₂Et₂). Reorientation of the acetylide was expected for (Cp)NiFe₂(CO)₆(C₂Bu^t) upon substitution, but was not observed.     

Direct Evidence for a [4+2] Cycloaddition Mechanism of Alkynes to Tantallacyclopentadiene on Dinuclear Tantalum Complexes as a Model of Alkyne Cyclotrimerization

A dinuclear tantalum complex, [Ta₂Cl₆(μ‐C₄Et₄)] ( 2 ), bearing a tantallacyclopentadiene moiety, was synthesized by treating [(η²‐EtC?CEt)TaCl₃(DME)] ( 1 ) with AlCl₃. Complex 2 and its Lewis base adducts, [Ta₂Cl₆(μ‐C₄Et₄)L] (L=THF ( 3 a ), pyridine ( 3 b ), THT ( 3 c )), served as more active catalysts for cyclotrimerization of internal alkynes than 1 . During the reaction of 3 a with 3‐hexyne, we isolated [Ta₂Cl₄(μ‐η⁴:η⁴‐C₆Et₆)(μ‐η²:η²‐EtC?CEt)] ( 4 ), sandwiched by a two‐electron reduced μ‐η⁴:η⁴‐hexaethylbenzene and a μ‐η²:η²‐3‐hexyne ligand, as a product of an intermolecular cyclization between the metallacyclopentadiene moiety and 3‐hexyne. The formation of arene complexes [Ta₂Cl₄(μ‐η⁴:η⁴‐C₆Et₄Me₂)(μ‐η²:η²‐Me₃SiC?CSiMe₃)] ( 7 b ) and [Ta₂Cl₄(μ‐η⁴:η⁴‐C₆Et₄RH)(μ‐η²:η²‐Me₃SiC?CSiMe₃)] (R=nBu ( 8 a ), p‐tolyl ( 8 b )) by treating [Ta₂Cl₄(μ‐C₄Et₄)(μ‐η²:η²‐Me₃SiC?CSiMe₃)] ( 6 ) with 2‐butyne, 1‐hexyne, and p‐tolylacetylene without any isomers, at room temperature or low temperature were key for clarifying the [4+2] cycloaddition mechanism because of the restricted rotation behavior of the two‐electron reduced arene ligands without dissociation from the dinuclear tantalum center.     

E4 Butterfly Complexes (E=P,As) as Chelating Ligands

The coordination properties of new types of bidentate phosphane and arsane ligands with a narrow bite angle are reported. The reactions of [{Cp′′′Fe(CO)₂}₂(μ,η^1:1‐P₄)] ( 1 a ) with the copper salt [Cu(CH₃CN)₄][BF₄] leads, depending on the stoichiometry, to the formation of the spiro compound [{{Cp′′′Fe(CO)₂}₂(μ₃,η^1:1:1:1‐P₄)}₂Cu]⁺[BF₄]^? ( 2 ) or the monoadduct [{Cp′′′Fe(CO)₂}₂(μ₃,η^1:1:2‐P₄){Cu(MeCN)}]⁺[BF₄]^? ( 3 ). Similarly, the arsane ligand [{Cp′′′Fe(CO)₂}₂(μ,η^1:1‐As₄)] ( 1 b ) reacts with [Cu(CH₃CN)₄][BF₄] to give [{{Cp′′′Fe(CO)₂}₂(μ₃,η^1:1:1:1‐As₄)}₂Cu]⁺[BF₄]^? ( 5 ). Protonation of 1 a occurs at the “wing tip” phosphorus atoms, which is in line with the results of DFT calculations. The compounds are characterized by spectroscopic methods (heteronuclear NMR spectroscopy and IR spectrometry) and by single‐crystal X‐ray diffraction studies.     

Konkurrierende bildung von heterometall-zweikern-komplexen mit μ-CCHPh und μ-ηPsu1,η3-CHCPhCO-brückenliganden bei der reaktion von C5H5Rh(PhCCH)PPri3 MIT Fe2(CO)9

The alkyne complex C₅H₅Rh(PhCCH)PPrⁱ₃ reacts wit Fe₂(CO)₉ to form two isomeric dinuclear products, C₅H₅(PPrⁱ₃)Rh(μ-CCHPh)(μ-CO)Fe(CO)₃ and C₅H₅(PPrⁱ₃)Rh(μ-η¹,η³-CHCPhCO)Fe(CO)₃. The X-ray crystal structure of the latter has been determined.     

Synthesis,characterization, and some electrocatalytic properties of heteromultinuclear FeI/RuII Clusters

A series of new heteromultinuclear Fe^I/Ru^II clusters are described. The complexes (η⁶-arene)RuFe₂S₂(CO)₆ (arene = p-cymene 1 , C₆Me₆ 2 ) and Fe₂[μ-S (Cp*Ru)(CO)₂]₂(CO)₆ (Cp* = η⁵-C₅Me₅) ( 3 ) were prepared by the reduction reactions of (μ-S)₂Fe₂(CO)₆ with 2 equiv of LiHBEt₃, followed by treatment (μ-SLi)₂Fe₂(CO)₆ with ruthenium-arene complexes Ru₂(μ-Cl)₂Cl₂(η⁶-arene)₂ or Cp*Ru (CO)₂Cl in 22–33% yields. Further reactions of 1 and 2 with 1 equiv of triphenylphosphine in the presence of the decarbonylating agent Me₃NO·2H₂O, afforded the corresponding monophosphine-substituted Fe^I/Ru^II complexes (η⁶-arene)RuFe₂S₂(CO)₅(Ph₃P) (arene = p-cymene 4 , C₆Me₆ 5 ) in 75% and 78% yields. While treatment of parent complex 1 or 2 with 1 equiv of diphosphine Ph₂PCH₂PPh₂ (dppm) in xylene at reflux temperature resulted in the formation of the diphosphine-bridged RuFe₂S₂(CO)₉ derivate RuFe₂S₂(CO)₇(dppm) ( 6 ). The possible pathway for the formation was proposed. Two isomers of novel macrocyclic complexes involve the (η⁶-arene) Ru-bridged quadruple-butterfly Fe/S clusters [{μ-S (CH₂)₃S-μ}{(μ-CS₂)Fe₂(CO)₆}₂]₂[(η⁶-arene)Ru]₂ (arene = p-cymene 7a and 7b , C₆Me₆ 8a and 8b ) were isolated by reactions of two μ-CS₂-containing dianion [{μ-S (CH₂)₃S-μ}{(μ-S=CS)Fe₂(CO)₆}₂]²⁻ with [Ru₂(μ-Cl)₂Cl₂(η⁶-arene)₂], in which the propylene groups are attached to two S atoms by ee and ea types of bonds respectively. All the new complexes 1 – 8 have been characterized by elemental analysis, spectroscopy, and particularly for 1 – 6 , 7b and 8a by X-ray crystallography. In addition, the electrochemical properties of representative complexes 1 – 4 and 6 have been investigated.     

Electronic Excitation of [(μ4‐η2‐alkyne)Rh4(CO)8(μ‐CO)2]: An In Situ UV/Vis Spectroscopy,Spectral Reconstruction and DFT Study

Reactions of three alkynes, namely, 1‐heptyne, 3‐hexyne and 1‐phenyl‐1‐butyne, with [Rh₄(CO)₉(μ‐CO)₃] are performed in anhydrous hexane under argon atmosphere with multiple perturbations of alkynes and [Rh₄(CO)₉(μ‐CO)₃]. The reactions are monitored by in situ UV/Vis spectroscopy, and the collected electronic spectra are further analyzed with the band‐target entropy minimization (BTEM) family of algorithms to reconstruct the pure component spectra. Three BTEM estimates of [(μ₄‐η²‐alkyne)Rh₄(CO)₈(μ‐CO)₂], in addition to that of [Rh₄(CO)₉(μ‐CO)₃], are successfully reconstructed from the experimental spectra. Time‐dependent density functional theory (TD‐DFT) predicted spectra at the PBE0/DGDZVP level are consistent with the corresponding BTEM estimates. The present study demonstrates that: 1) the BTEM family of algorithms is successful in analyzing multi‐component UV/Vis spectra and results in good spectral estimates of the trace organometallics present; and 2) the subsequent DFT/TD‐DFT methods provide an interpretation of the nature of the electronic excitation and can be used to predict the electronic spectra of similar transition organometallic complexes.     

Reactions of metal carbonyl cluster complexes with multidentate phosphine ligands; preparation of bis(diphenylphosphino)methane derivatives of the trinuclear complexes M3(CO)12 (M = Fe,Ru and Os) and the X-ray crystal structure of Os3(CO)9(μ-dppm)(η1-dppm) (dppm = Ph2pch2ppH2)

The reaction of bis(diphenylphosphino)methane (dppm) with Fe₃(CO)₁₂ gave the known complexes Fe(CO)₄ (dppm), Fe₂(CO)₇ (dppm), in addition to Fe₂CO)₅(dppm)₂. Two new dppm derivatives of Ru₃CO)₁₂, Ru₃(CO)₉(μ-dppm)(η¹-dppm) and Ru₃(CO)₆(dppm)₃ have been isolated and spectroscopically characterised. From the reaction of Os₃(CO)₁₂ with dppm, the derivatives Os₃(CO)₁₀(dppm), Os₃(CO)₉(μ-dppm)(η¹-dppm) and Os₃(CO)₈(dppm)₂ have been isolated. The crystal structure of Os₃(CO)₉(μ-dppm)(η¹-dppm) has been determined.     

Reactivity of the M-(η-alkyne) bond [M = Cr, W]: A kinetic and DFT study

The displacement of η²-coordinated 1-hexyne and 3-hexyne by 2-picoline from the Cr(CO)₅, BzCr(CO)₂ and W(CO)₅ fragments was studied. For the Cr systems, the data is consistent with a dissociative mechanism of alkyne displacement from the metal center. For W(CO)₅(η²-1-hexyne), the alkyne displacement follows a largely associative mechanism. The bond dissociation enthalpies obtained from the kinetic analysis are in good agreement with the values obtained by detailed DFT calculations. The calculations indicate that the energy required for the steric reorganization of the alkyne ligand prior to binding with the metal is an important factor in the determination of the overall metal-(η²-alkyne) bond strength.     

Synthesis and Structures of ansa‐Titanocene Complexes with Diatomic Bridging Units for Overall Water Splitting

The synthesis of a series of ansa‐titanocene dichlorides [Cp′₂TiCl₂] (Cp′=bridged η⁵‐tetramethylcyclopentadienyl) and the corresponding titanocene bis(trimethylsilyl)acetylene complexes [Cp′₂Ti(η²‐Me₃SiC₂SiMe₃)] is described. The ethanediyl‐bridged complexes [C₂H₄(C₅Me₄)₂TiCl₂] ( 2 ‐Cl₂) and [C₂H₄(C₅Me₄)₂Ti(η²‐Me₃SiC₂SiMe₃)] ( 2‐ btmsa; btmsa=η²‐Me₃SiC₂SiMe₃) can be obtained from the hitherto unknown calcocenophane complex [C₂H₄(C₅Me₄)₂Ca(THF)₂] ( 1 ). Furthermore, a heterodiatomic bridging unit containing both, a dimethylsilyl and a methylene group was introduced to yield the ansa‐titanocene dichloride [Me₂SiCH₂(C₅Me₄)₂TiCl₂] ( 3 ‐Cl₂) and the bis(trimethylsilyl)acetylene complex [Me₂SiCH₂(C₅Me₄)₂Ti(η²‐Me₃SiC₂SiMe₃)] ( 3 ‐btmsa). Besides, tetramethyldisilyl‐ and dimethylsilyl‐bridged metallocene complexes (structural motif 4 and 5 , respectively) were prepared. All ansa‐titanocene alkyne complexes were reacted with stoichiometric amounts of water; the hydrolysis products were isolated as model complexes for the investigation of the elemental steps of overall water splitting. Compounds 1 , 2 ‐btmsa, 2 ‐(OH)₂, 3 ‐Cl₂, 3 ‐btmsa, 4 ‐(OH)₂, 3 ‐alkenyl and 5 ‐alkenyl were characterised by X‐ray diffraction analysis.     

Nickel(0) Complexes with Fluorinated Alkyne Ligands and their Reactivity towards Semihydrogenation and Hydrodefluorination with Water

The current work describes the synthesis and full characterization of zerovalent nickel complexes of the type [(dippe)Ni(η²‐C,C‐F_n‐alkyne)] (dippe=1,2‐bis(di‐isopropylphosphino‐ethane), F_n‐alkyne=fluorinated aromatic alkyne, n=1, 3, 5; 3a , 3b , 3c ) and [{(dippe)Ni}₂(μ²‐C,C‐F_n‐alkyne)] ( 4 ). Reactions with complexes 3a , 3b , 3c , and water as the hydrogen source, yield selective semihydrogenation of the bound alkyne to the corresponding alkene, accompanied by partial hydrodefluorination of the aromatic ring. Different alkynes were tested; on using the alkyne with five fluorine atoms over the aromatic ring, partial defluorination was achieved under the mildest reaction conditions, followed in reactivity by the alkyne with three fluorine atoms. The alkyne with only one fluorine atom was barely defluorinated. The use of triethylsilane as a sacrificial hydride source resulted in an overall increase in reactivity towards defluorination.     

Hydrierung aromatischer Nitrile auf dem Fe3(CO)9-Cluster

Hydrogenation of Aromatic Nitriles on the Fe₃(CO)₉ Cluster The μ₃-nitrile bridged clusters Fe₃(CO)₉(μ₃-η²-N≡CR) ( 3 , R = phenyl, p-tolyl, p-anisyl) consume hydrogen upon heating in solution with formation of the acimidoyl- and the alkylideneimido-bridged clusters HFe₃(CO)₉(μ₃-η²-HN=CR) ( 1 ) and HFe₃(CO)₉(μ₃-η²-N=CHR) ( 2 ). These can be obtained in a better way by successive H⁺ and H^– addition with NaBH₄ and H₃PO₄. HFe₃(CO)₉(μ₃-η²-N=CHR) ( 2 ) adds P(OMe)₃ with concomitant hydrogen migration to form Fe₃(CO)₉P(OMe)₃(μ₃-η¹-N–CH₂R) ( 6 ). The phosphite-substituted cluster Fe₃(CO)₈P(OMe)₃(μ₃-η²-N≡CPh) ( 5 a ) on the other hand is converted by the H⁺/H^– addition to the products HFe₃(CO)₈P(OMe)₃(μ₃-η²-HN=CPh) ( 7 a ) and HFe₃(CO)₈P(OMe)₃(μ₃-η²-N=CHPh) ( 8 a ).     

Synthesis,structures, and electrocatalytic properties of phosphine-monodentate, −chelate,and -bridge diiron 2,2-dimethylpropanedithiolate complexes related to [FeFe]-hydrogenases

To further extend diiron subsite models of [FeFe]-hydrogenases, the various substitutions of all-carbonyl diiron complex Fe₂(μ-Me₂pdt)(CO)₆ ( A , Me₂pdt = (SCH₂)₂CMe₂) with monophosphines or small bite-angle diphosphines are studied as follows. Firstly, the monodentate complexes Fe₂(μ-Me₂pdt)(CO)₅{κ¹-P(C₆H₄R-p)₃} [R = Me ( 1a ) and Cl ( 1b )] and Fe₂(μ-Me₂pdt)(CO)₅{κ¹-Ph₂PX'} [X' = NHPh ( 2a ) and CH₂PPh₂ ( 2b )] are readily afforded through the Me₃NO-assisted reactions of A with monophosphines P(C₆H₄R-p)₃ (R = Me, Cl) and diphosphines (Ph₂P)₂X (X = NPh, CH₂ (dppm)) in MeCN at room temperature, respectively. Secondly, the chelate complexes Fe₂(μ-Me₂pdt)(CO)₄(κ²-(Ph₂P)₂X) [X = NPh ( 3a ) and NBuⁿ ( 3b )] can be efficiently prepared by the UV-irradiated reactions of A with small bite-angle diphosphines (Ph₂P)₂X (X = NPh, NBuⁿ) in toluene. Thirdly, the bridge complexes Fe₂(μ-Me₂pdt)(CO)₄(μ-(Ph₂P)₂X) [X = NPh ( 4a ) and CH₂ ( 4b )] are well obtained from the refluxing solutions of A and diphosphines (Ph₂P)₂X (X = NPh, CH₂) in xylene. Rarely, the diphosphine-bridge complex 4b may be produced in low yield via the UV-irradiated solutions of A and the dppm ligand in toluene emitting at 365 nm. Eight new complexes obtained above have been well characterized by using element analysis, FT-IR, NMR (¹H, ³¹P) spectroscopies, and particularly for 1a , 1b , 2a , 3b , 4a , 4b by X-ray crystallography. Meanwhile, the electrochemical and electrocatalytic properties of three representative complexes 2a , 3a , and 4a with pendant N-phenyl groups are investigated and compared by using cyclic voltammetry (CV) in the absence and presence of trifluoroacetic acid (TFA) as a proton source, indicating that they are all found to be active for electrocatalytic proton reduction to hydrogen (H₂).     

Ligand exchange between metals: synthesis and characterisation of binuclear and trinuclear iron-alkyne complexes. Crystal structures of [(η5-C5H5)2Fe3(CO)3(μ3-CO)(μ-CO)(CF3C2CF3] and [{μ-CF3CC(CF3)S} {Fe(CO)3}2]

Reaction of[(η⁵-C₅H₅)(CO)Fe{μ-C(CF₃)C(CF₃)SMe}₂Fe(CO)(η⁵-C₅H₅)] with Fe₃(CO)₁₂ leads to an exchange of ligands (hexafluorobut-2-yne, cyclopentadienyl or sulphur) between the metal centres and the formation of several new complexes.Two of These, [(η⁵-C₅H₅)₂Fe₃(CO)₃(μ₃-CO)(μ-CO)(CF₃C₂CF₃)] and [{μ-CF₃CC (CF₃)S Fe(CO)₃}₂], have been shown by X-ray diffraction to contain μ₃-η²-| CF₃C₂CF₃ units bridging Fe₃ and Fe₂S triangles, respectively.