New Ruthenium and Osmium Carbonyl Cluster Complexes With Main Group Bridging Ligands Having Unusual Structures and Bonding

The reaction of IrRu3(CO)13(µ-H), 2.1 with HSnPh3 in hexane solvent at reflux has provided the new mixed metal cluster compounds Ir2Ru2(CO)11(SnPh3)(µ-H)3, 2.2 and IrRu3(CO)11(SnPh3)3(µ-H)¬4, 2.3 containing SnPh3 ligands. Compound 2.2 which was obtained in low yield (3%) contains a closed cluster having two iridium and two ruthenium atoms, one SnPh3 ligand and three bridging hydride ligands. Compound 2.3 has a butterfly structure for the four metal atoms with three SnPh3 ligands and four bridging hydride ligands around the periphery of the cluster. When compound 2.3 was heated to 97 oC for 30min, IrRu3(CO)9(μ-η2-C6H5)(μ4-SnPh)2(μ-SnPh2), 2.4 was formed by cleavage of phenyl rings from the SnPh3 ligands in low yield. Compound 2.4 contain square IrRu3 clusters of the metal atoms with quadruply bridging SnPh ligands on opposite sides of the cluster, one bridging SnPh2 ligand on one of the Ir-Ru bonds and also a rare η2-bridging phenyl ligand. The new compound IrRu3(CO)11(GePh3)3(µ-H)¬4, 3.1 was obtained in 64% yield from the reaction of IrRu3(CO)13(μ-H) with HGePh3 at room temperature. Compound 3.1 is the Ge analog of compound 2.3, which contains an open cluster of one iridium and three ruthenium atoms with three GePh3 ligands and four hydride ligands. When the reaction was performed at hexane reflux for 10 min a second minor Ir2Ru2(CO)11(GePh3)(μ-H)3, 3.2 was formed. Compound 3.2 is two iridium atoms and two ruthenium atoms in a tetrahedral structure which must have formed by some metal-metal exchange process. When compound 3.1 was heated to 68 oC for 6h, two new compounds: IrRu3(CO)10(μ-η2-C6H5)(μ4-GePh)2, 3.3 and IrRu3(CO)9(μ-η2-C6H5)(μ4-GePh)2(μ-GePh2), 3.4 were formed by cleavage of phenyl rings from the GePh3 ligands. Compound 3.3 and 3.4 contain square IrRu3 clusters of the metal atoms with quadruply bridging GePh germylyne ligands on opposite sides of the cluster. Both compounds also contain a rare η2-bridging phenyl ligand. Compound 3.4 was found to react with dimethylacetylenedicarboxylate DMAD to yield new compound IrRu3(CO)9([μ4-Ge(Ph)C(CO2Me)C(CO2Me)](μ-GePh2)2, 3.5 by addition of DMAD to one of the bridging germylyne ligands. In the process the bridging phenyl ligand was transferred to the other bridging germylyne ligand to form a bridging germylene ligand. The compounds Ru4(CO)12(GePh3)2(μ-H)¬4, 4.1 and Ru4(CO)12(SnPh3)2(μ-H)¬4, 4.2 were obtained from the reactions of Ru4(CO)13(μ-H)2 with HGePh3 and HSnPh3, respectively. Both compounds contain a nearly planar butterfly structure for the four metal atoms with two GePh3 / SnPh3 ligands and four bridging hydride ligands around the periphery of the cluster. When heated, 4.1 and 4.2 were converted into the complexes Ru4(CO)12(μ4-EPh)2, 4.3, E = Ge, and 4.4, E = Sn, by cleavage of two phenyl groups from each of the GePh3 ligands. Compounds 4.3 and 4.4 contain square planar arrangements of the four ruthenium atoms with quadruply bridging germylyne and stannylyne ligands on opposite sides of the square plane. The bonding and electronic transitions of 4.3 were analyzed by DFT computational analyses. The electronically unsaturated complex [Ru3(CO)8(μ3-CMe)¬(μ-H)¬2(μ3-H)]2¬, 5.1 was obtained by silica gel induced reaction of Ru3(CO)8(μ3-CMe)¬(μ-H)¬3, 5.2. Compound 5.1 can be viewed as a dimer of the 46 electron fragment Ru3(CO)8(μ3-CMe)¬(μ-H)¬3, is held together by a delocalized bonding involving two triply-bridging hydride ligands. Compound 5.1 exhibits a dynamical activity in solution that equilibrates two of the three types of hydride ligands. Compound 5.1 reacts with 1,1-bis(diphenyphosphino)methane to form the macrocyclic complex [Ru3(CO)7(μ3-CMe)¬(μ-H)¬3]2(μ-dppm)¬2, 5.3. Compound 5.3 is a centrosymmetrical dimer linked by two bridging dppm ligands, each phosphorus atom of the dppm is coordinated to a different Ru3 cluster. However, Ru3(CO)7(μ3-CMe)(μ-H)3(μ-dppm), 5.4, was obtained from the reaction of Compound 5.2 with dppm. Reactions of Os3(CO)10(NCMe)2 with HGePh3 have yielded the compounds Os3(CO)10(NCMe)(GePh3)(μ-H)¬, 6.1 and Os3(CO)10(GePh3)2(μ-H)2¬, 6.2 by the sequential replacement of the NCMe ligands and the oxidative addition of the GeH bonds of one and two HGePh3 molecules, respectively, to the osmium atoms of the cluster. Compound 6.2 exists as two isomers in solution at low temperatures which interconvert rapidly on the 1H NMR time scale at room temperature. When heated, 6.1 was transformed into the pentaosmium complex Os5(CO)17(μ-GePh2), 6.3 which exhibits a planar raft structure with one bridging GePh2 ligand. Compound 6.1 reacts with the compound PhAu(PPh3) to yield the compound Os3(CO)8(μ-CO)(μ-O=CPh)(μ-GePh2)(μ-AuPPh3), 6.4 which contains a bridging O=CPh ligand and a Au(PPh3) group that bridges an Os-Ge bond, and compound PhOs4(CO)13(µ-GePh2)(µ-AuPPh3), 6.6 which contains four osmium atoms in a butterfly arrangement with one bridging GePh2 ligand, one bridging AuPPh3 ligand and one σ-bonded phenyl ligand to one of the osmium atoms. A minor product, Os(CO)4(GePh3)(AuPPh3), 6.5 was also obtained in this reaction. Compound 6.4 was also obtained from the reaction of 6.1 with CH3Au(PPh3). Compound 6.4 reacted with PhC2Ph to yield the complex Os3(CO)7(μ-GePh2)(μ-AuPPh3)[μ-(O)CPhCPhCPh)], 6.7 which contains a novel bridging oxa-metallacycle formed by the coupling of PhC2Ph to the bridging O=CPh ligand 6.4 and another example of a Au(PPh3) group that bridges an Os-Ge bond. The bonding of the bridging Au(PPh3) group to the Os - Ge bonds in 6.4 and 6.7 was investigated by DFT computational analyses. Three new compounds were obtained from the reaction of Os3(CO)10(NCMe)2, 7.1 with BiPh3 in a methylenechloride solution at reflux. These have been identified as Os3(CO)10(μ3-C6H4)¬, 7.2, Os3(CO)10Ph(μ-η2-O=CPh), 7.3, and HOs6(CO)20(μ-η2-C6H4)(μ4-Bi), 7.5. A fourth product HOs5(CO)18(μ-η2-C6H4)(μ4-Bi), 7.4 was also obtained from the reaction of Os3(CO)11(NCMe) with BiPh3. Cleavage of the phenyl groups from the BiPh3 was the dominant reaction pathway and two of the products 7.2 and 7.3 contain rings but no bismuth. Each of the new compounds was characterized structurally by single-crystal X-ray diffraction methods. Compound 7.2 contains a triply bridging benzyne (C6H4) ligand that exhibits a pattern of alternating long and short C - C bonds that can be attributed to partial localization of the π-bonding in the C6 ring. The localization in the π-bonding was supported by DFT calculations. Compound 7.3 contains a triangular cluster of three osmium atoms with a bridging benzoyl ligand and a terminally coordinated phenyl ligand. Compound 7.5 contains six osmium atoms divided into two groups of four and two and the two groups are linked by a spiro-bridging bismuth atom. The group of two osmium atoms contains a bridging C6H4 ligand. When heated, compound 7.3 was converted into 7.2 and the compound Os3(CO)10(μ-η2-O=CPh)2, 7. 6. Compound 7.6 contains two bridging benzoyl ligands

Zirconium Phosphate Supported MOF Nanoplatelets

We report a rare example of the preparation of HKUST-1 metal–organic framework nanoplatelets through a step-by-step seeding procedure. Sodium ion exchanged zirconium phosphate, NaZrP, nanoplatelets were judiciously selected as support for layer-by-layer (LBL) assembly of Cu­(II) and benzene-1,3,5-tricarboxylic acid (H₃BTC) linkers. The first layer of Cu­(II) is attached to the surface of zirconium phosphate through covalent interaction. The successive LBL growth of HKUST-1 film is then realized by soaking the NaZrP nanoplatelets in ethanolic solutions of cupric acetate and H₃BTC, respectively. The amount of assembled HKUST-1 can be readily controlled by varying the number of growth cycles, which was characterized by powder X-ray diffraction and gas adsorption analyses. The successful construction of HKUST-1 on NaZrP was also supported by its catalytic performance for the oxidation of cyclohexene

Polymnia uvedalia

Reactions of Os₃(CO)₁₀(NCMe)₂ with HGePh₃ have yielded the compounds Os₃(CO)₁₀(NCMe)­(GePh₃)­(μ-H) (<b>1</b>) and Os₃(CO)₁₀(GePh₃)₂(μ-H)₂ (<b>2</b>) by the sequential replacement of the NCMe ligands and the oxidative addition of the GeH bonds of one and two HGePh₃ molecules, respectively, to the osmium atoms of the cluster. Compound <b>2</b> exists as two isomers in solution at low temperatures which interconvert rapidly on the ¹H NMR time scale at room temperature. When it was heated, <b>1</b> was transformed into the pentaosmium complex Os₅(CO)₁₇(μ-GePh₂) (<b>3</b>), which exhibits a planar raft structure with one bridging GePh₂ ligand. Compound <b>1</b> reacts with the compound PhAu­(PPh₃) to yield the compound Os₃(CO)₈(μ-CO)­(μ-OCPh)­(μ-GePh₂)­(μ-AuPPh₃) (<b>4</b>), which contains a bridging OCPh ligand and a Au­(PPh₃) group that bridges an Os–Ge bond. A minor product, Os­(CO)₄(GePh₃)­(AuPPh₃) (<b>5</b>), was also obtained in this reaction. Compound <b>4</b> was also obtained from the reaction of <b>1</b> with CH₃Au­(PPh₃). Compound <b>4</b> reacted with PhC₂Ph to yield the complex Os₃(CO)₇(μ-GePh₂)­(μ-AuPPh₃)­[μ-(O)­CPhCPhCPh)] (<b>6</b>), which contains a novel bridging oxametallacycle formed by the coupling of PhC₂Ph to the bridging OCPh ligand in <b>4</b> and is another example of a Au­(PPh₃) group that bridges an Os–Ge bond. The bonding of the bridging Au­(PPh₃) group to the Os–Ge bonds in <b>4</b> and <b>6</b> was investigated by DFT computational analyses

Formation of Anti-Wear Tribofilms via α-ZrP Nanoplatelet as Lubricant Additives

Effective tribofilms are desirable to protect mechanical systems. In the present research, we investigated the formation of a tribofilm through the use of α-ZrP (Zr(HPO4)2·H2O) as an additive. Experiments were conducted on a base oil where 0.2 wt% of the additive was used. Experimental results showed a 50% reduction in friction and a 30% reduction in wear when compared to the base oil containing 0.8 wt% ZDDP. Spectroscopic characterization indicated that the tribofilm consists of iron oxide, zirconium oxide, and zirconium phosphates. The worn surface was seen to be smooth which renders it desirable for bearing systems

Linguistic Properties Matter for Implicit Discourse Relation Recognition: Combining Semantic Interaction, Topic Continuity and Attribution

Proceedings of the 32nd AAAI Conference on Artificial Intelligence (AAAI-'18).1-1

Linguistic Properties Matter for Implicit Discourse Relation Recognition: Combining Semantic Interaction, Topic Continuity and Attribution

32nd AAAI Conference on Artificial Intelligence / 30th Innovative Applications of Artificial Intelligence Conference / 8th AAAI Symposium on Educational Advances in Artificial Intelligence4848-485

Bonding and Reactivity in the Electronically Unsaturated Hydrogen-Bridged Dimer [Ru₃(CO)₈(μ₃-CMe)(μ-H)₂(μ₃-H)]₂

The electronically unsaturated complex [Ru₃(CO)₈(μ₃-CMe)­(μ-H)₂(μ₃-H)]₂ (<b>1</b>), viewed as a dimer of the 46-electron fragment Ru₃(CO)₈(μ₃-CMe)­(μ-H)₃, is held together by delocalized bonding involving two triply bridging hydride ligands. Compound <b>1</b> exhibits a dynamic activity in solution that equilibrates two of the three types of hydride ligands. Compound <b>1</b> reacts with 1,1-bis­(diphenylphosphino)­methane to form the macrocyclic complex [Ru₃(CO)₇(μ₃-CMe)­(μ-H)₃]₂(μ-dppm)₂ (<b>3</b>)

Crystal structure of <i>P</i>. <i>aeruginosa</i> TpbA.

<p>A: Cartoon representation of TpbA coloured from blue at the N-terminus to red at the C-terminus. Secondary structure elements are labelled and the phosphate ion is shown in stick representation. B: Electrostatic surface representation of TpbA. C: The PTP loop (residues 131–138) and phosphate ion are shown in stick representation. A 2mFo-DFc electron density map is shown contoured at 1.2 σ. D: 2mFo-DFc electron density for the orthophosphate and bound tyrosine from the Tpb (C132S)—pTyr structure. Electron density is shown contoured at 1.2 σ.</p

Kinetic constants for the hydrolysis of two periplasmic TpbB peptide substrates by TpbA.

<p>Kinetic constants for the hydrolysis of pNPP are included for comparison.</p><p>Kinetic constants for the hydrolysis of two periplasmic TpbB peptide substrates by TpbA.</p