Koordinativ ungesättigte Dirutheniumkomplexe: Synthese und Kristallstrukturen von [Ru2(CO)3L(μ‐η1 : η2‐C≡CPh)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] (L = CO,PnBu3)

Coordinatively Unsaturated Diruthenium Complexes: Synthesis and X‐ray Crystal Structures of [Ru₂(CO)₃L(μ‐η¹ : η²‐C≡CPh)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] (L = CO, PⁿBu₃) [Ru₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 1 ) reacts with several phosphines (L) in refluxing toluene under substitution of one carbonyl ligand and yields the compounds [Ru₂(CO)₃L(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] (L = PⁿBu₃, 2 a ; L = PCy₂H, 2 b ; L = dppm‐P, 2 c ; dppm = Ph₂PCH₂PPh₂). The reactivity of 1 as well as the activated complexes 2 a – c towards phenylethyne was studied. Thus 1 , 2 a and 2 b , respectively, react with PhC≡CH in refluxing toluene with elimination of dihydrogen to the acetylide‐bridged complexes [Ru₂(CO)₄(μ‐η¹ : η²‐C≡CPh)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ) and [Ru₂(CO)₃L(μ‐η¹ : η²‐C≡CPh)(μ‐P^tBu₂)(μ‐dppm)] ( 4 a and 4 b ). The molecular structures of 3 and 4 a were determined by crystal structure analyses.     

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.     

Ligand Substitution Reactions on Aquapentachloro‐ and Hexachloroplatinic Acid — Synthesis and Characterization of Tetrachloroplatinum(IV) Complexes with Heterocyclic N,N Donors

Reactions of aquapentachloroplatinic acid, (H₃O)[PtCl₅(H₂O)]·2(18C6)·6H₂O ( 1 ) (18C6 = 18‐crown‐6), and H₂[PtCl₆]·6H₂O ( 2 ) with heterocyclic N, N donors (2, 2′‐bipyridine, bpy; 4, 4′‐di‐tert‐butyl‐2, 2′‐bipyridine, tBu₂bpy; 1, 10‐phenanthroline, phen; 4, 7‐diphenyl‐1, 10‐phenanthroline, Ph₂phen; 2, 2′‐bipyrimidine, bpym) afforded with ligand substitution platinum(IV) complexes [PtCl₄(N∩N)] (N∩N = bpy, 3a ; tBu₂bpy, 3b ; Ph₂phen, 5 ; bpym, 7 ) and/or with protonation of N, N donor yielding (R₂phenH)₂[PtCl₆] (R = H, 4a ; Ph, 4b ) and (bpymH)⁺ ( 8 ). With UV irradiation Ph₂phen and bpym reacted with reduction yielding platinum(II) complexes [PtCl₂(N∩N)] (N∩N = Ph₂phen, 6 ; bpym, 9 ). Identities of all complexes were established by microanalysis as well as by NMR (¹H, ¹³C, ¹⁹⁵Pt) and IR spectroscopic investigations. Molecular structures of [PtCl₄(bpym)]·MeOH ( 7 ) and [PtCl₂(Ph₂phen)] ( 6 ) were determined by X‐ray diffraction analyses. Differences in reactivity of bpy/bpym and phen ligands are discussed in terms of calculated structures of complexes [PtCl₅(N∩N)]^— with monodentately bound N, N ligands (N∩N = bpy, 10a ; phen, 10b ; bpym, 10c ).     

Formation and Structural Characterization of Metal Complexes derived from Thiosalicylic Acid

The formation and structural aspects of some metal complexes of thiosalicylic acid (TSA) were studied. The μ‐bridging tetra‐coordinated Ru complex, [Ru(C₆H₄(CO₂)(μ‐S)(H₂O)]₂ ( 1 ) was formed by hydrothermal reaction of TSA with RuCl₃. The complexes [M(dtdb)(phen)(H₂O)]_n ( 2 – 4 ) (M = Zn^II, Co^II, Ni^II, dtdb = 2,2′‐dithiodibenzoate anion, phen = 1,10‐phenanthroline) were obtained by the slow diffusion technique and the in situ S–S bond formation was confirmed by elemental, spectral and X‐ray analysis. Reaction of TSA with CuCl₂ and 2,2′‐bipyridine (bipy) under the slow diffusion technique yielded the dimer [Cu(tdb)(bipy)] ( 5 ) (tdb = thiodibenzoic acid), where the in situ generation of 2,2′‐thiodibenzoic acid was observed.     

Nanoscale MnII‐Coordination Polymers for Cell Imaging and Heterogeneous Catalysis

A mixed ligand approach was exploited to synthesize a new series of Mn^II‐based coordination polymers (CPs), namely, CP1 {[Mn(μ‐dpa)(μ‐4,4′‐bp)]?MeOH}_∞, CP2 {[Mn₃(μ‐dpa)₃(2,2′‐bp)₂]}_∞, CP3 {[Mn₃(μ‐dpa)₃(1,10‐phen)₂]?2 H₂O}_∞, CP4 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]?H₂O}_∞, CP5 {[Mn₂(μ‐dpa)₂(μ‐4,4′‐bpe)₂]? DEF}_∞, and CP6 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]? DMA}_∞ (dpa=3,5‐dicarboxyphenyl azide, 2,2′‐bp=2,2′‐bipyridine, 1,10‐phen=1,10‐phenanthroline, 4,4′‐bpe=1,2‐bis(4‐pyridyl)ethylene, 4,4′‐bp=4,4′‐bipyridine, DEF=N,N‐diethylformamide, DMA=N,N‐dimethylacetamide), to develop multifunctional CPs. Various techniques, such as single‐crystal X‐ray diffraction (SXRD), FTIR spectroscopy, elemental analysis, and thermogravimetric analysis, were employed to fully characterize these CPs. The majority of the CPs displayed a four‐connected sql topology, whereas CP4 and CP6 exhibited a two‐dimensional SnS network architecture, which was further entangled in a polycatenation mode. Compound CP1 displayed an open framework structure. The CPs were scaled down to the nanoregime in a ball mill for cell imaging studies. Whereas CP2 and CP4 were employed for cell imaging with RAW264.7 cells, CP1 was exploited for both cell imaging and heterogeneous catalysis in a cyanosilylation reaction.     

Cadmium(II) Complexes with a Bulky Anthracene‐based Carboxylate Ligand: Syntheses,Crystal Structures,and Luminescent Properties

To explore the coordination possibilities of anthracene‐based ligands, three cadmium(ιι) complexes with anthracene‐9‐carboxylate ( L ) and relevant auxiliary chelating or bridging ligands were synthesized and characterized: Cd₂( L )₄(2bpy)₂(μ‐H₂O) ( 1 ), Cd₂( L )₄(phen)₂(μ‐H₂O) ( 2 ), and {[Cd₃( L )₆(4bpy)]}_∞ ( 3 ) (2bpy = 2,2′‐bipyridine, phen = 1,10‐phenanthroline, and 4bpy = 4,4′‐bipyridine). Structural analyses show that complexes 1 and 2 both take dinuclear structures by incorporating the chelating 2bpy or phen ligand, which are further interlinked by intermolecular hydrogen‐bonding, π ··· π stacking, and/or C–H ··· π supramolecular interactions to generate higher‐dimensional supramolecular frameworks. Complex 3 has a one‐dimensional (1D) ribbon‐like structure, which is further assembled into a two‐dimensional (2D) layer, and a three‐dimensional (3D) framework by the co‐effects of interchain C–H ··· O hydrogen‐bonding and C–H ··· π supramolecular interactions. Moreover, the luminescent properties of these complexes were further investigated in detail.     

Influence of Steric Hindrance of N‐Heterocyclic Ancillary Ligands on the Structure and Magnetic Properties of Manganese(II) Coordination Polymers

Three biphenyl‐3,5‐dicarboxylic acid (H₂ L ) based coordination polymers, namely, [Mn₃( L )₃(2,2′‐bpy)₂]_n ( 1 ), {[Mn( L )(phen)] · (MeOH)}_n ( 2 ), and [Mn( L )(dipt)]_n ( 3 ), (2,2′‐bpy = 2,2′‐bipyridine, phen = 1,10‐phenanthroline, and dipt = 2,9‐dimethyl‐1,10‐phenanthroline) were synthesized and characterized by single‐crystal X‐ray diffraction and analyses of their magnetic properties. 1 is a trinuclear manganese structure with a 2D motifs, which can join by hydrogen bond bridges to give 3D supramolecular architectures. 2 has a dinuclear center forming a 1D supramolecular ladder chain. The mononuclear complex 3 displays 1D metal‐organic chains driven by μ₂‐ L linkers. Their structural differences were investigated, revealing that the influence of steric hindrance on the structures of acid‐based coordination polymers is realized through changing the N‐heterocyclic ancillaries of diverse steric hindrance. Obviously, with decreasing of the steric hindrance of the N‐donor ligand, complexes 1 – 3 show structures from 1D to 2D and mononuclear to multinuclear. Magnetic susceptibility measurements indicate that 1 and 2 have dominating antiferromagnetic couplings between metal ions, whereas compound 3 is paramagnetic.     

μ1,3‐Azido‐di­azidotetrakis(1,10‐phenanthroline)dicopper(II) azide tetra­hydrate

In the title compound, [Cu₂(μ‐_1,3‐N₃)(N₃)₂(phen)₄](N₃)·4H₂O (phen is 1,10‐phenanthroline, C₁₂H₈N₂), each of the two Cu atoms is surrounded by two N atoms of two azide anions and by four N atoms of two 1,10‐phenanthroline ligands [Cu—N distances are 1.964 (3), 2.009 (3), 2.018 (3), 2.054 (3), 2.306 (3) and 2.759 (4) Å], forming an elongated CuN₆ octahedron. An ideally linear μ_1,3‐azide anion bridges two Cu atoms to form a dimeric structure with the central N atom located on a centre of inversion. Moreover, the adjacent dimeric units are connected by hydrogen‐bond interactions to produce one‐dimensional chains. A two‐dimensional supramolecular array is formed by π–π interactions between the aromatic rings of 1,10‐phenanthroline ligands of adjacent dimeric units.     

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.     

Rhenium(I) Polypyridine Diamine Complexes as Intracellular Phosphorogenic Sensors: Synthesis,Characterization, Emissive Behavior,Biological Properties,and Nitric Oxide Sensing

We report the development of a series of rhenium(I) polypyridine complexes appended with an electron‐rich diaminoaromatic moiety as phosphorogenic sensors for nitric oxide (NO). The diamine complexes [Re(N^N)(CO)₃(py‐DA)][PF₆] (py‐DA=3‐(N‐(2‐amino‐5‐methoxyphenyl)aminomethyl)pyridine; N^N=1,10‐phenanthroline (phen) ( 1 a ), 3,4,7,8‐tetramethyl‐1,10‐phenanthroline (Me₄‐phen) ( 2 a ), 4,7‐diphenyl‐1,10‐phenanthroline (Ph₂‐phen) ( 3 a )) have been synthesized and characterized. In contrast to common rhenium(I) diimines, these diamine complexes were very weakly emissive due to quenching of the triplet metal‐to‐ligand charge‐transfer (³MLCT) emission by the diaminoaromatic moiety through photoinduced electron transfer (PET). Upon treatment with NO, the complexes were converted into the triazole derivatives [Re(N^N)(CO)₃(py‐triazole)][PF₆] (py‐triazole=3‐((6‐methoxybenzotriazol‐1‐yl)methyl)pyridine; N^N=phen ( 1 b ), Me₄‐phen ( 2 b ), Ph₂‐phen ( 3 b )), resulting in significant emission enhancement (I/I₀≈60). The diamine complexes exhibited high reaction selectivity to NO, and their emission intensity was found to be independent on pH. Also, these complexes were effectively internalized by HeLa cells and RAW264.7 macrophages with negligible cytotoxicity. Additionally, the use of complex 3 a as an intracellular phosphorogenic sensor for NO has been demonstrated.     

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 .     

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.     

Structural Studies of Several Ru3 and Ru4 Carbonyl Clusters

The preparation, characterisation and single‐crystal XRD molecular structure determinations of the three Ru₃ carbonyl clusters attached to carbon ligands, Ru₃(μ‐H)₃(μ₃‐CBr)(CO)₉ ( 1 ), Ru₃(μ‐H)(μ‐dppm){μ‐C(OMe)}(CO)₈ ( 2 ) and AuRu₃(μ‐H)₂(μ₃‐C=C=CHPh)(CO)₁₀ ( 3 ) are reported, together with the structures of the tetranuclear hydrido‐carbonyls Ru₄(μ‐H)_4–2x(CO)_11+x(PPh₃) (x = 0 4 , 1 5 ).     

Near‐Infrared Light‐Driven Hydrogen Evolution from Water Using a Polypyridyl Triruthenium Photosensitizer

In order to realize artificial photosynthetic devices for splitting water to H₂ and O₂ (2 H₂O+hν→2 H₂+O₂), it is desirable to use a wider wavelength range of light that extends to a lower energy region of the solar spectrum. Here we report a triruthenium photosensitizer [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺ (dmbpy=4,4′‐dimethyl‐2,2′‐bipyridine, HAT=1,4,5,8,9,12‐hexaazatriphenylene), which absorbs near‐infrared light up to 800 nm based on its metal‐to‐ligand charge transfer (¹MLCT) transition. Importantly, [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺ is found to be the first example of a photosensitizer which can drive H₂ evolution under the illumination of near‐infrared light above 700 nm. The electrochemical and photochemical studies reveal that the reductive quenching within the ion‐pair adducts of [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺ and ascorbate anions affords a singly reduced form of [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺, which is used as a reducing equivalent in the subsequent water reduction process.     

In‐ and Out‐of‐Cavity Interactions by Modulating the Size of Ruthenium Metallarectangles

Cationic (arene)ruthenium‐based tetranuclear complexes of the general formula [Ru₄(η⁶‐p‐cymene)₄(μ‐N∩N)₂(μ‐OO∩OO)₂]⁴⁺ were obtained from the dinuclear (arene)ruthenium complexes [Ru₂(η⁶‐p‐cymene)₂(μ‐OO∩OO)₂Cl₂] (p‐cymene=1‐methyl‐4‐(1‐methylethyl)benzene, OO∩OO=5,8‐dihydroxy‐1,4‐naphthoquinonato(2?), 9,10‐dihydroxy‐1,4‐anthraquinonato(2?), or 6,11‐dihydroxynaphthacene‐5,12‐dionato(2?)) by reaction with pyrazine or bipyridine linkers (N∩N=pyrazine, 4,4′‐bipyridine, 4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine]) in the presence of silver trifluoromethanesulfonate (CF₃SO₃Ag) (Scheme). All complexes 4 – 12 were isolated in good yield as CF₃SO salts, and characterized by NMR and IR spectroscopy. The host–guest properties of the metallarectangles incorporating 4,4′‐bipyridine and (4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine] linkers were studied in solution by means of multiple NMR experiments (1D, ROESY, and DOSY). The largest metallarectangles 10 – 12 incorporating (4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine] linkers are able to host an anthracene, pyrene, perylene, or coronene molecule in their cavity, while the medium‐size metallarectangles 7 – 9 incorporating 4,4′‐bipyridine linkers are only able to encapsulate anthracene. However, out‐of‐cavity interactions are observed between these 4,4′‐bipyridine‐containing rectangles and pyrene, perylene, or coronene. In contrast, the small pyrazine‐containing metallarectangles 4 – 6 show no interaction in solution with this series of planar aromatic molecules.     

Neutrale Bis‐Aziridin‐Komplexe des Typs [M(CO)3XAz2] (M = Mn,Re; X = Cl,Br; Az = N(H)C2H2Me2)

The pentacarbonylhalogene complexes [XM(CO)₅] (M = Mn, Re; X = Cl, Br) ( 1a – 2b ) react with 2,2‐dimethylaziridine by thermally induced substitution reaction to give the neutral bis‐aziridine complexes [M(X)(CO)₃Az₂] (Az = N(H)C₂H₂Me₂) ( 3a – 4b ). As a result of the X‐ray structure analyses, the metal atoms are octahedrally configurated in the facial arrangement; the intact three‐membered rings coordinate through their distorted tetrahedrally configurated N atoms. All compounds 3a – 4b are stable with respect to the directed thermal alkene elimination to give the corresponding nitrene complexes (CO)₄(X)M=NH; their IR, ¹H and ¹³C{¹H} NMR, and MS spectra are reported and discussed.     

Koordinativ ungesättigte Dirutheniumkomplexe: Synthese und Kristallstrukturen von [Ru2(CO)n(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] (n = 4; 5) und [Ru2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]

Coordinatively Unsaturated Diruthenium Complexes: Synthesis and X‐ray Crystal Structures of [Ru₂(CO)_n(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] (n = 4; 5) and [Ru₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] The reaction of [Ru₂(μ‐CO)(CO)₅(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 2 ) with dppm yields the dinuclear species [Ru₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ) (dppm = Ph₂PCH₂PPh₂). Under thermal or photolytic conditions 3 loses very easily one carbonyl ligand and affords the corresponding electronically and coordinatively unsaturated complex [Ru₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ). 4 is also obtainable by an one‐pot synthesis from [Ru₃(CO)₁₂], an excess of ^tBu₂PH and stoichiometric amounts of dppm via the formation of [Ru₂(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)₂] ( 1 ). 4 exhibits a Ru–Ru double bond which could be confirmed by addition of methylene to the dimetallacyclopropane [Ru₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 5 ). The molecular structures of 3 , 4 and 5 were determined by X‐ray crystal structure analyses.     

Preparation, photophysical, and electrochemical properties of two polynuclear Ru(II) polypyridyl complexes containing imidazole-based ligands

A tripodal ligand L¹ and dipodal ligand L² containing imidazole rings have been synthesized by the reaction of 1,10-phenanthroline-5,6-dione with 2,2??-bipyridine-4,4??-dicarbaldehyde and 4-methyl-2,2??-bipyridine-4??-carbaldehyde, respectively, in the presence of ammonium acetate. Both ligands have two kinds of nonequivalent coordinating sites: one involving the phenanthroline moiety and the other involving the 2,2??-bipyridine moiety. The Ru(II) complexes, [(bpy)₆Ru₃(L¹)](PF₆)₆ and [(bpy)₄Ru₂(L²)](PF₆)₄ (bpy?=?2,2??-bipyridine), have been obtained by refluxing Ru(bpy)₂Cl₂·2H₂O with each ligand in solution. The two complexes display MLCT absorptions at 465 and 480?nm, respectively, and emission at 665 and 675?nm, respectively, in CH₃CN solution. Electrochemical studies of both complexes show one Ru(II)-centered oxidation at around 1.29?V and three ligand-centered reductions.     

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.     

First‐Row Transition‐Metal–Diborane and –Borylene Complexes

A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}₂] (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) with LiBH₄ ? thf at ?78 °C, followed by room‐temperature reaction with three equivalents of [Mn₂(CO)₁₀] yielded a manganese hexahydridodiborate compound [{(OC)₄Mn}(η⁶‐B₂H₆){Mn(CO)₃}₂(μ‐H)] ( 1 ) and a triply bridged borylene complex [(μ₃‐BH)(Cp*Co)₂(μ‐CO)(μ‐H)₂MnH(CO)₃] ( 2 ). In a similar fashion, [Re₂(CO)₁₀] generated [(μ₃‐BH)(Cp*Co)₂(μ‐CO)(μ‐H)₂ReH(CO)₃] ( 3 ) and [(μ₃‐BH)(Cp*Co)₂(μ‐CO)₂(μ‐H)Co(CO)₃] ( 4 ) in modest yields. In contrast, [Ru₃(CO)₁₂] under similar reaction conditions yielded a heterometallic semi‐interstitial boride cluster [(Cp*Co)(μ‐H)₃Ru₃(CO)₉B] ( 5 ). The solid‐state X‐ray structure of compound 1 shows a significantly shorter boron–boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using ¹H, ¹¹B, ¹³C NMR spectroscopy, mass spectrometry, and X‐ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant B?H?Mn, a weak B?B?Mn interaction, and an enhanced B?B bonding in 1 .