Dinuclear Products Research Articles

Aluminum Complexes Supported by Ph2P‐Functionalized Anilido‐Pyridine Ligand Platform: Synthesis, Structure and Evaluation as Frustrated Lewis Pairs

AbstractA simple direct condensation of 2,6‐bis(phenylamino)pyridine (1) and ClPPh2 under basic conditions allowed straightforward synthesis of the new multidentate Ph2P‐substituted anilido‐pyridine proligands 2 a and 2 b. Proligand 2 a was used in σ‐bond metathesis reactions with Me3Al affording either dinuclear product 3 a‐Al2 or mononuclear 4 a‐Al, depending on the reaction conditions. These complexes were authenticated by X‐ray crystallography, NMR spectroscopy and microanalysis. The analysis of the interaction between Me2Al and Ph2P fragments in 4 a‐Al was performed by structural and computational studies. The reactivity of 4 a‐Al was preliminary assessed in several representative reactions.

Lewis Acid Supported Nickel Nitrenoids.

Metalation of the polynucleating ligand F,tbs LH6 (1,3,5-C6 H9 (NC6 H3 -4-F-2-NSiMe2 t Bu)3 ) with two equivalents of Zn(N(SiMe3 )2 )2 affords the dinuclear product (F,tbs LH2 )Zn2 (1), which can be further deprotonated to yield (F,tbs L)Zn2 Li2 (OEt2 )4 (2). Transmetalation of 2 with NiCl2 (py)2 yields the heterometallic, trinuclear cluster (F,tbs L)Zn2 Ni(py) (3). Reduction of 3 with KC8 affords [KC222 ][(F,tbs L)Zn2 Ni] (4) which features a monovalent Ni centre. Addition of 1-adamantyl azide to 4 generates the bridging μ3 -nitrenoid adduct [K(THF)3 ][(F,tbs L)Zn2 Ni(μ3 -NAd)] (5). EPR spectroscopy reveals that the anionic cluster possesses a doublet ground state (S = ). Cyclic voltammetry of 5 reveals two fully reversible redox events. The dianionic nitrenoid [K2 (THF)9 ][(F,tbs L)Zn2 Ni(μ3 -NAd)] (6) was isolated and characterized while the neutral redox isomer was observed to undergo both intra- and intermolecular H-atom abstraction processes. Ni K-edge XAS studies suggest a divalent oxidation state for the Ni centres in both the monoanionic and dianionic [Zn2 Ni] nitrenoid complexes. However, DFT analysis suggests Ni-borne oxidation for 5.

Lewis Acid Supported Nickel Nitrenoids

AbstractMetalation of the polynucleating ligand F,tbsLH6 (1,3,5‐C6H9(NC6H3−4‐F−2‐NSiMe2tBu)3) with two equivalents of Zn(N(SiMe3)2)2 affords the dinuclear product (F,tbsLH2)Zn2 (1), which can be further deprotonated to yield (F,tbsL)Zn2Li2(OEt2)4 (2). Transmetalation of 2 with NiCl2(py)2 yields the heterometallic, trinuclear cluster (F,tbsL)Zn2Ni(py) (3). Reduction of 3 with KC8 affords [KC222][(F,tbsL)Zn2Ni] (4) which features a monovalent Ni centre. Addition of 1‐adamantyl azide to 4 generates the bridging μ3‐nitrenoid adduct [K(THF)3][(F,tbsL)Zn2Ni(μ3‐NAd)] (5). EPR spectroscopy reveals that the anionic cluster possesses a doublet ground state (S = ). Cyclic voltammetry of 5 reveals two fully reversible redox events. The dianionic nitrenoid [K2(THF)9][(F,tbsL)Zn2Ni(μ3‐NAd)] (6) was isolated and characterized while the neutral redox isomer was observed to undergo both intra‐ and intermolecular H‐atom abstraction processes. Ni K‐edge XAS studies suggest a divalent oxidation state for the Ni centres in both the monoanionic and dianionic [Zn2Ni] nitrenoid complexes. However, DFT analysis suggests Ni‐borne oxidation for 5.

Simple magnesium alkoxides: synthesis, molecular structure, and catalytic behaviour in the ring-opening polymerization of lactide and macrolactones and in the copolymerization of maleic anhydride and propylene oxide.

The synthesis of two chiral bulky alkoxide pro-ligands, 1-adamantyl-tert-butylphenylmethanol HOCAdtBuPh and 1-adamantylmethylphenylmethanol HOCAdMePh, is reported and their coordination chemistry with magnesium(II) is described and compared with the coordination chemistry of the previously reported achiral bulky alkoxide pro-ligand HOCtBu2Ph. Treatment of n-butyl-sec-butylmagnesium with two equivalents of the racemic mixture of HOCAdtBuPh led selectively to the formation of the mononuclear bis(alkoxide) complex Mg(OCAdtBuPh)2(THF)2. 1H NMR spectroscopy and X-ray crystallography suggested the selective formation of the C2-symmetric homochiral diastereomer Mg(OCRAdtBuPh)2(THF)2/Mg(OCSAdtBuPh)2(THF)2. In contrast, the less sterically encumbered HOCAdMePh led to the formation of dinuclear products indicating only partial alkyl group substitution. The mononuclear Mg(OCAdtBuPh)2(THF)2 complex was tested as a catalyst in different reactions for the synthesis of polyesters. In the ROP of lactide, Mg(OCAdtBuPh)2(THF)2 demonstrated very high activity, higher than that shown by Mg(OCtBu2Ph)2(THF)2, although with moderate control degrees. Both Mg(OCAdtBuPh)2(THF)2 and Mg(OCtBu2Ph)2(THF)2 were found to be very effective in the polymerization of macrolactones such as ω-pentadecalactone (PDL) and ω-6-hexadecenlactone (HDL) also under mild reaction conditions that are generally prohibitive for these substrates. The same catalysts demonstrated efficient ring-opening copolymerization (ROCOP) of propylene oxide (PO) and maleic anhydride (MA) to produce poly(propylene maleate).

Synthesis, anticancer and antimalarial activities of organosulfur and organoselenium derivatives of cyclopentadienyliron dicarbonyl as photoCORMs

The reactions of [CpFe(CO)2]2 with 2 mol equivalents of R2E2 (R = C6H11, C4H3S, CH2C6H5; E = S, Se) have yielded dinuclear products of [CpFe(CO)(μ-L)]2 (L = C6H11S (1), C4H3S2 (2) and CH2C6H5Se (3)), respectively. An additional trinuclear compound, C24H22O2Se2Fe3 (4) was isolated only from the reaction with dibenzyl diselenide. All the products have been fully characterized by FT-IR,1H and13C NMR, CHN elemental analysis, and structurally elucidated by single crystal X-ray diffraction. The stability of 1–3 both under dark and UV conditions were investigated by monitoring the changes in their respective UV–Vis spectra in phosphate buffered saline (PBS) solution. Their potential application as photoCORMs were also evaluated by standard myoglobin assay. 2 showed the shortest half-life and highest equivalent of CO-released. The anticancer studies of 1–3 were evaluated in-vitro on breast cancer cell lines (MCF-7, MDA-MB-231 and MDA-MB-468) and the cytotoxicity of 2 had increased approximately 4 times against MDA-MB-468 cell line upon UV irradiation, which was 11.5 ± 2.7 μM. All complexes exhibited cytotoxic effect on specific sub-types of breast cancer cells. Antimalarial activities of 1–3 had also been studied and reported in this work. Unfortunately, these complexes did not display any significant effect on the Plasmodium falciparum 3D7 strains.

Synthesis, structures, and reactivities of six-membered C[sbnd]N chelate protic pyrazole complexes of iridium

The reaction of the bis(acetato)iridium complex [Cp*Ir(OAc)2] with an equimolar amount of 3-benzyl-5-alkylpyrazoles followed by addition of an excess of potassium chloride afforded the six-membered, C–N chelate protic pyrazole complexes [Cp*IrCl(R-LH)] (2a, R = Me; 2b, R = tBu; R-LH = C6H4CH2-C3N2H2R-5-κC,κN). The reaction of 2a with carbon monoxide led to the formation of the carbonyl complex [Cp*Ir(CO)(Me-LH)]Cl (3a) featuring a CO stretching wavenumber comparable with that of the five-membered chelate complex. Meanwhile, dehydrochlorination of the methylpyrazole complex 2a with potassium tert-butoxide in toluene resulted in uptake of adventitious water to give the hydroxido-bridged dinuclear complex [(Cp*Ir)2{μ-Me-LH···(Me-L)}(μ-OH)] (4a). In 2-propanol, the reaction caused hydrogen transfer from the solvent to yield the hydrido-bridged dinuclear complex [(Cp*Ir)2{μ-Me-LH···(Me-L)}(μ-H)] (6a). These dinuclear products could not be obtained from the more sterically-demanding complex 2b, but the intermediary coordinatively unsaturated pyrazolato species can be trapped from both 2a and 2b by triphenylphosphine to give the pyrazolato–phosphine complexes [Cp*Ir(PPh3)(R-L)] (5a and 5b) The detailed structures of 2a, 2b, 3a, 4a, and 5b bearing a folded six-membered C–N chelate pyrazole ligand have been determined by X-ray analysis. The chlorido complexes 2a and 2b also catalyzed transfer hydrogenation of acetophenone with 2-propanol at 50 °C.

Synthesis of a carborane-substituted bis(phosphanido) cobaltate(i), ligand substitution, and unusual P4 fragmentation.

Oxidative addition of the P–P single bond of an ortho-carborane-derived 1,2-diphosphetane (1,2-C2(PMes)2B10H10) (Mes = 2,4,6-Me3C6H2) to cobalt(−i) and nickel(0) sources affords the first heteroleptic complexes of a carborane-bridged bis(phosphanido) ligand. The complexes also incorporate labile ligands suitable for further functionalisation. Thus, the cobalt(i) complex [K([18]crown-6)][Co{1,2-(PMes)2C2B10H10}(cod)] (cod = 1,5-cyclooctadiene) bearing a labile cyclooctadiene ligand undergoes facile ligand exchange reactions with isonitriles and tert-butyl phosphaalkyne with retention of the bis(phosphanido) ligand. However, in the reaction with one equivalent of P4, the electron-rich bis(phosphanido) moiety abstracts a single phosphorus atom with formation of a new P3 chain, while the remaining three P atoms derived from P4 form an η3-coordinating cyclo-P3 ligand. In contrast, when the same reaction is performed with two equivalents of the cobalt(i) complex, a dinuclear product is formed which features an unusual P4 chain in its molecular structure.

Dinuclear Complexes of Flexidentate Pyridine-Substituted Formazanate Ligands.

The utility of flexidentate pyridyl-substituted formazanate ligands for assembling dinuclear coordination complexes with iridium(III) and/or platinum(II) building blocks is demonstrated herein. The dinuclear complexes are prepared either via a stepwise strategy, adding one metal unit at a time, or via one-pot self-assembly. Eight of the new complexes, including both mononuclear precursors and dinuclear products, are structurally characterized by single-crystal X-ray diffraction and NMR spectroscopy, revealing several distinct binding modes of the formazanates. All complexes are characterized by UV/Vis absorption spectroscopy and cyclic voltammetry. The frontier orbitals are primarily localized on the formazanate ligand, and a characteristic, intense formazanate-centered π→π* absorption band is observed in the absorption spectra.

Synthesis of Mono- and Diiron Dithiolene Complexes as Hydrogenase Models by Dithiolene Transfer Reactions, Including the Crystal Structure of [{Ni(S2C2Ph2)}6

The dithiolene transfer reaction between the nickel bis(dithiolene) complex [Ni(S2C2Ph2)2] and iron carbonyls has been re-investigated, and the conditions for the production of the dinuclear product [Fe2(μ-S2C2Ph2)(CO)6] have been optimized. Interception of a purple intermediate, thought to be [Fe(CO)3(S2C2Ph2)], in the reaction of [Fe(CO)5] with [Ni(S2C2Ph2)2] by the addition of PPh3 affords the new dark blue mononuclear complex [Fe(CO)2(PPh3)(S2C2Ph2)] in good yield. The fate of the nickel dithiolene fragments in these reactions has also been established by crystallographic characterization of the hexamer [{Ni(S2C2Ph2)}6] and the trinuclear cluster [Ni3(μ-S2C2Ph2)3(PPh3)2]. The substitution reactions of [Fe2(μ-S2C2Ph2)(CO)6] with PPh3 in the presence of Me3NO to give monosubstituted [Fe2(μ-S2C2Ph2)(CO)5(PPh3)] and disubstituted [Fe2(μ-S2C2Ph2)(CO)4(PPh3)2] are also reported.

Synthesis, X-ray characterization, and in vitro biological approach of dimeric and polymeric mercury(II) complexes with α-keto stabilized sulfur ylide

Reaction of α-keto stabilized sulfur ylide (Me)2SCHC(O)C6H4-p-CN (Y) with HgX2 (X = Cl, Br, and I) led to the formation of new dinuclear products of the type [HgX2(Y)]2 (X = Cl (1), Br (2), and I (3)). Furthermore, the reaction of the corresponding sulfur ylide (Y) with Hg(NO3)2·H2O in equimolar ratio, using methanol as a solvent, was shown to produce the polynuclear complex [(Y)Hg(NO3)2]n (4). The obtained compounds were characterized using elemental analysis, IR, 1H and 13C NMR techniques. The structures of compounds Y and 1 were characterized by single-crystal X-ray diffraction (XRD) analysis. Also, in order to confirm the crystalline nature of complexes 1–3, powder XRD pattern was used. Likewise, the antioxidant property of the complexes was examined by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging which revealed the strong-to-moderate radical scavenging ability (IC50; 0.163 ± 0.004 to 0.936 ± 0.012 mg·mL−1) of the synthesized compounds. Further, results from this study indicated that the compounds possess moderate antibacterial activity.

Reactions of pyridine-2-ethyl/methyl cyclopentadienes with metal carbonyls

Thermal treatment of pyridine-2-ethyl cyclopentadiene (1) with Fe(CO)5 and Ru3(CO)12 gave novel intramolecular C–H activated dinuclear products (3 and 5). In the case of Fe(CO)5, the reaction also afforded the normal bis(cyclopentadienyl) diiron complex (4). However, similar reaction of pyridine-2-methyl cyclopentadiene (2) with Fe(CO)5 and Ru3(CO)12 only afforded the normal bis(cyclopentadienyl) dinuclear metal complexes (7 and 8). For Ru3(CO)12, the reaction also yielded a pendant η1-pyridyl-coordinated product (9). In addition, the reactions of 1 and 2 with Re2(CO)10 formed the corresponding pyridylethyl/pyridylmethyl cyclopentadienyl rhenium tricarbonyl complexes 10 and 11, which further underwent pyridine to rhenium cyclization via photoirradiation to provide the rhenium dicarbonyl complexes 12 and 13. The molecular structures of 3, 5, 6, 7, 8, 9, and 12 were determined by X-ray diffraction.

The Influence of β-diiminato Ligands on As4 Activation by Cobalt Complexes.

In a systematic study of the activation of As4, three [LCo(tol)] (L=β‐diiminato) complexes have revealed different steric and electronic influences. 2,6‐Diisopropylphenyl (Dipp) and 2,6‐dimethylphenyl (dmp) flanking groups were used, one of the ligands with H backbone substituents (β‐dialdiminate L0) and two with Me substituents (β‐diketiminates L3 and L1). In the reaction with As4, different dinuclear products [(LCo)2As4] (LM=L0 (1), L1 (2), L3 (3)) were isolated, with all showing differently shaped [Co2As4] cores in the solid state: octahedral in 1, prismatic in 2, and asterane‐like in 3. Thermal treatment of 3 leads to the abstraction of one arsenic atom to yield [(L3Co)2As3] (4). All products were comprehensively characterized by single‐crystal X‐ray diffraction, FD‐MS, and 1H NMR spectroscopy. A rational explanation for the different reactivity is also proposed and DFT calculations shed light on the nature of the highly flexible [Co2As4] cores.

Molybdenum and nickel atrane complexes with a rigid tripodal tetraphosphine ligand incorporating imidazole rings

Abstract Tripodal, tetradentate tetraphosphine ligand tris(1H-2-diisopropylphosphinoimidazol-1-yl)phosphine (1) was synthesized in three straightforward steps from widely available starting materials. The ligand crystallized in a C3-like conformation suitable for metal coordination. Nickel(II) complex 2 was prepared from 1 and Ni(dme)Br2 and adopted a classical atrane structure with trigonal pyramidal geometry at the metal, a bromide covalently bonded in the axial position, and a bromide ion in the outer coordination sphere. Molybdenum(III) complex 3 was prepared from 1 and MoCl3(thf)3 and could be structurally characterized using a co-crystal with Cp2Co and [Cp2Co]Cl. It displayed a face-capped octahedral geometry at the seven-coordinated metal. Complexes 2 and 3 proved prone to decomposition under reductive and oxidative conditions, hindering the investigation of their chemistry. Crystallization attempts from acetonitrile led to the isolation of dinuclear hydrolysis product 4, with the Mo(III) centres bridged by two chlorides and two 2-(diisopropylphosphino)imidazole moieties in a paddlewheel arrangement.

Kinetics of aquation of Ni(II) oxydiacetate complex induced by Fe(III) ions

The kinetics of the aquation reaction of [Ni(ODA)(H2O)3] (where ODA = oxydiacetate) promoted by [Fe(H2O)6]3+ ions were investigated. Spectrophotometry studies were carried out at temperatures within the range 293.15–313.15 K. The concentration of [Ni(ODA)(H2O)3] was 8.67 × 10–4 mol L–1 and the concentration of the [Fe(H2O)6]3+ ions was kept within the range 0.75 × 10–4–7.50 × 10–4 mol L–1. The observable reaction rate constants increased with the increase of [Fe3+] according to the rate law: kobs = k + k1K{[Fe(H2O)6]3+}. Based on the kinetic data, the activation parameters were determined for the spontaneous step of the reaction and for the step dependent on the concentration of Fe3+ ions. A mechanism for the aquation reaction has been proposed. In the first step (the reversible part of the aquation reaction) a dinuclear intermediate product is produced and in the next step the products of the reaction, ([Ni(H2O)6]2+ and [Fe(ODA)(H2O)3]+), are formed. Nevertheless, it has turned out that the spontaneous path of the aquation reaction is also possible concurrently (independent of the presence of Fe3+ ions). However, this process is too slow to be accurately measurable.

Ligand Attachment Chemistry in the Preparation of PCsp3P and PCsp2P Complexes of Rhodium

The attachment of electron-rich PCP pincer ligands bis(2-(dialkylphosphino)phenyl)methane (alkyl = isopropyl, tert-butyl) to rhodium via reactions with [(COE)2Rh(μ-X)]2 (X = Cl, OSO2CF3) through C–H bond activations is reported. The first C–H activation to produce PCsp3P derivatives is facile and favors products wherein the remaining benzylic C–H and the Rh–H hydrogens are trans-disposed across the new Rh–C bond. For the less bulky isopropyl-substituted ligand, chlorido- or triflato-bridged dinuclear products are favored, while for the tert-butyl-adorned ligand, monomers are formed. The favoring of both trans C–H/Rh–H and dinuclear systems hampers the second C–H activation, necessary to form the (more desirable) PCcarbeneP derivatives. Through spectroscopic and structural investigations, the factors that influence the ligand attachment chemistry through successive C–H activations in these ligands are discussed.

Multi-Uracil Arrays Built on Organostannoxane, Organotelluroxane, and Copper(II) Carboxylate Platforms. C–H···O Interactions Leading to Tetrameric Uracil Motifs

The reaction of 3-(N1-uracyl)propanoic acid (LH) with (t-Bu2SnO)3 in a 3:1 ratio afforded the hydroxide-bridged dimer [t-Bu2Sn(μ-OH)L]2 (1). A similar reaction involving bis(tri-n-butyltin)oxide, (n-Bu3Sn)2O, in a 2:1 ratio afforded the one-dimensional (1D) coordination polymer [(n-Bu3SnL)]n (2). Similarly, the reaction of LH with (MeOAr)2TeO in a 2:1 ratio afforded the mononuclear [(MeOAr)2TeL2]·H2O (3). On the other hand, a similar reaction in a 1:1 ratio gave the dinuclear product [{(MeOAr)2TeL}2O]·C2H5OH·CH3OH·H2O (4). The reaction of complex 1 with CuCl2 in a 1:1 ratio yielded [Cu(II)L2H2O]2·6H2O (5). All the complexes show an extensive supramolecular organization in the solid state as a result of several intermolecular interactions. The role of uracil substituents in determining the final course of the supramolecular assembly is discussed. A tetrameric uracil supramolecular motif is formed in the crystal structure of complex 1 as a result of C–H···O interactions. Uracil–water interactions involving only C–H···O interactions have been observed in complex 5.

Photoinduced Dimerization Reaction Coupled with Oxygenation of a Platinum(II)–Hydrazone Complex

Photoreactivities of Ni(II)- and Pt(II)-hydrazone complexes, [NiCl(L)] (Ni1) and [PtCl(L)] (Pt1), respectively [HL = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone], were investigated in detail via UV-vis absorption, (1)H nuclear magnetic resonance (NMR) spectroscopy, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry; the two photoproducts obtained from the photoreaction of Pt1 were also successfully identified via X-ray analysis. The absorption bands of the Ni1 and Pt1 complexes were very similar, centered around 530 nm, and were assigned as an intraligand charge transfer transition of the hydrazone moiety. The absorption spectrum of Pt1 in a CH3CN solution changed drastically upon photoirradiation (λ = 530 nm), whereas no change was observed for Ni1. (1)H NMR and ESI-TOF mass spectra under various conditions suggested that the photoexcited Pt1* reacts with dissolved dioxygen to form a reactive intermediate, and the ensuing dark reactions afforded two different products without any decomposition. In contrast to the simple photo-oxidation of HL to form a phosphine oxide HL(P═O), the X-ray crystallographic analyses of the photoproducts clearly indicate the formation of a mononuclear Pt complex with the oxygenated hydrazone ligand (Pt1O) and a dinuclear Pt complex with the oxygenated and dimerized hydrazone ligand (Pt2). The photosensitized reaction in the presence of an (1)O2-generating photosensitizer, methylene blue (MB), also produced Pt1O and Pt2, indicating that the reaction between (1)O2 and ground-state Pt1 is the important step. In a highly viscous dimethyl sulfoxide solution, Pt1 was slowly, but quantitatively, converted to the mononuclear form, Pt1O, without the formation of the dinuclear product, Pt2, upon photoirradiation (and in the reaction photosensitized by MB), suggesting that this photoreaction of Pt1 involves at least one diffusion-controlled reaction. On the other hand, the same complexes Pt1O and Pt2 were also produced in the degassed solution, probably because of the reaction of the photoexcited Pt1* with the biradical character and H2O.

Dinuclear CuII–CuII and CuI–CuII Complexes of a Compartmental Ligand – Syntheses, Structures, Magnetic, and Catalytic Studies

AbstractDinuclear CuII–CuII (1) and CuI–CuII (2) complexes were derived from a new N4O2 donor compartmental ligand (H2L) by changing the nature of the Cu precursors used. Single‐crystal X‐ray diffraction studies revealed that the Cu1 site in 1 has octahedral geometry and is in the inner compartment of the ligand axially coordinated by two ClO4– anions, whereas the outer Cu2 ion has square‐pyramidal geometry. In 2, there are two copper dinuclear complexes (A and B) in the asymmetric unit; the inner core is occupied by Cu1/Cu3 in the +2 oxidation state in a square‐planar geometry. The Cu2/Cu4 ion occupies the outer sites and has distorted tetrahedral geometry with a +1 oxidation state. Complexes 1 and 2 were obtained simply by changing Cu(ClO4)2 in 1 to Cu(ClO4)2 and Cu(bipy)(NO3)2 in 2; the bipyridyl (bipy) ligand induces the reduction of CuII to CuI, which is trapped in the CuI–CuII dinuclear product. The oxidation states of the metal ions were ascertained from charge‐balance considerations as well as from bond valence sum (BVS) calculations. No signature of intervalence charge transfer (IVCT) was observed by spectroscopy (UV/Vis/NIR) as well as from the low‐temperature magnetic studies. This might be because of the presence of two copper centers in two different geometries with a wide separation between them (ca. 3.27 Å). For 1, the best fit of the χT vs. T data to the dimer model gives J/kB = –262(1) K and gav = 2.05(5), which indicates that there is a strong antiferromagnetic coupling between the two Cu atoms. In 2, the CuI center is diamagnetic and, thus, the remaining S = 1/2 CuII magnetic center follows a Curie law with g = 2.06(5). Under homogeneous conditions, both complexes showed catalytic epoxidation of cyclooctene, styrene, and norbornene to the corresponding epoxides with high selectivities and turnover numbers (TONs), which seem to be slightly better than the reported values for CuII Schiff base complexes.

Synthesis and Characterization of η6‐Arene Ruthenium Complexes Bearing Oxopentadienyl and Phosphine Ligands

AbstractAn addition reaction of dinuclear [(η6‐C6Me6)Ru(η3, 1‐exo‐syn‐CH2CHCHCHO)]2(BF4)2 (1) with different Lewis bases in acetone results in the formation of mononuclear [(η6‐C6Me6)Ru(η3‐exo‐syn‐CH2CHCHCHO)(L)](BF4) (L = PMe3, 2; PPh3, 3; PHPh2, 4; Ph2PEtPy, 6; CO, 7) and dinuclear [{(η6‐C6Me6)Ru(η3‐exo‐syn‐CH2CHCHCHO)}2(μ2‐dppe)](BF4)2 (5). The addition of Ph2PCH2CH2PPh2 to the dinuclear product 1 affords 5 which show a bridging phosphine between two ruthenium centers. A comparative study of the new cationic arene derivatives and the corresponding isoelectronic Cp*Ru(heteropentadienyl) is established. All compounds were characterized by IR spectroscopy, high resolution mass spectrometry, NMR spectroscopy and the crystal structures of 2 and 3 are also described.

3-Phenyl-5-(2-pyridyl)pyrazolato Complexes of Lithium, Magnesium, Calcium, and Zinc

Abstract Metalation of 3-phenyl-5-(2-pyridyl)pyrazole (HPz, 1) with alkyllithium and -zinc compounds in tetrahydrofuran (thf) yields dinuclear products [(thf)Li(Pz)]2 (2) and [MeZn(Pz)]2 (3), respectively. Magnesiation of 1 with diethylmagnesium in tetrahydrofuran in the presence of 1,4-dioxane leads to cocrystallization of mononuclear [(thf)2Mg(Pz)2] (4a) and [(diox)2Mg(Pz)2] (4b). Metalation of 1 with KH followed by a metathesis reaction with CaI2 in tetrahydrofuran leads to the formation of dinuclear [{(thf)2Ca}(m-Pz)3Ca(Pz)] (5) with the calcium atoms in different coordination environments. The ligand precursor 1 crystallizes as a dimer with N-H···N bridges between the pyrazole fragments. The pyrazolate anions of the metal complexes 2 to 5 exhibit similar structural parameters regardless of a bridging or terminal coordination mode and the electronegativity of the coordinated metal.