Heteronuclear Cluster Complexes Research Articles

Fabrication of spinel CoMn2O4 hollow spheres for highly selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

• Spinel CoMn 2 O 4 hollow spheres were prepared by a solvothermal method via glycerate-mediated process. • Spinel structures of CoMn 2 O 4 hollow spheres can be tuned by different Co/Mn molar ratios. • Spinel CoMn 2 O 4 hollow spheres with Co/Mn molar ratio of 2/3 exhibits a 41.6% HMF conversion and a 100% selectivity to DFF. • The synergistic effect between Co and Mn species in CoMn 2 O 4 leads to significant improvement in catalyst performance. • The spinel CoMn 2 O 4 hollow spheres is highly stable under the applied reaction conditions. Spinel CoMn 2 O 4 hollow spheres were prepared by a solvothermal method, where uniform cobalt-manganese glycerate spheres as the precursor were self-assembled and converted into hollow spheres by calcination. The as-prepared catalysts were characterized by field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and desorption isotherms, thermogravimetric analysis, and H 2 temperature programmed reduction (H 2 -TPR). The results show that body-centered tetragonal and face-centered cubic spinel structures of CoMn 2 O 4 hollow spheres can be tuned by different Co/Mn molar ratios. Moreover, the spinel CoMn 2 O 4 hollow spheres exhibit high catalytic activity for the selective oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-diformyfuran (DFF). Importantly, the spinel CoMn 2 O 4 hollow spheres with Co/Mn molar ratio of 2/3 shows the highest catalytic performance with a 41.6% HMF conversion and a 100% selectivity to DFF. On one hand, the spinel CoMn 2 O 4 hollow spheres with large surface area have sufficient exposed active sites for the oxidation of HMF and oxidized product DFF can fast leave the catalyst surface leading to high selectivity, avoiding further oxidation. On the other hand, the synergistic effect between Co and Mn species in the binary oxides by the formation of heteronuclear cluster complexes CoMn 2 O 4 , which affects and promotes the electron-transfer process, results in significant improvement in catalyst performance. Additionally, the effects of different Co/Mn molar ratios, catalyst amounts, reaction time and temperatures of the catalyst for HMF oxidation were also investigated. Furthermore, the spinel CoMn 2 O 4 hollow spheres can be used for six consecutive runs without significant loss of its catalytic activity.

Synthesis and structures of new heteronuclear cluster complexes [PPh4][Fe4Rh3Se2(CO)16] and [PPh4]2[Fe3Rh4Te2(CO)15

The reaction of the K2[Fe3Q(CO)9] clusters (Q = Se or Te) with Rh2(CO)4Cl2 under mild conditions is accompanied by complicated fragmentation of cores of the starting clusters to form large heteronuclear cluster anions. The [PPh4][Fe4Rh3Se2(CO)16] and [PPh4]2[Fe3Rh4Te2(CO)15] compounds were isolated by treatment of the reaction products with tetraphenylphosphonium bromide. The structures of the products were established by X-ray diffraction. In both compounds, the core of the heteronuclear cluster consists of two octahedra fused via a common Rh3 face.

W( η2-PhCCPh) 3( η1-Ph 2PCCPPh 2) as a ligand to prepare homo- and hetero-nuclear cluster complexes

Reaction of W( η 2-PhCCPh) 3(NMe 3) ( 1) and Ph 2PCCPPh 2 (dppa) produces W( η 2-PhCCPh) 3( η 1-Ph 2PCCPPh 2) ( 2), which contains a pendant phosphine group. Treatment of 2 with W(CO) 4(NCMe) 2 yields [W( η 2-PhCCPh) 3]( μ, η 2-Ph 2PCCPPh 2)[W(CO) 4(NCMe)] ( 3). Compound 2 reacts with Os 3(CO) 10(NCMe) 2 to afford Os 3(CO) 10[( μ, η 2-Ph 2PCCPPh 2)W( η 2-PhCCPh) 3] 2 ( 4), and reacts with Ru 3(CO) 9(NCMe) 3 to afford Ru 3(CO) 9[( μ, η 2-Ph 2PCCPPh 2)W( η 2-PhCCPh) 3] 3 ( 5). The crystal structures of 2 and 3 are determined by an X-ray diffraction study.

The reaction of [Re2(CO)8(MeCN)2] with thiols. Formation of hydrido sulfido bridged dirhenium cluster complexes [Re2(μ-H)(μ-SR)(CO)8] (R = H, n-Bu, Cy, Ph, C6H4F-p, C6F5 or 2-naphthyl)

The complex [Re2(CO)8(MeCN)2] 1 reacted with thiols or H2S, respectively, by SH oxidative addition in toluene at 80 °C to give hydrido sulfido bridged dirhenium complexes of the general formula [Re2(µ-H)(µ-SR)(CO)8] (R = H 2a, n-Bu 2b, Cy 2c, Ph 2d, C6H4F-p 2e, C6F5 2f or 2-naphthyl 2g) in 60 to 80% yield. Complexes 2c and 2g have been characterised by crystal structure analysis. Complex 2a undergoes reaction with another equivalent of 1 to form the novel spirocyclic complex [{Re2(µ-H)(CO)8}2(µ4S)] 3. In order to demonstrate the acidity of the µ-H ligand 2g was deprotonated by the base 1,8-diazabicyclo[5.4.0]undec-7-ene to give the anion [Re2(µ-S(2-naph))(CO)8]– 4– (naph = naphthyl) which can be isolated as its PPh4+salt. This reacts with one equivalent of [MCl(PPh3)] (M = Au, Ag or Cu) to give the novel heteronuclear cluster complexes [Re2(MPPh3)(µ-S(2-naph))(CO)8] (M = Au 5a, Ag 5b or Cu 5c) and PPh4Cl. The molecular structures of 5a and 5b have been established by single crystal X-ray analysis.

Complexes with Platinum−Iridium Bonds: Stepwise Formation of a PtIr2Cluster Complex

The reaction of [Pt(dppm)2]Cl2 (dppm = Ph2PCH2PPh2) with [Ir(CO)4]- and dppm in a 1:2:1 ratio leads in a multistep reaction to the new heteronuclear cluster complex [PtIr2(CO)2(μ-CO)(μ-dppm)3], which contains a triangle of metal atoms with each edge bridged by a dppm ligand and in which only the platinum atom is coordinatively unsaturated. The initial step in the reaction leads to formation of the neutral and cationic binuclear complexes [PtIrCl(CO)2(μ-dppm)2] and [PtIr(CO)3(μ-dppm)2]+, respectively. The binuclear complexes then react with additional [Ir(CO)4]- to form the cluster [PtIr2(CO)4(μ-CO)(μ-dppm)2] by insertion into a Pt−P linkage; this cluster can exist in two isomeric forms, each containing a triangular PtIr2 group with the Ir−Ir and one Pt−Ir edge bridged by dppm ligands but differing in stereochemistry. These isomers equilibrate slowly at room temperature, and each reacts easily with dppm to form the final cluster complex [PtIr2(CO)2(μ-CO)(μ-dppm)3]. The structures of the complexes [PtIr2(CO...

Isomerization of methyl formate to acetic acid catalysed by the Ru(II)-Sn(II) heteronuclear cluster complex [Ru(SnCl 3) 5(PPh 3)] 3−

The Ru II-Sn II heteronuclear cluster complex [Ru(SnCl 3) 5(PPh 3)] 3− has been found to be catalytically active for the isomerization of methyl formate to acetic acid. The initial reaction rate showed a first order dependence on the catalyst concentration, and showed a saturation curve for the reactant concentration in its high-concentration region. Extra addition of PPh 3 and Cl − ion considerably retarded the reaction with almost linear relationships between the reciprocal of initial rates and the concentration of additives. A rate equation derived from these kinetic data indicates the presence of a pre-equilibrium of dual ligand dissociation from the catalyst (PPh 3 from Ru II and Cl − from Sn II) to form the catalyst-reactant complex, where the relatively soft Ru II and the hard Sn II interact simultaneously with the soft CO group and hard OCH 3 group of methyl formate, respectively. It is postulated that such a multi-center interaction in this cluster system facilitates the overall rearrangement of CH 3 group (from O atom to C atom) to realize the isomerization of methyl formate to acetic acid without CO atmosphere or iodide promoter, but with an activation energy comparable to that for Rh or Ni catalyst which requires both of them.

The synthesis and structural analysis of Pt2Ru4(CO)18 and the products obtained from its reactions with 1, 2-bis(diphenylphosphino)ethane

From the reaction of Ru(CO)5 and Pt(COD)2, COD = 1, 5-cyclooctadiene, the new platinum-ruthenium heteronuclear cluster complex Pt2Ru4(CO)18,1, was obtained in 60% yield.1 has a folded ladder-like structure with alternating pairs of ruthenium atoms and platinum atoms. The cluster of1 can be split to yield the known compound PtRu2(CO)8(η2-dppe),2, (54% yield) by reaction with 1, 2-bis(diphenylphosphino)ethane, dppe, at 25°C. When1 was treated with excess dppe at 40°C, thebis-diphos compound3, PtRu2(CO)6(μ-η2-dppe)2 was obtained (39% yield). Under the similar reaction conditions,2 was converted to3 in 44% yield. All these complexes were characterized by single crystal X-ray diffraction analyses. Compounds2 and3 both contain a triangular cluster of one platinum and two ruthenium atoms, but in2 the bidentate ligand, dppe, chelates the platinum atom and in3 the two dppe ligands bridge the two Pt-Ru metal-metal bonds. Crystal data for1: space group C2/c,a=12.542(2)A,b=15.350(4)A,c=15.252(3)A, β=105.32(2)°,Z=4, 2192 reflections,R=0.025. For2: space group P21/c,a=14.351(2)A,b=13.486(3)A,c=19.218(3)A, β=108.48(1)°,Z=4, 3029 reflections,R=0.027. For3: space group P21/c,a=18.836(6)A,b=15.559(5)A,c=23.259(7)A, β=111.26(2)°,Z=4, 4204 reflections,R=0.038.

Cluster synthesis. 38. Formation of high-nuclearity platinum-osmium cluster complexes. Synthesis, structural characterizations, and interrelationships of Pt4Os6(CO)22(COD), Pt5Os6(CO)21(COD)2, Pt4Os6(CO)19(COD)2, and Pt7Os6(CO)21(COD)2, (COD = cycloocta-1,5-diene)

The chemistry of heteronuclear cluster complexes containing Pt has attracted a great deal of interest becasue of the importance of Pt alloys to the process of catalytic petroleum reforming. Three new high-nuclearity Pt-Os carbonyl cluster complexes Pt[sub 4]Os[sub 6](CO)[sub 22](COD) (2), Pt[sub 5]Os[sub 6](CO)[sub 21](COD)[sub 2] (3), and Pt[sub 4]Os[sub 6](CO)[sub 19](COD)[sub 2] (4) were obtained in 17%, 13%, and 9% yields, respectively, from the pyrolysis of Pt[sub 2]Os[sub 3](CO)[sub 10](COD)[sub 2] (1) under a CO atmosphere at 128C. Compounds 2-4 were characterized by IR, [sup 1]H NMR, and single-crystal X-ray diffraction analyses. Compound 2 consists of two Pt[sub 3]Os[sub 3] octahedra sharing a Pt[sub 3] triangular face. A Pt(COD) group caps one of the Os[sub 3] triangular faces. Compound 3 is structurally similar to compound 2 but has an additional Pt(COD) group capping one of the PtOs[sub 2] triangular faces. The cluster of compound 4 can be viewed as a meta-bicapped Pt[sub 2]Os[sub 4] octahedron with an additional Pt(COD) group capping a PtOs[sub 2] traingle to one of the capping groups on the octahedron and a Pt(COD) group bridging the Pt-Pt edge of the octahedron. Compound 2 was converted to 4 in 65% yield, when it was irradiated inmore » the presence of COD. When compound 2 was treated with 1 equiv of trimethylamine N-oxide and 2 equiv of Pt(COD)[sub 2], compound 3 and a new higher nuclearity platinum-osmium carbonyl complex Pt[sub 7]Os[sub 6](CO)[sub 21](COD)[sub 2] (5; 8% yeild) were obtained. Compound 5 was characterized by a single-crystal X-ray diffraction analysis. It was formed by the loss of one CO from 2 and the addition of three Pt atoms and one COD ligand. Compound 2 was converted to the known compound Pt[sub 4]Os[sub 6](CO)[sub 21](COD)([mu]-H)[sub 2] in good yield (79%) by reacting with trimethylamine N-oxide and hydrogen.« less

Hydrogen-rich metal cluster complexes. Hexahydrido platinum-osmium carbonyl cluster complexes from the reaction of Pt2Os4(CO)18 with hydrogen

As part of a study of heteronuclear cluster complexes containing platinum, the reaction of Pt{sub 2}Os{sub 4}(CO){sub 18} with hydrogen was investigated. Two new compounds, Pt{sub 2}Os{sub 5}(CO){sub 17}(mu-H){sub 6} (I) and PtOs{sub 5}(CO){sub 16}(mu-H){sub 6} (II), have been isolated and characterized by ir, {sup 1}H NMR and single-crystal x-ray diffraction analysis. Compound II was found to be electron deficient, and it is proposed that the electron deficiency is associated with the short doubly hydride-bridged bond Pt-Os. It is also reported that I can be converted into II by reaction with Os{sub 3}(CO){sub 11}(NCMe). The concomitant formation of Os{sub 3}(CO){sub 12} suggests that Os{sub 3}(CO){sub 11}(NCMe) is acting simply as a decarbonylation reagent, but the fate of the Pt atom expelled from I in this transformation has not been explained. 14 refs., 2 figs.

The reactions of Mo2Ru(CO)7Cp2(η3-S) with phenylacetylene and Ru(CO)5

Abstract The reactivity of the heteronuclear cluster complex Mo2Ru(CO)7Cp2(η3-S) (1) toward HC2Ph was investigated and compared with the reactivity of the homonuclear complexes Ru3(CO)10(μ3-S) (2) and [Mo(CO)2Cp]2 (3). The reaction of 1 with HC2Ph yielded the new compound Mo2Ru(CO)2Cp2[μ3-η6-HCC(Ph)CHC(Ph)CHC(Ph)](μ3-S) (6), 15%. The compound contains a 1,3,5-triphenyldimetallahexatrienyl ligand formed by the head-to-tail coupling of three HC2Ph molecules. The C6-chain bridges one face of the triangular cluster. Three of the carbon atoms of the chain are π-bonded to one molybdenum atom. The other three carbon atoms are π-bonded to the ruthenium atom. The two ends of the chain are σ-bonded to the second molybdenum atom. When treated with CO at 100°C/25 atm, 6 eliminates 1,3,5,triphenylbenzene and reforms 1. At 125°C under nitrogen, the C6-chain in 6 is split at the C(3)C(4) bond to yield the two isomeric products Mo2Ru(CO)2Cp2[μ3-η3-HCC(Ph)CH][μ-η3-PhCC(H)CPh](μ3-S) (7) and Mo2Ru(CO)2Cp2[μ3-η3-HCC(Ph)CH][μ-η3-PhCC(Ph)CH](μ2-S) (8). Both products contain two dimetallaallyl ligands. One bridges the face of the cluster. The other bridges the MoMo edge. Compound 7 is converted into 8 at 125°C. When 1 is treated with Me3NO and HC2Ph at 25°C, the compound Mo2Ru(CO)5Cp2[μ-η4-PhCC(H)CC(H)Ph](μ3-S) (9) is formed in 11% yield. Compound 9 consists of an open cluster with a PhCC(H)CC(H)Ph ligand that bridges the open edge of the cluster. The four-carbon chain is π-bonded to a molybdenum atom while one carbon serves as the bridging link by bonding to the ruthenium atom. Compound 9 does not appear to be an intermediate en route to 6. When 1 is treated with Ru(CO)5 at 80°C, two higher nuclearity cluster products Mo2Ru4(CO)13(μ4-η2-CO)Cp2(μ4-S) (10) and Mo2Ru5(CO)14(μ4-η2-CO)2Cp2(μ4-S) (11) are formed. Compound 10 consists of a square pyramidal Mo2Ru4 cluster containing a quadruply bridging sulphido ligand on the square base. An Ru(CO)3 group bridges an RuRu edge of the square base. A dihapto quadruply bridging carbonyl ligand is bonded by its carbon atom to an MoRu2 triangle of the square pyramid and is bonded by its oxygen atom to the Ru(CO)3 group. Compound 11 is similar to 10 but has an additional Ru(CO)3 group bridging the second RuRu basal edge of the cluster and also has a second dihapto quadruply bridging carbonyl ligand. IR spectra show that the two quadruply bridging carbonyl ligands are vibrationally coupled by the appearance of two CO stretching absorptions at 1419 and 1453 cm−1. When 10 is heated to 80°C, it is converted to an isomer 12 by shifting the quadruply bridged carbonyl ligand to a terminal bonding mode. The cluster is transformed from an edge bridging form in 10 to a face capped form in 12.

Syntheses of metal carbonyls: XVII. Formation of a heteronuclear organometallic cluster containing ruthenium and rhodium; crystal and molecular structure of {[Rh(η-C 5Me 5)] 3Ru(CO) 3](μ 3-CO) 2}

Ru(C 6Me 6)(C 2H 4) 2 reacts with Rh(C 5Me 5)(CO) 2 to give the known dinuclear complex [Rh(C 5Me 5)(CO)] 2 and the new heteronuclear cluster complex {[Rh(C 5Me 5)] 3[Ru(CO) 3](μ 3-CO) 2} which has been fully characterized by a single crystal X-ray diffraction study.

Synthesis and X-ray structure of (η 5-C 5H 5) 2W 2Ir 2(CO) 7(CHCO 2Et) 2, a tetrahedral heterometal cluster with two different environments for ethylcarboxylatocarbene ligands

The tetrahedral heteronuclear cluster complex (η 5-C 5H 5) 2W 2Ir 2(CO) 10 reacts with N 2CHCO 2R (R = Et, Me) at room temperature to form the dicarbene species (η 5-C 5H 5) 2W 2Ir 2(CO) 7(CHCO 2R) 2. An X-ray diffraction study (R = Et) shows an intact tetrahedral metal framework with two distinct sites for the CHCO 2Et ligands. The first uses its carbon atom to bridge the IrIr bond; the second uses its carbon atom to bridge an IrW bond and, additionally, forms a donor bond from a carbonyl oxygen atom to the second tungsten atom.

Synthesis, crystal and molecular structure, and reactions of the bridging vinylidenedicobalt complex (.mu.-CCH2)(CpCoCO)2. Reaction with molybdenum hydrides to give a heteronuclear cluster complex

Synthese du premier complexe μ-vinylidene (μ−CCH 2 )(CpCoCO) 2 qui est rapidement protone par HBF 4 sur le C−β pour donner un sel μ-ethylidyne. Reaction avec CpMo(CO) 2 (L)H(L=CO,PPh 3 ) donnant un agregat heteronucleaire