Iron pyrrole‐based PNP pincer ligand complexes as catalyst precursors

The structure of a pincer ligand consists of a backbone and two `arms' which typically contain a P or N atom. They are tridentate ligands that coordinate to a metal center in a meridional configuration. A series of three iron complexes containing the pyrrole‐based PNP pincer ligand 2,5‐bis[(diisopropylphosphanyl)methyl]pyrrolide (PN^pyrP) has been synthesized. These complexes are possible precursors to new iron catalysts. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}carbonylchlorido(trimethylphosphane‐κP )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₃H₉P)(CO)] or [Fe(PN^pyrP)Cl(PMe₃)(CO)], (I), has a slightly distorted octahedral geometry, with the Cl and CO ligands occupying the apical positions. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}chlorido(pyridine‐κN )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₅H₅N)] or [Fe(PN^pyrP)Cl(py)] (py is pyridine), (II), is a five‐coordinate square‐pyramidal complex, with the pyridine ligand in the apical position. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}dicarbonylchloridoiron(II), [Fe(C₁₈H₃₄NP₂)Cl(CO)₂] or [Fe(PN^pyrP)Cl(CO)₂], (III), is structurally similar to (I), but with the PMe₃ ligand replaced by a second carbonyl ligand from the reaction of (II) with CO. The two carbonyl ligands are in a cis configuration, and there is positional disorder of the chloride and trans carbonyl ligands.     

(Carbonyl)Iron‐Selenolates: New Synthetic Methods and Reactions with Electrophiles. Crystal Structures of [(CO)6Fe2(μ‐SeR)2]; R = Me3SiCH2 and p‐O2NC6H4CH2, {(CO)6Fe2[μ‐η2‐Se,Se′‐o‐(SeCH2C6H4CH2Se)]}, and [(CO)6Fe2(μ‐SeFe(CO)2cp)2]

The reactions of Fe(CO)₅ or Fe₃(CO)₁₂ with NaBEt₃H or KB[CH(CH₃)C₂H₅]₃H, respectively and treatment of the resulting carbonylates M₂Fe(CO)₄, M = Na, K with elemental selenium in appropriate ratios lead to the formation of M₂[Fe₂(CO)₆(μ‐Se)₂]. Subsequent reactions with organo halides or the complex fragment cpFe(CO)₂⁺, cp = η⁵‐C₅H₅ afforded the selenolato complexes [Fe₂(CO)₆(μ‐SeR)₂], R = CH₂SiMe₃ ( 1 ), CH₂Ph ( 2 ), p‐CH₂C₆H₄NO₂ ( 3 ), o‐CH₂C₆H₄CH₂ ( 4 ) and cpFe(CO)₂⁺ ( 5 ) in moderate to good yields. A similar reaction employing Ru₃(CO)₁₂, Se and p‐O₂NC₆H₄CH₂Br leads to the formation of the corresponding organic diselenide. The X‐ray structures of 1 , 3 , 4 and 5 were determined and revealed butterfly structures of the Fe₂Se₂ cores. The substituents in 1 , 3  and 5 adopt different conformations depending on their steric demand. In 4 , the conformation is fixed because of the chelate effect of the ligand. The Fe–Se bond lengths lie in the range 235 to 240 pm, with corresponding Fe–Fe bond lengths of 254 to 256 pm. The ⁷⁷Se NMR data of the new complexes are discussed and compared with the corresponding data of related complexes.     

Synthesis of a series of new ruthenium organometallic complexes derived from pyridine‐imine ligands and their catalytic activity in oxidation of secondary alcohols

Reactions of pyridine imines [C₅H₄N‐2‐C(H) = N‐C₆H₄‐R] [R = H (1), CH₃ (2), OMe (3), CF₃ (4), Cl (5), Br (6)] with Ru₃(CO)₁₂ in refluxing toluene gave the corresponding dinuclear ruthenium carbonyl complexes of the type {μ‐η²‐CH[(2‐C₅H₄N)(N‐C₆H₄‐R)]}₂Ru₂(CO)₄(μ‐CO) [R = H (7); CH₃ (8); OMe (9); CF₃ (10); Cl (11); Br (12)]. All six novel complexes were separated by chromatography, and fully characterized by elemental analysis, IR, NMR spectroscopy. Molecular structures of 7, 10, 11, and 12 were determined by X‐ray crystal diffraction. Further, the catalytic performance of these complexes was also tested. The combination of {μ‐η²‐CH[(2‐C₅H₄N)(N‐C₆H₄‐R)]}₂Ru₂(CO)₄(μ‐CO) and NMO afforded an efficient catalytic system for the oxidation of a variety secondary alcohols.     

Intramolecular CH Activation and Metallacycle Aromaticity in the Photochemistry of [FeFe]‐Hydrogenase Model Compounds in Low‐Temperature Frozen Matrices

The [FeFe]‐hydrogenase model complexes [(μ‐pdt){Fe(CO)₃}₂], [(μ‐edt){Fe(CO)₃}₂], and [(μ‐mdt){Fe(CO)₃}₂], where pdt=1,3‐propanedithiolate, edt=1,2‐ethanedithiolate, and mdt=methanedithiolate, undergo wavelength dependent photodecarbonylation in hydrocarbon matrices at 85 K resulting in multiple decarbonylation isomers. As previously reported in time‐resolved solution photolysis experiments, the major photoproduct is attributed to a basal carbonyl‐loss species. Apical carbonyl‐loss isomers are also generated and may undergo secondary photolysis, resulting in β‐hydride activation of the alkyldithiolate bridge, as well as formation of bridging carbonyl isomers. For [(μ‐bdt){Fe(CO)₃}₂], (bdt=1,2‐benzenedithiolate), apical photodecarbonylation results in generation of a 10 π‐electron aromatic FeS₂C₆H₄ metallacycle that coordinates the remaining iron through an η⁵ mode.     

单铁氢化酶五配位模型化合物的合成、表征及催化反应性

氢化酶仿生化学是当前有机金属化学领域研究的前沿课题,其主要内容为针对氢化酶的活性中心结构和功能进行化学模拟研究.自然界中已经发现的氢化酶有三种,其中[NiFe]氢化酶、[FeFe]氢化酶研究较多.单铁氢化酶发现于1990年,是产甲烷杆菌在厌氧和镍缺乏的条件下合成的.区别于其他两种氢化酶,其活性中心不含Fe-S簇,且仅含有一个Fe原子,并且仅能在底物存在的情况下,催化异裂氢分子并选择性还原特定底物,为产甲烷杆菌代谢提供能量.研究单铁氢化酶的结构和功能,模拟其活化氢、利用氢的过程,对于探索清洁能源的利用和开发新的非贵金属催化剂具有重要意义.本文以单铁氢化酶(Hmd)结构和功能模拟为导向,针对单铁氢化酶一级配位结构,设计合成了两个新模型化合物.通过IR, NMR, X射线单晶衍射等手段表征分析了模型化合物的性质并确认其结构.探索了其质子化反应特性、电催化还原质子制氢的特性.为了进一步模拟Hmd催化裂解氢气、完成氢转移的功能,以所合成模型物为催化剂实现了在常温常压下,以乙醇作为质子源的催化转移氢化过程.新单铁模型配合物Fe(CO)2PR3(NN)(R = Cy (3), Ph (4), NN,邻苯二胺二价阴离子配体)由NN二齿配体与前体化合物Fe(CO)3I2PR3进行配体取代反应合成.模型化合物活性中心为一个二价铁原子,拥有两个处于cis-位置的羰基配体,一个邻苯二胺双齿配体(两个氮原子进行配位)以及一个有机膦配体.通过红外光谱表征所合成的具有不饱和五配位结构化合物的光谱性质,可以得到配合物Fe(CO)2PCy3(NN)的羰基红外特征谱峰为1974,1919 cm–1,配合物Fe(CO)2PPh3(NN)的红外特征谱峰在1985和1929 cm–1处.通过单晶X射线衍射表征确认了两个化合物结构,并获取晶体学数据.经研究发现, Fe(CO)2PR3(NN)能够发生酸碱调控下可逆的质子化/脱质子化过程.基于红外光谱和密度泛函理论计算推断邻苯二胺阴离子配体可以作为内部碱基.在酸性条件下, Fe(CO)2PR3(NN)分子内部碱基氮原子通过质子化反应结合一个质子,生成Fe(CO)2PR3(NN)·H+.加入碱之后,重新生成起始化合物Fe(CO)2PR3(NN).表明N原子作为内部碱基,具有结合和转移质子的能力.该性质与Hmd中半胱氨酸硫配体具有一致性.通过循环伏安曲线研究了配合物Fe(CO)2PCy3(NN)和Fe(CO)2PPh3(NN)的电化学性质.其中配合物Fe(CO)2PCy3(NN)和Fe(CO)2PPh3(NN)均具有两个不可逆的还原峰和氧化峰.在电化学制氢研究中,配合物Fe(CO)2PPh3(NN)的还原峰电流随着乙酸的加入增幅较大,展现出较强的催化质子还原的性质.通过与其他单铁模型配合物对比,可以推断第一个还原峰归属为配合物由FeI转化为FeI,第二个可逆还原峰归属为配合物由FeI转化为Fe0.同时,配合物Fe(CO)2PPh3(NN)第一个还原峰向高电位移动,该现象与双铁模型化合物的电化学性质较为一致.进一步研究发现,模型化合物具有催化转移氢化的活性.在常温下,乙醇溶剂中, Fe(CO)2PCy3(NN)能够催化对苯醌还原转化为对苯二酚,其中对苯醌的转化率达到89%,对苯二酚的产率达到40%.结合实验数据以及文献资料分析,认为乙醇在催化氢化中可以作为质子源,并且提出了催化转移氢化反应过程的机理.认为催化氢化过程中形成了-Fe-H-C-O-H-N-六元环,通过分子间相互作用完成了氢原子转移过程.该研究结论对单铁氢化酶活性中心模型化合物在催化氢化反应中的应用具有一定的参考价值.     

Alkynethiolate ligands in the syntheses of iron carbonyl derivatives. Crystal structure of [(η-C5H5)Fe(CO)2(SCCSiMe3)]

The complexes [(η⁵-C₅H₅)Fe(CO)₂(SCCR)] (R=^tBu, SiMe₃) have been obtained by reaction of [(η⁵-C₅H₅)Fe(CO)₂I] and the corresponding LiSCCR. These are the first examples of mononuclear iron compounds containing alkynethiolate ligands. The crystal structure of [(η⁵-C₅H₅)Fe(CO)₂(SCCSiMe₃)] has been determined by X-ray diffraction. The role of [(η⁵-C₅H₅)Fe(CO)₂(SCCSiMe₃)] as a metalloligand in its reactions with metal carbonyls has been explored.     

Zur koordination mehrfunktioneller thioether in cyclopentadienyleisen-komplexen

[C₅H₅Fe(CO)₂thf]⁺ reacts with the ligands LL and LLL to give the cations [C₅H₅Fe(CO)₂LL]⁺ (LL = RS(CH₂)_nSR, 1,4-dithiane) and [C₅H₅Fe(CO)₂LLL]⁺ (LLL = 1,3,5-trithiane, tris(methylmercapto)methane) containing monodentate coordinated sulfur ligands. In a similar way, sulfur ligand bridged dinuclear dications [(C₅H₅Fe(CO)₂)₂(μ-LL)]²⁺ and [(C₅H₅Fe(CO)₂(μ-LLL)]²⁺ and tri-nuclear trications [(C₅H₅Fe(CO)₂)₃(μ-LLL)]³⁺ are formed. Irradiation of the mononuclear cations gives the chelate complexes [C₅H₅Fe(CO)(η²-LL)]⁺.     

Hydrophilic Quaternary Ammonium‐Group‐Containing [FeFe]‐Hydrogenase Models: Synthesis,Structures, and Electrocatalytic Hydrogen Production

The first quaternary ammonium‐group‐containing [FeFe]‐hydrogenase models [(μ‐PDT)Fe₂(CO)₄{κ²‐(Ph₂P)₂N(CH₂)₂NMe₂BzBr}] ( 2 ; PDT=propanedithiolate) and [(μ‐PDT)Fe₂(CO)₄{μ‐(Ph₂P)₂N(CH₂)₂NMe₂BzBr}] ( 4 ) have been prepared by the quaternization of their precursors [(μ‐PDT)Fe₂(CO)₄{κ²‐(Ph₂P)₂N(CH₂)₂NMe₂}] ( 1 ) and [(μ‐PDT)Fe₂(CO)₄{μ‐(Ph₂P)₂N(CH₂)₂NMe₂}] ( 3 ) with benzyl bromide in high yields. Although new complexes 1 – 4 have been fully characterized by spectroscopic and X‐ray crystallographic studies, the chelated complexes 1 and 2 converted into their bridged isomers 3 and 4 at higher temperatures, thus demonstrating that these bridged isomers are thermodynamically favorable. An electrochemical study on hydrophilic models 2 and 4 in MeCN and MeCN/H₂O as solvents indicates that the reduction potentials are shifted to less‐negative potentials as the water content increases. This outcome implies that both 2 and 4 are more easily reduced in the mixed MeCN/H₂O solvent than in MeCN. In addition, hydrophilic models 2 and 4 act as electrocatalysts and achieve higher i_cat/i_p values and turnover numbers (TONs) in MeCN/H₂O as a solvent than in MeCN for the production of hydrogen from the weak acid HOAc.     

Synthesis and Spectra of Cationic Bis(tertiary phosphine) derivatives of cycloheptatrienyliummolybdenum and cyclopentadienyliron complexes

Reaction of [(η-C₇H₇)Mo(CO)₃][PF₆] and [(η-C₅H₅)Fe(CO)₂CH₃CN][PF₆] with ditertiary phosphine ligands afforded products of three types; the monosubstituted complexes [(Ring)M(CO)₂Ph₂P(CH₂)_nPPh₂][PF₆] (Ring = η-C₇H₇, M = Mo, N = 1; Ring = η-C₅H₅, M = Fe, N = 1 and 2), the chelated complexes [(Ring)M(CO)Ph₂P(CH₂)_nPPh₂][PF₆] (Ring = η-C₇H₇, M = Mo, N = 1 and 2; Ring = η-C₅H₅, M = Fe, N = 1 and 2), and the dinuclear complex [{(η-C₇H₇)Mo(CO)₂}₂ -μ- Ph₂PCH₂CH₂PPh₂][(PF₆)₂]. Spectroscopic properties, including ³¹P NMR, are reported.     

From Metallaborane to Borylene Complexes: Syntheses and Structures of Triply Bridged Ruthenium and Tantalum Borylene Complexes

Reaction of [1,2‐(Cp*RuH)₂B₃H₇] ( 1 ; Cp*=η⁵‐C₅Me₅) with [Mo(CO)₃(CH₃CN)₃] yielded arachno‐[(Cp*RuCO)₂B₂H₆] ( 2 ), which exhibits a butterfly structure, reminiscent of 7 sep B₄H₁₀. Compound 2 was found to be a very good precursor for the generation of bridged borylene species. Mild pyrolysis of 2 with [Fe₂(CO)₉] yielded a triply bridged heterotrinuclear borylene complex [(μ₃‐BH)(Cp*RuCO)₂(μ‐CO){Fe(CO)₃}] ( 3 ) and bis‐borylene complexes [{(μ₃‐BH)(Cp*Ru)(μ‐CO)}₂Fe₂(CO)₅] ( 4 ) and [{(μ₃‐BH)(Cp*Ru)Fe(CO)₃}₂(μ‐CO)] ( 5 ). In a similar fashion, pyrolysis of 2 with [Mn₂(CO)₁₀] permits the isolation of μ₃‐borylene complex [(μ₃‐BH)(Cp*RuCO)₂(μ‐H)(μ‐CO){Mn(CO)₃}] ( 6 ). Both compounds 3 and 6 have a trigonal‐pyramidal geometry with the μ₃‐BH ligand occupying the apical vertex, whereas 4 and 5 can be viewed as bicapped tetrahedra, with two μ₃‐borylene ligands occupying the capping position. The synthesis of tantalum borylene complex [(μ₃‐BH)(Cp*TaCO)₂(μ‐CO){Fe(CO)₃}] ( 7 ) was achieved by the reaction of [(Cp*Ta)₂B₄H₈(μ‐BH₄)] at ambient temperature with [Fe₂(CO)₉]. Compounds 2 – 7 have been isolated in modest yield as yellow to red crystalline solids. All the new compounds have been characterized in solution by mass spectrometry; IR spectroscopy; and ¹H, ¹¹B, and ¹³C NMR spectroscopy and the structural types were unequivocally established by crystallographic analysis of 2 – 6 .     

Synthesis,Characterization, and Crystal Structures of Diruthenium Complexes Containing Bridging Salicylato Ligands

The thermal reaction of Ru₃(CO)₁₂ ( 1 ) with salicylic acid, in the presence of triphenylphosphine, pyridine, or dimethylsulfoxide, afforded the dinuclear complexes Ru₂(CO)₄(μ‐O₂CC₆H₄OH)₂L₂ ( 2 ) [L = PPh₃ ( 2a ). C₅H₅N ( 2b ); (CH₃)₂SO ( 2c )]. Complex 2b was further reacted with the aromatic dimmines 2,2′‐dipyridine or 1,10‐phenanthroline to give the cationic diruthenium complexes [Ru₂(CO)₂(μ‐CO)₂(μ‐O₂CC₆H₄OH)(N∩N)₂]⁺ ( 3 ) [(N∩N) = 2,2′‐dipyridine ( 3a ); 1,10‐phenanthroline ( 3b )], which were isolated as their tetraphenylborate salts. All five novel complexes were characterized spectroscopically and analytically. For 2a – 2b and 3a – 3b , single‐crystal X‐ray diffraction studies were also carried out.     

Competitive reactions of coordinated carbon monoxide and methyl isocyanide with amines

The relative reactivities of CO and CNR ligands with CH₃NH₂ were investigated in complexes which contained both ligands. Like (C₅H₅Fe(CO)₃⁺; the (C₅H₅)Fe(CO)₂(CNCH₃)⁺ complex reacts with CH₃NH₂ to give the carbamoyl complex (C₅)Fe(CO)(CNCH₃)(CONHCH₃); this is a readily reversible reaction. In contrast, (C₅H₅)Fe(CO)(CNCH₃)₂⁺ reacts with CH₃NH₂ to give the amidinium or carbene complex, (C₅H₅)Fe(CO)(CNCH₃)[C(NHCH₃)₂]⁺]. In a slow reaction, (C₅H₅)Fe(PPh₃)(CO)(CNCH₃)⁺ forms the amidinium complex, (C₅H₅)Fe(PPh₃)(CO)[C(NHCH₃)₂]⁺. Factors that affect the site of CH₃NH₂ reaction are discussed. The complexes have been characterized by IR and NMR spectroscopy; a variable temperature NMR study of (C₅H₅)Fe(CO)(CNCH₃)[C(NHCH₃)₂]⁺ indicates restricted rotation around the CN bonds of the amidinium ligand.     

Investigations on the Synthesis,Structural Characterization,and Crystal Structures of Three Diiron and Tetrairon Azadithiolate Complexes

Three diiron and tetrairon azadithiolate complexes as models for the active site of [FeFe] hydrogenase were prepared. Reaction of complex Fe₂(SCH₂OH)₂(CO)₆ and NH₂CH₂CH₂CH₂OCH₃ resulted in the diiron azadithiolate hexcarbonyl complex Fe₂[(SCH₂)₂NCH₂CH₂CH₂OCH₃](CO)₆ ( 1 ) in moderate yield. Furthermore, treatment of complex 1 with mono phosphine ligand PPh₃ and diphosphine ligand Ph₂PCH₂CH₂PPh₂ in the presence of decarbonylation reagent Me₃NO · 2H₂O yielded the phosphine‐substituted azadithiolate complexes Fe₂[(SCH₂)₂NCH₂CH₂CH₂OCH₃]CO)₅(PPh₃) ( 2 ) and {Fe₂[(SCH₂)₂NCH₂CH₂CH₂OCH₃](CO)₅}₂(Ph₂PCH₂CH₂PPh₂) ( 3 ) respectively. The new complexes 1 – 3 were fully characterized by elemental analysis, IR, ¹H, ¹³C, ³¹P NMR spectroscopy and X‐ray crystallography. It is worthy to note that the crystallographic studies show the unusual difference of the methoxypropanyl substituent on the N atom of complexes 1 and 2 , largely because of the affection of phosphine ligand PPh₃. In addition, complex 1 was found to be a catalyst for H₂ production under electrochemical condition.     

Synthesis,structure and cytotoxic activity of binuclear phenyltin(IV) complexes with N,N′‐bis(2‐hydroxybenzyl)‐1,2‐ethanebis(dithiocarbamate) ligand

Two new dinuclear phenyltin(IV) complexes derived from N,N′‐bis(2‐hydroxybenzyl)‐1,2‐ethanebis(dithiocarbamate) ligand, [2‐HOC₆H₄CH₂N(CS₂SnPh₃)CH₂]₂ ( 1 ) and [2‐HOC₆H₄CH₂N(CS₂SnClPh₂)CH₂]₂ ( 2 ) have been synthesized and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ¹¹⁹Sn) spectra. The crystal structures of complexes 1 and 2 were determined by X‐ray single crystal diffraction and show that the dithiocarbamate ligand is coordinated to the tin atom in the anisobidentate manner and the tin atom is five‐coordinated. The coordination geometry of tin atom is best described as an intermediate between trigonal bipyramidal and square pyramidal with τ‐values of 0.63 and 0.53, respectively. Intermolecular hydrogen bonds (O H···S and O H···Cl) in 1 and 2 connect neighboring molecules into a one‐dimensional supramolecular chain with the centrosymmetric cyclic motifs. Complex 1 has potent in vitro cytotoxic activity against two human tumor cell lines, CoLo205 and Bcap37, while complex 2 displays weak cytotoxic activity. Copyright © 2011 John Wiley & Sons, Ltd.     

A Novel Pentadentate Redox‐Active Ligand and Its Iron(III) Complexes: Electronic Structures and O2 Reactivity

A novel redox‐active ligand, H₄^Ph2SL^AP ( 1 ) which was designed to be potentially pentadentate with an O,N,S,N,O donor set is described. Treatment of 1 with two equivalents of potassium hydride gave access to octametallic precursor complex [H₂^Ph2SL^APK₂(thf)]₄ ( 2 ), which reacted with FeCl₃ to yield iron(III) complex [H₂^Ph2SL^APFeCl] ( 3 ). Employing Fe[N(SiMe₃)₂]₃ for a direct reaction with 1 led to ligand rearrangement through C?S bond cleavage and thiolate formation, finally yielding [HL^APFe] ( 5 ). Upon exposure to O₂, 3 and 5 are oxidized through formal hydrogen‐atom abstraction from the ligand NH units to form [^Ph2SL^SQFeCl] ( 4 ) and [L^SQFe] ( 6 ) featuring two or one coordinated iminosemiquinone moieties, respectively. Mössbauer measurements demonstrated that the iron centers remain in their +III oxidation states. Compounds 3 and 5 were tested with respect to their potential as models for the catechol dioxygenase. Thus, they were treated with 3,5‐di‐tert‐butyl‐catechol, triethylamine and O₂. It turned out that the iron–catecholate complexes react with O₂ in dichloromethane at ambient conditions through C?C bond cleavage mainly forming extradiol cleavage products. Intradiol products are only side products and quinone formation becomes negligible. This observation has been rationalized by a dissociation of two donor functions upon coordination of the catecholate.     

Synthesis of a vinylcarbynetetrairon complex. Crystal and molecular structure of [(C5H5)2(CO)2Fe2(μ-CO)]2- (μ-C5H3)+BF4−

The diiron vinyl ether carbyne complex [(C₅H₅)(CO)Fe]₂(μ-CO)- (μ-CCHCHOCH₂CH₃)⁺ BF₄⁻ (1) reacted with the diiron ethenylidene complex [(C₅H₅)(CO)Fe]₂(μ-CO)(μ-CCH₂) (2) to yield the tetrairon complex [(C₅H₅)₂(CO)₂Fe₂(μ-CO)]₂(μ-C₅H₃⁺BF₄⁻ (3) which was characterized by spectroscopy and by single crystal X-ray diffraction.     

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.     

Chelating and Tellurolate Ligand‐Transfer Studies of the Complex fac‐[Fe(CO)3(TePh)3]−: Crystal Structures of Heterodinuclear (CO)3Mn(μ‐TePh)3Fe(CO)3 and CpNi(TePh)(PPh3)

Complex fac‐[Fe(CO)₃(TePh)₃]^? was employed as a “metallo chelating” ligand to synthesize the neutral (CO)₃Mn(μ‐TePh)₃Fe(CO)₃ obtained in a one‐step synthesis by treating fac‐[Fe(CO)₃(TePh)₃]^? with fac‐[Mn‐(CO)₃(CH₃CN)₃]⁺. It seems reasonable to conclude that the d⁶ Fe(II) [(CO)₃Fe(TePh)₃]^? fragment is isolobal with the d⁶ Mn(I) [(CO)₃Mn(TePh)₃]^2? fragment in complex (CO)₃Mn(μ‐TePh)₃Fe(CO)₃. Addition of fac‐[Fe(CO)₃(TePh)₃]^? to the CpNi(I)(PPh₃) in THF resulted in formation of the neutral CpNi(TePh)(PPh₃) also obtained from reaction of CpNi(I)(PPh₃) and [Na][TePh] in MeOH. This investigation shows that fac‐[Fe(CO)₃(TePh)₃]^? serves as a tridentate metallo ligand and tellurolate ligand‐transfer reagent. The study also indicated that the fac‐[Fe(CO)₃(SePh)₃]^? may serve as a better tridentate metallo ligand and chalcogenolate ligand‐transfer reagent than fac‐[Fe(CO)₃(TePh)₃]^? in the syntheses of heterometallic chalcogenolate complexes.     

Structure and Magnetization Dynamics of Dy−Fe and Dy−Ru Bonded Complexes

We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy³⁺) and either a first‐row (Fe) or a second‐row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp₂^2? (PyCp₂^2?=[2,6‐(CH₂C₅H₃)₂C₅H₃N]^2?) facilitates the isolation and characterization of PyCp₂Dy?FeCp(CO)₂ ( 1 ; d(Dy–Fe)=2.884(2) Å) and PyCp₂Dy?RuCp(CO)₂ ( 2 ; d(Dy–Ru)=2.9508(5) Å). Computational and spectroscopic studies suggest strong TM→Dy bonding interactions. Both complexes exhibit field‐induced slow magnetic relaxation with effectively identical energy barriers to magnetization reversal. However, in going from Dy?Fe to Dy?Ru bonding, we observed faster magnetic relaxation at a given temperature and larger direct and Raman coefficients, which could be due to differences in the bonding and/or spin–phonon coupling contributions to magnetic relaxation.     

New Heteronuclear Bridged Borylene Complexes That Were Derived from [{Cp*CoCl}2] and Mono‐Metal?Carbonyl Fragments

The synthesis, structural characterization, and reactivity of new bridged borylene complexes are reported. The reaction of [{Cp*CoCl}₂] with LiBH₄ ? THF at ?70 °C, followed by treatment with [M(CO)₃(MeCN)₃] (M=W, Mo, and Cr) under mild conditions, yielded heteronuclear triply bridged borylene complexes, [(μ₃‐BH)(Cp*Co)₂(μ‐CO)M(CO)₅] ( 1 – 3 ; 1 : M=W, 2 : M=Mo, 3 : M=Cr). During the syntheses of complexes 1 – 3 , capped‐octahedral cluster [(Cp*Co)₂(μ‐H)(BH)₄{Co(CO)₂}] ( 4 ) was also isolated in good yield. Complexes 1 – 3 are isoelectronic and isostructural to [(μ₃‐BH)(Cp*RuCO)₂(μ‐CO){Fe(CO)₃}] ( 5 ) and [(μ₃‐BH)(Cp*RuCO)₂(μ‐H)(μ‐CO){Mn(CO)₃}] ( 6 ), with a trigonal‐pyramidal geometry in which the μ₃‐BH ligand occupies the apical vertex. To test the reactivity of these borylene complexes towards bis‐phosphine ligands, the room‐temperature photolysis of complexes 1 – 3 , 5 , 6 , and [{(μ₃‐BH)(Cp*Ru)Fe(CO)₃}₂(μ‐CO)] ( 7 ) was carried out. Most of these complexes led to decomposition, although photolysis of complex 7 with [Ph₂P(CH₂)_nPPh₂] (n=1–3) yielded complexes 9 – 11 , [3,4‐(Ph₂P(CH₂)_nPPh₂)‐closo‐1,2,3,4‐Ru₂Fe₂(BH)₂] ( 9 : n=1, 10 : n=2, 11 : n=3). Quantum‐chemical calculations by using DFT methods were carried out on compounds 1 – 3 and 9 – 11 and showed reasonable agreement with the experimentally obtained structural parameters, that is, large HOMO–LUMO gaps, in accordance with the high stabilities of these complexes, and NMR chemical shifts that accurately reflected the experimentally observed resonances. All of the new compounds were characterized in solution by using mass spectrometry, IR spectroscopy, and ¹H, ¹³C, and ¹¹B NMR spectroscopy and their structural types were unequivocally established by crystallographic analysis of complexes 1 , 2 , 4 , 9 , and 10 .