Binuclear Iron(I) Complex Containing Bridging Phenanthrene‐4,5‐dithiolate Ligand: Preparation,Spectroscopy, Crystal Structure,and Electrochemistry

A diiron hexacarbonyl complex containing bridging phenanthrene‐4,5‐dithiolate ligand is prepared by oxidative addition of Phenanthro[4,5‐cde][1,2]dithiin to Fe₂(CO)₉. The complex is investigated as a model for the active site of the [Fe–Fe] hydrogenase enzyme. The compound, [(μ‐PNT)Fe₂(CO)₆]; (PNT = phenanthrene‐4,5‐dithiolate), was characterized by spectroscopic methods (IR, UV/Vis and NMR) and X‐ray crystallography. The IR and proton NMR spectra of [(μ‐PNT)Fe₂(CO)₆] ( 4 ) are in agreement with a PNT ligand attached to a Fe₂(CO)₆ core. The infrared spectrum of 4 recorded in dichloromethane contains three peaks at 2001, 2040, and 2075 cm^–1 corresponding to the stretching frequency of terminal metal carbonyls. X‐ray crystallographic study unequivocally confirms the structure of the complex having a butterfly shape with an Fe–Fe bond length of 2.5365 Å close to that of the enzyme (2.6 Å). Electrochemical properties of [(μ‐PNT)Fe₂(CO)₆] have been investigated by cyclic voltammetry. The cyclic voltammogram of [(μ‐PNT)Fe₂(CO)₆] recorded in acetonitrile contains one quasi‐irreversible reduction (E_1/2 = –0.84 V vs. Ag/AgCl, I_pc/I_pa = 0.6, ΔE_p = 131 V at 0.1 V · s^–1) and one irreversible oxidation (E_pa = 0.86 V vs. Ag/AgCl). The redox of [(μ‐PNT)Fe₂(CO)₆] at E_1/2 = –0.84 V can be assigned to the one‐electron transfer processes; [Fe^I–Fe^I] → [Fe^I–Fe⁰] and [Fe^I–Fe⁰] → [Fe^I–Fe^I].     

{1,1′‐(Dimethylsilylene)bis[methanechalcogenolato]}diiron Complexes [2Fe2E(Si)] (E=S,Se, Te) – [FeFe] Hydrogenase Models

(Bis‐selenolato) and (bis‐tellurolato)diiron complexes [2Fe2E(Si)] were prepared and compared with the known (bis‐thiolato)diiron complex A to assess their ability to produce hydrogen from protons. Treatment of [Fe₃(CO)₁₂] with 4,4‐dimethyl‐1,2,4‐diselenasilolane ( 1 ) in boiling toluene afforded hexacarbonyl{μ‐{[1,1′‐(dimethylsilylene)bis[methaneselenolato‐κSe : κSe]](2 ?)}}diiron(Fe? Fe) ( 2 ). The analog bis‐tellurolato complex hexacarbonyl{μ‐{[1,1′‐(dimethylsilylene)bis[methanetellurolato‐κTe : κTe]](2 ?)}}diiron(Fe? Fe) ( 3 ) was obtained by treatment of [Fe₃(CO)₁₂] with dimethylbis(tellurocyanatomethyl)dimethylsilane, which was prepared in situ. All compounds were characterized by NMR, IR spectroscopy, mass spectrometry, elemental analysis and single‐crystal X‐ray analysis. The electrocatalytic properties of the [2Fe2X(Si)] (X=S, Se, Te) model complexes A, 1 , and 2 towards hydrogen formation were evaluated.     

The conformations of two copper(I) complexes of 1H‐benzimidazole‐2(3H)‐thione and thiosaccharinate

(Acetonitrile‐1κN)[μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S][1H‐benzimidazole‐2(3H)‐thione‐2κS]bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₂(CH₃CN)] or [Cu₂(tsac)₂(Sbim)₂(CH₃CN)] [tsac is thiosaccharinate and Sbim is 1H‐benzimidazole‐2(3H)‐thione], (I), is a new copper(I) compound that consists of a triply bridged dinuclear Cu—Cu unit. In the complex molecule, two tsac anions and one neutral Sbim ligand bind the metals. One anion bridges via the endocyclic N and exocyclic S atoms (μ‐S:N). The other anion and one of the mercaptobenzimidazole molecules bridge the metals through their exocyclic S atoms (μ‐S:S). The second Sbim ligand coordinates in a monodentate fashion (κS) to one Cu atom, while an acetonitrile molecule coordinates to the other Cu atom. The Cu^I—Cu^I distance [2.6286 (6) Å] can be considered a strong `cuprophilic' interaction. In the case of [μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S]bis[1H‐benzimidazole‐2(3H)‐thione]‐1κS;2κS‐bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₃] or [Cu₂(tsac)₂(Sbim)₃], (II), the acetonitrile molecule is substituted by an additional Sbim ligand, which binds one Cu atom via the exocylic S atom. In this case, the Cu^I—Cu^I distance is 2.6068 (11) Å.     

Koordinativ ungesättigte Dieisenkomplexe: Synthese und Kristallstrukturen von [Fe2(CO)4(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] und [Fe2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]

Coordinatively Unsaturated Diiron Complexes: Synthesis and Crystal Structures of [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] and [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] [Fe₂(μ‐CO)(CO)₆(μ‐H)(μ‐P^tBu₂)] ( 1 ) reacts spontaneously with dppm (dppm = Ph₂PCH₂PPh₂) to give [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 2 c ). By thermolysis or photolysis, 2 c loses very easily one carbonyl ligand and yields the corresponding electronically and coordinatively unsaturated complex [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ). 3 exhibits a Fe–Fe double bond which could be confirmed by the addition of methylene to the corresponding dimetallacyclopropane [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ). The reaction of 1 with dppe (Ph₂PC₂H₄PPh₂) affords [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppe)] ( 5 ). In contrast to the thermolysis of 2 c , yielding 3 , the heating of 5 in toluene leads rapidly to complete decomposition. The reaction of 1 with PPh₃ yields [Fe₂(CO)₆(H)(μ‐P^tBu₂)(PPh₃)] ( 6 a ), while with ^tBu₂PH the compound [Fe₂(μ‐CO)(CO)₅(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 6 b ) is formed. The thermolysis of 6 b affords [Fe₂(CO)₅(μ‐P^tBu₂)₂] and the degradation products [Fe(CO)₃(^tBu₂PH)₂] and [Fe(CO)₄(^tBu₂PH)]. The molecular structures of 3 , 4 and 6 b were determined by X‐ray crystal structure analyses.     

Electron‐Rich Diferrous–Phosphane–Thiolates Relevant to Fe‐only Hydrogenase: Is Cyanide “Nature's Trimethylphosphane”?

The two‐step one‐pot oxidative decarbonylation of [Fe₂(S₂C₂H₄)(CO)₄(PMe₃)₂] ( 1 ) with [FeCp₂]PF₆, followed by addition of phosphane ligands, led to a series of diferrous dithiolato carbonyls 2 – 6 , containing three or four phosphane ligands. In situ measurements indicate efficient formation of 1 ²⁺ as the initial intermediate of the oxidation of 1 , even when a deficiency of the oxidant was employed. Subsequent addition of PR₃ gave rise to [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₃(PMe₃)₃]²⁺ ( 2 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₂(PR₃)₂]²⁺ (R=Me 3 , OMe 4 ) as principal products. One terminal CO ligand in these complexes was readily substituted by MeCN, and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₃(MeCN)]²⁺ ( 5 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)(PMe₃)₄(MeCN)]²⁺ ( 6 ) were fully characterized. Relevant to the H_red state of the active site of Fe‐only hydrogenases, the unsymmetrical derivatives 5 and 6 feature a semibridging CO ligand trans to a labile coordination site.     

Tricarbonylrhenium(I) Complexes with N‐Heterocyclic Thiones and Selenols

Reactions of (NEt₄)₂[Re(CO)₃Br₃] with N‐heterocyclic thiols such as 2‐mercaptobenzimidazole (H₂Sbenzim), 2‐mercaptothiazoline (HSthiaz), or 5‐mercapto‐1‐methyltetrazole (HSmetetraz) give rhenium(I) complexes of various compositions: (NEt₄)[Re(CO)₃Br₂(H₂Sbenzim)], [Re(CO)₃(HSthiaz)₃]Br, and (NEt₄)[Re₂(CO)₆(μ‐S‐Smetetraz‐κS)(μ‐N,S‐Smetetraz‐κS,N)₂]. Corresponding reactions with 2‐mercaptopyridine (HSpy) and bis(2‐pyridine)diselenide [(Sepy)₂] did not give defined products in reasonable yields, whereas [Re(CO)₅Br] reacts with HSpy and (Sepy)₂ with formation of [Re(CO)₃(HSpy)₃]Br and [Re₂(CO)₆(Sepy)₂], respectively. All reactions were performed without the addition of a supporting base and the sulfur‐containing organic ligands are coordinated in their thione forms with the exception of Smetetraz^– in its μS‐bridging coordination mode in (NEt₄)[Re₂(CO)₆(μ‐S‐Smetetraz‐κS)(μ‐N,S‐Smetetraz‐κS,N)₂], which can be regarded as thiolate. The bonding mode of the selenium containing ligands in the dimeric compound [Re₂(CO)₆(Sepy)₂] (C–Se distance: 1.93 Å) can also best be described as selenolate. The products are stable on air at an ambient temperature. They were studied spectroscopically and by X‐ray diffraction.     

An ethanol‐solvated centrosymmetric dimer of bismuth(III) and thiosaccharinate resulting from `semicoordination' contacts

In the title compound, bis(μ‐1,1‐dioxo‐1,2‐benzothiazole‐3‐thiolato)‐κ³N,S:S;κ³S:N,S‐bis[(1,1‐dioxo‐1,2‐benzothiazole‐3‐thiolato‐κ²N,S)(ethanol‐κO)bismuth(III)] ethanol hemisolvate, [Bi₂(C₇H₄NO₂S₂)₆(C₂H₅OH)₂]·0.5C₂H₅OH, three independent thiosaccharinate (tsac) anions chelate the metal centre through the endocyclic N and exocyclic S atoms. The complex also presnts two `semicoordination' contacts, one from a pendant ethanol solvent molecule and a second one from an S atom of a centrosymmetrically related molecule. This latter interaction complements two π–π interactions between tsac rings to form a dimeric entity which is the elemental unit that builds up the crystal structure. These dinuclear units are connected to each other via a second type of π–π interaction, generating chains along [11]. Two ethanol molecules, one of them of full occupancy at a general position and semicoordinated to the central cation, and a second one depleted and disordered around a symmetry centre, stabilize the structure. The complex was studied theoretically and the vibrational assignations were confirmed by employing theoretical density functional theory (DFT) methods.     

Mixed‐chalcogenide double‐butterfly complex [{(CO)6Fe2SSe}2{μ‐­C(H)—C(H)}]

Bubbling acetyl­ene gas slowly through a methanol solution of [(CO)₆Fe₂{μ‐SSe}] containing sodium acetate for 48 h at room temperature yields the double‐butterfly complex μ‐[ethane‐1,1,2,2‐tetra(selenido/sulfido)]bis[hexacarbonyldiiron(Fe—Fe)], [Fe₄(C₂H₂S₂Se₂)(CO)₁₂]. The molecular structure was established by single‐crystal X‐ray diffraction techniques. The structure consists of two Fe₂SSe butterfly units linked to each other through a bridging HC—CH group. The mol­ecule has twofold symmetry and the two Fe atoms have distorted octahedral geometries.     

[Fe2(μsb‐CO)(CO)3(NO)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]: Synthese,Kristallstruktur und Koordinationsisomerie

[Fe₂(μ_sb‐CO)(CO)₃(NO)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)]: Synthesis, X‐ray Crystal Structure and Isomerization Na[Fe₂(μ‐CO)(CO)₆(μ‐P^tBu₂)] ( 1 ) reacts with [NO][BF₄] at —60 °C in THF to the nitrosyl complex [Fe₂(CO)₆(NO)(μ‐P^tBu₂)] ( 2 ). The subsequent reaction of 2 with phosphanes (L) under mild conditions affords the complexes [Fe₂(CO)₅(NO)L(μ‐P^tBu₂)], L = PPh₃, ( 3a ); η‐dppm (dppm = Ph₂PCH₂PPh₂), ( 3b ). In this case the phosphane substitutes one carbonyl ligand at the iron tetracarbonyl fragment in 2 , which was confirmed by the X‐ray crystal structure analysis of 3a . In solution 3b loses one CO ligand very easily to give dppm as bridging ligand on the Fe‐Fe bond. The thus formed compound [Fe₂(CO)₄(NO)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ) occurs in solution in different solvents and over a wide temperature range as a mixture of the two isomers [Fe₂(μ_sb‐CO)(CO)₃(NO)(μ‐P^tBu₂)(μ‐dppm)] ( 4a ) and [Fe₂(CO)₄(μ‐NO)(μ‐P^tBu₂)(μ‐dppm)] ( 4b ). 4a was unambiguously characterized by single‐crystal X‐ray structure analysis while 4b was confirmed both by NMR investigations in solution as well as by means of DFT calculations. Furthermore, the spontaneous reaction of [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 5 ) with NO at —60 °C in toluene yields a complicated mixture of products containing [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 6 ) as main product beside the isomers 4a and 4b occuring in very low yields.     

Reduktive Dimerisierung von NO an Dirutheniumkomplexen und Bildung eines tridentaten 2, 2‐Bis(diphenylphosphanyl)ethanolato‐Liganden

The reaction of the trans‐hyponitrito complex [Ru₂(CO)₄(μ‐η²‐ONNO)(μ‐H)(μ‐PtBu₂)(μ‐dppen)] ( 1 , dppen = Ph₂PC(=CH₂)PPh₂) with tetrafluorido boric acid afforded the new complex salt [Ru₂(CO)₄(μ‐η²‐ONNOH)(μ‐H)(μ‐PtBu₂)(μ‐dppen)]BF₄ ( 2 ) containing the monoprotonate hyponitrous acid as the ligand in the cationic complex. Complex 1 showed a nucleophilic reactivity towards the trimethyloxonium cation resulting in the monoester derivative of the hyponitrous acid [Ru₂(CO)₄(μ‐η²‐ONNOMe)(μ‐H)(μ‐PtBu₂)(μ‐dppen)]BF₄ ( 3 ). During heating of compound 2 in ethanol under reflux for a short time nitrous oxide was liberated affording unexpectedly a new tridentate 2, 2‐bis(diphenylphosphanyl)ethanolato ligand formed by an intramolecular attack of an intermediate hydroxido ligand towards the unsaturated carbon carbon double bond in the bridging dppen ligand. Thus the complex salt [Ru₂(CO)₄{μ‐η³‐OCH₂CH(PPh₂)₂}(μ‐H)(μ‐PtBu₂)]BF₄ ( 4 ) was formed in good yields. The new compounds 2 , 3 , and 4 were characterized by spectroscopic means as well as their molecular structures were determined in the crystal.     

Iron carbonyl complex containing bis[2‐(diphenylphosphino)phenyl]ether enhancing efficiency in the palladium‐catalyzed Suzuki–Miyaura reaction

The reaction of [Fe₃(CO)₁₂] with bis[2‐(diphenylphosphino)phenyl]ether (DPEphos) in refluxing THF afforded a mononuclear complex, [Fe(CO)₄(η¹‐P‐DPEphos)] (1), as major product and a binuclear complex, [Fe₂(CO)₆(μ‐CO)(μ‐P,P‐DPEphos)] (2), as minor product respectively. The DPEphos ligand acts as a terminal P‐donor in complex 1 and a bridging P,P‐donor in complex 2. Complexes 1 and 2 were characterized by elemental analysis, fast atom bombardment mass spectrometry, FT‐IR, ¹H and ³¹P{¹H} NMR spectroscopy. The structure of complex 1 has been tentatively assigned by density functional theory calculations and its analogy with reported complexes. Combination of complex 1 and PdCl₂ furnished an active catalyst for the Suzuki–Miyaura cross‐coupling reactions of various aryl halides with arylboronic acids. Interestingly, under the same experimental condition, complex 1/PdCl₂ as catalyst showed superior activity over the DPEphos/PdCl₂ system. Copyright © 2012 John Wiley & Sons, Ltd.     

[Hg2(μ‐bpe)(μ‐OAc)2(μ‐SCN)2]n,a New Two‐Dimensional Coordination Polymer Involving Three Simultaneously Bridging Ligands: 1,2‐Bis(4‐pyridyle)ethene,Acetate, and Thiocyanate

A new mercury(II) complex of 1,2‐bis(4‐pyridyle)ethene (bpe) with anionic acetate and thiocyanate ligands has been synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. The single crystal X‐ray analysis shows that the complex is a two‐dimensional polymer with simultaneously bridging 1,2‐bis(4‐pyridyle)ethane, acetate and thiocyanate ligands and basic repeating dimeric [Hg₂(μ‐bpe)(μ‐OAc)₂(μ‐SCN)₂] units. The two‐dimensional system forms a three‐dimensional network by packing via π‐π stacking interactions.     

Aktivierung von Schwefelkohlenstoff an Trirutheniumclustern: Synthese und Kristallstruktur von [Ru3(CO)5(μ‐H)2(μ‐PCy2)(μ‐Ph2PCH2PPh2){μ‐η2‐PCy2C(S)}(μ3‐S)] und [Ru3(CO)5(CS)(μ‐H)(μ‐PtBu2)(μ‐PCy2)2(μ3‐S)]

Activation of Carbon Disulfide on Triruthenium Clusters: Synthesis and X‐Ray Crystal Structure Analysis of [Ru₃(CO)₅(μ‐H)₂(μ‐PCy₂)(μ‐Ph₂PCH₂PPh₂){μ‐η²‐PCy₂C(S)}(μ₃‐S)] and [Ru₃(CO)₅(CS)(μ‐H)(μ‐P^tBu₂)(μ‐PCy₂)₂(μ₃‐S)] [Ru₃(CO)₆(μ‐H)₂(μ‐PCy₂)₂(μ‐dppm)] ( 1 ) (dppm = Ph₂PCH₂PPh₂) reacts under mild conditions with CS₂ and yields by oxidative decarbonylation and insertion of CS into one phosphido bridge the opened 50 VE‐cluster [Ru₃(CO)₅(μ‐H)₂(μ‐PCy₂)(μ‐dppm){μ‐η²‐PCy₂C(S)}(μ₃‐S)] ( 2 ) with only two M–M bonds. The compound 2 crystallizes in the triclinic space group P 1 with a = 19.093(3), b = 12.2883(12), c = 20.098(3) Å; α = 84.65(3), β = 77.21(3), γ = 81.87(3)° and V = 2790.7(11) ų. The reaction of [Ru₃(CO)₇(μ‐H)(μ‐P^tBu₂)(μ‐PCy₂)₂] ( 3 ) with CS₂ in refluxing toluene affords the 50 VE‐cluster [Ru₃(CO)₅(CS)(μ‐H)(μ‐P^tBu₂)(μ‐PCy₂)₂(μ₃‐S)] ( 4 ). The compound cristallizes in the monoclinic space group P 2₁/a with a = 19.093(3), b = 12.2883(12), c = 20.098(3) Å; β = 104.223(16)° and V = 4570.9(10) ų. Although in the solid state structure one elongated Ru–Ru bond has been found the complex 4 can be considered by means of the ³¹P‐NMR data as an electron‐rich metal cluster.     

Low‐Spin Pseudotetrahedral Iron(I) Sites in Fe2(μ‐S) Complexes

Fe^I centers in iron–sulfide complexes have little precedent in synthetic chemistry despite a growing interest in the possible role of unusually low valent iron in metalloenzymes that feature iron–sulfur clusters. A series of three diiron [(L₃Fe)₂(μ‐S)] complexes that were isolated and characterized in the low‐valent oxidation states Fe^II? S? Fe^II, Fe^II? S? Fe^I, and Fe^I? S? Fe^I is described. This family of iron sulfides constitutes a unique redox series comprising three nearly isostructural but electronically distinct Fe₂(μ‐S) species. Combined structural, magnetic, and spectroscopic studies provided strong evidence that the pseudotetrahedral iron centers undergo a transition to low‐spin S=1/2 states upon reduction from Fe^II to Fe^I. The possibility of accessing low‐spin, pseudotetrahedral Fe^I sites compatible with S^2? as a ligand was previously unknown.     

Transition‐Metal‐Mediated Cleavage of a SiSi Double Bond

Reaction of carbene‐stabilized disilicon ( 1 ) with Fe(CO)₅ gives the 1:1 adduct L:Si?Si[Fe(CO)₄]:L (L:=C{N(2,6‐Prⁱ₂C₆H₃)CH}₂) ( 2 ) at room temperature. At raised temperature, however, 2 may react with another equivalent of Fe(CO)₅ to give L:Si[μ‐Fe₂(CO)₆](μ‐CO)Si:L ( 3 ) through insertion of both CO and Fe₂(CO)₆ into the Si₂ core, which represents the first experimental realization of transition metal‐carbonyl‐mediated cleavage of a Si?Si double bond. The structures and bonding of both 2 and 3 have been investigated by spectroscopic, crystallographic, and computational methods.     

Synthesis and structural characterization of a novel dimolybdenum(I) compound with mixed‐tribridging ligands: [Bu4N][Mo2(μ‐SPh)2(μ‐Cl(CO6]

A novel mixed‐tribridged dimolybdenum(I) compound [Bn₄N][Mo₂(μ‐SPh)₂(μ‐Cl)(CO)₆] (1) has been synthesized from the reaction of Mo₂(CO)₃(SPh)₂ with BU₄NCl. Compound 1 was characterized by IR, UV‐Vis and ¹H, ¹³C, ⁹⁵Mo NMR spectroscopic analyses. The electrochemical behavior was measured by cyclic voltammetry, indicating a quasi‐reversible two‐electron transfer in one step. The crystal structure determined by X‐ray crystallography shows that 1 contains a [Mo₂(μ‐S)₂(μ‐Cl)]^? core with a planar Mo₂S₂unit and a Cl bridge. The Mo? Mo distance is 0.28709(7) nm, and the Mo‐Cl‐Mo angle is 66.44(4)°. A newface‐sharing bioctahedral structure is discussed.     

Sulfido‐bridged rhenium–carbonyl complexes with planar and folded Re2S2 cores

The two sulfido‐bridged dirhenium complexes bis(μ‐4‐methoxy­phenyl­sulfido‐S)bis­(tetra­carbonyl­rhenium), [Re₂(C₇H₇­OS)₂­(CO)₈], and bis(μ‐naphthyl­sulfido‐S)bis[tricarbonyl(dicyclohexylphosphane)rhenium], [Re₂­(C₁₂­H₂₃P)₂(C₁₀H₇S)₂­(CO)₆], show different geometries of the common Re₂S₂ core. The 4‐methoxy­phenyl derivative has crystallographic symmetry and the naphthyl derivative has C² symmetry. This results from intramolecular repulsion due to different substitution patterns at the Re and S atoms.     

Ligand‐forced dimerization of copper(I)–olefin complexes bearing a 1,3,4‐thiadiazole core

As an important class of heterocyclic compounds, 1,3,4‐thiadiazoles have a broad range of potential applications in medicine, agriculture and materials chemistry, and were found to be excellent precursors for the crystal engineering of organometallic materials. The coordinating behaviour of allyl derivatives of 1,3,4‐thiadiazoles with respect to transition metal ions has been little studied. Five new crystalline copper(I) π‐complexes have been obtained by means of an alternating current electrochemical technique and have been characterized by single‐crystal X‐ray diffraction and IR spectroscopy. The compounds are bis[μ‐5‐methyl‐N‐(prop‐2‐en‐1‐yl)‐1,3,4‐thiadiazol‐2‐amine]bis[nitratocopper(I)], [Cu₂(NO₃)₂(C₆H₉N₃S)₂], (1), bis[μ‐5‐methyl‐N‐(prop‐2‐en‐1‐yl)‐1,3,4‐thiadiazol‐2‐amine]bis[(tetrafluoroborato)copper(I)], [Cu₂(BF₄)₂(C₆H₉N₃S)₂], (2), μ‐aqua‐bis{μ‐5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine}bis[nitratocopper(I)], [Cu₂(NO₃)₂(C₅H₇N₃S₂)₂(H₂O)], (3), μ‐aqua‐(hexafluorosilicato)bis{μ‐5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine}dicopper(I)–acetonitrile–water (2/1/4), [Cu₂(SiF₆)(C₅H₇N₃S₂)₂(H₂O)]·0.5CH₃CN·2H₂O, (4), and μ‐benzenesulfonato‐bis{μ‐5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine}dicopper(I) benzenesulfonate–methanol–water (1/1/1), [Cu₂(C₆H₅O₃S)(C₅H₇N₃S₂)₂](C₆H₅O₃S)·CH₃OH·H₂O, (5). The structure of the ligand 5‐methyl‐N‐(prop‐2‐en‐1‐yl)‐1,3,4‐thiadiazol‐2‐amine (Mepeta ), C₆H₉N₃S, was also structurally characterized. Both Mepeta and 5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine (Pesta ) (denoted L ) reveal a strong tendency to form dimeric {Cu₂L ₂}²⁺ fragments, being attached to the metal atom in a chelating–bridging mode via two thiadiazole N atoms and an allylic C=C bond. Flexibility of the {Cu₂(Pesta )₂}²⁺ unit allows the Cu^I atom site to be split into two positions with different metal‐coordination environments, thus enabling the competitive participation of different molecules in bonding to the metal centre. The Pesta ligand in (4) allows the Cu^I atom to vary between water O‐atom and hexafluorosilicate F‐atom coordination, resulting in the rare case of a direct Cu^I…FSiF₅²⁻ interaction. Extensive three‐dimensional hydrogen‐bonding patterns are formed in the reported crystal structures. Complex (5) should be considered as the first known example of a Cu^I(C₆H₅SO₃) coordination compound. To determine the hydrogen‐bond interactions in the structures of (1) and (2), a Hirshfeld surface analysis has been performed.     

Stereoselectivity in Diphos Addition to Molybdenum Complex with Pyridine‐2‐thionate (pyS) and η3‐Methallyl Coordinated Ligands

The conformational isomers endo‐ and exo‐[Mo{η³‐C₃H₄(CH₃)}(η²‐pyS)(CO)(η²‐diphos)] (diphos: dppm = {bis(diphenylphosphino)methane}, 2 ; dppe = {1,2‐bis(diphenylphosphino)ethane}, 3 ) are prepared by reacting the double‐bridged pyridine‐2‐thionate (pyS) complex [Mo{η³‐C₃H₄(CH₃)}(CO)₂]₂(η¹:η²:μ‐pyS)₂, 1 with diphos in refluxing acetonitrile. Stereoselectivity of the methallyl, C₃H₄(CH₃), ligand improves the formation of the exo‐conformation of 2 and 3 . Orientations and spectroscopy of these complexes are discussed.     

Using polyethyleneimine (PEI) as a scaffold to construct mimicking systems of [FeFe]‐hydrogenase: preparation,characterization of PEI‐based materials,and their catalysis on proton reduction

Ten branched polymeric materials (PEI‐P‐Fe₂s) derived from polyethyleneimine (PEI) functionalized with [Fe₂(CO)₅]‐units to mimic [FeFe]‐hydrogenase were prepared. Before the functionalization, PEI was first premodified using diphenylphosphinamine (NPPh₂) group. In the premodification, three approaches were employed: (i) using PEI with an average molecular weight of 1800 and 600, respectively; (ii) grafting NPPh₂ group by either direct reaction of chlorodiphenylphosphine with PEI or Br(CH₂)₁₁OPPh₂; and (iii) further premodification with BrCH₂COOH after immobilization of the NPPh₂ group. Reaction of the premodified PEI with diiron hexacarbonyl complexes, [Fe₂(μ‐S)₂(CO)₆] (1), or [Fe₂(μ‐S₂C₂H₄)(CO)₆] (3) produced 10 functionalized materials, PEI‐P‐Fe₂s. These materials were characterized using a variety of spectroscopic techniques, FTIR, NMR, TGA, and cyclic voltammetry. Spectral comparison with two control complexes, [Fe₂(μ‐S)₂(CO)₅PPh₃] (2) and [Fe₂(μ‐S₂C₂H₄)(CO)₅PPh₃] (4), suggested that the immobilized diiron units of PEI‐P‐Fe₂s were dominantly pentacarbonyl analogous to complexes 2 and 4, although tetracarbonyl units may also exist because the amine groups of PEI could also be involved in substituting CO, as was the NPPh₂ group. The catalysis of these materials on proton reduction was examined in 0.1 mol l^?1 [NBut₄]BF₄/DMF containing acetic acid by using cyclic voltammetry. Our results indicated that both the presence of carboxylic acid and dangling the diiron units at the end of a long aliphatic chain improved catalytic efficiency by one‐fold. The improvement was attributed to the increase in flexibility of the catalytic center and enhancement of proton transfer during the catalysis. Copyright © 2013 John Wiley & Sons, Ltd.