Monophosphine‐substituted diiron azadithiolate complexes: New syntheses,characterization and electrochemical properties

Investigating the synthesis and properties of diiron azadithiolate complexes is one of the key topics for mimicking the active site of [FeFe]‐hydrogenases, which might be very useful for the design of new efficient catalysts for hydrogen production and the development of a future hydrogen economy. A series of new phosphine‐substituted diiron azadithiolate complexes as models for the active site of [FeFe]‐hydrogenases are described. A novel and efficient way was firstly established for the preparation of phosphine‐substituted diiron azadithiolate complexes. The reaction of Fe₂(μ‐SH)₂(CO)₆ and phosphine ligands L affords the intermediate Fe₂(μ‐SH)₂(CO)₅L ( A ). The intermediate reacts in situ with a premixed solution of paraformaldehyde and ammonium carbonate to produce the target phosphine‐substituted diiron azadithiolate complexes Fe₂[(μ‐SCH₂)₂NH](CO)₅L ( 1a – 1f ) (L = P(C₆H₄–4‐CH₃)₃, P(C₆H₄–3‐CH₃)₃, P(C₆H₄–4‐F)₃, P(C₆H₄–3‐F)₃, P(2‐C₄H₃O)₃, PPh₂(OCH₂CH₃)). Furthermore, reactions of the intermediate A with I‐4‐C₆H₄N(CH₂Cl)₂ in the presence of Et₃N give the phosphine‐substituted diiron azadithiolate complexes Fe₂[(μ‐SCH₂)₂NC₆H₄–4‐I](CO)₅L ( 2a – 2e ) (L = P(C₆H₄–4‐CH₃)₃, P(C₆H₄–3‐CH₃)₃, P(C₆H₄–4‐F)₃, P(C₆H₄–3‐F)₃, P(2‐C₄H₃O)₃). All the complexes were fully characterized using elemental analysis, IR and NMR spectroscopies and, particularly for 1a , 1c – 1e , 2a and 2c , single‐crystal X‐ray diffraction analysis. In addition, complexes 1a – 1f and 2a – 2e were found to be catalysts for H₂ production under electrochemical conditions. Density functional theory calculations were performed for the reactions of Fe₂(μ‐SH)₂(CO)₆ + P(C₆H₄–4‐CH₃)₃.     

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.     

两种新型μ－氧桥联－双铁(III)席夫碱配合物：X-衍射分析，IR, UV-Vis, CD光谱，磁性质和电化学性质

热力学稳定的带有大环配体的μ－氧桥联－双铁配合物，由于其两个铁中心之间的有趣的电子结构和磁相互作用而受到广泛关注。μ－氧桥联－双铁席夫碱配合物，[{Fe(tbusalphn)}₂(μ-o)] (1)和[{Fe(R,R-salchxn)}₂(μ-o)] (2), 通过用咪唑或N－甲基咪唑的水溶液处理相应的单核铁氯化物，Fe(L)Cl，而获得。1和2的晶体结构通过x-射线结构分析而被确定。1属于三斜晶系，P－1空间群。2属于单斜晶系，P2₁/c空间群。由于1的配体带有庞大的叔丁基取代基，导致形成μ－氧桥联－双铁配合物时的空间拥挤，因此，其Fe-O-Fe夹角为176.5 ^o，几乎成平角。而2则由于配体上没有庞大的取代基，其Fe-O-Fe夹角为149.6^o，明显小于1的Fe-O-Fe夹角。 本文还对两种μ－氧桥联－双铁席夫碱配合物及相应的单核铁氯化物的红外光谱、紫外－可见吸收光谱及圆二色光谱性质进行了研究。与相应的单体铁配合物相比较，生成μ－氧桥联－双铁席夫碱配合物后，出现一新的红外吸收带，归属于ν_Fe-O-Fe振动。有趣的是，其数值与Fe-O-Fe夹角大小相对应。1和2除具有明显不同的Fe-O-Fe夹角外，它们的圆二色光谱却是相似的。 对1和2的磁性质研究表明，在这类化合物中两个铁(III)离子之间存在着强烈的分子内抗铁磁性偶合作用。另外，本文还采用循环伏安法对1和2的电化学性质进行了研究。     

Synthesis,characterization and electrochemistry of diiron 1,2-dithiolate complexes with a trans-cinnamate ester

Three diiron 1,2-dithiolate complexes with a trans-cinnamate ester have been characterized. Esterification of [Fe₂(CO)₆{μ-SCH₂CH(CH₂OH)S}] (1) with trans-cinnamic acid in the presence of N,N′-dicyclohexylcarbodiimide and 4-dimethylaminopyridine afforded [Fe₂(CO)₆[μ-SCH₂CH(CH₂O₂CCH?=?CHPh)S}] (2) in 94% yield. Carbonyl substitution of 2 with a monophosphine ligand tris(4-fluorophenyl)phosphine or tris(2-methoxyphenyl)phosphine in the presence of Me₃NO·2H₂O resulted in formation of the corresponding monophosphine-substituted complexes [Fe₂(CO)₅ {P(C₆H₄F-4)₃}{µ-SCH₂CH(CH₂O₂CCH?=?CHPh)S}] (3) and [Fe₂(CO)₅{P (C₆H₄OCH₃-2)₃}{µ-SCH₂CH(CH₂O₂CCH?=?CHPh)S}] (4) in 79% and 84% yields, respectively. Complexes 2-4 were structurally characterized by elemental analysis, spectroscopy and X-ray crystallography. Moreover, electrochemical properties of 2-4 were investigated.     

Tandem β‐Boration/Arylation of α,β‐Unsaturated Carbonyl Compounds by Using a Single Palladium Complex To Catalyse Both Steps

Diphenyl(3‐methyl‐2‐indolyl)phosphine (C₉H₈NPPh₂, 1 ) gives stable dimeric palladium(II) complexes that contain the phosphine in P,N‐bridging coordination mode. On treating 1 with [Pd(O₂CCH₃)₂], the new complexes [Pd(μ‐C₉H₇NPPh₂)(NCCH₃)]₂ ( 2 ) or [Pd(μ‐C₉H₇NPPh₂)(μ‐O₂CCH₃)]₂ ( 3 ) were isolated, depending on the solvent used, acetonitrile or toluene, respectively. Further reaction of 3 with the ammonium salt of 1 led to the substitution of one carboxylate ligand to afford [Pd(μ‐C₉H₇NPPh₂)₃(μ‐O₂CCH₃)] ( 4 ), in which the bimetallic unit is bonded by three C₉H₇NPPh₂^? moieties and one carboxylate group. Using this methodology, [Pd₂(μ‐C₆H₄PPh₂)₂(μ‐C₉H₇NPPh₂)(μ‐O₂CCX₃)] (X=H ( 7 ); X=F ( 8 )) were synthesised from the ortho‐metalated compounds [Pd(C₆H₄PPh₂)(μ‐O₂CCX₃)]₂ (X=H ( 5 ); X=F ( 6 )). Complexes 3 , 4 , 7 , and 8 have been found to be active in the catalytic β‐boration of α,β‐unsaturated esters and ketones under mild reaction conditions. Hindrance of the carbonyl moiety has an influence on the reaction rate, but quantitative conversion was achieved in many cases. More remarkably, when aryl bromides were added to the reaction media, complex 7 induced a highly successful consecutive β‐boration/cross‐coupling reaction with dimethyl acrylamide as the substrate (99 % conversion, 89 % isolated yield).     

Pressure‐Assisted Hetero‐ and Homodialkylation of Sulfide in [Pt2(μ‐S)2(dppp)2]: One‐Pot Conversion of {Pt2(μ‐S)2} into {Pt2(SR)2} and {Pt2(SR)(SR′)}

Heterodialkylation of [Pt₂(μ‐S)₂(dppp)₂] (dppp=Ph₂P(CH₂)₃PPh₂) was achieved under high pressure (10 kbar). This enabled the synthesis of rare diplatinum complexes with structurally diverse thiolate bridges, such as [Pt₂(μ‐SC₅H₁₀CO₂CH₂CH₃)(μ‐SC₃H₇)‐(dppp)₂](PF₆)₂, which was crystallographically identified. Complete homodialkylation was also achieved under similar conditions (6 kbar at room temperature), thus permitting the isolation of [Pt₂(μ‐SC₂H₄CO₂CH₂CH₃)₂(dppp)₂]‐(PF₆)₂. The isolation of these complexes extends the applications of high‐pressure chemistry to thiolato homo‐ and heterobridged complexes that are otherwise not accessible.     

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.     

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.     

Synthesis,Characterization, and X‐ray Crystal Structure of Macrocyclic Nickel/Iron/Sulfur Cluster Complexes

A series of macrocyclic Ni/Fe/S cluster complexes were synthesized and structurally characterized. The macrocyclic type of (diphosphine)Ni‐bridged double butterfly Fe/S complexes [μ‐SCH₂CH₂OCH₂CH₂S‐μ][(μ‐S=CS)Fe₂(CO)₆]₂‐[Ni(diphosphine)] ( 1 – 3 ; diphosphine = dppe, dppv, dppb) were prepared by treatment of the dianion [{μ‐SCH₂CH₂OCH₂CH₂S‐μ}{(μ‐CO)Fe₂(CO)₆}₂]^2–, generated in situ from Fe₃(CO)₁₂, Et₃N, and HSCH₂CH₂OCH₂CH₂SH with excess CS₂ followed by treatment of the resulting dianion [{μ‐SCH₂CH₂OCH₂CH₂S‐μ}{(μ‐SC=S)Fe₂(CO)₆}₂]^2– with (diphosphine)NiCl₂. The three complexes 1 – 3 were characterized by elemental analysis and IR, ¹H NMR, and ³¹P NMR spectroscopy. In addition, the molecular structures of 2 and 3 were established by X‐ray crystallography.     

Synthesis,characterization, and electrochemistry of phosphine-substituted diiron butane-1,2-dithiolate complexes

Abstract

The reactions of the starting complex, [Fe₂(CO)₆{μ-SCH₂CH (CH₂CH₃)S}] (1), with the phosphine ligands tris(4-methylphenyl)phosphine, diphenyl-2-pyridylphosphine, tris(4-fluorophenyl)phosphine, 2-(diphenylphosphino)benzaldehyde, or benzyldiphenylphosphine in the presence of the decarbonylating agent Me₃NO·2H₂O yielded the corresponding phosphine-substituted diiron butane-1,2-dithiolate complexes [Fe₂(CO)₅(L){μ-SCH₂CH(CH₂CH₃)S}] (L?=?P(4-C₆H₄CH₃)₃, 2; Ph₂P(2-C₅H₄N), 3; P(4-C₆H₄F)₃, 4; Ph₂P(2-C₆H₄CHO), 5; Ph₂PCH₂Ph, 6) in 75%–87% yields. The complexes have been characterized by elemental analysis, IR, ¹H, and ³¹P{¹H} NMR spectroscopy, as well as by single-crystal X-ray diffraction analysis. Moreover, the electrochemistry of 2–4 was studied by cyclic voltammetry, suggesting that they can catalyze the reduction of protons to H₂ in the presence of HOAc.     

Synthetic and structural studies of the diiron toluenedithiolate carbonyl complexes with monophosphine ligands

Four diiron toluenedithiolate complexes 2–5 with monophosphine ligands are reported. Treatment of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₆ (1) with tris(3-chlorophenyl)phosphine, tris(4-chlorophenyl)phosphine, tris(4-methylphenyl)phosphine or 2-(diphenylphosphino)benzaldehyde, and Me₃NO?2H₂O in MeCN resulted in the formation of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(3-C₆H₄Cl)₃] (2), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄Cl)₃] (3), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄CH₃)₃] (4), and [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[Ph₂P(2-C₆H₄CHO)] (5) in 64–82% yields. Complexes 2–5 have been characterized by elemental analysis, IR, ¹H NMR, ³¹P{¹H} NMR, ¹³C{¹H} NMR and further confirmed by single crystal X-ray diffraction analysis. The molecular structures show that 2–5 contain a butterfly diiron toluenedithiolate cluster coordinated by five terminal carbonyls and an apical monophosphine.     

Dimeric copper(II) 3,3‐dimethyl­butyrate adducts with ethanol, 2‐methylpyridine, 3‐methylpyridine, 4‐methylpyridine and 3,3‐dimethylbutyric acid

In the crystals of the five title compounds, tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(ethanol‐O)dicopper(II)–ethanol (1/2), [Cu₂(C₆H₁₁O₂)₄(C₂H₆O)₂]·2C₂H₆O, (I), tetrakis(μ‐3,3‐dimethylbutyrato‐O:O′)bis(2‐methylpyridine‐N)di­copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (II), tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(3‐methylpyridine‐N)di‐copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (III), tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(4‐methylpyridine‐N)di‐copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (IV), and tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(3,3‐dimethylbutyric acid‐O)dicopper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₁₂O₂)₂], (V), the di­nuclear Cu^II complexes all have centrosymmetric cage structures and (IV) has two independent molecules. The Cu?Cu separations are: (I) 2.602 (3) Å, (II) 2.666 (3) Å, (III) 2.640 (2) Å, (IV) 2.638 (4) Å and (V) 2.599 (1) Å.     

η4‐HBCC‐σ,π‐Borataallyl Complexes of Ruthenium Comprising an Agostic Interaction

Thermolysis of [Cp*Ru(PPh₂(CH₂)PPh₂)BH₂(L₂)] 1 (Cp*=η⁵‐C₅Me₅; L=C₇H₄NS₂), with terminal alkynes led to the formation of η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)B{R‐C=CH₂}(L)₂] ( 2 a – c ) and η²‐vinylborane complexes [Cp*Ru(R‐C=CH₂)BH(L)₂] ( 3 a – c ) ( 2 a , 3 a : R=Ph; 2 b , 3 b : R=COOCH₃; 2 c , 3 c : R=p‐CH₃‐C₆H₄; L=C₇H₄NS₂) through hydroboration reaction. Ruthenium and the HBCC unit of the vinylborane moiety in 2 a – c are linked by a unique η⁴‐interaction. Conversions of 1 into 3 a – c proceed through the formation of intermediates 2 a – c . Furthermore, in an attempt to expand the library of these novel complexes, chemistry of σ‐borane complex [Cp*RuCO(μ‐H)BH₂L] 4 (L=C₇H₄NS₂) was investigated with both internal and terminal alkynes. Interestingly, under photolytic conditions, 4 reacts with methyl propiolate to generate the η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)BH{R‐C=CH₂}(L)] 5 and [Cp*Ru(μ‐H)BH{HC=CH‐R}(L)] 6 (R=COOCH₃; L=C₇H₄NS₂) by Markovnikov and anti‐Markovnikov hydroboration. In an extension, photolysis of 4 in the presence of dimethyl acetylenedicarboxylate yielded η⁴‐σ,π‐borataallyl complex [Cp*Ru(μ‐H)BH{R‐C=CH‐R}(L)] 7 (R=COOCH₃; L=C₇H₄NS₂). An agostic interaction was also found to be present in 2 a – c and 5 – 7 , which is rare among the borataallyl complexes. All the new compounds have been characterized in solution by IR, ¹H, ¹¹B, ¹³C NMR spectroscopy, mass spectrometry and the structural types were unequivocally established by crystallographic analysis of 2 b , 3 a – c and 5 – 7 . DFT calculations were performed to evaluate possible bonding and electronic structures of the new compounds.     

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands. Syntheses,Spectroscopic Properties and Molecular Structures of [Cp°MoCl4(PH2R)] (R = But, 1‐Ad,Cy, Ph, 2, 4, 6‐Me3C6H2, 2, 4, 6‐Pri3C6H2, Cp° = C5EtMe4)

[Cp°MoCl₄] (Cp° = C₅EtMe₄) reacts with primary phosphines PH₂R to give the paramagnetic phosphine complexes [Cp°MoCl₄(PH₂R)] [Cp° = C₅EtMe₄, R = Bu^t ( 1 ), 1‐Ad (1‐Ad = 1‐adamantyl; 2 ), Cy ( 3 ), Ph ( 4 ), Mes (Mes = 2, 4, 6‐Me₃C₆H₂; 5 ), Tipp (Tipp = 2, 4, 6‐Prⁱ₃C₆H₂; 6 )]. 1 — 6 were characterized spectroscopically (IR, MS), and X‐ray crystal structures were determined for 1 — 4 and 6 . EPR investigations in liquid and frozen solution confirmed the presence of Mo^V species, and the data were used to analyze the spin‐density distribution in the first coordination sphere. Complexes 3 and 4 react with two equivalents of NEt₃ with formation of [Cp°MoCl₂(η³‐P₄Cy₄H)] ( 7 ) and [Cp°₂Mo₂(μ‐Cl)₂(μ‐P₄Ph₄)] ( 8 ), respectively, in low yield. Complexes 7 and 8 were characterized by X‐ray crystallography.     

Synthesis and X‐ray Crystal Structures of Ru3(CO)9(μ‐arphos)(L) [L = AsPh3, As(m‐C6H4Me)3, As(p‐C6H4Me)3]

Three new triruthenium clusters, Ru₃(CO)₉(μ‐arphos)AsPh₃ ( 1 ), Ru₃(CO)₉(μ‐arphos)As(m‐C₆H₄Me)₃ ( 2 ), and Ru₃(CO)₉(μ‐arphos)As(p‐C₆H₄Me)₃ ( 3 ) were synthesized via thermal reactions of Ru₃(CO)₁₀(μ‐arphos) with different tertiary arsine ligands [AsPh₃, As(m‐C₆H₄Me)₃, As(p‐C₆H₄Me)₃]. All these complexes were fully characterized by elemental analysis, FT‐IR, NMR spectroscopy, and single‐crystal X‐ray diffraction.     

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.     

Zur Reaktivität von alkylthioverbrückten 44‐CVE‐triangularen Platinclustern: Umsetzungen mit bidentaten Phosphanliganden

On the Reactivity of Alkylthio Bridged 44 CVE Triangular Platinum Clusters: Reactions with Bidentate Phosphine Ligands The 44 cve (cluster valence electrons) triangular platinum clusters [{Pt(PR₃)}₃(μ‐SMe)₃]Cl (PR₃ = PPh₃, 2a ; P(4‐FC₆H₄)₃, 2b ; P(n‐Bu)₃, 2c ) were found to react with PPh₂CH₂PPh₂ (dppm) in a degradation reaction yielding dinuclear platinum(I) complexes [{Pt(PR₃)}₂(μ‐SMe)(μ‐dppm)]Cl (PR₃ = PPh₃, 3a ; P(4‐FC₆H₄)₃, 3b ; P(n‐Bu)₃; 3e ) and the platinum(II) complex [Pt(SMe)₂(dppm)] ( 4 ), whereas the addition of PPh₂CH₂CH₂PPh₂ (dppe) to cluster 2a afforded a mixture of degradation products, among others the complexes [Pt(dppe)₂] and [Pt(dppe)₂]Cl₂. On the other hand, the treatment of cluster 2a with PPh₂CH₂CH₂CH₂PPh₂ (dppp) ended up in the formation of the cationic complex [{Pt(dppp)}₂(μ‐SMe)₂]Cl₂ ( 5 ). Furthermore, the terminal PPh₃ ligands in complex 3a proved to be subject to substitution by the stronger donating monodentate phosphine ligands PMePh₂ and PMe₂Ph yielding the analogous complexes [{Pt(PR₃)}₂(μ‐SMe)(μ‐dppm)]Cl (PR₃ = PMePh₂, 3c ; PMe₂Ph, 3d ). NMR investigations on complexes 3 showed an inverse correlation of Tolmans electronic parameter ν with the coupling constants ¹J(Pt,P) and ¹J(Pt,Pt). All compounds were fully characterized by means of NMR and IR spectroscopy. X‐ray diffraction analyses were performed for the complexes [{Pt{P(4‐FC₆H₄)₃}}₂(μ‐SMe)(μ‐dppm)]Cl ( 3b ), [Pt(SMe)₂(dppm)] ( 4 ), and [{Pt(dppp)}₂(μ‐SMe)₂]Cl₂ ( 5 ).     

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,characterization and molecular docking of new C,N‐palladacycles containing pyridinium‐derived ligands: DNA and BSA interaction studies and evaluation as anti‐tumor agents

Four new monomeric Pd (II) complexes with formulas [Pd(C,N)‐(2′‐NH₂C₆H₄)C₆H₄ (N₃)(L)] ( A ), ( B ) and [Pd(C,N)‐C₆H₄CH₂NH(C₄H₉)(N₃)(L)] ( C ), ( D ), [L = isonicotinamide for ( A ) and ( C ), L = 4‐N,N‐dimethylaminopyridine for ( B ) and ( D )] have been synthesized using four initial dimers [Pd₂{(C,N)‐(2′‐NH₂C₆H₄)C₆H₄}₂(μ‐OAc)₂] ( 1 ), [Pd₂{(C,N)‐ (2′‐NH₂C₆H₄)C₆H₄}₂(μ‐N₃)₂] ( 3 ) for A and C , and [Pd₂{(C,N)‐C₆H₄CH₂NH(C₄H₉)}₂(μ‐OAc)₂] ( 2 ) and [Pd₂{(C,N)‐C₆H₄CH₂NH(C₄H₉)}₂(μ‐N₃)₂] ( 4 ) for B and D . Then synthesized complexes have been characterized by Fourier transform‐infrared, NMR spectroscopy and thermal gravimetric‐differential thermal analysis. Furthermore, UV–Vis spectroscopy, fluorescence spectroscopy, circular dichroism (CD) and helix melting temperature measurements have been employed to study the binding interaction of them with calf thymus‐deoxyribonucleic acid (DNA). The results reveal that all synthesized complexes can interact with DNA via groove‐binding mode. Bovine serum albumin (BSA)‐binding studies have been carried out using UV–Vis spectroscopy, emission titration and CD. However, competitive binding studies using warfarin, ibuprofen and digoxin on site markers demonstrated that the complexes bind to different sites on BSA. The results also indicated that the binding site was mainly located within site‐III for complex A , and site‐I for complexes B , C and D of BSA. In addition, molecular docking studies have been executed to determine the binding site of the DNA and BSA with complexes. Eventually, in vitro cytotoxicity of synthesized palladium complexes and cisplatin were carried out against human promyelocytic leukemia cancer (Hela) and breast cancer (MCF‐7) cell lines. Pursuant to the IC₅₀ values, the cytotoxicity of complexes against MCF‐7 was more than Hela.     

Aktivierung von Schwefelkohlenstoff an Trirutheniumclustern: Synthese und Kristallstruktur von [Ru3(CO)4(μ‐PCy2)2(μ‐Ph2PCH2PPh2)(μ3‐S){μ3‐η2‐CSC(S)S}]

Activation of Carbon Disulfide on Triruthenium Clusters: Synthesis and X‐Ray Crystal Structure Analysis of [Ru₃(CO)₄(μ‐PCy₂)₂(μ‐Ph₂PCH₂PPh₂)(μ₃‐S){μ₃‐η²‐CSC(S)S}] [Ru₃(CO)₄(μ‐H)₃(μ‐PCy₂)₃(μ‐dppm)] ( 2 ) (dppm = Ph₂PCH₂PPh₂) reacts with CS₂ at room temperature and yields the open 50 valence electron cluster [Ru₃(CO)₄(μ‐PCy₂)₂(μ‐dppm)(μ₃‐S){μ₃‐η²‐CSC(S)S}] ( 3 ) containing the unusual μ₃‐η²‐C₂S₃ mercaptocarbyne ligand. Compound 3 was characterized by single crystal X‐ray structure analysis.